Q45 won't start (cranks easily) how to diagnose?

I removed the fuel filter & cranked the engine with a result that no gasoline whatsoever eminated from the open hose going INTO the fuel filter. Proof positive, I guess of one of four broken parts:

These two I've found the location of: - fuel pump fuse, 15 amp (located to the left of steering wheel) - fuel pump (is apparently in the gas tank behind the rear seat)

Would Q45 experts help me find these two items? - fuel pump relay (dunno where to find this fuel-pump relay) - fuel pump control unit (dunno where to find this control unit)

QUESTIONS for Q45 experts: a. Where is the fuel pump relay (is it in the engine compartment)? b. Where is the fuel pump control unit (is it near the fuel tank)? c. Do I access the fuel pump from the trunk, back seat, or underside?

Thanks for your kind assistance, Alora

I've read EVERYTHING on this topic and I have only a few remaining questions.

Q: What is the Infiniti Q45 "package tray" & "storage compartment"? Q: What is the Infiniti Q45 "trunk room"?

I read the shop manual (from

searched the USENET groups (from searched NICO (Nissan/Infiniti owners) searched Yahoo Since there is no fuel eminating at the fuel filter inlet, I suspect: - The fuel pump, or, - The fuel pump relay, or, - The fuel pump control unit.

To further diagnose, I need to get a Fluke meter onto each of the above.

Apparently, the fuel pump relay & fuel pump control unit are in the so-called "trunk room". My first question is how to access that trunk room. I know I remove the rear seats (done already). But, then I'm supposed to remove the "package tray" & "storage compartment". I can see what the storage compartment is (not the one on the middle arm rest but on the shelf at the rear of the car); but what is the package tray?

Q: Is the package tray the horizontal shelf that is in the back of the car between the top of the rear seats and the rear window?

Alora

I see you're crossposting to 3 different groups.

Was not going to reply because of this, but--

Try the easiest things first.

Get a hammer or crowbar, and bang on the bottom of the fuel tank a couple of times. Then try to start the car. If the engine starts, its probably the fuel pump.

Jim

I've got everything out of the car now and am testing. Understanding the fuel system is the key component of this test.

Electrically, the battery feeds juice to the FUEL PUMP 15 amp FUSE on to the FUEL PUMP RELAY which is activated by the ON position of the IGNITION SWITCH to cause 13.8 volts to go to the FUEL PUMP which is grounded through the FUEL PUMP CONTROL UNIT which basically provides three (5.6v, 7.8v, 11-14v) pathways back to the negative terminal of the battery (like a large-wattage three-position potentiometer). (Fuel gage is separate.)

Hydraulically, the FUEL PUMP sucks fuel through a white FILTER SOCK and pushes the benzene onward to the FUEL FILTER and then to each FUEL INJECTOR and into the engine for the 14:1 pow part of the combustion chamber pull/push/pow/puey sequence. Any left-over fuel is apparently sent back past the FUEL REGULATOR into the FUEL TANK.

If a jumper wire grounding the fuel pump starts the fuel pump, then the FPCU is suspect. It's also a very good emergency procedure to limp along the five miles or so to the nearest help sans towing.

I took photos of the step-by-step removal sequence (the rear bench and seat back, storage tray and storage compartment, rear brake light, etc. all need to be removed as access is thru the rear seat).

I'll document the entire sequence (so the next person doesn't have to) and post it to the Nissan Infiniti Owners Club web site (apparently rec.autos.tech folks don't know much about this so this is probably the last posting to rec.autos.tech on this topic).

Alora

After studying ALL fuel-pump-related posts & searching the Q45 FSM), I emphatically state NONE mention the LOCATION of the

1990 Infiniti Q45 fuel pump relay hide-and-seek is simply: > The fuel pump relay is behind the right trunk panel ... > The green one is the one you want to test ...

----------------------------------------------------------------- Also, none seem to mention exactly HOW TO REMOVE the 1990 Infiniti Q45 fuel pump control unit, which is simply: > Remove the rear seat bench, rear seat headrests, rear seat back, > rear shelf tail lamp, rear shelf, rear shelf storage basin, > trunk divider (between the trunk & the rear seat back) ... And then: > Remove the thick black sound-deadening material on the rear > shelf to access the four bolt heads holding the fuel pump > control unit to the underside of the rear shelf via brackets.

----------------------------------------------------------------- The next question appears to be about seemingly magic connections. Oh, where is a good Infiniti Q45 owner when I really need them?

The factory shop manual (FSM) says (on page EF & EC-185) to DISCONNECT the fuel pump control unit (FPCU) harness connector; and then inexplicably, the FSM says to re-connect it magically: - Connect proper terminal wires between the fuel pump control unit harness terminals. Then it says to "Start engine" and check the voltage between terminal 7 and terminal 4.

Well, the engine won't start unless the connector is connected. Yet, testing connections can't be done with the connector connected.

