having a very strange fuel pump issue

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having a very strange fuel pump issue

July 11, 2014, 06:38:33 PM

I am encountering an unusual problem with my fuel pump. A friend of mine has been borrowing the car, everything has been going fine until a couple of days ago.... He said he was going up a slight incline when the car started to lose power and would not respond to the gas pedal, and he pulled over and once he stopped the engine shut off. And he could not get it to start again. Once he called me to ask about it he said that the engine would turn over but would not start, and that there was a sort of electrical burning smell in the car. I asked him to listen for the fuel pump priming but it was raining very heavily so he couldn't hear it at all. I said ok, go check the inertia switch. He said the switch was up and he clicked it down, I'm like ok great problem solved, go start the car now. Nothing. So I told him to wait until I could get up there later that night.

I get up there and check it out myself, and there is in fact an electrical smell in the car. I checked to listen for the fuel pump priming myself, and turns out it does, but it never stops. The typical 2 sec hum when you first turn the key never stops until you turn it back off again. Now my initial thought would be ok, the pump is obviously working so why won't the engine start, something must be clogging the line and it's not getting fuel to the engine, but then I have to wonder about the far more serious question, why is my pump not ending the initial prime, and what is the electrical fire smell that I was noticing in the car??? I tried to sniff out the source but it was very vague and I could not pinpoint it.

Does anyone have any experience with a situation like this? I can't think of what would cause it to lock up like that. The pump and relay were both replace 3-4 years ago, I'm not sure exactly, so I would hope they are not already failing although I'm sure it is possible, it's just that "failure" to me brings up the idea of in not coming on at all, not the idea of it getting stuck on permanently.....

having a very strange fuel pump issue

Reply #1 – July 11, 2014, 07:38:02 PM

First thing the pump is not timing out so that points to the ECM. That has the timeout circuit. Sounds like a bad ECM. Second the inertia switch popped that just might have been hitting a bump That is why i remove them from my cars. So you did not post the symptoms while cranking. Do you have spark?? Do you have injector Pulses ETC. Do some trouble shooting and post back. Sounds like the ECM went out and released some burning odors in the car. Just a guess at this point. Have a good weekend guys.

The pump and relay are clearly working as the pump runs and it runs through the relay. It also shuts down when you turn the key off. A quick pressure check will confirm pump is OK if the pressures are correct. So square one would be the ECM. That is my thinking.

having a very strange fuel pump issue

Reply #2 – July 13, 2014, 12:51:26 AM

Tom is right, it probably is the EEC.
There is a timer circuit in the EEC that the software must reset before it times out. If the software is hung up or stops running ( like a blue screen on a PC) the timer times out and the hardware goes into LOS(Limited Output Strategy) mode.
The fuel pump is held on, the injectors are pulsed at a fixed pulse width and the TFI provides the ignition at the base timing.

This is an attempt to keep the car drivable with the EEC not able to process any sensor inputs.

Give the EEC the sniff test.

I think it is possible for an out of specs voltage to cause the EEC to act up. You should have battery voltage on EEC pins 1, 37 and 57 with the key on.

having a very strange fuel pump issue

Reply #3 – July 13, 2014, 08:19:06 AM

yup, pin 23 at the eec times out the ground it supplies to the fuel pump relay in the trunk.

odd situation, we rarely have these old tech eec's go completely bad.

usually they will go bad only when someone is jumping out the fuel pump relay to bypass it not knowing they back-fed 12v up the ground side of the eec.

having a very strange fuel pump issue

Reply #4 – July 13, 2014, 10:29:52 AM

Quote

Now my initial thought would be ok, the pump is obviously working so why won't the engine start, something must be clogging the line and it's not getting fuel to the engine, but then I have to wonder about the far more serious question, why is my pump not ending the initial prime, and what is the electrical fire smell that I was noticing in the car??? I tried to sniff out the source but it was very vague and I could not pinpoint it.

While there may be a computer issue I do not believe it to be the source of the reason for the car not running. Check the portion of the fuel feed line INSIDE THE TANK. I'd put a few bucks on the fact that it has disconnected/cracked.

I've seen 2 cars exhibit the very symptoms you describe as far as the running part. One was a friend's. The other was mine. Same thing. Hill, sputter, die, almost catches but just won't.

Like I said you may have an ECU issue AS WELL due to the smell so check that out too. Drop that tank and take a look though. I'd be extremely surprised if the line wasn't compromised in some way.

having a very strange fuel pump issue

Reply #5 – July 13, 2014, 02:18:47 PM

EEC was one of my first thoughts, esp due to the burning smell... TBH though, I do not know where to look for the thing.... how do I get at it? I believe it is somewhere behind the pass side footwell but I have had that off in the past looking for it and couldn't find it... the other thing was when I was doing the initial sniff test I did smell around that area and I didn't smell any burning odor at the time. I'm also not sure if the inertia switch had popped or not, as I wasn't the one to check it initially... he told me it seemed up at first and it clicked when he pushed it back down but as we all know that thing has a bit of travel and click even when it is not triggered so I'm not sure about that.

Also I just haven't really had a chance to inspect it further.... I am away from home 13 hours a day so when I get home it's usually too late for me to take a look at anything. My next day off is Tuesday and even though it's going to be hot as #*#@#@$% outside I'm going to try to dig into it some and see what I can find out. I just wanted to get some initial suggestions from you guys so I have some educated idea of what I need to be checking, which so far has been quite helpful. I'll let you guys know what I find out. Thanks

having a very strange fuel pump issue

Reply #6 – July 13, 2014, 02:29:59 PM

And also I think if I do find that the ECU is toast, it may be time to go ahead and swap the whole thing to MAF/SEFI rather than buy a computer now, and then again later....

...here's to hoping the ECU is not toast lol:cheers:

having a very strange fuel pump issue

Reply #7 – August 01, 2014, 09:11:38 PM

Any update?

having a very strange fuel pump issue

Reply #8 – January 25, 2016, 10:49:07 PM

So..... Yes! Here's an update. After way too much undue procrastination I finally pulled out the ECU and took a look. And yes, I do believe I've found the problem:)

having a very strange fuel pump issue

Reply #9 – January 25, 2016, 10:54:19 PM

Awesome. Keeping the car still?

having a very strange fuel pump issue

Reply #10 – January 25, 2016, 11:04:51 PM

yep just put an update on the project thread. I've already ordered a new (old) ECU to replace it and hope to have it going again by summer. Along with a lot of other work since I left it sitting dead in my driveway for well over a year like an @sshole but hey big plans are on the way lol.

having a very strange fuel pump issue

Reply #11 – February 08, 2016, 12:01:23 PM

Shame you already bought another ecu. I have one out fo my 1988 i could have sold ya.