In need of some serious advice

bigmanwill · May 16, 2019

So i have a 2000 chevy silverado 1500 4x4 with the 5.3L V8. I have replaced the seals on the injectors, new fuel pump, new fuel filter and new spark plugs and wires.

The issue i am facing that i cannot figure out is why im still losing pressure in the fuel. It is no problem when it is cold it fires right up. But when its warm and i leave it shut off for more than five minutes, it takes three or four cycles of the key to start. I know im losing pressure but i do not know where or how. there is no fuel leaks anywhere that i can see. and with replacing everything i am stumped and need some help.

davester · May 16, 2019

you checked and/or replaced the fuel-pressure regulator on the fuel rail?

Maybe leave a fuel pressure guage hooked up to the port and see how the fuel pressure changes from a cold start vs a hot start?

bigmanwill · May 16, 2019

Fuel pressure cold shows standard 55

But when it's hot and warmed up its zero until primed. I changed the regulator out on the fuel rail. All brand new.

davester · May 16, 2019

Maybe check FP when hot, but just turning the key on once and waiting. If after say, 5 seconds you still get no FP, cycle the key once and wait a bit again to see if you get FP.

Next see if the fuel pump is getting power right away when you turn the key on, when the engine is hot. You can't really check at the pump, but find the other end of the wiring harness and test there.

Because you should get full FP almost immediately after turning the key to on.

silveradosid · May 16, 2019

check the fuel pump relay

Wayne3593 · May 18, 2019

My moms 2001 Suburban has a faulty check valve on the fuel pump where it won't hold the pressure in the high pressure valve. Takes her two attempts most of the time to start.

bigmanwill · May 19, 2019

So it turns out the knock sensor was bad.

I have checked everything you guys have suggested. and i appreciate all the input. My truck just threw the code P0327 which is knock sensor low voltage input. I still have the fuel pressure issue but i am chasing that as well. Im thinking it is a leak in one of the actual lines itself. once i figure it out i will post it here so anyone else having this issue can solve their problem as well.