Intermittent fuel issue
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4wd Low
Joined: Jul 2017
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Intermittent fuel issue
Alright, I'm in a puzzlement. First, I've got a '84 F250 4x4, 460, 4v, dual tanks. Coming back from camping this weekend it just died while moving. It started back up after a couple of minutes and ran for about a minute. It did this several times, and ran a shorter amount each time. I finally had to get towed home. I went out this morning and it fired right up. Only to die again after a couple of minutes.
So, I pulled off the air filter and looked down the carb while opening the throttle. No fuel pumped out of the jets. It will start up if I put gas directly in the carb (so I don't think it's the oil pressure switch. although that just cuts power to the fuel pump so it still could be). So, I waited a while, primed the carb and it stayed running for about a minute. Then, I pulled off the fuel line and hit the starter, no fuel was pumping out. So, I waited a while again. Hit the starter and it pumped a bunch of fuel.
It doesn't matter which tank I'm on, it does the same thing. And, I followed all the gas lines and didn't find a fuel filter (which seems odd). Right now I am totally clueless as to what is going on. I don't have too much experience working on these rigs, so I'm hoping one of you with more knowledge than I have an idea what is going on. Or hopefully, you'll laugh at me for being a moron because it is something really simple.
The road was pretty rough and washboarded, inertia switch?
Any help is greatly appreciated.
So, I pulled off the air filter and looked down the carb while opening the throttle. No fuel pumped out of the jets. It will start up if I put gas directly in the carb (so I don't think it's the oil pressure switch. although that just cuts power to the fuel pump so it still could be). So, I waited a while, primed the carb and it stayed running for about a minute. Then, I pulled off the fuel line and hit the starter, no fuel was pumping out. So, I waited a while again. Hit the starter and it pumped a bunch of fuel.
It doesn't matter which tank I'm on, it does the same thing. And, I followed all the gas lines and didn't find a fuel filter (which seems odd). Right now I am totally clueless as to what is going on. I don't have too much experience working on these rigs, so I'm hoping one of you with more knowledge than I have an idea what is going on. Or hopefully, you'll laugh at me for being a moron because it is something really simple.
The road was pretty rough and washboarded, inertia switch?
Any help is greatly appreciated.
Laughing Gas
Joined: Apr 2013
Posts: 1,047
Likes: 63
With the key in start and the starter engaged the fuel pump gets power from the small I terminal of the starter solenoid. Since you get fuel with the motor cranking it sounds like this circuit is working.
The main fuel pump power supply starts at the big hot lug on the starter solenoid and the first thing to check is the 20 gauge fusible link to make sure it’s not burned.
Next check the inertia switch which is over on the passenger side kick panel up under the dash. It’s desiged to cut the power to the fuel pump in the event of a crash and if its tripped the little button will pop out. If the button is popped out push it back in. You can also unplug the inertia switch and jump the two terminal of the plug together and bypass this safety device altogether.
Next you you can check the oil pressure switch circuit. The oil pressure switch is on top of the motor back by the fire wall underneath the oil pressure sender (if you have a gauge). You can unplug the switch and you should have power on one of the wires with the key in the run position. If you don’t have power then you may have blown a fuse.
If you do have power at the oil pressure switch with the key in run you can jump the two terminals on the plug together and the pump should run with the key in the run position.
If all that that is good but the pumps still don’t run you can check for power at the fuel pump relay. The main power supply from the starter solenoid should be hot all the time and if you’ve jumped the oil pressure switch you should have power on that wire too. If that checks out try replacing the fuel pump relay, they’re pretty cheap.
Good luck, let us know what you find.
The main fuel pump power supply starts at the big hot lug on the starter solenoid and the first thing to check is the 20 gauge fusible link to make sure it’s not burned.
Next check the inertia switch which is over on the passenger side kick panel up under the dash. It’s desiged to cut the power to the fuel pump in the event of a crash and if its tripped the little button will pop out. If the button is popped out push it back in. You can also unplug the inertia switch and jump the two terminal of the plug together and bypass this safety device altogether.
Next you you can check the oil pressure switch circuit. The oil pressure switch is on top of the motor back by the fire wall underneath the oil pressure sender (if you have a gauge). You can unplug the switch and you should have power on one of the wires with the key in the run position. If you don’t have power then you may have blown a fuse.
If you do have power at the oil pressure switch with the key in run you can jump the two terminals on the plug together and the pump should run with the key in the run position.
If all that that is good but the pumps still don’t run you can check for power at the fuel pump relay. The main power supply from the starter solenoid should be hot all the time and if you’ve jumped the oil pressure switch you should have power on that wire too. If that checks out try replacing the fuel pump relay, they’re pretty cheap.
Good luck, let us know what you find.
Thread Starter
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4wd Low
Joined: Jul 2017
Posts: 14
Likes: 0
Thank you Brnfree! I finally got time to look at it today. I had no idea how that complete system worked, or where the parts were located. But today I got it all scoped out and now pretty much understand it. I was about to start tearing into everything, but then something in your message made me think KISS. So, it took a while (Haynes manuals are pretty worthless on some things, and the owners manual didn't show it) but I figured out where fuse 18 is located. Burnt. Changed it and now it runs perfect.
Thanks. I feel like a moron but I learned a lot.
Thanks. I feel like a moron but I learned a lot.
Laughing Gas
Joined: Apr 2013
Posts: 1,047
Likes: 63
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