93 f150 dual tank fuel pump issue

[black_demon69]

I know not a ranger I have a 93 f150 4.9l with dual tanks and the front tank runs great without issue when you switch to the rear tank it will run fine for a min or 2 but then seems to loose fuel pressure until you swap back to the front tank. it will idle all day long on the rear tank just can't drive it. both pumps are new fuel filter is new fuel pump relay is good.. when I check power to the rear tank it is @ about 14 volts running.. any Ideas ?

 

[lil_Blue_Ford]

Hate to say it but check the fuel pressure the rear pump is actually putting out, I have had new pumps that are bad out of the box.

 

[black_demon69]

Hate to say it but check the fuel pressure the rear pump is actually putting out, I have had new pumps that are bad out of the box.

just replaced it again forgot to mention that

 

[black_demon69]

i cleaned connections there are no leaks..

 

[alwaysFlOoReD]

Check the fuel tank selector solenoid. They get old and can stick partially open or closed.

 

[black_demon69]

Check the fuel tank selector solenoid. They get old and can stick partially open or closed.

no solenoid in this system switch simply turns off one pump then turns on the other there are flow back valves on each pump

 

[Eddo Rogue]

DId you replace it with the same pump from the same store again? If so You might have gotten 2 bad pumps out of the box. Maybe try a different brand from a different store. or maybe even swap in the front pump that you know works and see if pump is the problem.

 

[black_demon69]

DId you replace it with the same pump from the same store again? If so You might have gotten 2 bad pumps out of the box. Maybe try a different brand from a different store. or maybe even swap in the front pump that you know works and see if pump is the problem.

different store and different brand
what is currently in the rear tank is a carter

also pumps are different

 

[black_demon69]

could it a bad ground ?

there is NO rust as this is an Arizona truck

 

[Roert42]

Check the fuel pressure on both tanks. At idle and while revving the engine. Confirm for sure it’s a fuel issue. Otherwise we are just guessing.

Then, it we confirm it’s a fuel issue. Measure voltage at the leads connecting to both the fuel pumps to be sure the fuel pumps have the same voltage.

If the voltage is low at one pump, find the bad connection.

If the voltage is good at both the pumps, we have an issue with flow between the pickup and wherever the two lines from the fuel pumps meet.

 

[black_demon69]

found the issue took apart and cleaned valve

on the front tank...

 

[alwaysFlOoReD]

So how did the front tank valve prevent fuel flow from the rear tank?

 

[black_demon69]

was dirty and letting fuel pass into the front pump

 

[alwaysFlOoReD]

was dirty and letting fuel pass into the front pump

Do you have a link to a pic that shows the whole fuel system?

 

[black_demon69]

I do not
what I know about it is from tracing lines back and figuring out the wiring.

-----FUEL PRESSURE REGULATOR--------FILTER--------|--------------FRONT TANK/FUEL PUMP
|----------------------------------------------------------------REAR TANK/FUEL PUMP

There is no valve between tanks just a Y in the fuel line. Each pump on the outlet has an anti flow back valve like the one pictured above.