95 GMC Jimmy CPI OBD 1.5/II however you want to look at it.

Alright Im still battling fuel issues... Heres where I stand, the fuel spider, nut kit, and fuel pump are all brand new within the last few days. I get the new pump in and the tank reinstalled and go to start it. Its having problems building pressure. Finally get it started and its only maintaining about 50-52 PSI, open the throttle and it drops to around 35-40 PSI. I guess my question is a matter of opinion. Should I drop the tank and see if Im not holding pressure there? Ive checked all the external lines for leaks at the top of the tank at the back of the intake adn at the fuel filter with nothing. So my next guess is something in the tank isnt right.

And one further question because IM not sure. Can I drop the tank and leave it on the ground but leave the lines hooked and try to do some investigating that way or will that depressurize the tank to much and give me the same or more of a problem.

Thanks for any help guys

 

All fuel pressure and leakdown tests are done with the engine off. For your 1995 CMFI system: key ON, engine OFF, fuel pump running, pressure must be 55psi to 61psi and must remain above 50psi for at least 10 minutes after the fuel pump shuts off. Post your results.

 

Guess I should of went into more detail. Doing the actual leak down test if you flip the key on in builds to about 50. When it peaks tho it bleeds off immediately.. It's not slow it's instant

 

The only way to tell for sure where the excessive leakdown is coming from, is to isolate the pump from the plenum just after pressurizing the system. It's done with a tool like this:



The tool can be made for around $40 with parts readily available at a good plumbing store and an auto parts store. Without isolating the fuel pump, it's a guess as to where the leak is.

 

Yeah I have a regular fuel pressure test kit but Ive been thinking of ways to isolate the fuel pump. Where do you hook your contraption into? The fuel filter?

 

Yes, it connects inline at the fuel filter. This particular one is for 96 and newer. They use one quick connect fitting at the filter. 95 and older doesn't have quick connect fittings so it requires different fittings to adapt to the fuel lines.

 

Yeah the 95 has the "bolt in" filter. If I have to build one I will but I really can't spend the money as of right now. Ive been thinking back and I think I know what is causing it. Off to start investigating

 

You can remove the plenum and look for a leak while the pump is running, but that only eliminates a couple of things. You can remove the injector nozzels and watch for leaks as well, but without the shut off valve, you can't diagnose an internal leak in the fuel pressure regulator, or anything in the tank.

 

Yeah I know. Will the lines pressurize properly if the filler neck and vent tube isn't hooked up? There is a method to my madness

 

Absolutely.