I have a strange problem maybe somebody can help me with. I have a fuel pressure gauge mounted on the dash. When I start my engine I have 15 lbs of fuel pressure. As soon as I drop it into gear (Automatic) the fuel pressure immediately drops to less than 5 lbs, the engine briefly stalls, and then the pressure jumps back up to 15 and everything is fine. This all happens in two to three seconds. When the pressure drops the engine stalls for just a second or two, not long enough to stall out. Sometimes the pressure will drop two or more times within a few seconds. This only happens right after startup. It does it either cold or hot. Under full load towing I have 10 lbs of pressure. Any ideas?

 

It sounds like a loose wire on the sending unit. Check your connections at the sensor, if you are using an electrical gauge. Mine did that untill I figured out that the engines initial torque and a bad connection was the problem.

 

I neglected to mention that the guage is mechanical. Thanks for the reply though.

 

You may have a wiring problem, or dirty connection, to your lift pump. The symptoms you describe sound like the connection gets broken to the lift pump for a second when you put it in drive. This could be caused by the engine twisting a little. I suggest having someone watch the gauge while you wiggle wires going to the lift pump.
The alternative, since this is driven by the ECM, is there is a computer problem. Let me know because I have an extra, but it is a 48 state-legal, not a Cali.

Chris

 

Check for air in the system also. Sitting over night the air gets in, with the need for fuel more than idle, gulps it. That would be from my experience to be an air leak past the pump, like in the filter area. Remember one thing that old detriots were famous for, a leak small enough for air but not large enough for fuel to leak from will cause havoc. Detroits used to do this in the lines between the pump and the head(s), never leaked a drop but would pull air with the engine off.

 

I think Stamey hit the nail on the head, sounds like loose/corroded wiring or connector at the lift pump.

 

Thanks for the input everybody, I will check this out. I may have a very small leak because sometimes I get a diesel smell in the cab for just a second. I haven't seen any other symptoms of a leak.