How can I even GET to the metal terminals 7 & 4 when the connector is connected? +------++---------+ 4-------| || |-----D 5-------| || |-----E 6-------| Male || Female |-----F 7-------| || |-----G +------++---------+

Am I to (somehow) connect (magic) wire jumpers BETWEEN the connector? +------+ +---------+ 4-------| || |-----D 5-------| || |-----E 6-------| Male || Female |-----F 7-------| || |-----G +------+ +---------+

And then (somehow) attach a VOM to terminals #7 & #4? +-------------------------+ | | +------+ | +---------+ | 4-------| || |-----D +--+--+ 5------| || |-----E | | 6-------| Male || Female |-----F | VOM | ==> 13.8 V 7-------| || |-----G | | +------+ | +---------+ +--+--+ | | +-------------------------+

The FSM diagrams (SEF882J, SEF883J, & SEF884J) show (somehow, magically) a VOM inserted IN THE MIDDLE of the CONNECTED terminals #7 & #4! How can that be? What is this magic?

And, how do I (one by one) connect ADDITIONAL wires? The very next diagram shows a fifth wire (#2) connected: +-------------------------+ | | +------+ | +---------+ | 4-------| || |-----D | 2-------| || |-----B +--+--+ 5-------| || |-----E | | 6-------| Male || Female |-----F | VOM | ==> 7.5 V 7-------| || |-----G | | to +------+ | +---------+ +--+--+ 8.1 V | | +-------------------------+

And the last diagram shows (yet another) sixth wire (#1) connected: +-------------------------+ | | +------+ | +---------+ | 4-------| || |-----D | 1-------| || |-----A | 2-------| || |-----B +--+--+ 5-------| || |-----E | | 6-------| Male || Female |-----F | VOM | ==> 5.5 V 7-------| || |-----G | | to +------+ | +---------+ +--+--+ 5.7 V | | +-------------------------+

QUESTION for q45 owners: How (the heck) can I (possibly) insert the VOM into the MIDDLE of the CONNECTED terminal?

Q: Is there a magic 6-wire bare-metal jumper somehow?

Likewise, given the seemingly explicit statement: > When a car gets towed in the first thing we do is use a > jumper [wire with two alligator clips] to directly ground > the fuel pump ground terminal [the junction of pump and > controller] ... supplying 12-14 volts to pump.

QUESTION: How do I get the METAL connection to ground for the fuel pump when the fuel pump harness has to be CONNECTED in order to supply power to the fuel pump - and when the harness is connected, there is NO BARE METAL wires to connect to?

Said another way, when the connectors are connected, there is NO METAL SHOWING. And when the connectors are unconnected, there is NO POWER TO THE FUEL PUMP. So, what is the MAGIC that gets a metal alligator clip into the middle of the connected connector?

Is there a magical 4-wire jumper that has bare metal in the middle so both power to the fuel pump and ground to the car body can be accomplished at the same time?

Please advise a poor soul who doesn't have the money to pay for full service yet who would like to diagnose this problem.

This seems to be the last of my LOCATION & DIAGNOSIS dilemmas.

---------------------------------------------------------------- Alora

A fuel pump relay are easily located by a click, then followed by another click when ignition is first switch to run, if it or what ever is powering it is still working.

Remove the four bolts holding it, he's suggesting the unit with four bolts.

Normally, you don't test a fuel pump with a car running, unless pressure testing. You don't need to start it, just turn it to run position.

Easy, use a sewing needle and drive it into the wire. Connect an aligator clip to the needle. Don't listen to manual about test harness, you won't find one but you can always make one, but you won't need it.

I heat my probes with MAP torch first and my probes sinks right into any wires, connectors, etc. It's like magic. I do this all the time.

I'm struggling with English, here goes. Splice the intended wire, wrap another pre-spliced wire (same type) onto this and solder it or crimp it with a pair of pliers. You now have a split wire capable of handling the currents demanded by the fuel pump. Tape this wire securely with only electrical tape to prevent fires. Note that without proper currents, your fuel pump won't spin if it's slighty seized from formations to the prepellars.

The other cleaner but difficult method is to remove the lead(s) you want from the male or female connector. Attach a copper wire to this carefully, and securly. Solder it. Inserted the lead(s) back into the male or female connector.

There's no such thing, I can solve a fuel pump problems with no tools on hand, I just rip a wire and a bulb from anywhere in the car and diagnose fuel problems in seconds. The SM are suggesting a test harness that jumps from the male to female. I've made several of these myself. They work fine in controlled enviroment but in reality, cars don't die inside a well lit garage. They always die in a dark, windy, rainy bad neighborhood.

I'm aiming for financial security myself by working hard to gain knowledge, which is what you're doing. Knowledge is what you need. Rick

A fuel pump relay are easily located by a click, then followed by another click when ignition is first switch to run, if it or what ever is powering it is still working.

