1985 2.5 / automatic. Put in a shrader valve, car will go to exactly 13 PSI "while It's RUNNING". as soon a,s (immediately) when the key is shut off, it goes to" 0"! not gradually, within a half second ! isn't it supposed to HOLD pressure for at least a couple of minutes ??? Thanks
pinched the inlet tube, then shut it down, No Difference. I installed a" used" Pressure regulator I have and it did not make any difference in the "DROP", BUT, the" Volume" of fuel from the cone sprayed from the injector got to be a "FINER Mist" ! took apart the old regulator, no rips, but had a very small chip of metal in it (Maybe blocking the valve )? But still, WHY the PRESSURE DROP so fast ?
There is a check valve on the pressure side, I believe it's in the fuel pump, that should maintain fuel pressure after the pump shuts off. They are frequently bad on most older gm's.
the car now has Literally EVERYTHING , every sensor, pump, ECM, icm, pickup coil, realays......NEW, yet it will still quit without warning. sometimes go 5 miles fine, another time won't move 50 feet without stalling 5 times! but always starts right back up. sometimes stalls again, sometimes another 5 miles.
well it does Hold fuel pressure for awhile (could be 1- 20 min) then it ll drop to zero. car stalls. turn the key on again, fuel pump pumps, and it will run and hold pressure again... untill it won't ! LOL is the computer the only thing responsible for keeping the fuel pump pumping to" MAINTAIN" fuel flow ???
Have you checked all the grounds? Especially the ones for the computer. You could have an intermittently open wire in a harness somewhere. Perform a wiggle test on all the wire looms. Start the engine and move the harnesses around, if there is a bad wire or bad connection somewhere this should show it. Wiggle the connectors on all the sensors, this will show if you have any pins that are opened up a little and losing contact intermittently. If any of these tests cause a stall, you've found your culprit. Replacing parts is only half the job, you still need to test the wiring and connectors that link them all together.
If it just shuts down and won't start until the ignition is turned off then back on again, check the ignition switch down on the steering column. Several of us have had that problem to include L4's, 2.8's and 3800SC's. Changing out the ECM, coils, ICM or other sensors didn't work. The ignition had to be turned off for it to restart.
just put a NEW one on this afternoon, absolutely No Difference. I've been chasing this for an entire YEAR now, this is gettin' old. Is there a way to just "direct wire" the fuel pump to run whenever the key is on ??? adverse effects ?
The fuel pump relay is held on by the ECU when the engine starts. The oil pressure sensor is a backup power supply that bypasses the F/P relay to the pump as long as the engine is making oil pressure. GM wired it this way to keep the car running and to be able to start in the event of a F/F relay failure. Do you have a spare injector you could try?
[This message has been edited by olejoedad (edited 09-06-2019).]
Has the ignition coil been replaced? My Dad's 63 Chevy would do that. After turning it off and sitting for a moment, it would restart. Turned out that it was the ignition coil that was breaking down.
believe it or not, the Ign COIL is the ONLY part that has not yet been replaced. I've got a new one, will try it (at this point I'll try anything ! ) LOL the injector is also brand new .
this engine is quitting because it "Runs out of fuel"! it runs just fine, then you can Watch the fuel pressure gauge "drop" (it RUNS until the pressure is ZERO,( takes about about 5 seconds to go from 10psi to nothing,) when it reaches zero, it shuts off. then "Immediately", restarts and it runs fine again !! Can the fuel Pump be HOT WIRED to run "full time". the "ECM" was changed, the "Relay" was changed, the "Pump" was changed as were the Hoses. Ign COIL, Pickup Coil, IGN SWITCH ,IAC, TPS, Injector, Regulator, tb REBUILT... "something" is shutting off the pump ! ( and there is no telling WHEN or how long that will be). all plugs we unplugged, & cleaned. wires were "wiggled" and did nothing, no bad grounds. there is no Obvious reason to this. ****CAN THE PUMP JUST BE "HOT WIRED" TO "RUN" AS LONG AS THE IGN SWITCH IS IN THE ON POSITION ???? (cutting out the ECM,and relays)****
****CAN THE PUMP JUST BE "HOT WIRED" TO "RUN" AS LONG AS THE IGN SWITCH IS IN THE ON POSITION ???? ****
Sure... but the results could sure be ugly if you ever had a crash and the car caught fire. There's a reason why the fuel pump is designed to shut off if the engine's not running.
