'88 325 Fuel delivery problem,..

Excellent!

Are you using a high-Z voltmeter, or are you using a test light? Use a test light. Sometimes a broken connection will have just enough leakage to trigger a modern digital meter but not enough to actually drive a motor.

An old analogue meter will usually be fine.

This is going to the relay winding? You don't care about that because yu KNOW the problem is after the relay, since hotwiring the relay doesn't solve the problem.

I'd stick a test light right on the fuel pump and make SURE it doesn't come on. I bet it does come on, and consequently the problem isn't electrical. The output of the computer drives the winding of the relay that turns on the voltage to the pump. You know that bypassing the relay doesn't do any good, so that probably has nothing to do with it.

Unless of course the Motronic ECM isn't getting power either because the run relay is bad....

Make yourself a test lamp by soldering leads to an indicator bulb.

--scott

Excellent!

Are you using a high-Z voltmeter, or are you using a test light? Use a test light. Sometimes a broken connection will have just enough leakage to trigger a modern digital meter but not enough to actually drive a motor.

An old analogue meter will usually be fine.

This is going to the relay winding? You don't care about that because yu KNOW the problem is after the relay, since hotwiring the relay doesn't solve the problem.

I'd stick a test light right on the fuel pump and make SURE it doesn't come on. I bet it does come on, and consequently the problem isn't electrical. The output of the computer drives the winding of the relay that turns on the voltage to the pump. You know that bypassing the relay doesn't do any good, so that probably has nothing to do with it.

Unless of course the Motronic ECM isn't getting power either because the run relay is bad....

Make yourself a test lamp by soldering leads to an indicator bulb.

--scott

-- "C'est un Nagra. C'est suisse, et tres, tres precis.

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Is there any chance of trying another ECU for the car, just to see if it starts? It would almost immediately rule it out as a source of the problem and would take 5 minutes. I was thinking timing signal issue, too. Where are you located, country-wise?

Bill in Omaha '86 535i

The OP could do that, but at this point it is almost 100% sure to be the fuel pump. In fact, the symptoms from the start have pointed to a fuel pump in my experience.

Precisely. A lamp across the fuel pump wires will tell you for sure.

--scott

Do the fuel pump delivery test that's in the Bentley manual.

$35 craftsman digital meter. The manual said use an LED or digital meter.

Well I thought it was the "secondary" side of the relay. The circuit the relay controls- which drives the fuel pump. It sounds like the book is saying if you have no voltage here the FP relays bad or not getting battery voltage from the main relay.

thanks again.

A spare ECU? Are you joking? I can't even find 6 godam spark plugs for this thing? I live the pacific nw, usa. I will try and find the fuel pump, which was replace 3 months ago by the previous owner and check that ooot. tanks again.

A spare ECU? Are you joking? I can't even find 6 godam spark plugs for this thing? I live the pacific nw, usa. I will try and find the fuel pump, which was replace 3 months ago by the previous owner and check that ooot. tanks again.

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I posted earlier that I may have a spare ECU and I may even have a line on the fuel pump you need. At this point, if it isn't the fuel pump, and my ECU matches yours, you pay shipping and I'll loan it for free. If that fixes the problem, I'll cut you the second best deal you ever thought on it.

Bill in Omaha '86 535i

Contact me at snipped-for-privacy@yahoo.com. I've got some specific info for you. Lots of colloected stuff you can use, all on CD.

Bill in Omaha

86 on the main relay. I can light a test lamp at the main relay r/w wire by turning the key on with the air idle stabilizer valve harness disconnected. I have voltage at term 30 of the fuel pump relay. If I pull the FP relay and jump term 30 to 87 I still can't start the car. This should hot wire the fuel pump, if I'm following things correctly and jumped the right wires. With the relay plugged in I test for voltage between term 85 and 86 while turning the key on. I get no voltage- which is a fault condition but I don't see where the fault is. That's as far as I got today. What's the next logical thing to try? If I have to test at the Motronic brain thing behind the glove box I'm disconnecting the main harness and probing the connectors not the computer, right? You're really testing the wiring and sensors, not the chip, right? For those of you joining our program already in progress, this is a continuation of the "325 dies under way" thread. 1988 325 auto 2.7L, red. Thanks as always.