Remove the four bolts holding it, he's suggesting the unit with four bolts.

Normally, you don't test a fuel pump with a car running, unless pressure testing. You don't need to start it, just turn it to run position.

Easy, use a sewing needle and drive it into the wire. Connect an aligator clip to the needle. Don't listen to manual about test harness, you won't find one but you can always make one, but you won't need it.

I heat my probes with MAP torch first and my probes sinks right into any wires, connectors, etc. It's like magic. I do this all the time.

I'm struggling with English, here goes. Splice the intended wire, wrap another pre-spliced wire (same type) onto this and solder it or crimp it with a pair of pliers. You now have a split wire capable of handling the currents demanded by the fuel pump. Tape this wire securely with only electrical tape to prevent fires. Note that without proper currents, your fuel pump won't spin if it's slighty seized from formations to the prepellars.

The other cleaner but difficult method is to remove the lead(s) you want from the male or female connector. Attach a copper wire to this carefully, and securly. Solder it. Inserted the lead(s) back into the male or female connector.

There's no such thing, I can solve a fuel pump problems with no tools on hand, I just rip a wire and a bulb from anywhere in the car and diagnose fuel problems in seconds. The SM are suggesting a test harness that jumps from the male to female. I've made several of these myself. They work fine in controlled enviroment but in reality, cars don't die inside a well lit garage. They always die in a dark, windy, rainy bad neighborhood.

I'm aiming for financial security myself by working hard to gain knowledge, which is what you're doing. Knowledge is what you need. Rick

I've been driving on the new fuel pump & resoldered fuel pump control module for a few weeks now. I wrote up the entire sequence (with pictures) and will post to the yahoo & NICO newsgroups for the next Q45 do-it-yourself mechanic. (This writeup will be especially useful because the procedure to follow is NOT the procedure in the factory shop manual. The yahoo & Nico newsgroups were especially helpful so I feel I should give something back to them.)

The new Infiniti Q45 fuel pump barely makes a sound. Even hot-wired to ground (with full battery voltage), the new fuel pump was still MUCH quieter than the original Q45 fuel pump. Next time, when I hear a Q45 fuel pump hummin', I'm going to replace it BEFORE it eventually destroys the fuel pump control unit.

If I had simply replaced the fuel pump control unit (which exhibited the classic Q45 #4 ground-wire solder melted-open problem), the old fuel pump would have still drawn enough current to burn the new fuel pump control unit out in a short while.

If I had simply replaced the noisy fuel pump, the Q45 still would not run because the destroyed fuel pump control unit left open the circuit to ground.

The non-intuitive repair consisted of replacing the working fuel pump (which drew too much current) with a new $312 dollar fuel pump; and resoldering (after reinforcing) the non-working #4 ground-wire circuit to ground in the Q45 fuel pump control unit (saving a $500 dollar replacement cost).

I left the trunk bulkhead loose so I could check for overheating, but, the resoldered Infiniti Q45 fuel pump control unit appears only slightly warm to the touch, even after 50 miles of highway driving.

Total time for repair: About 3 weeks elapsed time; maybe 5 hours actual, of which 4 were debugging which could have been replaced with 10 minutes of debugging time had I known what I know now about Q45 fuel pump diagnostics).

Total cost for repair: $312 for the Q45 fuel pump; $12 for the 0 ring.

===========================================================================Diary of a classic 1990 Infiniti Q45 fuel pump & pump control unit failure By Alora Duncan

===========================================================================Note: Photos were taken of every step below; but I do not know how to post these revealing photos to this forum.----------------------------------------------------------------------------0. One morning, my 1990 Infiniti Q45 (125K miles) wouldn't start: The 4.5 liter 8-cylinder engine cranked wonderfully, but would not catch. It wasn't the starter motor nor the battery (as it rotated perfectly). As always, it had to be either gas, air, spark, compression, or timing.

Following is an idealized path others can follow to debug & repair.

Note: My actual debug & repair path took three weeks and much trial & error; which is exactly why I wrote this howto for others to follow.

Note: Re-assembly, in all cases, is the reverse of the dis-assembly procedures described below.

Note: This dozen-step diagnostic, removal, & replacement procedure is accompanied every step of the way with digital photos illustrating every described action.

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1. I ran a quick visual/audible gas, air, spark, compression & timing check:

GAS: The gas tank was completely full (filled the night before). The 15 amp fuel pump fuse was intact (replaced it anyway). I could NOT hear the fuel pump humming (at any time). AIR: The air intake & air filter were not clogged (left it open). SPARK: I did not know how to run a quick test for spark. COMPRESSION: The engine did sound like cylinder wash (no compression?). TIMING: The camshaft rotated (looking in the oil-filler hole).

