My carb. and fuel pump set-up works well in cool weather, but in 80 plus degree temp the fuel pressure drops off to 0 @ about 4000 rpm in second @ wot. This causes the car to fall flat until the throttle is released. It pulls well to 5500 in first. The stock mechanical fuel pump was replaced with a 70 gph carter electric pump mounted back by the fuel tank and the fuel lines are insulated. The fuel filter is new and the a.v. tension has been adjusted up and down but the problem still persists. Any thoughts? Thanks. Mods to 86 TA- GMPP 300 h.p. crate 350, rebuilt q-jet from 83 350, dual snorkel air cleaner + fresh k+n, port matched zz4 intake, pocket ported heads, comp cams 268 xe cam, edelbrock tes + cat-back.

 

fuel pump starting to go out or not enough volume for your motor.

 

I have that pump on my Malibu right now. 72 GPH, 7 PSI, internally regulated, right?

How do you hold pressure up at the carb at all? If I run mine by itself (also mouted by the tank) fuel pressure will drop off as I accelerate as the weight of the fuel fights against the (fixed) pressure the pump is capable of producing. The fact that it happens only in 2nd gear is even more mysterious EXCEPT IF YOU TYPICALLY SPIN THE TIRES PRETTY GOOD IN 1ST GEAR.

I run this same pump but also a block-mounted mechanical pump. This basically has the effect of making the electric pump just a "booster" to get the fuel up to the mechanical (against the force of acceleration), and the mechanical pump pushes it up to the carb AND ALSO REGULATES THE FINAL PRESSURE.

This combo of pumps on my Mailibu results in DEAD SOLID 6PSI at the carb inlet right on into the 11s.

 

BTW- regardless of all that, above, remember that pump is rated at 72 GPH FREE FLOW. It is NOT rated 72 GPH @ 7 PSI.

It's not a a really huge pump.

 

Thanks for the advice Damon. Yes, the Carter is 72 GPH, 7 PSI, internally regulated. I will re-install a mechanical pump and see what happens. The warm weather is still several weeks away up here.