Fuel Pump Didn't shut Off Today

vristang · Mar 29, 2006

When I shut down the car this afternoon the fuel pump kept running. I figured it may shut off after a few minutes so I went inside, and checked on it about 15 min later. The pump was still running!
I started the car for a minute, then shut it down. This time the pump stopped with the motor.

Is this a sign of the pump failing?
Is the relay going out?
Other?

Thanks for the help,
jason

sgthooligan · Mar 29, 2006

My vert just started that yesterday. I think it's the relay.

Roland69 · Mar 29, 2006

sounds like a relay

HISSIN50 · Mar 29, 2006

I would check the FP relay. If it looks good, a latched EEC relay can cause the pump to stay on too.

Good luck Jason.

bsedwebt70-5.0 · Mar 29, 2006

my car did the same thing - sometimes it worked normal and other times it hung on - easy fix - $8 fuel pump relay from local parts store

vristang · Mar 29, 2006

Thank you guys for the responses. Good to hear it probably is not the pump.

Well I was just out messing with tweecer. Again the pump would not shut off. This time when I started the car it ran incredibly rich, almost flooding, and making some rather large plumes of smoke. As far as I know the fuel pump is still running right now, because it didn't shut off this time.

Is the fuel pump relay under the drivers seat?
How can I check its functionality?
Can I unplug the relay and get the pump to shut off?
Hissin, what's a latched eec relay?

thanks guys,
jason

vristang · Mar 29, 2006

So the relay could be bad causing the pump to stay on.

But in my mind that does not explain the extremely rich condition that I experience when the motor is running. It bad enough to where the car won't idle.

Did the pump staying on cause an injector to stick open?

thanks
jason

HISSIN50 · Mar 29, 2006

A leaky injector would flood the motor while the pump runs non-stop. If this happens again (till it is fixed), pull the FP relay out of the car. It should be under your driver seat, like you said. There might be a small bracket and bolt holding the relay in there (I think they might have done away with this by 90 though).

WHen the car is off and the pump is runnin, look at the FP relay socket. If the positive coil wire has 12 volts with the key off, the EEC relay could be latched (stuck closed, or energized).

If the coil wires are dead but the FP relay has output on the N.O. terminal (output to the pump), the FP relay being latched is likely (it's staying energized even though the coil doesnt have a field.).

I would post wire colors but I seem to recall that '90 is kind of a bastard year with wiring colors. Saleen, JRichker, et al might be able to help. Your meter should tell you what is what (esp if you can test it once when the pump is off, so you can tell which thick wire is the feed).

Good luck Jason.

EDIT: in case that was confusing: If the FP-relay coil is energized with the car off, the EEC relay is probable.

If the FP relay-coil is dead (no 12 volts, no ground) but the pump runs, the FP relay is likely.

I think that is much easier to follow since we know I'm not short on wordy posts.

90lxfoxbody · Mar 29, 2006

hissin you are a wealth of information. some idiot(s) attempted to steal my car a few months back. they couldn't steal it ( starter kill switch ) so they tried to mess with the other wiring. end result - mangled up fuel pump wires, i repaired the wires but the fuel pump wouldn't shut off. now i have a switch set up for the fuel. i will replace that relay tomorrow - i am certain it will do the trick. thanks again!

vristang · Mar 29, 2006

HISSIN50 said:
A leaky injector would flood the motor while the pump runs non-stop. If this happens again (till it is fixed), pull the FP relay out of the car. It should be under your driver seat, like you said.

Awesome! Thank you.

I pulled the relay, then started the car. It ran for a few seconds then died, I take it no relay = no fuel pump?

Earlier when I was messing around, I was able to get the pump to shut off by messing with the relay under the seat. This implies a faulty fp relay?

Is it possible that a bad relay is causing the rich mixture? This doesn't seem likely to me, but I am now realizing that I am not very familiar with the e- part of our fuel systems.

I will do some volt meter testing in the morning (it gets dark early in Seatown ).

