Fuel Pressure? Opinions Please

[frank700]

K here's my problem. Fuel pressure set at 42 at idle. Drops a little when car is started and idling. Have used three different fuel pressure gauges to make sure it's correct. Take car for a drive and after a while pressure increases. 45-50. Cruise around get into a little boost and pressure won't go back to say 39-38. I have used two different fuel pressure reg. no change same thing. Has a walbo pump. If return line was restricted it would be high all the time. Not after driving car. I just blew pressurized air thru the return line for about 3 seconds. It pressurized the tank and I had fuel come out the return line after I stopped the air. I opened gas cap to let air out to stop fuel from coming back out return line. So do you think tank is not vented good enough and after a while it's restricting return flow? Whats confusing is why does this problem happen after it's been running a while and not all the time. any help would be great. Thanks

 

[Chuck Leeper]

The vent line is the line to the charcoal cannister. Is it plugged off?

 

[frank700]

No it's plugged into the charcoal can but do not have line from can hooked up to a vacuum.

 

[frank700]

top

 

[Chuck Leeper]

Some thots/ideas:
1. Lines crossed at the hardline connections near the tank.
2. The vent is not working. Remove it from the canister, and insert a plastic fuel filter to keep the dirt out. Make sure it flows both ways. Drive w/ the gas cap loose, and see what happens.
3. If the gauge is in the engine compartment, and is filled, heat will/can affect the accuracy when the glycerin expands.

 

[frank700]

Put a vacuum hand pump on vent line that goes to the charcoil canister and could not pull a vacuum so it is clear. I think if lines were crossed I would have pulled fuel through that line with the pump. I should have checked this stuff before I blew the compressed air thru. I am going to try the loose gas cap once this damn weather clears. Thanks