CPI injection I've had it! need help

87_bigbadzuk · Jun 10, 2014

I have a 4.3 CPI vin w out of a blazer installed in my samurai. Since day one it has gave me nothing but problems. I keep blowing out the fuel pressure regulator. I am running a e2000 airtex fuel pump. I have switched to cheap eBay e2000 pump also but no diffence as both put out 100psi. When I set the reg it runs perfect for a couple trips then I start having part throttle issues falling on its face and the reg is leaking fuel. I have tried a rock auto, orielly and autozone reg is currently in it now. I have checked vent lines on the stock zuk gas tank and the return line also and all seems good. I'm so ready to pull this injection off. Right now my only other option is to put a carb intake on it and a hei disty and a propane kit. I believe its a impco 225 setup I have setting here but I'm afraid I'll lose power. Any ideas here?

TacomaJD · Jun 10, 2014

Why would you lose power switching to propane?

muddinmetal · Jun 10, 2014

TacomaJD said:
Why would you lose power switching to propane?

He would lose 50 horsepower at the flywheel, easy. Propane needs more than factory compression and a propane specific cam to really shine

zukimaster · Jun 10, 2014

I have the same motor in mine, 100psi of fuel pressure sounds like the problem, but anyway, I think those cpi engines are set around 53-55 psi, I use a stock fuel pump from a late 80's ford truck, they had the pump mounted on the outside of the tank in the frame rail, kinda just like a fuel filter, super easy to install, and they are around the same pressure as the chevy, gave around 120.00 for a bosch at advanced auto about 4 year ago. never give any problem!

TacomaJD · Jun 10, 2014

muddinmetal said:
He would lose 50 horsepower at the flywheel, easy. Propane needs more than factory compression and a propane specific cam to really shine

Ahhh, gotcha :dblthumb:

muddinmetal · Jun 10, 2014

zukimaster said:
I have the same motor in mine, 100psi of fuel pressure sounds like the problem, but anyway, I think those cpi engines are set around 53-55 psi, I use a stock fuel pump from a late 80's ford truck, they had the pump mounted on the outside of the tank in the frame rail, kinda just like a fuel filter, super easy to install, and they are around the same pressure as the chevy, gave around 120.00 for a bosch at advanced auto about 4 year ago. never give any problem!

100 psi will blow apart any stock gm regulator

87_bigbadzuk · Jun 10, 2014

The pump is rated to 100 psi. I have the reg set to 55-58 per factory specs. The e2000 pump is the pump fords run in the frame rail same as what your running.

zukimaster · Jun 10, 2014

Well dam, Only think i can think of would be to make double sure the return side is not kinked up somewhere, and is big enough, and go back with a GM regulator

TBItoy · Jun 10, 2014

how about using an aftermarket FPR? like a Holley or such that is rated for EFI pressures?

87_bigbadzuk · Jun 10, 2014

So your saying regulate it down before it gets to the stock reg?

muddinmetal · Jun 10, 2014

I'd go with a 425 and an e if you go pane btw. Your 4.3 makes as much if not more horsepower than half the small blocks on the trails 5 years ago

zukimaster · Jun 10, 2014

Only difference i have read between yours and mine would be the fuel tanks, i have a 8 gallon fuel cell with ( i think ) #6 fitting and lines, had a fitting tig weled on the end of the return line coming out of the back of the engine to hook up the line, dont think it would be the problem, but that stock sammy tank has tiny lines and holes! :dunno:

87_bigbadzuk · Jun 10, 2014

I do admit it moves pretty good! 4.10 gears 38.5s th350 and dual yoga cases. 1-1 its a turd but any reduction I run and it gets up and goes. We just put dual 425s on a buddies 454 powered jeep and it runs flawless. I really like pane but when the injection works it runs real good. I'm thinking of redoing my return line with larger line. I think it reduces down about half way back so that could be the culprit. I don't really know.

87_bigbadzuk · Jun 10, 2014

You might be onto something about the fuel tank. It feeds the fuel fine. Return is pretty small into the tank though.

Bubba1 · Jun 10, 2014

Don't know much about them but it sounds like you have some kind of restriction on the return line. I think the diaphragm ruptures at 75 psi. It would be easiest and first thing I tried if it were mine.

87_bigbadzuk · Jun 12, 2014

Got a gauge on it. Key on engine off pump running I set it to 55 psi. Put it back together and started it. It drops to 40-45 and if I give it gas it jumps to 55. If I punch it it stumbles till the pressure comes up then picks back up. I guess I need to check voltage at the pump At idle. I had jumper wire when I set it so could be the difference.