Yes 90 is the red headed step child when it comes to electrical. Most of my wire colors are correct for a 91.

Thanks again

jason

HISSIN50 · Mar 29, 2006

You got it Jason. As you know, the FP relay is just a high current switch for the FP. WHen the relay is yanked or one of its terminals interrupted (e.g., the inertia switch is tripped, as it feeds the positive coil terminal in the relay), the car will crap out pretty quick.

The FP simply cant work with no FP-relay. But if the EEC relay is latched, it can still be the culprit. Just checking the thin gauge control wires at the FP relay will tell you if a signal is being erroneously sent to the FP relay (and it's simply doing what it is being told to do), or if the FP is staying on, even though it's 'not being told to.'

Oh, the relays have no bearing on the Air fuel ratio. It's just that if you have a slightly leaky injector, normally it only leaks if there is pressure in the rails, and that's normally while the car is running or just after shutting it off. But having pressure ramming the back of the injector non-stop with the car off (without the motor burning said fuel) could flood a cylinder. I kinda doubt this is your issue at all - it is likely something else. You might need to tweak a file in the TwEECer or something.

I remember the dark and dreary days up there. Not as bad as Alaska in the winter, but still not nice (at least snow reflects light at night. Dark and rainy is just dark and miserable).

vristang · Mar 29, 2006

HISSIN50 said:
You got it Jason. As you know, the FP relay is just a high current switch for the FP. WHen the relay is yanked or one of its terminals interrupted (e.g., the inertia switch is tripped, as it feeds the positive coil terminal in the relay), the car will crap out pretty quick.

The FP simply cant work with no FP-relay. But if the EEC relay is latched, it can still be the culprit. Just checking the thin gauge control wires at the FP relay will tell you if a signal is being erroneously sent to the FP relay (and it's simply doing what it is being told to do), or if the FP is staying on, even though it's 'not being told to.'

Oh, the relays have no bearing on the Air fuel ratio. It's just that if you have a slightly leaky injector, normally it only leaks if there is pressure in the rails, and that's normally while the car is running or just after shutting it off. But having pressure ramming the back of the injector non-stop with the car off (without the motor burning said fuel) could flood a cylinder. I kinda doubt this is your issue at all - it is likely something else. You might need to tweak a file in the TwEECer or something.

I remember the dark and dreary days up there. Not as bad as Alaska in the winter, but still not nice (at least snow reflects light at night. Dark and rainy is just dark and miserable).

JT, thanks for all the help.

The part that gets me is that today was going to be my first day with the tweecer; so I still haven't even read the stock file from the x3z.

Yeah, I didn't think that the relays would cause the rich problem, but it was nice to hope for a little while.

I plan on calling in sick tomorrow (cough, cough), to figure this out. If anyone has any good diagrams of the relays, I would appreciate it. I am sure I can find something though.

thanks again
:SNSign:
jason

HISSIN50 · Mar 30, 2006

vristang said:
If anyone has any good diagrams of the relays, I would appreciate it.

Courtesy of TMoss (diagram author) and S&2B's (site host) is this diagram. Of course, note that the colors will likely be different for your ride (this is based off an 88 GT). The upper left hand corner is where you wanna be.

Good luck Jason and I hope you 'feel' better.

Saleen0679 · Mar 30, 2006

When DNeinstadt was troubleshooting his starting nightmare he compared the 90 wiring for his FP relay. There was one wire color different. The O/LB in the diagram was G/LG at his relay socket.

vristang · Mar 30, 2006

thanks hissin and saleen for the tips and diagrams. With that and the diagram I found on Autozone I should get by.

cough, cough

jason

vristang · Mar 30, 2006

I found out why it was running rich.

When you install the tweecer chip on the computer, be sure to set the selector switch to the off position. I'm not sure what tune I was trying to run on, but the car did not like it.

This still does not resolve the issue with the pump staying on, but I am one step closer.

jason

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