quick question - fuel pressure test

[sandrew]

TSB 97-6-7 http://www.v8sho.com/SHO/TSB9767LowSpeedStall.htm talks about testing fuel pressure but doesn't say if that's with Key On, Engine Running or Key On, Engine Off.

Thanks!

Scott

 

[SHOZ123]

You can check it with the key on engine off, or with the engine running.

Best is with it running, you should have a range of ~30-~40 psi. 40 with the vacuum line off, 30 at high vacuum, 35 is the normal cruising range.

 

[sandrew]

Thanks, Paul.

Engine off cold started at about 10psi but after 3 on/off key cycles went up to 30psi and stayed there. Engine on in park was 32psi and in gear it rose to 34psi then dropped to 32psi again after a few seconds. It stayed around 32 throughout the rev range. I couldn't say about cruising since this is a tester and not an in-the-car gauge.

I've had a P0172 code forever, even with Paul messing around with tunes. It still ran okay until yesterday when it started stalling when coming to a stop about 75% of the time. The rest of the time the rpms would drop to below 500 then start to hunt. After seeing this TSB I was hoping the solution would be something easy.

Oh well. Time to take it down to the heads & start putting on some parts I've had sitting around. New upper & lower intake gaskets, cleaned/flow-matched injectors, new PCV valve and hose/elbow, new plugs, etc.

Already has (within the last year):
New fuel filter
New IAC
New MAF (correct metal Ford unit)
New coils (even swapped the new ones front to back last time I had the intake off - no change, still threw the p0172)
New TPS (have but did not install the TPS connector recall kit yet)
New O2 sensors (upstream & down)
Magnaflow Y-pipe
3rd cat delete and new flex-pipe

Has been smoke tested for vacuum/air leaks and none found.

The last time I had the intake off I did a compression test and all cylinders were fine. I will do another round this weekend.

Any other suggestions? Crank sensor? PCM? 12 gauge?