okay dumb question but is the cmfi trhe same as the cpi? in the chiltons book I was tryin to look up fuel pressure numbers an the cmfi is callin from 58-64 psi is that what I should be getting at the rail? also what adaptors do I need to test it at the filter? The shop couldnt guarentee that thats gonan fix the problem so I brought it home.. Took the plenum off an everything looks good an new under there so now its leading me back to the fuel pump, I check all the lines for kinks or anything ordinary everything looks good! an it has a new filter. So I called the dealership an a another new pump is on its way will be in tomm am but now they want the Vin number an milege of the vehicle is this normal?

thanks alot for all the help!!!

 

The fuel pressure requirements between the CPI motor that is in your truck and the newer SCFI is the same. You need in excess of 52psi for proper opening of the poppet nozzles that are used.

 

Yes, CMFI = CPI

 

so it wasnt normal for when I turn the key on it went to 45 an after the pump shut off it dropped to 20ish psi?

 

No, not at all normal.

 

would that be the pump faulty then? or is there another place that it can lose pressure like that?

 

Um, someone else can better answer that, but there are 2 places that could cause leakdown: one is the fuel pressure regulator, the other the fuel pump.

I can't remember what test tells you which is bad, though...

 

Run down through the test in the DIY section. Even though I think I wrote it up for the SCFI motors, the components are very similar and the pressures are the same. The diagnostic chart that I posted will point you at the appropriate component at fault.