C4SS

My 1988 starts right up and sounds great, for about 6-10 sec.
then quits. starts right back up, but quits again. code flashes
12 only. If the gas pedal is touched, it quits.
Any ideas?
I've replaced fuel filter; cap & rotor; ICM; coil: points & condenser;
EGR valve; checked all fuses; idle air control; tps; checked vacuum
connections.

don hall

You present a quandary. Since there are no codes, 12 is just the beginning of the code process.

Starting immediately after stopping might lead one to suspect lack of fuel over electrical as the source of
the problem, but there is no certainty to either source.

You replaced the fuel filter, but not the fuel pump in
the tank. That is not a difficult task.... you might replace the fuel pump.

C4SS

Do the fuel pumps fail gradually, or all at once?
I don't hear the pump, but never did before.
The fact that it starts right back up, makes me
wonder if some sensor is shutting engine down.
But , yes, I am about ready to try new pump.

Thanks for the reply.

don hall

Normally, the pump will fail, not gradually. There is a primary filter (sock) attached to the pump, that may
be a problem.

Also, a fuel pressure gage may be useful to measure fuel pressure at the time the engine stops.

colter

Could be MAF sensor.

Could try disconnecting MAF sensor and starting it to see if that changes anything.

C4SS

I replaced the fuel pump, still runs and stops.

tried it without MAF, same, but not quite as long.

Could it be the EGR solenoid?

Thanks for all the advise, it's helpful.

crowz

Unplug the tps sensor with the motor off. Crank the motor and see if it still acts up. If it does cut the motor off and reconnect the tps sensor.

Next you need to get ahold of a fuel pressure gauge. There are still things in the fuel system that could be the culprit on this and the gauge will spot them instantly.

C4SS

I tried it unplugged, no difference, plugged it back in, no difference.

What sensors have the ability to shut the engine off?

crowz

Well basically there isn't any. But if its "barely running" the ones mentioned earlier might of been it.

I still believe its fuel related. Get a fuel pressure gauge. Its handy to have anyways and they are about $39 at autozone.

colter

You can "rent" a fuel pressure tester.

C4SS

OK. I'll get a pressure tester tomorrow. Where do I test it at and how sensitive is the variation? My manual doesn't cover it. There always is tank pressure release when
the cap is removed. What else could it be? It's strange I get no codes after 12.

crowz

There is a port to screw the tester onto on the fuel rail under the hood. Once connected we need a reading key off, key on with engine off, running and when it quits. The when it quits is the key reading but all are useful.

SurfnSun

Iac?

crowz

I could see it being the iac if it was quitting on its own but giving it gas kind of takes it away from the iac I would think.

playsdixie

the fuel line above the pump could be separating from the pulsator...when the system is charged, it separates and fuel dumps back into the tank...when off, the line reconnects enough to charge it up momentarily the next time....watch the fuel pressure guage when starting...it will drop to 0 immediately.....just my 02 cents...it happened to me.....good luck...

C4SS

I checked fuel pressure and got nothing with key on or while running. Tried
another gauge and same results, nothing at all. Yet had fuel come out when
disconnecting test hose. So fuel is going past test port hookup.
Baffling, starts right up and runs for awhile, with gauge hooked up and without.
New pump,new filter, pressure build up when cap taken off.

SurfnSun

yeah I missed that part.

crowz

Bad fuel pressure regulator is my guess or the line in the tank like mentioned earlier.

WW7

When you turn the key to the on position do you hear the fuel pump run for 2 to 3 seconds? If you don't hear it run , then you have a bad fuel pump, the relay is bad, or there's no power to the relay or no power to the pump...If you have no pressure to the full rails it almost has to be one of these things, or possibly a blockage or internal leak in the fuel system somewhere...There is a test you can do that involves pinching off the rubber lines at the top of the fuel tank to check for internal leaks ,and a leaking valve, but I can't remember exactly how it's done...Maybe one of the other forum members will chime in with the exact test procedure...WW

C4SS

Thanks WW7 and everyone for the advise. Still the same.
New pump, filter, pump relay.
Never got even a wiggle of the gauge needle. Tried two.
How long for fuel to come out of gauge pressure release/
overflow line. It never did for me. But fuel came out when
disconnected from test port on fuel log. Don't hear pump
when key turned on, but never did before when running.
Starts right up like a champ, every time after quitting.
Baffled. Seems like some sensor is turning engine off.