fuel pump prime - increase time?

[350SS]

Does anyone know how to increase the time the pcm primes the pcm when the ignition is turned on? I went to an aeromotive pressure regulator, and it doesn't seem to hold the pressure once the pump turns off after priming like the stock regulator did. This results in having to turn the engine over a few more times if I don't start the truck right away. Or even sometimes, the pressure doesn't get up to operating pressure during the prime, if the truck has been sitting for a bit, probably due to the fact that the overall volume of my fuel rail and lines up to the regulator has increased alot over the stock system (went to an aftermarket intake manifold). Thanks guys for any insight, i've looked all over for the answer and didn't find anything, but it may be right under my nose

Max

[GMPX]

Max, not sure exactly what PCM you are using, but it is not a modify-able value it's fixed in the PCM code. Having said that, I did modify this for someone a while back as a one off, so it can be done.
Just let us know what PCM you are trying to do this on.

Cheers,
Ross

[350SS]

That's kinda what I thought...I'm sure it's in there but doesn't sound like many people need access to it.

I'm using a 12200411 pcm on a 98 Chevy truck (swapped out the old pcm). Initially it was using OS 12212156 but I recently went to COS1 SD 02020001 in case you need to know that too. Any help is appreciated, thanks Ross

Max

[GMPX]

PM me your Email address and how long you want the prime.
Problem is that it's not even something GM calibrators would have access to, the code guys fix it at 2 seconds (from memory).

Cheers,
Ross

[VT LS1 NZ]

This increased time is something I'd be interested in also.Normally I'd wouldn't have bothered as I turn the key off then on again but since somone else has meanioned it.
My problem has been worsened by running a lower voltage pump reg at low Map/Rpm so as to keep fuel cooler and I don't want to run a one way valve in the fuel line to hold pressure when the car is switched off.

If you can help me also Ross that would be very much appreciated.

Darren

[GMPX]

No problem Darren, PM me your Email address and how long you want the prime.

Cheers,
Ross

[hquick]

Could you email this to me as well.
I believe I'm running the same setup as Max.
98 converted to 0411 and (soon to be installed) marine intake.

[350SS]

Thanks Ross, sending PM right now



Max

[hquick]

Hi Max,
how long do you think you need the prime to go?
I'll be installing the Marine Intake shortly so I expect I'll be experiencing the same thing.
I know standard is on for 2 sec's with key on and off for 3 sec's with key off.

[350SS]

Hi Max,
how long do you think you need the prime to go?
I'll be installing the Marine Intake shortly so I expect I'll be experiencing the same thing.
I know standard is on for 2 sec's with key on and off for 3 sec's with key off.

Not sure, I just PM'd Ross saying I needed to check the prime time currently to know where to start. I figure I'd at least double it to give me some time to be lazy before having to hit the ignition. It would probably be better to have more time than less. One thing to consider though, is you might not have a problem since you're using a factory style fuel pressure regulator, whereas I'm using an aftermarket Aeromotive regulator, which I think bleeds down alot faster, but I'm not 100% sure that is even the problem. I'm running a different manifold setup than the marine one, maybe James B. would be able to let us know if he's experiencing any problems with fuel pressure holding. Nice job on the 411 swap btw It's a great feeling to know you're going to have alot more tuning options now, especially with 2bar.

Max