Page updated on 05-22-2018

1995 Gmc Jimmy 4.3 Vortec CPI Flooding on #3 Cylinder Stalling and Misfireing

02-24-2005, 10:59 PM
Trying to figure out some issues on my 1995 GMC Jimmy and having a hell of a time. Have been having issues for a while with hard starting, the engine has to rotate maltiple times before it starts and runs rich when it does start and often times seems like it is running rough. I had the codes read and and found multiple misfires detected as well as a egr controle module.So i replaced the EGR and didn't help. i replaced the plugs, wires, rotor,& distributor cap and still no luck. Recently THe vehical began stalling when comming to a stop, started running extramly rough as if it was missing one or more cylinders or like the timeing was off. I pulled the plugs to check for spark and spark was good. pulled the #3 plug out and it was soaked in gas, turned the motor over and quite a bit of gas came out of the cylinder, but had spark on the plugs. the rest of the plugs are a little carboned up but not bad. My understanding of CPI is that there is only 1 injector. If the injector was bad or leaking wouldn't there be gas flooding into all cylinders? Or are there also individual injectors for each cylinder. At this point I'm lost as to why I am getting all this fuel dumped into just the #3 cylinder... Hopefully someone has a clue cause I'm at my wits end. the only thing i can think of is to splint the intakeand look for fuel leaking from the CPI??? :confused:

02-25-2005, 07:16 AM
Actually it's a single injector with 6 poppets... Sounds like the # 3 poppet is becoming toast and your injector is leaking. Replace the CPI unit... Not worth trying to work on the poppet. Change your cap and rotor and do an oil change (to remove the gas from the oil as that will kill your crank bearings)

02-27-2005, 01:44 AM
i got around to pulling the upper part of the intake off, i am fairly sure that i have found my problem judging by the 2 large 1/4 inch melted holes in the fuel return line, and the multiple pin holes in the supply line.Judgeing by the amount of gas that was in the intake on both sides I'm thinking i should replace the CPI while i got it apart , the majority of of the fuel was on the drivers side so more than likely will just pick up the new nut kit and see if that solves the problem. I figure if it doesn't i'll only be out the extra 10 on the gasket if i have to take it back apart.

02-27-2005, 04:29 AM
I think you found your problem... :iceslolan If any washing happened on the passenger side though, your cpi needs to be replaced too, as you will keep dumping fuel. Don't forget that oil change!

02-27-2005, 01:16 PM
Might as well replace the fuel lines and the CPI injector at the same time and have it fixed for good.

Also, remember to install a new plenum gasket.

04-26-2005, 07:20 PM
Hey guys I'm having the same problem, Is their a site where I can find the CPI Unit cheap or low coast.

04-26-2005, 08:32 PM

07-21-2006, 08:13 AM
The CPI has a chronic problem with injectors failing. I just replace mine since two injectors poured fuel and the diaphram inside the pressure regulator was leaking. The CPI has six separate injectors extended off of three hoses off each side of the unit. Make sure you get new O-rings for the fuel lines that connect into the right side of the unit.

Add your comment to this topic!