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1. I soon realized no gasoline was being pumped INTO the fuel filter:

- I removed the 15 amp fuel pump fuse (by the driver-side right kneecap); - I cranked the engine in order to release any residual fuel pressure; - I removed the two 10mm bolts holding the fuel filter clamp to the body; - I removed the two #2 phillips screws holding the fuel filter hoses on; - I replaced the 15 amp fuel pump fuse and cranked the engine again. - No gasoline spurted out of the open fuel line hose.

Note: One clue was that, after an overnight sitting, with the fuel filter and activated carbon fuel cannister still on the car, the engine started for a split second. This happened for two mornings. I suspect this momentary ignition was due to the burning of fuel fumes collecting in the fuel system over long periods of time.

Note: I blew through my fuel filter and there was almost no resistance; so, despite the fact almost everyone says that a clogged fuel filter can cause the fuel pump to overwork and therefore heat up and therefore melt the solder connections on the fuel pump control unit, I suspect a clogged fuel filter was not my problem.

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1. I studied the 1990 Q45 fuel system electrical & hydraulic circuits:

ELECTRICAL: - Battery voltage goes to the fuel pump relay ... - to the fuel pump (in the gas tank) ... - to the fuel pump control unit (under the rear sundeck platform) ... - which provides three resistive paths (fuel pump speeds) to ground ... - based on input from the engine control unit (passenger side dash).

HYDRAULIC: - Fuel is pumped out of the fuel tank ... - to the inlet of the fuel filter ... - to the fuel line & fuel plenum ... - to each of the 8 fuel injectors (which open at the same time) ... - with pressure regulated by the 43 psi fuel pressure regulator ... - which sends unspent fuel back to the fuel tank for recovery ...

- and which allows fuel vapors to be trapped in the carbon cannister.

INTERNET: - Factory shop manual & technical service bulletins & recall notices:

- Infiniti mechanics and afficianados on line to help you: - Basic USENET newsgroups (not much help compared to the above): - New parts: Fuel Pump Control Unit: $379.05 + sh & tax Fuel Pump (includes the fuel pump 0-ring): $234.99 + sh & tax Fuel Injector: $142.71 + sh & tax Fuel Gauge Sending Unit: $ 97.38 + sh & tax Fuel Filter: : $ 10.49 + sh & tax Note: For some strange reason, searches on locate the fuel pump control unit only as the "Fuel Modulator" (nobody else uses that naming convention). Fuel Modulator Q45 1990-1996 $379.05 - Used parts: Fuel Pump: 1990 to 1996 Fuel Pump Control Unit: 1990 to 1996 Fuel Gauge Sending Unit: 1990 to 1996

LOCATIONS: - The fuel tank is located in the center of the trunk room (between the rear seat and the trunk). - The fuel pump & fuel pump resistive gauge & filter sock is located in the top of the fuel tank. - The fuel pump control unit is located on the underside of the rear metal sundeck (near the rear passenger side speaker housing). - The fuel pump relay (lime green) is located next to the antenna and fuel tank gasoline inlet in the area between the rear passenger side fender and the rear passenger side trunk fiberboard lining. - The fuel filter is located on the passenger side of the engine compartment bolted to the inside of the passenger side fender wall.

ACCESS: - Access the fuel pump, fuel pump relay, fuel pump control unit, & the related fuel system harnesses for test from the rear trunk area. - Access the fuel pump for removal & replacement either by removing the rear seat & sundeck & storage binnacle or by dropping the fuel tank (rear seat removal access is preferred over tank removal by most).

TERMINOLOGY (don't get these mixed up): - The harness connector (white, female) to the fuel pump control unit is called the fuel pump control unit harness connector. - The harness connector (green) to the fuel pump relay is called the fuel pump relay harness connector. - The harness connector (blue, female) to the fuel pump is called the fuel pump harness connector. Likewise: - The connector (white, male) on the fuel pump control unit is called the fuel pump control unit connector. - The connector (green) on the fuel pump relay is called the fuel pump relay. - The connector (blue, male) to the fuel pump is called the fuel pump connector.

TOOLS: - Two #2 phillips screwdrivers (one six inch, & 1 two-inch stubby). - One thin flathead screwdriver (for prying plastic butterfly clips). - Two box wrenches (one 8 mm box & one 10mm) for bracket bolts. - One 19 mm open-end wrench (for the gas tank fuel line lock nuts). - One 16 AWG wire, about a foot long, with an alligator clip on each end. - One volt-ohm-amp-meter (Fluke 77 or equivalent) with alligator clips. - One needle-nose or standard pliars (for spring-closed hose clamps). - One paring knife (or similar) for removal of sound-proofing material.

