Increasing Prime in SCT PRP

[SnakeBoostE85]

Does anyone know of a way to increase the length of the fuel pump prime in the SCT PRP for a 03/04 Cobra (AMZ1/AMZ2).

This will cure my hot start issues... I notice if I prime it 2-3 times when its hot, it starts right up. I'm running a return fuel system, but I have the FPDM's wired up so that it primes like stock vs. running all the time for safety reasons.

 

[crfrider16]

I'm a PRP guy and I don't think I've ever seen or heard any option for increasing pump prime. I'm also wired the same way as you with the FPDM, and I also used to get sluggish starts until I played with the crank lambda and cold start table. I'd be willing to bet that is your problem and here's why I say that.

If you have a fuel pressure gauge on your regulator, have someone turn the key and watch the gauge. You will get instant full pressure. And then it will almost as quickly start to bleed down. It's not like you need to prime the pumps 2-3 times to get it to build full pressure. I was going to put a check valve in-line before I started to mess with the previously mentioned things, but didn't need to afterwards.

I'm still learning and discovering every time I pick up my tuning laptop, so it's just a thought man, hope it helps!

 

[SnakeBoostE85]

Yep - so I solved my *very* cold start issues by increasing crank Lambda. I have a fuel pressure gauge and after prime my pressure drops almost instantly. I have a FORE pressure regulator, it doesn't maintain pressure unless its running.

Are you running E85? If so, send me a screen shot of your crank lambda table. Here's what mine looks like. Adding pedal during my hot starts doesn't help, so I guess I need to add fuel.

 

[Mach828]

I too just used the crank lamba table. I've never seen any options available to adjust the priming time. Its not really meant to be adjusted from the factory, considering Ford used the pprv valve to keep fuel in the lines which makes it so you don't need to ever prime it.

 

[crfrider16]

Yep - so I solved my *very* cold start issues by increasing crank Lambda. I have a fuel pressure gauge and after prime my pressure drops almost instantly. I have a FORE pressure regulator, it doesn't maintain pressure unless its running.

Are you running E85? If so, send me a screen shot of your crank lambda table. Here's what mine looks like. Adding pedal during my hot starts doesn't help, so I guess I need to add fuel.

View attachment 47081

Good stuff. I'm not E85 so no help there. I had to increase crank lambda significantly to pull fuel. Took a while to find the sweet spot, but it starts perfectly now without touching the pedal, hot or cold.

 

[cj428mach]

Older ECM's had a table where you could increase your fuel prime pulsewidth. The newer ecm's use the crank lambda.

 

[SnakeBoostE85]

ok my only concern with going crazy on the crank lambda especially being on E85 is just the sheer amount of Fuel you are dumping into the cylinders that might get by the piston rings and drop into the crank case. I think they call it piston washing.

Thats why I was more interested in increasing the prime length because all I really need to do is cool down the fuel in the rail system by running more fuel through it, rather than making the injectors spray more into the cylinders, but I guess that is not possible.