Adjusting Fuel Pressure

[Scorcher2005]

I just got the engine back together. On the AFPR, which screw is the adjustment screw? There is an allen key stud on top w, a nut, a vaccum line on the side w/ a nut, and a 1/4" NPT fitting w/ a nut. Which do i turn to bump/lowwer fuel pressure?

 

[Michael Yount]

Surprised you haven't figured it out - the way you've described it there's only one thing you can adjust. Loosen the nut - turn the allen screw til the gauge reads what you want (38-39 psig with vacuum line off and plugged at warm idle) and then tighten the nut to lock the allen screw in place.

 

[Scorcher2005]

ok, thats what i thought, just wanted to make sure before i started loosening/tightening the wrong things.

Secondly, just tried to start the car w/ the stock fuel pump. The guage was reading 20psi. Will the car even start w/ 20 psi?

 

[04sleeper]

Your fuel pressure might be a little different on the gauge until you actually start it.
Did it not start?

 

[HISSIN50]

One can cycle the key a few times before cranking for the first time. This helps build pressure if the pump is weak (the FPR can be cycling too much fuel back to the tank also).

Good luck.

 

[vristang]

Surprised you haven't figured it out - the way you've described it there's only one thing you can adjust. Loosen the nut - turn the allen screw til the gauge reads what you want (38-39 psig with vacuum line off and plugged at warm idle) and then tighten the nut to lock the allen screw in place.

The difference between this guy and me is that he is smart enough to know when he doesn't know the answer. (Whatever that means)

I tend to mess with something till its fixed or I break it even more.

The large screw on the side is probably for a pressure gauge if it is like mine.

OFF TPOPIC What is the g in "psig"

 

[Michael Yount]

psig - pounds per square inch GAUGE, as compared to psia - pounds per square inch ABSOLUTE (add ambient pressure to the gauge reading)

It'll probably start with 20 psig. But try to run it very hard and you won't have enough fuel. My buddy did a 5.0 conversion on another Volvo and accidentally got the in-tank primer pump wired up, but not the main in-line fuel pump. He was getting about 25 psig. The car actually ran good 80% of the time - but anytime he got into it for a bit, drivability issues showed up because it was running out of fuel. Problem solved when he wired in the in-line pump and got the pressure up to about 40 - psiG.

 

[vristang]

psig - pounds per square inch GAUGE, as compared to psia - pounds per square inch ABSOLUTE (add ambient pressure to the gauge reading)

It'll probably start with 20 psig. But try to run it very hard and you won't have enough fuel. My buddy did a 5.0 conversion on another Volvo and accidentally got the in-tank primer pump wired up, but not the main in-line fuel pump. He was getting about 25 psig. The car actually ran good 80% of the time - but anytime he got into it for a bit, drivability issues showed up because it was running out of fuel. Problem solved when he wired in the in-line pump and got the pressure up to about 40 - psiG.

Thanks for the answer, I probably should have known that.

That's what your buddy deserves for putting a 5.0 in a Volvo.
I love the fact that you guys did something different. Very cool!:worship:

 

[Scorcher2005]

ok, well, its up to around 40 psi...still no luck. I think some spark plug wires may not be clicked on all the way. Ill have to check tomorrow. Other than that, the only thing i can think of is the distributor might be 180* off.

 

[HISSIN50]

ok, well, its up to around 40 psi...still no luck. I think some spark plug wires may not be clicked on all the way. Ill have to check tomorrow. Other than that, the only thing i can think of is the distributor might be 180* off.

Sorry if I missed it (just tell me where) but what is the car doing? IMHO if the dizzy had been stabbed 180* out, you would know it. But we (or I) dont know what the issue is.

On the FP, as long as it is in the ball park, the puter will adapt the injector pulsewidth to get it stoich.

Good luck.

 

[Scorcher2005]

All its doing is cranking over at about 200-300 rpm. I have spark, at least in the one cylinder i checked. I am about to go make sure all plug wires are pushed down.

 

[vristang]

All its doing is cranking over at about 200-300 rpm. I have spark, at least in the one cylinder i checked. I am about to go make sure all plug wires are pushed down.

Just a few weeks ago I had the dist. off by 180. Very confusing, since I could verify very strong spark (OUCH!), fuel pressure was good, and I knew there was no air restriction. If you have spark, fuel, and air the only other thing that can go wrong enough to keep the motor from running is timing.

Check that you have the dist in correct. Sounds like the prob from here in Seattle.