Quick 8

Hello,

I have an 88 c4 that is having problems. It starts and then immediately dies. It has fuel pressure ~42psi at the rail when I turn it on, so I know it is getting fuel. It fires every single time, but then dies in about 1 second there after. Any ideas?

Your help is greatly appreciated.

Thanks in advance,
~Jim

0Paul Ruggeri

Sounds like you have power to the ignition in start, but not run. Check the ignition switch.

Good luck, Paul

Quick 8

Thanks a lot for the reply. It appears that the ignition still has power after key is released.

Anyone have any other ideas?

staugur

sounds like a bad fuel pump relay.It's definatly nothing to with the ignition as it will start.When you turn on the ignition it energises the fuel pump enable relay for two seconds then when the car starts and builds 4psi oil pressure the oil switch should close and activate the fuel pump which in your case it isn't.you need to check to see if you are getting voltage to the pump after start up.You can probe the wires going to the pump at the gas filler to check.Do a search for fuel pump relay to find where yours is located as it sounds like that's your culprit.
Just checked and your relay is on the firewall right next to the wiper motor.If you jump terminals D&E on the relay plug it should start the pump.
You can also check the pump by applying 12V to terminal G on the ALDL.That's the furthest to the left on the bottom row.And check the fuse.

VistaVette

Will it keep running if you stay on the gas?

h0troddin

It looks like we have the exact same problem. Check to see if you have any codes. Do you hear the fuel pump prime at all?

CFI-EFI

What a pain to try to follow with limited punctuation, capitalization, and sentence spacing!

If it were a bad "fuel pump enable relay" there would be no 2 second priming period.



That is wrong. When the engine starts turning over on the starter, the ECM senses the pulses from the distributor and once again closes the fuel pump relay. Whenever the engine is turning, whether cranking or running, the ECM energizes the fuel pump via the fuel pump relay. Then, IN ADDITION, when the oil pressure is approx 4 psi or greater the oil pressure switch is closed by the oil pressure and the switch feeds a parallel, redundant, 12 volt power supply to the fuel pump.



If there were no voltage to the fuel pump after start up, it wouldn't be running.

RACE ON!!!

Quick 8

It will not run if I stay on the gas.

It does perform the 2 sec. prime, and I do have fuel pressure at the rail, so the fuel pump is working.

The car is at my house, and nobody local has a code reader for a vette "this old". The closest chevy dealer is 35 miles away. That would be a long tow just for a code read. That is why I am trying to figure this one out without the codes.

USAsOnlyWay

You can use a paper clip to pull codes. Look in the tech tip section for the write up.

staugur

Here we go again.
Read my post again and see where I mentioned "bad fuel pump enable relay". I didn't.
As for "if there were no voltage to the fuel pump after start up,it wouldn't be running" read his post again and you will find that's exactly his problem.It fires on the two second prime and dies.
It speaks volumes about you that all you can do is come on here and berate people about a couple of typing mistakes, with absolutely no input about the original posters problems. I think we would all be better off if you joined your friends over on the guru site.

KevinRR

My 85 does this, except it will keep running if you apply extra throttle.

It also takes several seconds to catch and run, when starting either cold or hot, but runs well enough afterwards with a fairly steady idle. I have new injectors, cleaned coldstart injector, new intake gaskets, new IAC valve, cleaned throttlebody, new plugs, new fuel in the tank (cleaned inside the tank due to old gas), new fuel filter and pickup strainer on the pump. Timing is dead on.

CFI-EFI

Here we go again.

Since you have no memory and can't read your own post. Here is the very first, and non-capitalized sentence (?), of your post that I quoted:THAT is where you "mentioned 'bad fuel pump enable relay'". Does it look familiar now?



Assuming it COULD fire on the fuel provided during the 2 second prime, why do you suppose the ECM energizes the fuel pump for the priming period, but not the cranking period? If it "sounds like a bad fuel pump relay.", It couldn't prime. Either the fuel pump relay is good or it isn't. If the relay works for the priming, then it should work for the cranking, unless the pulses from the distributor aren't reaching the ECM. Based on your incorrect description of how the fuel pump gets power, a bad oil pressure switch makes more sense than a bad relay which you say is working for the priming period. You have given your own proof that you are wrong.



What speaks volumes is YOUR incorrect posting of the how the fuel pump is energized. I admit I don't know what the problem is, but at least I have corrected your fairy tale of the fuel pump operation so he can trouble shoot knowing how it really works. Your illiteracy was not the reason for the post, but it certainly made it harder to read and understand. If you really think "that all you can do is come on here and berate people about a couple of typing mistakes, you didn't read much of my post.

RACE ON!!!

jfb

Watch the fuel pressure while someone starts the engine. You may find that you have 2 seconds of priming but no fuel pressure after that. The problem could be the ECM that goes through the 2 second prime interval but doesn't turn the pump back on after starting. I would think that the oil pressure switch though should turn on the fuel pump when the engine runs momentarily, of course the oil pressure switch could be defective too. While someone starts the engine, I would also connect your timing light and see if you still have spark while the engine coasts down when it quits running. Engines need fuel, air , and spark to start and run.

rick lambert

You may want to check your pickup coil, that's where the ECM gets the pulses. Or you could get a noid light and check for pulses at the injectors.

jfb

No pickup coil pulses, then no spark and therefore never starting. Can't be the pickup coil, it does start.

CFI-EFI

I have to apologize for, and retract the statement:Staugur is correct in stating that IS when the problem exists, just as the engine first catches. A fuel pressure gauge and/or a voltmeter at the fuel pump connections at the tank are worth checking. That doesn't excuse giving the OP the wrong poop on the fuel pump operation, but checking the voltage, as staugur suggested, is a good idea.

RACE ON!!!