I am confused and annoyed...Fuel Pump...

5.0Torx

Active Member
Dec 30, 2007
252
3
29
Hey all,

Ill try to make this as brief and concise as possible.

Before Today
A while ago, my '93 LX 5.0 fuel pump would just run constantly when i turned the key to the on position. I had it towed to a shop, and the genius there threw some iso-heet in the gas tank and voila - she fired right up. The next day the same thing happened, so i went to the store and bought 6 bottles of the stuff. It seemed that whenever i wanted to start the car, i'd have to throw at least half a bottle in. The fuel pump would prime and prime and prime, but when it stopped, that was its signal to me that it would start. Once started, I'd have no issues whatsoever. Finally, i had to actually ditch the car in a parking lot because it would not start. The next day i got lucky, and drove 110 miles home (from college) to avoid having to tow it home. This is further evidence that once its started, she'll go forever. I had exams to deal with, so it has sat in the same spot for a while. Im moved back home now, so ive been futzin with it...

Last week
Turn the key, heard the fuel pump goin for longer than usual. Usual is about 2 seconds. This time it took about 20, but it stopped priming, and voila - fired right up. I let it idle in the parking lot. She went for about a minute and then cut out, and the fuel pump again started going non-stop. I pulled codes, and the only ones i got were 67 - because i left it in first gear since its on an incline and my parking brake cable broke - and 11 - system pass. WTF!? I ditched it, went to autozone and get a fuel pump relay.

Today
Today i replaced what i thought was the FP-Relay. I have a '93, so its under the MAF with the AC WOT switch. I checked the wiring on the relay closer to the front of the car and found the solid red and orange/black, so i figured that was the one. Is that correct? The FPR is further towards the front of the car, and the AC WOT relay is the one closer to the back of the car? Regardless, i replaced it and voila - she fired right up. Again, i let it idle for as long as she could, to see if it would cut out like last week. I made it about 5 minutes. Now the fuel pump does NOTHING. I even tried to pull codes and my code reader isnt getting ANYTHING out of the ecu.

It really burns my ass that this thing fires up like a champ, idles for 5 minutes solid - 19" Hg steady on my vac gauge, 750 rpm steady on the tach, cuts out, and then wont restart. GRRRRRRR!

Any ideas? Sorry so long.

TIA
 
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Sounds like a longshot but it could have to do with the pickup in your distributor as the distributor has to do with the signal to the fuel pump relay. When it cuts out does it lose fuel pressure first? Making it prime for that long and it's not the relay, that's either a computer or the distriburor.
 
Only problem I have with that suggestion. Is that the pump should still prime. The signal from the ECM to prime is not dependant on a signal from the Distributor. Now after the pump primes, and shuts off, it will then start back up as the PIP signal is received at the ECM.

And the fact that he can no longer get the ECM to communicate with the scanner, indicates that the ECM is not powering up. Ignition switch, ECM relay, or possible fuse link problems would be the case. Worst case scenario, is a faulty ECM.