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Strange starting issue.

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I have an '02 Sierra 1500, 4WD, Canadian built, 4.8L V8.  It starts perfectly every morning and I have no issues while the engine is running.  After the first start if i turn the engine off for more than 10 minutes I have a rough start and get intense fumes in the cab.  If it's off for 10 mins or less it starts up without issue.  Within the past 8 months I have replaced:

Fuel pump 

Fuel filter 

All four O2 sensors

MAF sensor

Catalytic converter

Spark plugs & wires


I'm not getting a check engine light and a code reader comes up empty.  Any suggestions?



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As for the hard-starting, you might consider hooking up a fuel pressure tester just after turning the engine off, then watching how the FP changes as you turn on the ignition, and then start the engine.  Could be the fuel-pressure regulator has failed and is draining the fuel back to the tank (could also possibly be an injector leaking down into the intake).


The strong gas smell could be a problem with the EVAP system,

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