Other causes of low fuel pressure?

[RussJ]

I just finished up my DiPricol f/p guage install and the results have me wondering. With only 5 psi. at idle, the first thing that springs to mind is of course a bad l/p. But thinking more simply, could too much air in the system or some other install snafu be causing a low reading? The reading is solid and moves smoothly, not erratic at all if that matters.

 

[jelag]

If there is air in the system... . and the pump is pumping some air, than the pressure can be low... however if the pump is pumping fuel, the pressure reading should be correct. . All the air would do is serve as a shock absorber so to speak and would work its way out...



Hope this helps. .

 

[RussJ]

I can't think of any reason why there would be any significant amount of air in the system up to where I tapped the banjo bolt. There should be little or no air between the banjo and the isolater due to me bleeding it twice. Any trapped air would be between the isolater and the guage. Does that make sense?

 

[nickleinonen]

Any trapped air would be between the isolater and the guage. Does that make sense?

if you do have any air there in the line to the gauge from isolator, it too will cause low readings

 

[RussJ]

One other thing I just remembered, I mounted the isolater vertically rather than horizontally. Anybody else do it that way? Does it make a big difference?

 

[TMoe]

I would check your pressure against a mechanical test type gauge if it is possible. The 2nd gens had a nice test schrader valve on the VP. Why didn't they put one on the 3rd gens or is there one somewhere?