It seems the fuel pump is working after all. I pulled the cover and stuck the hose in a pop bottle. When I crank the engine fuel comes out a plenty. Still no start. I'm kind of stuck here at this point.

I'm not sure what you mean by 'the cover'. This sounds like you are checking the transfer pump ( the one that's in the tank). You need to check the main pump. (The one in front of the left rear tire) Disconnect the rubber line from the cold start valve or the firewall end of the fuel rail. The Bentley manual also recommends checking the fuel pressure at the fuel rail.

Good news! Okay, now measure fuel pressure at the rail. If fuel is coming out of the pump but not appearing at the rail, you have a limited number of things that can be wrong. These include the regulator and the filter.

Remember, to run, cars need FAST: Fuel, Air, Spark, and Timing. You have verified you have spark, now you need to make sure you have air coming in, exhaust going out, fuel in the cylinder, and that all this stuff is happening at the same time.

If you DO have pressure at the rail, pull an injector and see that the injectors are opening and spraying a nice even burst. If there is pressure at the rail, but the injectors aren't opening, it's time to look at the ECM.

--scott

That's what has me confused. According to Bentley the 1988 325 has no separate transfer pump; just a main pump inside the tank, which is accessed by removing the back seat. However, on my '88 the item under the oblong cover on the passenger side looks exactly like the picture of a transfer pump for '84 - '87 models- one fuel outlet, a white two wire connector (fuel gauge sender) and a black 3 wire connector to power the pump. Go figure. This looks to be brand new and may be what was replaced in August- not the main pump as stated in the shop bill. I will have to get under this thing somehow and try to find the main pump. There's a round cover on the drivers side which is, I guess, the tank sender for the second half of the gas tank- just one white connector with two wires. The plot thickens.

That's what has me confused. According to Bentley the 1988 325 has no separate transfer pump; just a main pump inside the tank, which is accessed by removing the back seat. However, on my '88 the item under the oblong cover on the passenger side looks exactly like the picture of a transfer pump for '84 - '87 models- one fuel outlet, a white two wire connector (fuel gauge sender) and a black 3 wire connector to power the pump. Go figure. This looks to be brand new and may be what was replaced in August- not the main pump as stated in the shop bill. I will have to get under this thing somehow and try to find the main pump. There's a round cover on the drivers side which is, I guess, the tank sender for the second half of the gas tank- just one white connector with two wires. The plot thickens.

Crossover year! My '88 325is had a single pump in the tank, passenger side. The drivers side tank opening is not for a pump. The fuel filter is under the car, just forward of the rear wheel on the drivers side. It may be under a plastic cover. Prior to 1987 switch to 1988 "model year", there were 2 fuel pumps (like my '86 535i has). That internal fuel pump for the Vega is more than enough to get the required fuel pressure at the fuel rail. Like I said, it can pressurise the system even without the main external pump on my car. You may check the wiring and connector at the top of the fuel tank. Jumper the fuel pump (at the relay, per the Bentley) to run while you check the connectors at the tank lid.

Bill in Omaha '86 535i

Ok, better weather today,.. Yep, the filter is under a plastic cover forward of the tank, drivers side. I don't see any other pump. I have no fuel at the firewall side of the fuel rack. I have no fuel at the engine end of the filter. If I pull the filter I can pour fuel through it unoccluded in both directions- at least that's the way it seems to me. With the filter removed I can pump fuel onto the ground but it doesn't seem like a constant thick stream. It just comes in spurts. With the filter removed I can blow through the fuel line from the pump outlet to where the filter plumbs in. I can blow from the fuel rack inlet to where the filter plumbs in too. I have to blow pretty hard but it does pass air. I guess I should pull the pump and check the sock but it's all supposed to be new. Any idea how to do the current test with the 3 wire connecter that's fit to the '88 FP? The manual just gives a procedure for the outboard pump. Thanks again to everyone- Bill, I'm still trying to download your attachments. I'm less browser savvy than I used to be.

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Summary: If your auxilliary fuel pump (in-tank pump) is shot, this is an inexpensive way to replace it. The mod removes the aux pump assembly from the fuel tank, dismantles the pump from the assembly, and replaces the pump with a aux fuel pump from a 1976 Chevy Vega.

Tips: This task will go much smoother and faster for you if you get all the tools and parts ready before you start. You're installation will be better if you do. Give yourself plenty of time to work, so you don't feel rushed.