Yes, the fuel pump can be wired to run full time with the IGN switch ON.
Understand, the ECM could turn off the F/P relay, but the pump is still getting power via the Oil Pressure sending unit backup circuit whenever the engine has oil pressure above a few pounds.
I dont think the ECM is your problem.
Scenario - Fuel Pump relay is not functioning, all power to pump is coming through backup circuit. When coming to a stop, oil pressure drops below backup circuit switch threshold, kills fuel pump. Cranking to start raises oil pressure enough to restore fuel pump power, car starts.
Symptom of this scenario would be a long crank on initial start.
[This message has been edited by olejoedad (edited 09-07-2019).]
the car (when started cold) turn the key on, pump pumps, hit the key, immediately starts ! then runs fine, until it doesn't. oil pressure and voltage voltage have absolutely NO effect on the "stalling." (it will have at least 12 volts, and at least 25psi oil pressure, until it quits, even then it stays 12 volts, oil doesn't drop "at all" until it's NOT Running at all.
Leave gas cap off - see what happens... Just wondering if tank is venting properly or building a vacuum.
Bad pump maybe? They can be faulty out of the box. I know it sucks, but it has happened.
Years ago - different car. Car died on side of road in middle of nowhere. Called for tow truck. After 1/2 hour of waiting, tried engine and it started !! Cancelled tow. Repeat two more times before diagnosis of bad in-tank fuel pump. It would shut down when "hot" and start working again after it cooled off.
You don't have the exact same situation. Temporarily run 12V power direct to fuel pump connector. If test light/voltmeter shows pump is getting 12V power even as PSI drops to zero - it has to be the fuel pump.
From 1986 Factory Service Manual... A picture is worth 1000 words.
so, if I were to run a wire from the switched "ON" terminal at the fuse box to the ALCL . the pump would HAVE TO run all the time. and if the pump DID" stop" running,(or stop providing pressure) it would HAVE TO BE the pump itself, correct ?
so, if I were to run a wire from the switched "ON" terminal at the fuse box to the ALCL...
You've got a 12v source at the cig lighter right by the ALDL port to supply what you need... for test purposes only of course.
quote
Originally posted by Lou6t4gto:
... the pump would HAVE TO run all the time. and if the pump DID" stop" running,(or stop providing pressure) it would HAVE TO BE the pump itself, correct ?[
Correct. The ALDL fuel pump terminal is connected directly to the fuel pump.
[This message has been edited by Patrick (edited 09-08-2019).]
I NOW HAVE a wire coming from the lighter hot, out to the console, and a wire from the fuel pump plug at the acl out onto the console. not connected, (Just in case) .I took it for a few mile ride, acted just fine ! Maybe just the "threat" of being hotwired Scared It ! LOL
1985 2.5 / automatic. Put in a shrader valve, car will go to exactly 13 PSI "while It's RUNNING". as soon a,s (immediately) when the key is shut off, it goes to" 0"! not gradually, within a half second ! isn't it supposed to HOLD pressure for at least a couple of minutes ??? Thanks
NO. I don't think it will hold the pressure for a couple of minutes. All the TBI cars I've ever checked, lose pressure immediately and go back to zero within 20-30 seconds. Now a SFI/MPI car will hold pressure for minutes, or hours, but not a TBI.
Soooooo, what happen when you tried running with the gas cap loose or off like Fierosound suggested?
Spoon
------------------ "Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut
