Start problems/1986 F250
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From: Fort Jones, Ca
OK. I've taken all you've given me and this is what I've come up with. The power does make it to the fuel pump relay, and should then go to the impact switch via a brown wire. The wire that goes in and out of the impact switch is yellow and there's no juice at the switch, which would explain why there's none at the fuel pump either, correct?
I inspected the FPRelay and couldn't see anything that needed attention, including corrosion. I did figure that maybe the relay was bad, so I bought a new one, but it didn't do the trick either. That's where I'll stop throwing parts at it.
I'm stumped.
Might be a good time for a traveling mechanic.
I inspected the FPRelay and couldn't see anything that needed attention, including corrosion. I did figure that maybe the relay was bad, so I bought a new one, but it didn't do the trick either. That's where I'll stop throwing parts at it.
I'm stumped.
Might be a good time for a traveling mechanic.
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From: In my own world
You have a blown fuseable link. It comes from the solenoid, and is behind the battery
There are several of these tied together.
They look like a regular wire with a splice in them. The purpose is for them to melt like a fuse when you have a short.
tug on them, and if the wire stretches, you have found the bad link
There are several of these tied together.
They look like a regular wire with a splice in them. The purpose is for them to melt like a fuse when you have a short.
tug on them, and if the wire stretches, you have found the bad link
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From: Virginia
Not the greatest diagram, but it's free. Start at the middle of the diagram at the top(fuel pump relay), and work your way back down. You will run into the fuel pumps going down in the middle of the diagram, and the computer is to the right of the diagram which powers the relay.
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From: Fort Jones, Ca
I was thinking about doing that today, but decided it would be smarter to see what you guys had to say. Sometimes, things that seem like a good idea, don't always end up that way. For me anyway.
I'll try that tomorrow and see what we get.
I'll try that tomorrow and see what we get.
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From: In my own world
Does the truck still have the factory battery ends on it?
There is a wire, that comes out of the harness, at the core support, and goes to the neg post on the battery.
Many times people replace the terminal, or cable, and forget this ground wire. It controls the fuel pump circuit.
There is a wire, that comes out of the harness, at the core support, and goes to the neg post on the battery.
Many times people replace the terminal, or cable, and forget this ground wire. It controls the fuel pump circuit.
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From: In my own world
I have had it go bad on one of my trucks, and ended up cutting it out, and replacing it.
There is also a ground from the computer to the driver's side fender mount. I know it's there on the 87-91 trucks, I'm sure it's there on the 86 truck, even though the computer is located in a different spot
Grounds are a real problem most of the time, so I guess it wouldn't hurt to run through all of them.
There is also a ground from the computer to the driver's side fender mount. I know it's there on the 87-91 trucks, I'm sure it's there on the 86 truck, even though the computer is located in a different spot
Grounds are a real problem most of the time, so I guess it wouldn't hurt to run through all of them.
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From: Fort Jones, Ca
Well....I hooked up the bypass wire at the relay and heard a buzzing sound under the truck. When under there, I found the high pressure pump buzzing/humming and just about at that moment it stopped and then I could hear the intank pump working. I have power to the HP pump, but it isn't working after that short noise I got from it. I priced it and they got it at about $120. More parts to throw at it???
But I still don't know why the pump relay has to be hot wired to work. Once I DO hot wire it, the power is everywhere it's suppose to be, even the HP fuel pump, which doesn't work.
I think it's beer 30.
But I still don't know why the pump relay has to be hot wired to work.
Once I DO hot wire it, the power is everywhere it's suppose to be, even the HP fuel pump, which doesn't work.I think it's beer 30.
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From: In my own world
The pump fires to charge the system, then shuts off when the key is first turned on. The distributer sends a signal to the computer, to tell it the engine is turning, and it's ok to fire the pumps again. If there is no signal from the distributer, the pumps will not stay on.
I think we're on to something here.
Do you have spark when cranking the engine?
I think we're on to something here.
Do you have spark when cranking the engine?
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From: Fort Jones, Ca
When I sprayed fuel into the injector housing throat?, it ran briefly. And keep in mind, that was at the very beginning of all this. I haven't tried it since.
I also checked to see if any fuel was coming out at the little valve stem at the front/right of the manifold while the tank pump was running and nothing.
By the way, I did check the ground wire at the battery and it was good.
I also checked to see if any fuel was coming out at the little valve stem at the front/right of the manifold while the tank pump was running and nothing.
By the way, I did check the ground wire at the battery and it was good.
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From: In my own world
Tank pump is a lift pump. There is no real fuel pressure here, it is just a supply for the rail pump, which builds the pressure.
when you turn on the key, does the tank pump come on and go right back off?
when you turn on the key, does the tank pump come on and go right back off?
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From: Fort Jones, Ca
No. It keeps running. Again, that's with the pump relay plug hot wired. It's a no go with the relay switch plugged in to it. For some reason or other, the switch is not allowing power through it.
I never was much of a fan of electrical. So many possibilities.
I never was much of a fan of electrical. So many possibilities.
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From: In my own world
Both pumps should be running. Climb under, and see if you have power to the front pump.If you are hot wired, both pumps should be running at the same time then. You may have a bad wire in the harness.