ASSUMING the gage is accurate, that pressure is too high.
It should be no more than 38 psi with the vacuum off and drop about 5 to 8 psi with normal vacuum applied.
With wide open throttle as it is now, the fuel pressue would likely go past 50 psi and drown the motor in fuel.
The Ox sensor sees this and tries to shift the fuel tables lean causing a code.
The excess fuel distroys mileage, can foul plugs, contaminte crank case oil and the like.
Good luck.

 

He has a 4.9. Pressure should be 50-60, Engine off. Running it should be 45-60, with vac hose connected to FPR. Running with vac hose disconnected it should increase 5-10.

 

Tis true. So does tht mean I have a bad fpr if engine off its sittn round 30 and idle its hittn a max of 48psi. Then disconect the vacuum from fpr n it hits 60.

 

Is there any fuel in vac hose of the FPR? Is there any fuel present in the nipple if the FPR? If so, replace.

When testing fuel pressure with engine off, does the pressure max out at 30 and stay, or does it max out at 45 or 50, then bleed down to 30? If it does, possible bad FPR. Mine did the same, but new pump kept it around 35, but testing with engine off confirmed bad FPR. I checked for open/stucked injectors even though new to rule that out as well.

 

theres no fuel in the vacuum line. but i went ahead and replaced the FPR and fuel filter. pressure at idle is jus under 50psi and removing vacuum line makes it go up ta 54psi. engine off it sets on 30 with no leak down. took it on another test drive and yet again nothings changed. wth. im seriously stumped.

 

Sounds like pump is weak or there is restriction from the strainer on bottom of pump. Check voltage to pump with key on. Is it less than 12volts? If so, check ground for fuel pump. If voltage checks good, I'd be leaning to weak fuel pump or restriction. I'm unsure of the 91 had an in tank pump and frame mounted pump, though I don't believe you do. Just the in tank pump.

Note: Is the lean code still there? You corrected the distributor problem but don't know if you cleared the ECM? Have you disconnected battery to reset ECM? If not, do so for minimum of 10 mins. Drive truck and vary throttle for 5miles @55 mph. You can also let it idle for around 10 mins or so to relearn idle parameters. Re-run test for codes to see what comes up.

 

ok.. well the truck is a 1989 but a put a 91 engine in it. so it has the booster pump. but how could it be the pump if its gettn the correct fuel pressure. i wiped the codes and the lean code and code 212 was still there. i got a air fuel ratio gauge that taps into the o2 sensor jus for an actual reading and low and behold it shows lean aswell. ive even gone as far as to hook up a computer out of a good running 91 4.9 and it still did the same thing. ive read that as long as it show code 212 that itll run in limp mode but ive checked all wireing for the spout and its all good. and the icm is new so im stumped.