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Hey Guys, I have an LS3 running an early (2001) 24x crank and 1x cam sensors. I'm also running Holley intake, injectors, and a Holley 4150 style throttle body. All this said, my engine starts immediately on every other try whether hot or cold. My fuel pressure is holding 60 psi. Every other time I start the engine it just cranks and won't fire. If I keep cranking like for over 2 seconds it sounds like it coughs (not a good sound). I have gotten used to just turning it off if it doesn't fire immediately and then starting it again and it fires right up. I am not getting a fault code light or anything. It just has this weird starting issue. I have changed both the cam and crank sensors and I have a Speartech harness made custom for my components.
Just wondering if anyone has any experience with this type of problem? I would think right off it was the cam sensor but it has been checked and replaced just to be sure.
Thanks in advance!
It sounds like your are not getting a cam signal. Cam signal is used to determine on what stroke the cylinders are on. If it doesn,t receive the signal it just guesses (so 50/50 chance). The cough noise is probably a backfire through the intake. I would verify cam signal to start.
One thing to also consider is if it has fuel pressure when the injectors prime the engine. I don't use the stock ECU so I'm not familiar with the sequence they use. I use the Holley system and if you don't have enough fuel pressure when the ECU commands the engine to prime it won't fire on the first try.
I would check the starter interlock is disabled in the tune as well as VATS and the wiring of the feeds to 12v+bat and 12v+ign. If you get any of those crossed up it can make starting tricky although it will run fine once started.
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LS3 starting every other try (??) 
