87 F150 Won’t Start

[Mhfco6]

Bad selector meaning, the dash switch or the assembly in the frame rail? If you could help me troubleshoot Tank A and get it working that would be great! I'm currently trying to get the truck running again so I can get back to fine tuning the timing and move forward with the restoration. I cannot hear Tank A pump running but I CAN hear Tank B Pump running. As I mentioned there is no fuel from either tank supply lines when key is ON and tank selector switch is toggled.

You mentioned slim chance of both tank pumps crapping out at once. This truck has been sitting since 2008.

 

[rusty ol ranger]

Bad selector meaning, the dash switch or the assembly in the frame rail? If you could help me troubleshoot Tank A and get it working that would be great! I'm currently trying to get the truck running again so I can get back to fine tuning the timing and move forward with the restoration.

Im not sure on how to really troubleshoot that...but...

If the gauge goes straight to full its grounding out. Im going to make a educated guess that it grounds through the selector switch (more then likely the frame valve), because it would make sense to "switch" grounds between the front and rear tanks when changing tanks....ya follow me?

Im not real sure...ive never had an issue with the electronic valves. I would maybe replace the valve and clean up the wireing surrounding it before going any deeper.

 

[Mhfco6]

The switching valve in the rail isn't electronic. Its all mechanical and switches using the in tank pump pressure. The switch on the dash electronically controls the tank pumps, and whichever pump is running sends pressure to the selector valve in the frame rail.

I found that the selector valve only wants to work properly, OR is stuck in the front tank supply position. I had cleaned and tested in using compressed air and was only able to find air flowing out of the selector valve when applied to the front tank inlet.

 

[rusty ol ranger]

The switching valve in the rail isn't electronic. Its all mechanical and switches using the in tank pump pressure. The switch on the dash electronically controls the tank pumps, and whichever pump is running sends pressure to the selector valve in the frame rail.

Ok i musta misunderstood you. I thought they basically changed out the vaccuum valve on the frame for a electronic one.

Possible it is the dash switch then. Cause thats pry one of the first stops for pump power.

 

[Mhfco6]

This is great, quick responses almost as if we were talking face to face. Any quick tips for checking the selector switch in the dash?

 

[rusty ol ranger]

This is great, quick responses almost as if we were talking face to face. Any quick tips for checking the selector switch in the dash?

No, ive never had one go bad lol. Id hit up a junkyard buy 2 or 3 (im sure theyll be cheap) and see what happens. 92-96 switches should also work if they plug in for testing puposes...but look for 87-91s

 

[Mhfco6]

No, ive never had one go bad lol. Id hit up a junkyard buy 2 or 3 (im sure theyll be cheap) and see what happens. 92-96 switches should also work if they plug in for testing puposes...but look for 87-91s

After watching a video, its seems possible that all the fuel that was being used from the rear tank was then getting returned into the front tank, via the problematic tank selector valve in the frame.

 

[rusty ol ranger]

After watching a video, its seems possible that all the fuel that was being used from the rear tank was then getting returned into the front tank, via the problematic tank selector valve in the frame.

Thats also possible. And more common then a dash switch.

Thought you looked into that though the first go round?

 

[Mhfco6]

Thought I did. But someone noted they had an issue where the selector valve was stuck in the rear tank operation like mine. He switched it over to run on the rear tank but the valve pushed all the return gas into the front tank. I have the selector off sitting in the garage, ill have to play with it again using compressed air and see what its doing.

I also read that using more than 5psi of compressed air will rupture the diaphragm. Whoops.

 

[rusty ol ranger]

Thought I did. But someone noted they had an issue where the selector valve was stuck in the rear tank operation like mine. He switched it over to run on the rear tank but the valve pushed all the return gas into the front tank. I have the selector off sitting in the garage, ill have to play with it again using compressed air and see what its doing.

I also read that using more than 5psi of compressed air will rupture the diaphragm. Whoops.

Id replace the sumbitch.

Yeah there pricy but then ya know.

 

[Mhfco6]

Need to make sure my in tank pump(s) aren't gone too. Troubleshoot, or just assume since no flow out of the lines, they are shot even though they are hummin'.

 

[RonD]

Found this wiring diagram for the switch and pumps: https://cimg1.ibsrv.net/gimg/www.fo..._71076ad56547a7f1434de453ee5f5cc5f29245da.jpg

Yes, it does look like the fuel pump power from inertia switch passes thru the switch and to either front or rear pump
The canister just has check valves that prevent back flow or out flow on returns

You should be able to Ground the fuel pump relay full time at the OBD1 connector in engine bay, then you can test for fuel pump voltage at the switch and High Pressure pump

 

[Mhfco6]

Perfect, I have printed this out. I was playing around with the OBD1 connector under the dash and got one pin to light up with my test light. I didn't hear any of the fuel pumps kick on. Do you know which pin needs to be grounded. If this pic is correct, ill try that pin shown.

 

[RonD]

Fuel pump relay ground is labelled here: https://www.therangerstation.com/tech_library/OBD_I.shtml

That slot should show 12v with key on
When slot is grounded(jumper wire) fuel pump relay should "click" closed with key on, and fuel pumps should come on full time, well until key is turned off

Your picture is labelled correctly for fuel pump slot

 

[Mhfco6]

Fuel pump relay ground is labelled here: https://www.therangerstation.com/tech_library/OBD_I.shtml

That slot should show 12v with key on
When slot is grounded(jumper wire) fuel pump relay should "click" closed with key on, and fuel pumps should come on full time, well until key is turned off

Your picture is labelled correctly for fuel pump slot

I may need some help with this. I put my meter on a fuse with power and ground probe in the fuel pump test hole. Fuel Tank A was 0.31, Fuel Tank B was 0.33. The dash tank switch was hot on Tank B but got no signal from Tank A. Where do I need to put the jumper wire?