1991 Chevrolet K1500, 4.3 V6, TBI. Was cutting out. Mechanic checked the fuel pressure by hooking into the fuel line at the fuel filter. Pressure was low. Installed new fuel pump. Since then, vehicle has been hard starting, needing to pump the accelerator and crank the engine longer than usual. What else might be the issue? I just replaced plugs, rotor and cap prior to replacing the fuel pump.
Fuel issues, 1991 Chevrolet K1500
- Thread starter otis24
- Start date
Does it have a fuel pressure regulator? Sometimes hard starting is the result of fuel leaking back from the fuel rail. This makes starting take extra time to build back pressure. Had this problem on my '92 Volvo even after installing a new Bosch fuel pump.
Nick1994
$100 site donor 2024
I’d replace the injectors if you haven’t in a while, if anything just because they’re cheap and easy to do.
Does pumping do anything? if so, sounds like it is going into flood mode, and cutting fuel, which point to injectors bleeding down and flooding the engine. Could try holding the pedal during cranking, that may clear it out faster. [I thought you had to hold the pedal down, not pump, in order to cut fuel.]
If holding the throttle open isn't the "fix" then I'd suspect the regulator not holding pressure. Not sure where the regulator is, that'd be next step I'd think, although... just because the fuel pump is new doesn't mean it's actually good. Just saying.
If holding the throttle open isn't the "fix" then I'd suspect the regulator not holding pressure. Not sure where the regulator is, that'd be next step I'd think, although... just because the fuel pump is new doesn't mean it's actually good. Just saying.
Is this a TBI motor or a MPFI motor?
It has a check valve to hold pressure somewhere, i'm reasonably sure it is in the pump on that one.
The first thing i would check is if it is holding pressure (leave gauge connected while sits overnight).
Second thing why? Leaking check valve leaking injector leaking line?
You can sorta test it by letting the pump prime 3 or 4 times and seeing if its better.
The first thing i would check is if it is holding pressure (leave gauge connected while sits overnight).
Second thing why? Leaking check valve leaking injector leaking line?
You can sorta test it by letting the pump prime 3 or 4 times and seeing if its better.
I think these prime the line for a couple of seconds when you turn the key on but don't crank (if that is the case, you will hear the pump running). Repeat the key on and don't crank 2 or 3 times, then see if it starts right away.
The system also depends on the idle air control motor moving to the full open position to facilitate starting without having to press the gas.
The system also depends on the idle air control motor moving to the full open position to facilitate starting without having to press the gas.
Fuel pressure has not been checked with new pump as far as I know.
TBI motor.
Fuel filter has been changed.
These should have a Schrader valve somewhere, right? Should be easy to give a quick little pop, test after/while running, then test again before a cold start. My money is that it’s losing pressure overnight, question is, where.
That.
I do not remember them having a Schrader valve, you disconnect the line at the throttle body and insert a hose with a gauge.
Fuel pressure has to be checked by disconnecting the fuel line where it goes from tank to fuel filter. And, I suppose that you could tap into the opposite side of the fuel filter to check for leak down(?).
I cycled my key three times this morning; key on, engine off. Truck started right up without any need to pump or press the accelerator.
I cycled my key three times this morning; key on, engine off. Truck started right up without any need to pump or press the accelerator.
Did that this morning and the truck started right up. So what does that mean? Fuel pressure regulator or leak down somewhere in the system?
Yep, keying multiple times primes the system. If you key (but don’t start) and jump right out, you should be able to hear the pump on, then cycle off. When running you might be able to hear it running, it is a high pitched sound.
Leak someplace in the system. I’m not familiar with this system, but I thought it needed to hold pressure between fuel pump and regulator, and between regulator and throttle body. Perhaps the new fuel pump and its higher pressure was the death bell for the regulator? sounds like next step. But I’m still not convinced that it could not be the fuel pump losing prime.
Leak someplace in the system. I’m not familiar with this system, but I thought it needed to hold pressure between fuel pump and regulator, and between regulator and throttle body. Perhaps the new fuel pump and its higher pressure was the death bell for the regulator? sounds like next step. But I’m still not convinced that it could not be the fuel pump losing prime.
What brand of fuel pump was installed? Some of the aftermarket stuff isn't that good. You need to test the fuel pressure again with the new pump. It sounds like the pressure is bleeding down too quickly when it sits. It could be a bad new pump, the pressure regulator, an injector leaking, or a leak in the lines somewhere.
In my other thread about CSFI clinebarger said a healthy pump might put out 90+psi back at the tank outlet.
I don't know if the 4.3 TBI used a different pump than early Vortec V8s?
Also is there a check valve in the pump? That was often the problem with Chrysler products of the era, although those were often return-less systems (not sure it should matter here, though)
I don't know if the 4.3 TBI used a different pump than early Vortec V8s?
Also is there a check valve in the pump? That was often the problem with Chrysler products of the era, although those were often return-less systems (not sure it should matter here, though)
