Ruff starting engine when the engine is warm

bdja

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My 2000 Sierra (4.8) doesn't want to start very well when the engine is warm. The engine has 323,000 mile on it and is well maintained but starting to show signs of age. Any help? Thank you.
 
My 2000 Sierra (4.8) doesn't want to start very well when the engine is warm. The engine has 323,000 mile on it and is well maintained but starting to show signs of age. Any help? Thank you.

I have seen a few Vortec with very dirty injectors that leak. But more often than not vortec hard start problems(the newer 4.8/5.3/6.0s) are caused by a leaking fuel pressure regulator, they leak fuel through the vacuum hose and fill the plenum full of fuel. Inspect your regulator and any signs of fuel leak in to your upper intake.

The other thing also would be a bad check valve at your fuel sending unit and your losing your fuel pressure when the engine is shut down. Try cycling your ignition switch three times to build up your fuel pressure and post me back. After your cycle the ignition switch three times and the engine starts fine, than it's your check valve or a dirty fuel filter.

If you still have the hard start after your pressurize your fuel line, you may have a flooded upper intake from a leaky fuel pressure regulator or a leaky injector. On the 4.8, you remove the vacuum hose from the FPR and if there is any trace of gas in it. The driver side of the engine I believe coming out of the fuel rail is the FPR with a metal retaining clip. Theres also a small vacuum line running up under the intake manifold cover or somewhere up there. Once the truck is warm shut it off and pop that line off at the regulator. If there is any moisture in there what so ever it's no good and needs to be replaced, it's like $60 and 10 minutes to fix.:D

The lifter noise you also have mentioned earlier in your post could also indicate one of your injectors dirty or stuck which would be leaking the fuel when the engine has been turned off. A noisy injector can also make it seem like a bad cam lifter, since they have similar ticking sound.
 
Thanks, Molson. Used the MMO and no more lifter noise so far...keeping fingers crossed. Fuel filter is pretty new, but will check the FPR next and so what happens. At this point, $60 is a blessing. Thanks for your help. bdja
 


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