Need help/ideas as to the cause of this No start on first try issue

[98Camarod]

Fixed for you.
Its in the tune. It is not a mechanical problem.

No help, just a blanket statement, nice.

[BAD LS1]

Well I think I got it close. Leaning out the VE didn't help at all. So I figured the tune must be lean already. That would make sense because it usually takes two-three cranks to start it. It must need the 2-3 prime pulses to get enough fuel to fire. So I added .200 to the entire prime pulse table. That caused a rich condition where it would fire first piston up and then die immediatley. So basically I zeroed out the prime pusle table and almost trippled the first pulse table in the hotter regions. From about 90 degrees to 220, it tapers from .250 to .150. The addition of fuel seems to be what this combo needed.

I now can tell when cranking is rich or lean. If it continuously cranks without fire, its lean. And when it fires but dies real fast, it is rich. I figured I would post up my findings for someone who can use it down the road. Thanks guys for your help

Nice work man! thats falls in line with that 2003 SS i just delbt with, it would do the false starts and farted around with that stage 1 mult up and down till i found the sweet spot and now lights off on a half a twist everytime too

[oakley6575]

Nice work man! thats falls in line with that 2003 SS i just delbt with, it would do the false starts and farted around with that stage 1 mult up and down till i found the sweet spot and now lights off on a half a twist everytime too

Cool man. Thanks for posting this thread

[98Camarod]

i've tried messing with the cranking ve and it's not helping. Any other suggested tables?

[oakley6575]

i've tried messing with the cranking ve and it's not helping. Any other suggested tables?

Yea all the other cranking fuel tables.

First pulse mass, second pm, prime pm, cranking fa, ect.

[SICKstySEViN]

Read the whole thread had a thought. Seems your having trouble with a 2-3 minute restart with a lean condition. Vapor Lock? fuel vaporizing in rail due to heat soak? somebody said it only happened with increased temp. We do a lot of things to increase underhood temps, headers, lowering, leaner tunes, heavy right foot, etc. When the pump shuts off, pressure drops. The only thing keeping the fuel from turning to vapor at that temp is the pressure. when restart happens there is nowhere for vapor to go except through injectors....hard stumbling lean starts until the bubbles are cleared out. Just a thought.

[homebuilt]

Good input but would this apply to the vehicles he has with a return style fuel system?

I was thinking that the second start attempt is working because the VCM is delivering another set of startup pulses (ref first pulse and second pulse). Maybe try shortening the prime pulse enable time to make it active on the hot start or enable it if it wasn't active in the first place.

[SICKstySEViN]

Good input but would this apply to the vehicles he has with a return style fuel system?

I don't think it would be as prevelant on return style systems, however it might depend a little on where the regulator/return is located. If it doesn't clear the entire rail, like truck regulators make a short loop through a part of the rail, i guess there could still be a vapor bubble....

something that could make it more likely to happen would be a leaky injector, bad pump, or regulator allowing the rail pressure to significatly drop after the pump stops. as the pressure drops so does the boiling point of the fuel. might throw a fuel pressure guage on and monitor pressure after shutdown.

underhood and engine temps also increase dramatically in the first minutes after shutoff, just raising the hood could have an effect on rail temps and make diagnosis difficult. if it is possible to reproduce nostart then cool rails with wet rags or something and try.

[redline_customs]

If it is a swap you did. Most of the time it is not having a constant 12v going to relays when cranking, to turn on ECM and all engine components. You might be using an ignition on 12v but cuts off when you start to crank.