1986 250 fuel problem
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1986 250 fuel problem
I have a 1986 F250 460, dual tank elec fuel pumps,I keep blowing #18 fuse,the pumps have been replaced not to long ago.This is a new problem that just showed up yesterday.I replaced the fuel pump cutoff relay, bypassed the oil pressure switch (Temp.)to try and trouble shoot but not much help.If anybody has any ideas I sure would appreciate it.
Thanks JWH2
Thanks JWH2
pedant
Joined: Jan 2008
Posts: 23,576
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From: EXTREME southwest CT
Here's a schematic.
You'll see fuse 18 runs through the oil pressure switch and pulls down the pump cutout relay.
Obviously the wire is shorted, or the relay or it's socket is bad.
Click on the thumbnail for a better view if you need it.
You'll see fuse 18 runs through the oil pressure switch and pulls down the pump cutout relay.
Obviously the wire is shorted, or the relay or it's socket is bad.
Click on the thumbnail for a better view if you need it.
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Ok thought I found the problem ,found a crack in the insulation of the r/y wire at the fuel relay and repaired,that wasn't it.Let me know if I need to move to the elec. thread,anyway my chilton's schematic shows fuses #6,11,14,17 tied together and 18,15 tied together all show continuity to ground but the only fuse that blows is #18.I know what #15,18 are for but 6 thru 17 it doesn't show.I kind of lost any ideas??
thanks jwh2
thanks jwh2
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pedant
Joined: Jan 2008
Posts: 23,576
Likes: 38
From: EXTREME southwest CT
What are the ohms to ground on #18?
Take out the fuse and probe from there, use the metal dashboard support for ground.
Pull the relay out and see if the circuit goes open.
If it does, the wire to the socket is okay, and the relay is bad.
If not, I'd suggest you separate the wires where you jumped the oil pressure switch.
Probe the wire from the fuse panel where it was attached to the OPS.
And then the wire from the OPS to the relay socket.
Just keep narrowing down the area where the short is.
Chris posted the fuse panel diagram in post #2...
Take out the fuse and probe from there, use the metal dashboard support for ground.
Pull the relay out and see if the circuit goes open.
If it does, the wire to the socket is okay, and the relay is bad.
If not, I'd suggest you separate the wires where you jumped the oil pressure switch.
Probe the wire from the fuse panel where it was attached to the OPS.
And then the wire from the OPS to the relay socket.
Just keep narrowing down the area where the short is.
Chris posted the fuse panel diagram in post #2...
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Thanks again for the reply, I finally got it through my thick head that the red/yellow wire
is a control voltage circuit.Once it leaves the fuse block it splits before going thru the firewall to the op switch.I found it all thru the dash including the Black box?? I bought this truck brand new in 1986 and I love it! I replaced motor, transmission,and acc. three years ago, I thought I got every thing but I missed the black box what is it for ?? Anyway ran out of time today,will be back at tomorrow
is a control voltage circuit.Once it leaves the fuse block it splits before going thru the firewall to the op switch.I found it all thru the dash including the Black box?? I bought this truck brand new in 1986 and I love it! I replaced motor, transmission,and acc. three years ago, I thought I got every thing but I missed the black box what is it for ?? Anyway ran out of time today,will be back at tomorrow
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From: Denver Metro Area, CO
Thanks again for the reply, I finally got it through my thick head that the red/yellow wire
is a control voltage circuit.Once it leaves the fuse block it splits before going thru the firewall to the op switch.I found it all thru the dash including the Black box?? I bought this truck brand new in 1986 and I love it! I replaced motor, transmission,and acc. three years ago, I thought I got every thing but I missed the black box what is it for ?? Anyway ran out of time today,will be back at tomorrow
is a control voltage circuit.Once it leaves the fuse block it splits before going thru the firewall to the op switch.I found it all thru the dash including the Black box?? I bought this truck brand new in 1986 and I love it! I replaced motor, transmission,and acc. three years ago, I thought I got every thing but I missed the black box what is it for ?? Anyway ran out of time today,will be back at tomorrow
If so:
https://www.ford-trucks.com/forums/6...k-box-i-d.html might help (pix are gone, though).
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The vacuum valve contrrols the throttle kicker, fed from main vac. port to switch back to kicker on the carb.If anybody has info. as where to buy these kind of parts that would be a big help, tried local auto parts,rock auto,LMC no luck
Thanks Jeff
Thanks Jeff
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Well I spoke wayyy to soon. As soon as I pulled the plug on the solenoid valve the problem seemed to go away,replaced it with a used one (all I could find) drove it yesterday alittle and took another ride today and its back, it even took the tach. and pegged it,I had to wire the pumps to a hot wire to get home??? back to square one.Yes I have cruise control, the book I'm looking at describes it as used to control the A/C throttle kicker & choke pull down.It sits on top the pass. side valve cover.The fuse box chris shows seems to be different than what I see in my chilton and haynes,F1& F2 are F17 & F18 anyway its marked warning lights on the box cover.Sorry so long winded.