My 1991 F150 won't start. Dual tanks, 2 fuel pumps. I can hear the fuel pumps run but don't get fuel to the intake. Fuel filter is clean. I can hear a vacuum leak near the intake where there is a small vacuum pump but can't pinpoint the leak. I'm not sure why neither fuel pump will get gas to the intake. Any suggestions?
I should add that this has been an intermittent problem but has gotten worse.

 

Provided there is fuel in each tank, for sure, then the next step would verify that you have a pressure reading, off each tank, at the fuel rail.

There is a vacuum operated fuel pressure regulator on the intake manifold, near the coupling of the fuel lines to the fuel rail, that sounds like it may be worth a look.

 

I think the FPR is probably the problem. It's a bear to change since the mounting screws are upside down!

 

I would dough the FPR is the problem. The way they go bad most of the time is they leak fuel into the vacuum line going to the intake from the nipple on top of the FPR.

You more than likely have fuel pressure to start the engine so I would check to see if you have spark when it does not start.
If you have spark then I would change the PCM Computer.

 

No fuel to the intake?

or

no pressure in the fuel rail?

Testing required narrow down the cause would differ.

 

I can hear a vacuum leak around the FPR and the fuel pump won't shut off. I don't think it's an electrical problem because when it starts( less frequent know) it will run rough for a few minutes then smooth out and usually will start back up again unless it sits for a few hours or overnight.

 

A vacuum leak at the FPR will cause higher fuel pressure for a max of 40psi.
I would say you need another PCM Computer.
When the fuel pumps are running all the time the engine will not start will it?

 

No, as soon as it shuts off, it will start.

 

That says bad computer.
Open it up and see what it looks like inside.
You may be able to replace the caps and then it may be OK.

 

Ok where is the PCM computer?

 

It is located in the drivers kick panel. You will have to unplug it from under the hood and then take it out at the drivers kick panel inside the cab.

The plug has a 10mm wrench size bolt in the middle:




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Ok Thanks for your help!