Gun Jam

Ive got what I think is the original fuel line that runs from the tank to the fuel pump. Im not sure how nasty it is inside or any of its history.

The issue im having is reduction in fuel pressure under load. I dont believe the fuel pump is bad.

The issue is worse with heat. When carb body temps get up past 120f and parts have been heat soaked for a bit say in traffic. Its very easy to run fuel pressure down to below 3psi.. Its for sure enough to cause fuel mix issues. Its most obvious under load but can occur at idle as well.

When its 38f out and ive got frost accumulating on the carb body its not an issue but under load I do see fuel pressures drop off maybe more than I would like.

Its a 9psi pump thats regulated to 6.25lbs and can support 120GPH. So the pump its self should easily keep up with engine demand.

If I wanted to improve flow and reduce the work on the pump and help overcome some of this heat problem I could do this with a larger fuel line right?

From the pump to the carb I am running all 3/8th line (6/16th) and -6 an hose and fittings. But the tank to carb is running 5/16th which maybe slighly obstructed or have increased resistance.

Im guessing my best bet is to run fresh 3/8th stainless steel line from the tank to the pump. I am also considering replacing the fuel sender with one that has a 3/8th output.

Any other suggestions?

Thanks

bop11

At 10 gal/hr you will get a pressure drop in an 8 foot 1/4 OD pipe of about 1.6 psi. At 20 you will lose 6.9 psi approximately and that is in a clean pipe. So make sure the pipe is clean.