How much pressure does a mechanical pump put out at idle?

[fussfeld]

How much pressure does a STOCK mechanical fuel pump put out at idle----say 400-600rpm?

 

[CSFJ]

60psi

 

[Frankenchevy]

I think csfj may be referring to a more modern efi electric pump. I think most stock carbureted setups like around 5-7 psi. I'd imagine they'd put out somewhere in that neighborhood.

gpm is another factor to consider.

 

[1987 GMC Jimmy]

People have complained about an output of up to 10 psi with the stock pumps, but they are supposed to be lower than that in a perfect world.

The ones that people have complained about are the Delphi pumps, but that’s what I run with an E4ME Quadrajet with no issues.

 

[yevgenievich]

4-5psi, but some that go above create problems by overpowering the needle in the carb

 

[Honky Kong jr]

60psi

Oops it’s gonna get messy you forgot your period.....

 

[fussfeld]

But even at idle do they put out 5-7? Like at 400 to 600 rpms?

i'll get into why in a sec.

 

[78C10BigTen]

Oops it’s gonna get messy you forgot your period.....

I was gunna say that my eddy is ideal recieving 5-6 psi. but i looked to see a honky post.... and low and behold lol so say what you will...

 

[Frankenchevy]

Iirc, when I had an in-line pressure gauge between the mech pump and carb; it would fluctuate with throttle blips. Who knows, maybe that pump was tired. One would think that higher rpm would change flow of the pump, but I’m not sure about pressure. The return line alleviates accumulation, and it was before the pressure gauge. Also the float bowl is more quickly drained at WOT. So with fuel flowing into the carb more readily, you’d think pressure would even out or lower, but not gpm—it should increase.

 

[75gmck25]

Its been a long time since I put the gauge on my fuel pump line, but IIRC the pressure didn't vary that much with RPM. It had at least 4 psi all the time, and peaked at about 6. My pump has a return line to the tank, so maybe that helped stabilize pressure.

Bruce

 

[WHEELMAN]

The V8 engines in the Z28 their fuel pump had the deeper.deal under them.for extra volume.so at high speed.you did not starve the carb.of fuel.