Fuel Gauge Open Circuit Diagnostics Help
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Postmaster
Joined: Apr 2003
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From: Virginia Beach
Fuel Gauge Open Circuit Diagnostics Help
1987 F250 carb'd 460, dual tanks
Electric in-tank pumps, 6-line electric selector valve
Both tank pumps work as far as I can hear. Motor runs fine when either tank is selected. The selector switch can be felt operating when the tanks are switched.
My problem is the fuel gauge is pegged past "full" when either tank is selected. At the fuel selector switch, I've grounded the y/w wire and the gauge will peg to "empty". At the selector valve (5 wires), when I ground the rear tank with the rear tank selected it will read "empty" (front tank will read "full"). With the front tank grounded and selected it will read "empty" (rear tank will read "full").
So far from what I could garner off the net and this site, all the wiring is good from the gauge to at least the selector valve and the selector valve itself is good. I assume I have an open circuit between the tanks and the selector valve? Is there anything else I can test, or am I just unlucky enough to have 2 bad fuel senders?
Thanks!!
Electric in-tank pumps, 6-line electric selector valve
Both tank pumps work as far as I can hear. Motor runs fine when either tank is selected. The selector switch can be felt operating when the tanks are switched.
My problem is the fuel gauge is pegged past "full" when either tank is selected. At the fuel selector switch, I've grounded the y/w wire and the gauge will peg to "empty". At the selector valve (5 wires), when I ground the rear tank with the rear tank selected it will read "empty" (front tank will read "full"). With the front tank grounded and selected it will read "empty" (rear tank will read "full").
So far from what I could garner off the net and this site, all the wiring is good from the gauge to at least the selector valve and the selector valve itself is good. I assume I have an open circuit between the tanks and the selector valve? Is there anything else I can test, or am I just unlucky enough to have 2 bad fuel senders?
Thanks!!
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From: Virginia
Try to explain that again.
I've grounded the y/w wire and the gauge will peg to "empty". And when you take the wire off ground the gauge goes to full correct? If so, we will call this good.
At the selector valve (5 wires), when I ground the rear tank with the rear tank selected it will read "empty" And when you take this wire off, the gauge goes to full? Then that is correct also.
With the front tank grounded and selected it will read "empty" And when the wire is taken off ground it reads full? If so, that's correct also.
If it all works like the above, and you can do the same at the tank sending unit wires, then it must be the sending units are bad.
I've grounded the y/w wire and the gauge will peg to "empty". And when you take the wire off ground the gauge goes to full correct? If so, we will call this good.
At the selector valve (5 wires), when I ground the rear tank with the rear tank selected it will read "empty" And when you take this wire off, the gauge goes to full? Then that is correct also.
With the front tank grounded and selected it will read "empty" And when the wire is taken off ground it reads full? If so, that's correct also.
If it all works like the above, and you can do the same at the tank sending unit wires, then it must be the sending units are bad.
Thread Starter
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Postmaster
Joined: Apr 2003
Posts: 3,587
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From: Virginia Beach
Groovy, that's how it all works 
I need to change out the fuel valve though. I caught the rear tanking pumping into the front tank on Saturday
Only done it this once that I know of, but I guess that's enough, lol. . .
Checking the sending units come after. . .need to drop the tanks for that which I'm not looking for
I need to change out the fuel valve though. I caught the rear tanking pumping into the front tank on Saturday
Only done it this once that I know of, but I guess that's enough, lol. . .Checking the sending units come after. . .need to drop the tanks for that which I'm not looking for
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