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

I searched the USENET groups (from I searched NICO (Nissan/Infiniti owners) I 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.

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

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