air pressure in fuel tank

[csandifur]

What would air pressure in fuel tank mean? I had completed the FTB mod all new 3/8" supply / return lines and new PMD with #9 resistor I have 5lbs(wot) 9lbs(idle) fuel pressure at IP, no problems, got more power/fuel but notice air pressure when opening the fuel cap.

 

[dka99burb]

It's probably vacuum. May need a fuel cap. Mine typically had a little vac when I opened the cap. Not enough to be a problem.

 

[Burning oil]

X2

Welcome to TTS.

 

[THEFERMANATOR]

The diesel caps will let air in, but not out. So if the fuel in the tank warms up it will expand and pressurize the tank.

 

[csandifur]

Thanks Guys