Tools Required:

· Rachet · 8mm socket · Regular screwdriver · Phillips screwdriver · Dremel with sanding/grinding disc - or - fine metal file

Optional Tools Recommended:

· Soldering Iron · Solder · Soldering paste

Parts Required:

· Auxilliary (in-tank) fuel pump for a 1976 Chevy Vega (2.2 liter) - $41.00 · Cable ties $1.00 · Two 3/4 inch hose clamps · One 1 inch hose clamp

Time Required:

· 30-60 minutes

TEXT ONLY INSTRUCTIONS

1. Open the trunk, remove the carpet, and remove the 3 screws holding the cover on to access the auxilliary fuel pump.

1. Disconnect the two electrical wire harnesses. One is to the fuel pump assembly (2 pin) and the larger (3 pin) is to the fuel sender unit.

2. Remove the four nuts and washers securing the fuel sender unit. We will remove the fuel sender unit to facilitate removal of the fuel pump assembly. Set the nuts and washers aside for now. You will re-use them.

1. Slide the sender out until it is barely in, then tilt it to let it drain. Let it drain for several minutes. The holes on the bottom are very small. After several minutes, pull it out completely and set it somewhere dry and clean.

2. Remove the six fuel pump assembly mounting bolts. Disconnect the two fuel lines. Save the metal bands that are underneath the hose clamps. You can throw the old hose clamps away, you should replace them with new ones.

1. Here's the fuel pump assembly.

2. Let the fuel completely evaporate from the assembly before starting this step. When it is completely dry, carefully file off the tops of the two rivets that are holding the electrical terminals in place. Be careful not to damage the terminals, since we will re-use them to connect to the new pump.

1. Here you can see the rivets have been filed off, and the terminals broken free.

2. The grounding strap is connected to the assembly with a screw mounted to a clip nut. Remove the screw and set the screw and the clip nut aside, along with the grounding strap. We will re-use all these again later.

1. Disconnect the fuel pump from the small portion of rubber hose and set the assembly aside for now.

2. Under the old pump is a filter screen piece - on the bottom is the mounting screw. Remove this screw, then gently wiggle the screen filter free from the old pump. You can discard the pump now.

1. Here's the screen filter.

2. Remove the old bit of hose from the assembly. The new pump should have come with a new replacement piece of hose that you can use.

1. Here's the new pump box.

2. The new pump - remove the fuel intake cap.

1. Here's the "accessories" that came with the new pump. We'll need the hose - that's all.

2. Attach the new piece of hose to the new pump.

1. Attach the new bit of hose (with the new pump) onto the assembly exactly how the old pump was mounted. I then used some cable ties to secure it. Reattach the clip nut, grounding strap, and screw to the assembly. You will need to reattach the screen filter to the bottom of the pump. You should be able to use the 1 inch hose clamp to secure it to the bottom of the pump, or use some cable ties to hold it on. You cannot see the screen filter in this picture, but you can see I've attached it in step

1. Not attaching this screen filter will most surely cause premature failure of your new vega fuel pump.

1. Now we're ready to attach the wires. We need to make sure we get the polarity correct, since most electrical pumps will run IN REVERSE if the polarity of the wires is reversed. This would not be helpful to your fuel situation, and may damage your new pump. In the next picture (step 20) you can see that the polarity of the terminals on the pump is labeled on the pump in a very inconspicuous place.

2. It was very hard for me to see the polarity marked on the pump, but here you can see where I found the + mark. The - mark was in the same place on the opposite side. Obviously, you should wire the grounding strap to the - side and the black wire that comes down from the top of the assembly to the + side. When attaching the positive cable, it may be tight. You shouldn't wire it if it is too tight - it could cause the cable to break and the pump will then not work. There are three things you can do (in this order) to get it to reach: 1) push the new bit of hose farther onto the assembly, thereby decreasing the distance from the cable to the positive terminal, 2) cut a portion off of the new bit of hose and reattach the new fuel pump, thereby decreasing the distance and providing slack, or 3) solder a longer wire and new terminal on to replace the original wire. - I did both #1 and #2, and had just enough length to connect it without stressing the wire.

All done. Installation is reverse of removal. Use your new 3/4 inch hose clamps when reattaching the fuel lines. Then fire it up.