i just bought a 2000 gmc yukon 4x4 with a 5.7? off a private party and now when i try to start it in the morning it just cranks for a while. Then after a few minutes it starts.it won,t do it after i have been driving it around awhile,just on the first start in the morning.anybody know whats going on?thx.

 

Get a fuel pressure gauge on there. Could be a weak pump.

 

will do,and is the fuel preesure port on the fuel rail?

 

Air fuel and spark are needed for combustion, im sure you know that, but it gives you a "simple" reference point to start with. But this does sound like a fuel issue. I am almost positive a 2000 is a 5.3, not a 5.7 350. Like lowrider said, low fuel pressure caused by a weak pump or clogged fuel filter sound like the simple culprit by what you described. I hope that fixes your issue. As for as the test port, im thinking its on a line coming off of your passenger side fuel rail.

Also, note that when you turn your key, you should hear your fuel pump prime for about 2 seconds, im curious what the pressure is at your rails during that priming...


There are alot of things it could be, i suggest you start by eliminating the simple

 

Keep us posted on your progress

 

Yes there is a shrader port on the manifold you can hook up a fuel psi gauge.

Should see around 55 -58 i believe while cranking.

I bet your fuel pump is going bad Like Aklowrider said.

Give her a shot of starting fluid in the intake and if it fires well you know your pump or pump relay is bad.

 

my gauge says 48 psi @ cranking,and it is a 5.3 sorry guys.

 

What's the key on-engine off pressure?

48 is too low.

 

Possible bad crank sensor. Do you have access to a scan tool? You want to watch for cranking RPM. If it stays at 0 while cranking you have no signal to the PCM. Sometimes a sensor can fail intermittently depending on temperature.

 

Fuel pump for sure... Chevy is known for this.. They keep auto parts in business.. Bad fuel pumps..