After replacing the fuel pump on my 96 Chev V6 half ton pickup truck, I have to crank it for something like 35 seconds or more before it starts. Giving it gas seems to help. I can hear the fuel pump relay working, but it seems like the truck isn't getting any gas for a few seconds. I also replaced the fuel filter with a WIX filter at the same time with the FP.
Before the new FP, the truck started instantly. Could the fuel pressure be bleeding off, or the new filter be too "dense" or something? Would anyone have any ideas?
"Nothing much, I just worked on the two main suspects for the new problem I am having..."
"Any chance you may have screwed this up?"
Check your fuel pressure and volume. And is your fuel filter the type that can be put in bass-ackwards very easily? I would expect that you might also get poor performance at high power load and open throttle if your fuel filter is blocking flow or the pump isn't putting out enough volume.
I replaced the fuel pump because it died. I verified the problem with my ohmmeter before replacing it. The factory fuel pump had some kind of anti - turbulance inline thing on it but the new one didn't so I transferred the old one to the new one. Maybe I shouldn't have done that... was hoping someone who had replaced the fuel pump on this kind of truck had encountered this. Fuel filter is installed correctly. I kept my old one, maybe I'll swap it (fuel filter) out temporarily and see if that makes a difference in the starting.
Roscoe, Here is a post I made some time ago when someone was having a similar problem. One question, did you have the slow starting before the fuel pump failed?
Check Valve: In the fuel feed line is a check valve that only allows fuel to flow to the fuel rail and not drain back into the tank through the pump (when it is not running). This check valve ensures that there is always fuel in the pump and in the fuel line to the fuel rail hopefully still under pressure.
Fuel Pump: The fuel pump feeds gas under high pressure to the fuel rail. There two different paths to run the pump: 1. If the ECM senses that the motor is running (it has oil pressure) the pump runs. If there is no oil pressure, then the pump stops. This is to prevent a situation where the motor is not running but the fuel pump is, as in an accident, where there is a high likelyhood of fuel leaking. 2. The two second burst when you turn the key to run. This "refreshes" the pressure in the fuel rail, so that full pressure is available when you crank.
Injectors: Feed fuel into the intake system, usually at the rear face of the intake valve.
Pressure Regulator: The pressure regulator bleeds off the pressure from the fuel rail that is in excess of the needs of the engine. The fuel that is bled off is returned to the tank, via a fuel return line.
There are a few ways this pressure can be compromised.
The pump is producing less than optimum pressure. This usually results in driveability complaints like poor throttle response, or surging.
There is a leaking injector/s. Usually only evidenced at idle, may cause the engine to "load up" during long periods of idle. Might even stall. Usually takes all night to bleed the pressure down to a level that causes starting problems. A leaking injector WILL cause a strong gas odor about one hour after stopping the engine.
The pressure regulator is defective and is venting more pressure than necessary, or just plain leaking. Usually a slow leak, but faster than an injector. Might bleed down pressure over a few hours.
There is a defective check valve allowing fuel to drain back into the tank. This is the most variable failure. It might have a slow leak, resulting in any of the symptoms above, or it might be fast and vent pressure as soon as the motor is shut off. If the fuel drains out of the rail, and back to the tank, then the pump might lose it's prime. If the prime is lost, then it will take an extended amount of pump on-time to regain the prime. If the tank is full it will be short, as the pump is submerged, if the tank is low it could take some time to prime the pump. If you leave the tank low and the pump loses it's prime on a regular basis, it will damage the pump, as the pump is cooled by the gas it is submerged in.
Many systems have a schrader valve in them that allows checking the fuel pressure. Attach an approved gas pressure guage, run the engine, turn it off and monitor the pressure. The pressure may drop a little overnight. It should never drop to zero overnight. It sounds like yours is.
Clear as mud eh?
Roscoe Coaltra> I replaced the fuel pump because it died. I verified the problem with
What happens if you leave the key on for at least 35 seconds before trying to start it, will it start immediately then? If so then I would really suspect some kind of blockage/underpressure of the fuel system.
What butthairs are you smoking, the ECM determines the engine is running through the CKP, oil pressure cannot stop the fuel pump, it is a parallel circuit
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