Hi guys,
TYhis is really werid I just bought this car. Drove it home 125 miles and it was fine. now when it's on level ground it has 11 psi fuel pres. Then I jacked it up to change the fuel pump because it was acting weird. When the rear of the car is up on jack stands the pressure is 45 psi. Did some thing fall off in the tank or is the sending unit faulty? The fuel guage does not read correctly either. Any help would be appreciated.

 

Sounds like a weak fuel pump, broken strainer may have sucked something up, or the fuel filter may be plugged. Start with the easiest first. Did you check it idling or WOT for the 45psi? Is the gauge on the schrader valve where you found the 11psi?

 

11 psi @ schrader valve on intake. brand new fuel filter. Fuel pres goes up to 45 psi @ schrader valve when car is on 2 foot jack stands. these reading were taken whth car at a running idle.

 

Is this 11 psi and 45psi with the engine running?
If the psi stayed high after letting the car down, I'd suspect something is getting past the filter sock, or the sock has deteriored, and is being sucked into the pump. change the sock while you have the tank out.

Depending on the type of sending unit, keeping the tank filled to a particular level for a long time can wear a spot in the sender windings causing false readings.
Be sure to do a flow test. Attach a hose into a container from the junction at the frame near the power steering pump from the return line coming from the fuel rail. The flow should be aprrox. 1 gal in about 4 minutes. or 1 pint in 30 seconds.

 

With the car on jack stands 45psi @ idle. let the car down that psi craps out to around 11 psi, jack it back up it pegs 45 psi and smooths out.

 

Your pump is ready to die on you. Keep it jacked up next time and get a new pump in there.

 

At 7lbs/gal a full tank will be quite heavy so use the ALDL connector pump test terminal to pump out as much fuel as you can while it's on jeck stands.
Disconnect the tank side of the fuel filter and connect that line to a hose into a container and apply 12v to the aldl "G" pin with the ingnition off, run it until it the fuel stream begins to sputter.