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1. The fuel pump relay checked out OK for proper operation under load: FROM THE TRUNK: - I removed the trunk room fiberboard bulkhead (between the rear seat back & the trunk) by removing the 7 black #2 phillips screw-type butterfly anchor clips holding the fiberboard bulkhead to the steel supports. - I removed the trunk passenger-side bulkhead (between the trunk and the rear fender near the radio antenna & fuel filler opening) by removing the 5 black #2 phillips screw-type butterfly anchor clips from their supports. - I removed the single 10mm bolt holding the two-pronged relay bracket which held a blue relay (courtesy lamp relay) on one prong and a lime-green (fuel pump relay) relay on the other. - I pulled the lime-green fuel pump relay off the bracket tang. - I jumped 12 volts DC across pins #1 and #2 (hearing a sharp click). - The resistance fell (from infinity) as the actuator closed (to zero).

Note: I also checked power to the fuel pump relay, continuity from the fuel pump relay to the fuel pump relay harness, continuity from the fuel pump relay harness to the fuel pump harness, & continuity from the fuel pump harness to the fuel pump control unit harness (all as per the factory shop manual EF & EC-169); but, not surprisingly, I'm told the fuel pump relay and these fuel electrical system wires almost never go bad; so consider the entire diagnosis procedure in the factory shop manual a severe case of over diagnosis.

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1. The old fuel pump passed the basic factory shop manual test: FROM THE TRUNK: - I disconnected the fuel pump harness connector (blue, in the trunk room). - As per the factory shop manual (EF & EC-185), I checked the resistance between the top-left and the top-right (tab on top, facing terminal side) of the six male terminals on this fuel pump connector. - My resistance was 0.9 to 1.1 ohms which was inconclusive since the factory shop manual merely states the resistance to be 0.5 ohms but the factory shop manual does not supply a range value. Note: It seems this factory shop manual test is almost useless. When I tested the new fuel pump, it too tested about the same at 0.6 to 0.8 ohms. The online Infiniti mechanics noted the resistance test merely checks one (of many) commutators. Online mechanics say the clearest sign of a bad pump is audible HUMMING.

I must admit, the new pump barely made a sound, even when jumped directly to ground providing it full battery voltage. I didn't realize it at the time, but, the old pump actually hummed loudly. (There is so much soundproofing that I never heard the old fuel pump motor hum until the rear trunk room lay bare & exposed.) Basic recommendation: If the fuel pump has 100K miles on it; or if the fuel pump is humming at all audibly; then replace it (before it burns out the ground wire on the fuel pump control unit).

Note: The two most basic tests should have been (in hindsight): - Did the 1990 Infiniti Q45 have more than 100K miles? - Did the 1990 Infiniti Q45 fuel pump have an audible hum? If either answer were yes, then replace the '90 Q45 fuel pump.

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1. The old fuel pump control unit failed the basic bypass test:

FROM THE ENGINE COMPARTMENT: - I reconnected the fuel filter (passenger side of the engine compartment).

FROM THE TRUNK: - I reconnected the fuel pump harness connector (blue, in the trunk room). - I removed the fuel pump control unit harness connector (white, female) from the fuel pump control unit connector (white, male) mounted directly on the fuel pump control unit. - Note: Nothing else was removed at this time; the fuel system was otherwise completely intact. - I filed an alligator clip's teeth so that it fit into the small female tab on the bottom left (terminal side, with the clip up) of the white fuel pump control unit harness connector. - I connected the other side of the alligator-clip one foot long 16 AWG wire to a convenient ground (expecting as much as 7.5 amps to 10 amps based on 15-amp fusing). - I turned the ignition to "ON" and listened for the fuel-pump humming. - It hummed for about 10 seconds after turning the ignition to ON. - I started the 1990 Infiniti Q45; it ran like a charm. - The current draw was about 5.8 amps on the old humming fuel pump. - The engine starved approximately 2 seconds after disconnecting this fuel pump control unit bypass jumper.

Note: I drove the car for more than a week (about 200 miles) with this thin alligator clip shorting the fuel pump to ground bypassing the three-position (slow@5.5 to 5.7 volts, medium@7.5 to 8.1 volts, & fast@11 to 14 volts battery voltage) fuel pump control unit settings.

Note: Online mechanics estimate the old fuel pump might last a few weeks (running full speed as it is when jumpered to ground); while a new fuel pump may last a few months in this temporary full-power state.

Note: It is recommended the fuel tank be kept full whenever operating the Infiniti Q45 in this state as the fuel pump is cooled by the gasoline in the fuel tank.

Note: This is NOT the procedure in the factory shop manual (EF & EC-185). This procedure is much simpler than that in the factory shop manual. The procedure in the factory shop manual requires three test jigs, of four, five, and then six wires between the white female fuel pump control unit harness connector and the white male fuel pump control unit connector. In most cases, this test is overkill.

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1. Reconcile yourself to the fact you have a few hours of work to perform:

Q: Why? A: Because of these three basic facts.

FACT 1: The first fact is that the proper removal of the fuel pump control unit is from the rear-seat direction & not from the (otherwise more convenient) trunk-room direction.

FACT 2: The second fact is that experienced Infiniti Q45 mechanics have concluded most fuel pump control unit failures are due to the fuel pump itself beginning to fail (and thereby to draw excessive current, which melts the weak solder joints on the ground wire printed circuit board connection on the fuel pump control unit).

