Double Pumper base pressure question


Well-Known Member
Jun 26, 2001
Ok.. this is for guys that are running double in-tank pumps.

I'm trying to do a "rule of thumb" diagnosis on a fuel system.

Can you engage both of your fuel pumps with the key on, motor not running and tell me what your base fuel pressure does? What was your base pressure and what does it climb to?

My friend's car bumped up 5psi from the single pump base. I expected it to climb much more than 5psi because of the limited relief/return on a stock fuel lined car.

I understand that the "best" diagnosis is flowing the pumps, but that's hard to do correctly at full pressure.

Thanks in advance for your help.
base 45 one pump
both engine cold 54
both when warm operating temp 50

twin 340s hotwired , stock lines feed and return , accufab regulator

remember thats at battery voltage
now start the car and voltage will be almost 14v to the pumps , i see nearly 60 with both on ,running ,line off
i run a VB so thats over 15v above 10psi

i have both pumps on a switch (separate switches actually mounted in the ps bracket ) so i can check regularly to be sure one isn't getting weaker than the other
The pressure shouldn't climb a bunch IF your regulator is able to keep up. The primary reason you want the pumps "staged" because the 340's or other aftermarket pumps are too much for the stock system for them to be running all the time.

I run a pair of stock pumps (old ATR setup). and when turning on the second pump with the engine idling, the pressure gauge shows a little flicker upward but immediately returns to normal pressure. The two stock pumps are more than enough for my setup, but not so much as to overwhelm the system.
This is the rule of thumb reply I was looking for.

Thanks guys. Helps a bunch.