cumminsdriver635

Hey guys. My buddy has a 93 4x4 250 ext cab cummins. He has been wanting to get a little more out of it. I will start off with what it has done to it. Basically all it has done is straight pipe with stacks, K&N filter, 12cm housing, and some tweaking of the fuel screw on the pump, along with gauges which we just installed today, and a governor spring that is going in this weekend. My question is...Tonight, we pulled the top cover off the pump(AFC part) and took the spring out from under the rubber plunger connected to the top of the fuel pin. We cant really tell that it smokes or runs any better, but my question is; i had to twist the fuel pin counterclockwise some to get it to come out, and then didnt really have an idea of how it came out, so i could put it back in the same. Do they have to be turned a certain way because of the way the fuel pin has an eccentric(sp?) to it. It seems to run about the same to me. Boost is the same, but we dont have the pyro tapped yet(probably doing that tomorrow). Boost climbs right to 19psi in 4th or 5th right before it starts defueling. Does this sound right for the only mods he has or is this low sounding? Anyway. Main thing i wanted to ask was about turning the fuel pin a certain way, so if anyone could answer that i would be happy. Thanks for the help guys!

Eric

rockjeep73

you want to rotate the fuel pin so that the deepest part of it is oriented towards the front of the motor. There is a metering rod that rides against the eccentric cone, you can see where it makes contact on the fuel pin, it is visibly worn in that spot. you want the rod inside the pump extending out further for more fuel, this is done by rotating the fuel pin.

hopefully that makes sense to you, I think there may be more detailed instructions in the tech facts

rockjeep73

by rotating the fuel pin and removing the afc spring you will not notice a big difference in power, but by installing the gov spring and tweakin the full power screw more you will.

apwatson50

You mentioned that you put a 12cm housing on, so did you hook up the waste gate? If so it opens at 18-19psi. I have one but I don't have the wastegate hookedup, I have the actuator on to hold it closed but the reference line is unhooked. With this setup I see 28psi and have about the same mods as you. I tried hooking up the wastegate and was limited to 18-19 psi. Lost all topend. I'm working on a MPC so I can have it hooked up.

cumminsdriver635

Thanks for the help guys! No. The 12cm housing isn't hooked up to wastegate. But... He got the governor spring in, and MAN what a difference!!! Went from slowly creeping to 20psi, to getting to about 15, and then banging 30psi in 3rd-5th gears! He is all . This sucker runs dang good now!! Best running 1st gen i know of around here. I thought the governor spring kit made a big difference on my truck, but it brought his from being dead, to haulin butt! Thanks for the help guys, and he is happy now. lol

Eric