Jcomeau85 Posted April 18 Share Posted April 18 Where are all the relays for the fuel system. I have a 1986 F250 carb 460 manual trans Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 18 Share Posted April 18 Have a look in the 1986 EVTM. https://www.garysgaragemahal.com/1986-evtm.html Section 18 (pg 95-101) is for the selector and senders Section 19 (pg 102-107) is the safeties/crank bypass and pump control. Grounds can be found somewhere in the front of the book. What problem do you have? Link to comment Share on other sites More sharing options...
Jcomeau85 Posted April 18 Author Share Posted April 18 Have a look in the 1986 EVTM. https://www.garysgaragemahal.com/1986-evtm.html Section 18 (pg 95-101) is for the selector and senders Section 19 (pg 102-107) is the safeties/crank bypass and pump control. Grounds can be found somewhere in the front of the book. What problem do you have? Rear tank shows empty. Tank is physically full. Fuel won’t pump. Link to comment Share on other sites More sharing options...
85lebaront2 Posted April 18 Share Posted April 18 Rear tank shows empty. Tank is physically full. Fuel won’t pump. That is a somewhat complex system. one item on the 1986 system, the selector switch changes the big motor driven 6 port valve on the frame near the front tank. The system has two power sources, one is a blue wire with a fusible link that is fed power when cranking the engine from a small stud on the starter relay, the second source and the one that keeps power to the system is an oil pressure switch in the back of the block behind the intake manifold. Here is a link to the 1986 EVTM on the site: https://www.garysgaragemahal.com/1986-evtm.html If you take the blue wire off it's stud and touch it to the battery stud on the starter relay, you should be able to hear the selected pump run. Set the selector switch to front or rear and try that test, first if the tank selection was changed, you should hear a "clunk" from the selector valve and a faint whirring noise from the pump followed by a hissing sound from the vapor seperator in the fuel line near the carburetor. I would try both directions when checking, front and rear tank. Good luck with it and feel free to ask more if needed. Link to comment Share on other sites More sharing options...
viven44 Posted April 18 Share Posted April 18 That is a somewhat complex system. one item on the 1986 system, the selector switch changes the big motor driven 6 port valve on the frame near the front tank. The system has two power sources, one is a blue wire with a fusible link that is fed power when cranking the engine from a small stud on the starter relay, the second source and the one that keeps power to the system is an oil pressure switch in the back of the block behind the intake manifold. Here is a link to the 1986 EVTM on the site: https://www.garysgaragemahal.com/1986-evtm.html If you take the blue wire off it's stud and touch it to the battery stud on the starter relay, you should be able to hear the selected pump run. Set the selector switch to front or rear and try that test, first if the tank selection was changed, you should hear a "clunk" from the selector valve and a faint whirring noise from the pump followed by a hissing sound from the vapor seperator in the fuel line near the carburetor. I would try both directions when checking, front and rear tank. Good luck with it and feel free to ask more if needed. I have never thought about testing them that way. Take advantage of the "hot when cranking" loop.. Nice tip!! Link to comment Share on other sites More sharing options...
85lebaront2 Posted April 18 Share Posted April 18 I have never thought about testing them that way. Take advantage of the "hot when cranking" loop.. Nice tip!! I came very close to adding a "prime" push button switch to Darth as he wasn't a daily driver and usually needed the carburetor filled for a cold start. Now that I have the MAF/SEFI system, it isn't needed. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 18 Share Posted April 18 Rear tank shows empty. Tank is physically full. Fuel won’t pump. But the front tank reads correctly and will drive the truck? The problem is either the switch valve, or beyond, from what you've just told me Try jumpering around the valve, and see if the rear tank works. Link to comment Share on other sites More sharing options...
Jcomeau85 Posted April 18 Author Share Posted April 18 But the front tank reads correctly and will drive the truck? The problem is either the switch valve, or beyond, from what you've just told me Try jumpering around the valve, and see if the rear tank works. Front tank works. On the documentation from that link at the top it seems like the selector relay is LH corner behind dash??? Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 18 Share Posted April 18 Front tank works. On the documentation from that link at the top it seems like the selector relay is LH corner behind dash??? There's no selector relay shown, just the switch and the valve... Link to comment Share on other sites More sharing options...
Jcomeau85 Posted April 18 Author Share Posted April 18 There's no selector relay shown, just the switch and the valve... Link to comment Share on other sites More sharing options...
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