FACT 3: Therefore, if you merely replace or re-solder the broken fuel pump control unit, you'll eventually burn out the new or newly repaired (and much more expensive) fuel pump control unit.

The good news is the Infiniti mechanics online have reported very few (if any failures of the repaired or replaced fuel pump control unit once the fuel pump is replaced (for another 100K miles or so anyway).

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1. Remove the rear seats, rear sundeck shelf, and rear package binnacle:

REMOVE REAR BENCH: - Move the front seats forward as far as they will go and tilt the front seat backs forward as far as they will go to obtain working room. - Locate the two black clip extensions on the rear seat floor area and pull out those two black clip extensions simultaneously pulling up on the leading edge of the rear seat bench to lift it upward and out. The rear seat bench removal requires no bolts to be removed. There are only four clips in the leading edge; and two clips in the trailing edge of the rear seat bench to take into account for removal. - Scavenge the $1.35 (on average) in loose change under the rear bench that the federal government suggests wreckers earn per car on wrecked cars for tax-reporting reasons.

REMOVE REAR SEAT BACK: - Pop out or pry out (with a thin flathead screwdriver) the four blue solid butterfly anchor clips from the leading edge of the rear topside sundeck where the sundeck overlaps with the rear seatback. - Remove the two rear headrests by pressing the driver-side knob under each & simultaneously lifting upward until the posts clear the seatback. - Push down the rear seat armrest and pull back on the vertical backing which is velcroed to the steel bulkhead behind rear seat back. - Remove the two #2 phillips screws behind this velcroed rear armrest compartment. - Remove the four #2 phillips screws holding the U-brackets at the bottom of the rear seat back. - Pull up the rear seat back vertically, to clear three reverse-u-shaped wire brackets from their u-shaped metal brackets in the rear bulkhead metal wall. This should remove the seat (except for the seat belts). - Pull out the two side rear seat shoulder belts as far as they will go and jam a pen or other object to eliminate the return tension. The seat belts will be less of a nuisance if you perform this task. - Flip the rear seat back (still attached by the seat belts) upside down so that the foam side is facing the front & the leather side is facing the rear and the headrest portion is on the floor of the automobile (this provides maximum room to work, especially if you've already moved the front seats as far forward as possible). - Replace all screws loosly in their original holes so as not to lose any.

REMOVE REAR UPPER TAIL-LIGHT & REAR SUNDECK: - After removing the three blue solid butterfly clips on the leading edge of the rear sundeck ... - Pull toward the front and upward on the rear upper tail-lamp housing; and disconnect the rear upper tail-lamp harness connector from the rear upper tail-lamp connector. Remove the rear tail lamp housing. - Pull up on the rear sundeck everywhere you can to unclip the 11 solid white anchor clips (4 equally spaced in the rear, two in the middle on each side of the package binnacle, and 5 near the front of the sundeck shelf, three of which are closely spaced near the middle front of the sundeck shelf and the other two nearer the outside edges). - Collect all anchor clips in a zip-lock bag marked "rear shelf".

REMOVE REAR SUNDECK PACKAGE BINNACLE: - With the rear upper tail-lamp & rear sundeck removed, unscrew the seven #2 phillips screws holding down the black plastic rear sundeck package binnacle (aka storage compartment basin).

Note: This rear sundeck black plastic storage binnacle is the key to removing the fuel pump since the fuel pump (with the attached fuel pump float, fuel pump housing, fuel pump level gauge, etc.), can only come out undamaged through the rectangle left by the removal of this rear sundeck storage binnacle (aka package binnacle).

Note: Almost none of this removal procedure is explained in the factory shop manual.

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1. Remove fuel pump assembly from the top of the fuel tank from the trunk:

FROM THE TRUNK: - Disconnect the blue male fuel pump connector from the blue female fuel pump harness connector. - If you haven't done so already, bleed pressure out of the fuel system by cranking the engine with the fuel pump fuse (driver side dash, by your kneecap) removed. Also remove the fuel tank inlet gas cap. Have a large hotel towel handy because it's inevitable that fuel will leak as you remove the fuel pump assembly from the fuel tank. - With a 19mm open-end wrench, remove the two 19 mm tubing nuts holding the metal fuel pump outlet and vapor lines to the top of the fuel pump assembly. Be careful not to break the three-line plastic separator (as I did) when bending the rigid metal fuel lines out of the way. - With an 8mm box-wrench or a three-inch stubby #2 phillips screwdriver, remove the six 8mm bolts holding down the fuel tank assembly cover plate to the fuel tank. - Gently pull up on the fuel pump assembly taking care to prevent the six-inch black rubber O-ring from falling into the fuel tank. - From the trunk, twisting gently as needed through the rear sundeck shelf package binnacle opening, remove the fuel pump assembly. - From the rear seat area, look down into the opening left by the removal of the rear sundeck package binnacle and inspect the fuel tank for debris (mine was as clean as a galvanized chambered whistle).

