How does a fuel sending unit work?
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Senior User
Joined: Aug 2003
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From: Central TEXAS
How does a fuel sending unit work?
1986 f-250 diesel
I found a burnt wire coming through the firewall and traced it down to either the sending unit or selector switch. Everything works fine, I just don't like idea that something could smoke while going down the road. I unplugged the 4 wire plug that contains this wire at the firewall and the fuel gauge does not work, so I know it has something to do with it.
When I put a test light on it two of the wires swap with the selector switch. One wire pulses all the time (with the switch on) like a blinker and the last wire is the burnt one.
Does a sending unit pluse like that?
The burnt wire has continuity to ground. I don't know if it is a ground wire or shorted to ground. If it is a ground, then why would it go all the way up into the cab instead of grounding locally?
thanks
stephen
I found a burnt wire coming through the firewall and traced it down to either the sending unit or selector switch. Everything works fine, I just don't like idea that something could smoke while going down the road. I unplugged the 4 wire plug that contains this wire at the firewall and the fuel gauge does not work, so I know it has something to do with it.
When I put a test light on it two of the wires swap with the selector switch. One wire pulses all the time (with the switch on) like a blinker and the last wire is the burnt one.
Does a sending unit pluse like that?
The burnt wire has continuity to ground. I don't know if it is a ground wire or shorted to ground. If it is a ground, then why would it go all the way up into the cab instead of grounding locally?
thanks
stephen
Thread Starter
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Senior User
Joined: Aug 2003
Posts: 107
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From: Central TEXAS
Okay, I googled it and it does pulse, but what about that ground, or burnt wire?
I have no idea why, but none of my 3 different books shows the wire colors that I have.
stephen
I have no idea why, but none of my 3 different books shows the wire colors that I have.
stephen
Fleet Owner
Joined: Aug 2005
Posts: 23,666
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From: Easton,Ks
At the selector switch you have four wires:
1. Black is ground
2. Red goes to fuse #15 for power
3. Orange wire that turns into a red wire and then goes to the valve motor.
4. Brown wire with a white stripe goes to the valve motor.
Note 3 & 4 swap from neg (-) to pos (+) to reverse the valve motor.
There is also a wire running from the gauge to the valve motor gauge contacts, this is a Yellow wire with a white stripe. This one does pulse and the pulses come from the cluster voltage regulator.
1. Black is ground
2. Red goes to fuse #15 for power
3. Orange wire that turns into a red wire and then goes to the valve motor.
4. Brown wire with a white stripe goes to the valve motor.
Note 3 & 4 swap from neg (-) to pos (+) to reverse the valve motor.
There is also a wire running from the gauge to the valve motor gauge contacts, this is a Yellow wire with a white stripe. This one does pulse and the pulses come from the cluster voltage regulator.
Last edited by subford; Aug 11, 2007 at 09:25 AM.
