samaf

I posted this on the emergency section but later thought i would post it here also. I just installed a fuel pressure gage and my pressure seems to be low. At idle I have 10 psi and at speed 8-10 psi. With hard acceleration it goes to 4-6 and stays there until I let off the throttle. Is this a sign of a transfer pump going bad? I have a 1999 3500 and the engine is stock.

Thanks in advance.

Dr. Evil

Yup you need a lift pump. 4 psi is getting pretty low.

Airdog, Mitusa, Fass - your choice. Do not get the intank pump.

Busboy

While 4 psi is getting low I would change the filter first. New the stock pump is only 11 psi at idle and 5-6psi at WOT so its not that far off stock and perhaps a dirty filter is causing the pressure drop.

Midnite

If the fuel filter change doesn't improve things, I wouldn't mess with a stock lift pump replacement. If it were me I'd look at one of the heavy duty aftermarket ones like a FASS or Airdog. I have an early FASS 150 on my 2000 truck and get a rock-stable 16psi whether it's idling or 3000 rpm full throttle.

One thing you have to remember is that the injection pump relies on a certain amount of excess fuel from the lift pump. This extra fuel flow cools the pump, and since it sounds like you have a stock injection pump with the early electronics this is something you should be concerned with. The heavy duty aftermarket pumps provide a much, much greater volume of fuel vs. the stock pump.

Mike