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1. Remove the fuel pump from the fuel pump assembly: OUT OF THE CAR: - Pull out the two one-inch brown plastic alignment clothes-pins in the fuel pump wing bracket. - Remove the two #2 phillips bolts bracing the fuel pump body to the fuel pump assembly. - Remove the one #2 phillips bolt holding the fuel filter sock to the metal fuel assembly (and push out the alignment tab). - Remove the #2 phillips bolt attaching the power wire and the #2 phillips bolt attaching the ground wire to the fuel pump itself. - Gently force the fuel pump motor black rubber wings out of their braces in the fuel pump assembly leaving just the fuel hose attached. - Once the fuel pump wings are outside their slots, use pliars to open the spring hose clamp on the plastic fuel pump outlet nipple. - Remove the (now unattached) fuel pump from the fuel pump assembly. - Compare the old fuel pump (in size & shape) to the new pump (the two fuel pumps should match exactly). - The replacement follows the reverse procedure.

Note: I purchased a new fuel pump from a parts store for $312.oo while the Infiniti dealership listed the fuel pump for $320. The Infiniti dealership sold me the six-inch fuel pump O-ring for $13.oo (all numbers include tax). I noticed, afterward, that online, I could get the same pump (including the six-inch O-ring) for $235 plus shipping & tax. Go Internet, if you have the time.

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1. Remove the fuel pump control unit for replacement or repair:

FROM THE TRUNK: - From the trunk, on your left side with your head facing the driver side rear fender, with your right arm through the opening left by the removal of the rear sundeck package binnacle, place your index finger on the topside location of the bolt head for the two bolts holding the fuel pump control unit bracket to the underside of the rear sundeck. - Have a partner mark the location of the two bolt heads (the actual bolt heads are buried under 1/8th inch thick rubberized soundproofing material) using whiteout or other suitable marking on the black gunky material.

FROM THE REAR SEAT AREA: - With a small paring knife, cut out the rubberized gunky black sound- proofing material on top of the two 10mm bolt heads. - Use a 10mm box wrench to remove the two bolts holding the clamp on the underside of the package shelf. Note that the clamp itself forms a U, with one portion of the bracket above and one portion below the metal horizontal sundeck shelf.

BACK IN THE TRUNK: - Check that the fuel pump control unit (white, female) harness connector is disconnected from the fuel pump control unit (white, male) connector. - Remove the fuel pump control unit (with the bracket assembly attached) by pulling it toward the rear of the car, and downward.

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1. Inspect, repair, or replace the fuel pump control unit:

OUT OF THE CAR: - Remove the four #2 phillips head screws holding the top plate (with bracket assembly) of the fuel pump control unit. - Remove the four #2 phillips head screws holding the bottom plate of the fuel pump control unit. - Inspect the wiring everywhere; notice any charred or burned areas (my ground wire on the bottom right (terminal side, tab on top) of the white male fuel pump control unit connector was charred a bit. - Also, there was infinite resistance between that bottom-right male terminal and the corresponding printed circuit board connection (marked #4 on the PCB) on the underside of the printed circuit board. - I used a 25-watt soldering iron & a blue solder sucker to vacuum up the solder around that #4 pin and I re-soldered that ground pin. - I also added a two-inch patch of 16AWG copper wire, soldered to that #4 pin and to all the connections on the printed circuit board I could identify as being that same ground connection. - Test with a ohm meter that the resistance for that one ground lead is near zero; and that accidental shorts to other traces did not occur. - Replace the now-repaired fuel pump control unit in the reverse order of removal. Note: Do not power-up the fuel pump control unit out of the car as the holding bracket supplies the main ground for the fuel pump control unit itself.

Note: The #4 terminal is the ONLY terminal on the male white fuel pump control unit connector which is surrounded by EMPTY pins in the white female fuel pump control unit harness connector.

