2.5 Fuel Pressure ? something is not right here (Page 2/3)
Lou6t4gto SEP 05, 11:52 PM
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 ?
olejoedad SEP 06, 08:15 AM
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).]

fierofool SEP 06, 08:19 AM
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.
Lou6t4gto SEP 06, 01:41 PM
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 .
Lou6t4gto SEP 06, 07:09 PM
NOW even the Ign Coil has been replaced ! ran for about 1/2 hr without event. now we'll see. LOL
Lou6t4gto SEP 07, 04:03 PM
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)****
Patrick SEP 07, 04:17 PM

quote
Originally posted by Lou6t4gto:

****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.
Lou6t4gto SEP 07, 04:26 PM
other than a toggle switch, I'm not Hearing any other "workable" alternative.
olejoedad SEP 07, 04:28 PM
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).]

Lou6t4gto SEP 07, 05:25 PM
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.