Fuel Switch Wiring
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Fuel Switch Wiring
I have a 1987 Ford F-150 4x4 with a 351 motor. It has the manual fuel pump on the block.
Here is my problem: When checking the Fuel tank selector swith on the dash. Everything I read gives the wiring for the tanks and gauges.
When I get under mine. This is what I found. From the back of the switch there is a short pig tail maybe 5 inches long. That plugs into a wiring harness. The wires in the harness are all that everone talks about. Red Blue/White -Yellow/White -Red -Red/White- Yellow and Blue.
Now from there to the short pig tail the wires are Red -Blue/White -Yellow/White- Red(again) Red/White -Yellow and Blue.
When the tank is on the front. I have power to both reds (at the switch) When switched to the rear I do not have power except one red.
How do you check this switch. I've checked it at rhe wire harness and still do not have power on the rear tank
Here is my problem: When checking the Fuel tank selector swith on the dash. Everything I read gives the wiring for the tanks and gauges.
When I get under mine. This is what I found. From the back of the switch there is a short pig tail maybe 5 inches long. That plugs into a wiring harness. The wires in the harness are all that everone talks about. Red Blue/White -Yellow/White -Red -Red/White- Yellow and Blue.
Now from there to the short pig tail the wires are Red -Blue/White -Yellow/White- Red(again) Red/White -Yellow and Blue.
When the tank is on the front. I have power to both reds (at the switch) When switched to the rear I do not have power except one red.
How do you check this switch. I've checked it at rhe wire harness and still do not have power on the rear tank
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There is no brown and white at the switch. The colors at the switch are 2 reds a yellow and white a blue and yellow and a yellow and blue. That is all the wires at the switch
At the selonoid on the frame rail the wire are a black wire and a red wire .
At the selonoid on the frame rail the wire are a black wire and a red wire .
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
Diagrams do not always exactly match what you find on a truck regardless who published said diagram.
Wire colors can match yet two swapped circuit for circuit for example, verify same circuit serviced as shown in diagram for each one a minute, can really cut down on the "head scratch" time take a moment to verify at least the first few.
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Thank you for the input. As the head scratching on this project leaves me thin haired. What you explained is what I figured was happening.
But now my question still remains. If one of the reds are hot, and the other red is hot with the switch in the foward position. No other wires have juice except one red when switch to the rear position. So am I looking at a bad switch ? Or if the Red wire runs to the solenoid vaulve does it active the vaulve when it has juice going to it( front tank position) and deactivate it when switched to the rear. And the deactivation allows it to draw from the back tank ?
But now my question still remains. If one of the reds are hot, and the other red is hot with the switch in the foward position. No other wires have juice except one red when switch to the rear position. So am I looking at a bad switch ? Or if the Red wire runs to the solenoid vaulve does it active the vaulve when it has juice going to it( front tank position) and deactivate it when switched to the rear. And the deactivation allows it to draw from the back tank ?
Postmaster
Joined: Nov 2011
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From: SW Florida
That appears to be the intention, looking at the schematic... and it makes sense because a solenoid would fit the bill perfectly for that purpose.
Fleet Owner
Joined: Aug 2005
Posts: 23,666
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From: Easton,Ks
The fuel gauge power would be an AC voltage of about 6-8VAC.
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Postmaster
Joined: Nov 2011
Posts: 3,533
Likes: 17
From: SW Florida
AC voltage? I take it the cluster has an oscillator circuit to provide this? Only time I've seen AC voltage on a truck outside of the alternator is from an inductive pickup like the VSS.
Sorry for the thread hijack OP.
Sorry for the thread hijack OP.
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From: Easton,Ks
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