Long start

TOOLMAN.JIMSCOTT

MEMBER
2002 CHEVROLET SILVERADO
5.3L
V8
2WD
AUTOMATIC
263,000 MILES

Truck does not want to start. Takes 3 to 6 times, maybe more to get it to start up.

Have replaced fuel pump twice and is only making 50 PSI at key on and drops to 45 at idle when running. If you disconnect fuel pressure regulator while running pressure goes to 55 PSI.
I have replaced the fuel pressure regulator as well as the coolant temperature sensor and MAF sensor.
If you disconnect the coolant temperature sensor wire while the engine is running it shutting off the engine like you shut the key off.

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

Sounds like you have a leaking injector. If you unplug the regulator and it jumps to 55 then that is the max pressure it can produce and that is the low end of the spec which tells us that it is loosing pressure somewhere. The pump is the most likely cause but if you put that in then the injectors are the next place to look.

One way to try and test this is to use a borescope and remove the plugs and look in the engine but this is not that effective as you will most likely not see it drip. The way I have done this is to hook up the gauge and watch how long it takes for the pressure to drop after you shut it off.

It should hold pressure for a while but I suspect this will drop quickly.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Let me know what the pressure is with the engine off and how quickly it drops and we can go from there.

Image (Click to make bigger)