1989 F250, 7.5 EFI, 39K original miles....yes, 39K original. Used mostly to tow my fifth wheel. Can sit for up to two weeks at a time. Truck is in fantastic condition.

First, a little background. I'm driving one day, and I switch tanks. It runs another mile or so then quits. I'm only two blocks from home, so I walk home and call for a tow truck. I walk back to it, and it starts right up and I drive it home. No problems for another month or so.

I go out to drive it, no start. I check fuel pressure on schrader valve, no fuel pressure. I pinch off the return line, and it cranks right up. Ahhh....regulator, right? Maybe not. It's then when I notice every time I go to start it, there's a groaning noise, which I discover is the high pressure pump (can feel it vibrating). OK, time to replace the pump.

Today, I replaced the pump with a new Ford dealer unit. I hook up my pressure gauge, it has 36 lbs. Starts and runs fine, no problems. I take it out and drive it about 7 miles. About a mile from home, I switch tanks (both are full). When I pull into my driveway, I notice a vibration and noise, which is coming from....(drum roll please)....the high pressure pump. The truck promptly dies and won't restart. Lucky devil, aren't I??

No fuel pressure. When I turn the key on, it primes the pumps for two seconds, or I can ground the test terminal and they all run continually (I can feel the H/P pump running, and can hear a slightly different pitch when I change from front to rear). I pinch off the return line, nothing. Switch tanks back and forth, nothing.

I'm starting to think I missed the target on this one. I hate replacing parts until I'm 99% sure they're bad, but I think my noisy H/P pump was a symptom, and not a problem. It's quiet as it should be now, but no fuel pressure.

The only common denominator I can come up with is that it seems to happen most when I switch tanks. Changing H/P pumps did nothing, I can hear the relay click and prime the pumps, it just won't build pressure. I figure that if it was one of the in-tank L/P pumps, it would start when I switched to the other one. The odds of both L/P pumps quitting at the same time are.....well, it just doesn't happen.

Where do I look next? Is there any feasable way to test the switch on the frame rail (the one with 4 hoses entering and two leaving) to see if it's faulty? Would it produce the symptoms I'm having?

TIA....any help is greatly appreciated.

Dan

 

I had some simular problems, I have a 88 F150 5.8 engine. The repair manual says that the selector valve is servicable, that there is a filter in it. I took mine apart and there was no filter and I replaced the O-Ring and put it back together and now it works. On my truck the top hoses are for the rear tank, I think it is the blue hose and the gray is to the front tank.
I ran out of gas with gas in the rear tank, now I only run off the rear tank. My gas gauge does not work nor does the speedometer so I am always getting gas. I probally have the front tank almost full as well but I just am not good with electrical problems and am stuck with what I have. The fuse is pulled to the dash and when I install it, the gas gauge pegs out. All the other gauges have been relocated under the ashtray with sunpro gauges.

 

It is?? My Haynes manual says the selector valve should be replaced if it fails any of the prescribed tests. Is your valve electrically operated, or pressure operated?

At any rate, I'm gonna pull it off the truck in the morning and run the tests on it. I'm seriously hoping that this is the problem, as I'm running out of things to look at. Thanks for the reply....

Anyone else have any input or wisdom they care to share?

 

It is electricly operated. The dealer now only sells replacements that are not servicable. Mine, the bottom just screws off. Good luck to you.

 

Some of the later 80's 150 and 250 have a recall for the fuel selector valve,
(91S39 DEC 91 Recall - Fuel Tank Selector Valve Replacement )
I had alot of trouble with my 87 150, my switch ended up being the problem, when it would cut off I could toggle the switch back and forth while turning the key off and on and hear when the hi pres pump drew gas into it

 

Ray......turns out mine is mechanical. Must have been the difference in year models....

In any event.....IT'S FIXED!!!!!

It was the fuel tank selector on the frame.....or dual tank reservoir, in Ford parlance. When I pulled if off, I tested both low pressure tank pumps for flow and they passed just fine. But it was then I noticed that pulling the reservoir off, there was no fuel on the high pressure exit side. I ran the tests that the Haynes manual calls for and the reservoir failed all of them.

Anyhow, a quick trip to Casa Ford, and my truck is running and my wallet is $103 lighter. What sucks is I misdiagnosed it the first time and wound up spending $191 on a H/P fuel pump I didn't need. Oh well, live and learn. I a pretty decent wrench, but this was my first foray into dual tank EFI systems, so I can pass it off as a rookie mistake. And as my wife said, it was still $200 cheaper than taking it to the dealer to be fixed. Plus I got to learn a little about my truck in the process.


Jhn....I did read about the recall, but what it involved was the internal check valves failing and siphoning fuel from one tank to the other. Mine wasn't doing this. I might have been able to fight with Ford to at least get the part for free, but for $100, it ain't worth my time. Plus the guys at Casa Ford are great to deal with and I don't want to burn any bridges.

Thanks for the help guys.....now time to go hook up the fifth wheel and get ready to head for the mountains....

 

BTW, same symptom Jhn.....I could hear my H/P pump gasping for fuel. I originally mistook this for a failing pump and replaced it. The learning curve gets pricey sometimes....

 

Thank you for the update, updates as to what the problem actually was are as valueable as the post of answers to the problem. I am glad you got your problem solved. I had a good day with my gauge problems as well and now at least know what is in the rear tank. That is good enough for me.