Hi all,

I have a 2002 F150 4.2L V6 with 261,000 miles. I've been doing a bit of my own work on it lately, which has been both fun and rewarding, but I've had a few questions along the way.

So I recently got an OTC 5630 fuel pressure gauge and hooked it up tonight to see what's what. My Chilton F150 repair manual says the fuel pressure at idle should be:

30-45 psi. (Vacuum @ regulator attached)
40-50 psi. (Vacuum @ regulator detached)
30-40 psi. fuel system hold pressure (5 minutes after key off)

My fuel pressure at idle is a little under 32 psi.
With the vacuum detached, it's 40 psi.
Key off, and waiting 5 minutes, the fuel system pressure is 28 psi.

The only reading that is a little below spec is the fuel system hold pressure, but it seems like a 5 psi drop might be normal, if looking at the upper range of numbers. Do you think that a 3.5 psi drop in 5 minutes is anything to worry about or look into? Or maybe just keep an eye on it?

I suppose the bottom of the scale fuel pressure might be just because of the original equipment and the high miles? I put a brand new fuel filter on a few weeks ago, and recently had the injectors out to inspect, bench test, clean and replace o-rings.

 

I wouldn't worry at all with those numbers.

 

How does the engine run?

 

It runs 100% better since I've solved the vacuum leak (replaced valve cover gaskets, intake plenum gaskets, isolator bolts, pcv valve, throttle gasket, etc). Once it's reached operating temperature, the idle is fairly smooth between 825 and 850 rpms. I say fairly smooth because I'm not sure how much the graph should jump around, but it sounds like a sewing machine when it's running, better than it ever has.

Fuel trims look pretty good, and are usually even on both banks, but occasionally bank 1 will seem to run a little more rich, as the SHRTFT1 %'s are in the negative numbers more often than SHRTFT2's are.

I have not had any stored codes since I did that work to it about 2 or 3 weeks ago. But a couple times it has given me a P0302 & P0316- a misfire on cyl 2. That, plus the fuel trim #'s make me suspect that maybe it is a leaking fuel injector. Once when I parked the truck and got back in about 10 min later, it ran very rough at idle when I started it, acting flooded. To me, that seems consistent with an occasional leaking injector.

But like I said, it's running really good 99% of the time, which I'm pretty pleased with. It's just that now that I have the "tinker bug" I can't seem to leave well enough alone. I'm kicking around replacing the fuel injectors sometime, but it means tearing apart the intake plenums for the 3rd time... which I'm starting to get pretty good at. LOL