cold start - EFI tune? - Lateral-g Forums

67ragtp · #1 03-03-2008, 10:02 AM

My 427 sb FAST XFI EFI(4150 throttle body) set up stalls on cold start about 2-4 seconds after it fires up. It just falls right off and dies. If I catch the pedal with my foot it, and give it one little pump its fine and I can get out and let her warm up. Afterstart enrichment vs cts has already been increased from my original tune its around 45 to 52% @ 36 to 70deg. Any suggestions on what to try next?

Thanks Rich

Blown353 · #2 03-03-2008, 12:05 PM

You probably need to play with the delay until afterstart fuel is introduced. As you increase the cranking PW the chance of flooding it just after lightoff becomes higher so you need to delay the introduction of more fuel until the cranking fuel is burned.

If it stumbles & dies unless you pedal it there is a chance it's too rich from cranking fuel and the additional air you give it when you crack the throttle keeps it running-- so increase the # of revs before afterstart to slow the addition of warmup fuel.

You may also want to try maxing out the IAC position during starting; I've found this helps quite a bit. If the rpm's "flare" too much then back it down some.

You may have to do all this in tandem with backing down the cranking fuel some.

**camcojb** · #3 03-03-2008, 12:15 PM

good info above. It's a balance and one of the hardest things to get perfect. Plus, you only get one shot per day to see if the changes helped or hurt.

Jody

67ragtp · #4 03-03-2008, 03:12 PM

Thanks for the advice, I believe these are the two tables you are refering to. Thought I would post them and see what you think, how much change should I make?

Thanks again Rich

JimM · #5 03-03-2008, 08:00 PM

yup those are them. Your FAST s/w is much prettier than my holley stuff, but same tables.

You have virtually zero afterstart delay unless it's freezing or less.

Your IAC park is plenty high when cold, but low when warm.

I'm working this same issue right now. She fires then quits and is flooded. Where are you when you do your first start?
I'm in a heated garage, so I'll be working those tables at the 65-70 degree point.
Guess I'll hafta leave the car outside overnight to work the low end?
(I think not....)

**Mike Norris** · #6 05-10-2008, 05:09 PM

If you are still having any issues, you can feel free to send me a cold start up data log as well as your tune and I will see what I can do. Try to get the log without touching the accelerator pedal and let it stall. The also a data log with touching the pedal and not stalling.

I went through this on John Parson's II much and got it very good.

If it is resolved then congrats are in order for sure. Hope this helps.

Mike Norris