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Hey guys, I'm new to the forum and looking any suggestions on a problem that has me stumped with my avalanche. It has a hard start condition. It seems to be related to the outside temperature. I didn't do it all winter and started back as the weather warmed up. It starts fine if the engine is completely cold and it starts fine if you crank it within about 15-20 minutes after cutting it off. If I cut the truck off and let it sit for two hours and try to start it it cranks for several seconds before starting. it's a 2004 with the 5.3. It doesn't have an inline fuel filter or a fuel pressure regulator on the fuel rail. Everything is in the tank module, which I have replace with a new AC Delco unit. I have also replaced the evap vent and purge solenoid. I'm going to try a crank sensor just for the heck of it tomorrow. It doesn't set any codes. Does this sound familiar to anyone. Any suggestions would be much appreciated!!

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Start simple battery alternator starter than move to fuel system leaking down. Do a fuel leak down test after testing all the basics with the ignition system.

 

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I haven't taken the starter and had it tested but it spins fast and sounds normal. The battery is only a couple months old and the alternator makes 13.8v

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Try turning on the key, BUT do not attempt to start. Wait 5 seconds, turn key off. Then try to start normally and report your results.

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My 2002 starts like a champ. I just replaced my starter but it still caught when it cranked.

 

I'd say it might be fuel injection pressure or spark related to air flow sensor. The air mass flow sensor might be off when it warms and is mixing air and gas too lean and causing ignition delays ?

 

 

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Alright, I fought with this truck all day yesterday. I put a crank sensor it it first and as I expected it didn't help. I checked spark, fuel pressure and everything else I could think of. Everything checked out fine. I noticed when I could duplicate the hard start I would smell raw gas for a sec right when it started. So I got the truck to spin over for about 4-5 seconds and stopped right before the engine fired. I pulled all the spark plugs and when I got to #5 the plug looked damp and smelled strongly of gas! I finally got a clue. The injector seemed to be leaking down. I called around and found an injector locally. I installed it it starts up perfectly every time.

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