cold start - EFI tune?

[67ragtp]

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]

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]

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]

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]

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]

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

[67ragtp]

Mike,

Thanks- I may just take you up on the offer, Im still having issues but I have not played with the IAC position vs coolant temp. I tryed all sorts of different settings with no luck. The last couple times I had the car out warm temp 120 to 150 degrees the car would not fire on its own. All I had to do was barely touch the gas pedal and it fires right off. Its strange because its never done this in the past always fires right up when leaving a cruise night after hanging out for an hour or so. It almost seems like the throttle blades need to be opened a little, is this what the IAC should be doing? Thanks Rich

[Mike Norris]

There is quite a few different things that could be affecting it and I would hate to shoot from the hip and get you in a worse spot. Here is what I would like to look at from you.

1) The current tune file in the car.

2) Cold start data log and even if it does not start let it crank and record.

2a) If it does not start without a little throttle on the first data log, then a second log cranking then a little throttle to get it started and idle.

3) Once it does start keep data logging till it gets to running temp.

4) Warm start data logs just like the cold start logs.

This should get me a good idea on what needs to be done. You cna send the files to [email protected]

Mike Norris

[67ragtp]

Thanks Mike- will do as soon as I return from year one. Thanks Rich

[Mike Norris]

Will do Rich, have a safe trip

Mike