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View Full Version : LIFT PUMP PRESSURE



Scooby
02-14-2005, 06:45
I wanted to check my lift pump pressure, so I put a gauge on the end of the water drain hose and read it there. Engine off, it peaks at about 5.5 . enging idling, it reads 4.5 . rev it a little (in park) and it drops to 2 or less. I thought maybe my Dahl 3 micron filter might be restricting it a little, so I bypassed it. No change in pressure.

Is the lift pump supposed to maintain the 4.5 psi?? I checked the factory manual, and it doesnt say. It just says to check pressure, then check flow in a container. No running pressure check.

Before all my mods, I used to get a lot of smoke under acceleration. Now I dont see much smoke. Maybe now there is enough air to burn all the fuel. Also, I havent towed anything heavy, and dont have big hills in Fla to really put it to it. When I stomp it, it just goes. I look down, there goes 85---90---95... then some. EGT doesnt go too high with no heavy load. Just want to make sure the fuel is there if I want it.

AndyL
02-14-2005, 08:26
My GM lift pump holds about 12psi with engine off and about 3-4 PSI at full throttle. Maybe 8 or so idling.

Scooby
02-14-2005, 09:24
ANDY- Where did you hook the pressure gauge? I wonder if I am getting an accurate reading going thru the water drain. I also have about 14000 miles on the factory fuel filter, but it is downstream of my Dahl 3 micron filter, so I dont think the factory filter is plugged. Is your full throttle pressure under load, or just sitting still ???

AndyL
02-14-2005, 10:30
My measurment is on the water drain. 3-4 is under 100% load. Taken with a newer OEM fuel filter.