Greetings everyone! I have a new to me 89 f150 with the straight 6 that I got for a grand.

it had fuel issues when I picked it up but I was able to get it running (ish) so now it’s my project, just in time for the snow!!

So here is the issue: at first it seemed it would only run on the the rear tank which was pretty much empty. I put a fuel gauge to it and I would not get the 40-50 psi with KOEO. Sometimes I would get it running on the rear with KOER on the REAR tank it would get about 45 psi when it would run. Looked under the dash at the fuse pane and the fuel tank selector fuse was missing (even though it’s mechanical) tried it anyway and bam I got 40 psi! It would run longer on the fist tank but only seemed to like the rear tank to stay running. Now I’m not getting fuel pressure on either tank. The fuse isn’t blown. If you have any ideas it would be greatly appreciated. I did the fuel pump test and all 3 pumps are working but the psi slowly rises and seems to stop at 30 psi. I used my gauge to try to bleed any air out while testing but didn’t help.

Here is what I’ve tried so far.
previous owner replaced i tank fuel pumps and fuel filter.
I have replaced:
Hp fuel pump
fuel tank selector switch
fuel tank selector valve
fuel pressure regulator
fuel pump relay
other non fuel related parts (chasing a vacuum leak)

The fusible link was replaced (not by me) with an inline fuse with a 15 amp fuse which was not blown. Is this something that should be changed to another style? When I pulled that fuse the pumps would not kick on, when I replaced it they would.

I bought this truck thinking it would be a fairly easy fix but I’m at a loss. I’m missing something. And I’m tempted to replace the other pumps myself but I’m getting tired of throwing money at something it could be.

 

Do you remember the name brand, and part # for fuel pressure regulator, your pressure should be 50-55psi running and go up to, 55-60psi with vacuum line removed from regulator.

 

Standard ignition.PR18I can’t even get it running right now. Hopefully it will stop snowing for a day or 2 and I’m going to remove the bed and check the fuel pump screen filters in the and see if I can clean out the fuel lines. It the only other thing I can think of right now. Maybe my lines are plugged. I had pressure issue before which is why I changed it.

 

I suspect the inline fuel pump. Sounds like the check valve in it is not working anymore.

 

I replaced it yesterday and no change. Unless the check valve is located somewhere else?

 

Interesting idea, bear with me. There is a piece on the fuel line after the filter, upper back behind the engine. I’ve included a photo of a fuel line with the piece. After some research I figured out it is a spring lock fuel line connector. It’s a little before the test valve. I thought it was a valve of some kind. I can’t find any info online but is it designed to close when removed? Or is it just an open hole with a locking piece to make disconnecting easier? If so maybe it failed close?

 

Are you sure you are getting 12V at the fuel pump?

 

its the wrong one but it would still start and run(idle may be like crap) see pic of different operating pressure, this is why it is always suggested to buy motorcraft, sometimes you need it up and going NOW!, and you do what is necessary, until you can fix right.

 

I’ll definitely take a look but right now I’m not getting fuel to start it up enough to even start it up. I’ll check the voltage and see where it’s at. But the pumps are working I’m barley getting pressure. I got a buddy next week helping me take the bed off and I’m going to look at the previous owners work on the in tank fuel pumps. I suspect he didn’t change the filter screens in the tank.

 

Pretty sure I solved the issue. Pulled the bed off and looked at the fuel pumps. Changed both assemblies. The front one wasn’t working at all even though I heard it running but it had no flow. Plus I believe the PO but the wrong assembly on. So I put got the one for the 19 gallon front which I believe is on mine. I had no clearance issues. It works hopefully I didn’t put the wrong one on but the pump works. The rear tank gasket was put on wrong and was spilling fuel out the top plus the plug was so rotted and cracked I ended up replacing it. So I also replaced the whole rear tank fuel pump to ensure it would not be in issue soon down the line. So hopefully this solves the issue. I have about 47 psi when running and it’s drivable. If I have more issue later I’ll definitely update you guys.