---------------------------------------------------------------------------- POST MORTEM: THINGS I LEARNED THE HARD WAY: - Basically, I should've replace the fuel pump at 100K miles! Apparently they all eventually go bad. I should have also listened for the now tell-tale hum (I never even noticed it before). - Also, once before, about six months ago, my car would not start for about an hour; and then, all of a sudden, started. At the time, I chalked it up to cylinder wash (loss of compression due to gasoline washing the oil off the piston walls causing rings to temporarily not seal); but now I realize it was probably the fuel pump control unit #4 pin solder heated up and, when it cooled, it re-connected itself. - It was recommended we should fill up when just about on one quarter of a tank (or so). The (unsubstantiated) argument states that the fuel pump heats up, causing more current draw (how?) which causes the solder connection on the fuel pump control module ground circuit to heat up which, if it melts, can cause the open circuit that I found in mine. - You can diagnose everything from the trunk (after merely removing just the bulkhead between the rear seat back & the trunk); but you must remove the seats, package shelf, and storage bin in order to remove and replace either the fuel pump or the fuel pump control unit. - The new six-inch fuel pump O-ring looked EXACTLY the same as the old one (condition was imperceptably different). So much, I ended up mixing the two accidentally, and I couldn't tell them apart. Be advised. - The new pump made almost NO SOUND. I didn't even realize that until I had replaced it. Even with the full-power jumper bypassing the fuel pump control, the new fuel pump hummed vastly less than the old fuel pump hummed. - The current draw and resistance measurements of the old fuel pump and the new fuel pump were almost the same; so do not rely on these figures as a diagnosis test (listen for hum or check your odometer): OLD FUEL PUMP: NEW FUEL PUMP: 0.9 to 1.1 ohms 0.6 to 0.8 ohms 5.6 to 5.8 amps 5.8 to 6.7 amps both of these numbers are from the blue male fuel pump connector to ground with the fuel pump control unit bypassed to ground; this runs the fuel pump at an unregulated full speed. - The factory shop manual makes NO MENTION of the quick and easy test jumpering the fuel pump control unit harness connector to ground. Instead, the factory shop manual walks you through an apparently unnecessary lengthy step-by-step debugging process requiring the use of a three, four, and then a five wire jig to debug the fuel pump control unit. Don't overdiagnose. Just use the jumper and if the fuel pump operates, then replace BOTH the fuel pump and the fuel pump control unit (or repair the fuel pump control unit). - If I had diagnosed following the factory shop manual, I would have concluded only that the fuel pump control unit needed replacement; yet, had I replaced only the fuel pump control unit, the humming fuel pump (drawing excess current) would have burned out the new fuel pump control unit in months. - For the longest time I was confused about the various debugging procedures in the factory shop manual. What cleared it up was the realization of all the proper connector names! I've made a sincere attemp in this note to use the proper names at all times. - Many folks say you can test the deliver of fuel past the fuel filter (in the engine compartment) by squeezing the fuel hose while the engine is cranking to feel for fuel pressure. I can't tell. I recommend removal of the fuel filter. It provides proof positive. - The factory shop manual goes into the engine control unit debugging. It was not needed in my case so I'm glad I skipped that part. - The hardest thing in the world was to find the locations of the various units; and to find out how to remove some of them. In this note, I take special care to describe both the name of the unit and the precise location, for others to benefit. - Most folks recommend disconnecting the battery & removing it from the car when working on the fuel tank. I didn't do this, but you should.

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Thank you very much for the detailed information. My wife and I have a 93 Q with 101K on it and at some point it is going to need a fuel pump. The dealer is great but very expensive as I'm sure you know. I have printed out your information and will keep it handy.

Thanks again!

Dave

diagnostics).

I'm glad to be of service. Every Infiniti Q45 owner (up to 1996 I think) should learn about this Q45 engineering fault.

Just remember two things: - Do NOT follow the factory shop manual! - Keep a 1-foot 14 AWG aligator clip wire in your trunk.

When your Q45 dies in the middle of nowhere, you merely remove the rear trunk fiberboard bulkhead; unclip the white fuel pump control unit harness connector; jump the correct wire to ground; and voila! You're on your feet again!

Back at the farm, if you follow the factory shop manual, you'll correctly diagnose the burned-out fuel pump control unit (aka the fuel pump modulator); but you'll likely conclude the old fuel pump was good (it still works). Second opinion is that the old fuel pump is what burned out the Q45 fuel pump control unit in the first place; so, you're in for a repeat episode of chronic fuel-pump 'modulitis' if you follow the FSM prescription.

The recommended prophylaxis is to resolder & reinforce the fuel pump control unit ground cnnections and to perform a fuel-pump'ectomy.

Alora

replying to Alora Duncan, Allen wrote: Fuel pump in trunk.have to take out back seat an cover to take fuel rail an pump out trunk.I have a q45 1991 an it has the same problems.

replying to Alora Duncan, Allen wrote: Its in the window area.when taking it out the trunk it has to come through the hole

replying to Alora Duncan, grod wrote: Cranks over teally hood n t wont start

It ran out of gas 14 years ago and has been sitting in his driveway ever since.

97 Q45 won?t start and I don?t hear the fuel pump I need to know where the fuel relay and control module is located

Not if his local Nissan service center is anything like mine is. The service writer seems to have a preset list of services that every car needs.

--scott

They might be able to diagnose my X, but they are more worried about telling me that my Y and Z are about to fail and need immediate attention and that if I don't replace my windshield wipers for $75 the sky will fall on me. And that rip in the upholstery has to be fixed immediately, and those tires are not authorized tires from the dealer but are third-party tires that are suspicious and should be replaced. They don't _want_ to fix my car, they want to sell me a new car and take my car in as trade-in.

--scott