Fuel Pump Pressure with Two Pumps - Two Pump Ranger

[Mader86]

Just pressure tested my 86 2.3L Ranger, and the fuel pressure at the rail is 32psi at idle (38 on key on, drops to 32 when running).

The service manual that came with the truck says that the psi reading should be 40! So, I guess I need a pump (I am having fuel pump-like problems that led me to check it), but WHICH ONE. There's a low-pressure in the tank, and a high-pressure on the frame rail below the cab (so I've been told). How do I determine which pump?

Any/all help greatly appreciated!

 

[BRUTUS_T_HOG]

that would be the high pressure pump on the frame. how old is your fuel filter? a clogged filter can drive the pressure down.

 

[Mader86]

The fuel filter was the first thing I checked - replaced it with a new Wix cartridge! No change...

 

[Mader86]

Sooo.... the low pressure indicates that the high-pressure pump is at fault?

 

[BRUTUS_T_HOG]

yes, the low pressure pump in the tank supplies the fuel for the high pressure pump to deliver fuel to the fuel rail

 

[martin]

The fpr drops the fuel pressure when vacuum is applied to it so around 30 at idle would be about normal. If you pull the vacuum line whilst idling the pressure should go up to approx 40. if you pinch off the return line the pressure should climb above 40. If the aforementioned things happen I would start looking elsewhere for the problem.

 

[Mader86]

Makes sense...thanks!

The truck seems to lose power at cruising speeds, and "wicking" to accelerate the pedal makes it sort of catch-up and run normally again. I thought that the fuel pump might be starving the engine for fuel...

 

[Mader86]

OK - Martin, ran the tests and everything falls into line. SO, I put a tuneup on it, new plugs, wires, cap, and rotor, and the sort of "surging" thing went away. The wires were NOT tightly snapping onto the plugs (quite loose actually), so I guess I had an ignition thing going on there!

Thanks all for the help on the fuel pump diagnosis!!