85lebaront2 Posted March 5, 2021 Share Posted March 5, 2021 The main difference I see is that the inertia switch is after the relay on the smaller engines. It's interesting that Ford would choose to complicate things by adopting two different setups. Jim, you have to remember, EFI was being rolled out in steps, 1985 - 5.0L EFI, 1987, 4.9L, and base 5.8L EFI, 1988, all gas engines got EFI. The other item was the 460 hot fuel handling package was used when certain criteria were met, AC, hot climate or ambulance chassis where vapor lock would be an issue. The EFI had one or two in-tank pumps, probably 10-15 psi and a high pressure pump 35 psi on V8s and early 6s, 55 psi on later 6s, the hot fuel handling package was 2 low pressure pumps 6 psi is the spec and those needed a 6 port motor operated selector valve that also changed the sender connection as 6 psi wasn't enough to work the selector valve for the EFI system. 351 carbureted engines used a mechanical pump and 3 port valve. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted March 5, 2021 Share Posted March 5, 2021 Jim, you have to remember, EFI was being rolled out in steps, 1985 - 5.0L EFI, 1987, 4.9L, and base 5.8L EFI, 1988, all gas engines got EFI. The other item was the 460 hot fuel handling package was used when certain criteria were met, AC, hot climate or ambulance chassis where vapor lock would be an issue. The EFI had one or two in-tank pumps, probably 10-15 psi and a high pressure pump 35 psi on V8s and early 6s, 55 psi on later 6s, the hot fuel handling package was 2 low pressure pumps 6 psi is the spec and those needed a 6 port motor operated selector valve that also changed the sender connection as 6 psi wasn't enough to work the selector valve for the EFI system. 351 carbureted engines used a mechanical pump and 3 port valve. My 460 uses a mechanical pump and a 3 port valve..... I'm not certain why an EFI system that has a lift pump in each tank and a reservoir/boost pump on the frame rail needs the inertia switch after the fuel pump relay, but a Hot Fuel truck should have the inertia switch feeding the fuel pump relay. I'm just to dumb to understand what Ford engineers reasons were. Link to comment Share on other sites More sharing options...
L.R.D. Posted March 6, 2021 Author Share Posted March 6, 2021 Ok, first, the E series wiring is different than the F series, for one thing the grounds for the tank units are at the nearest cross member, not brought up inside the body like the pickups. The diagrams I am finding show the three pump system, but since I do not have what I believe to be completely correct information regarding the reservoir for the high pressure pump (maybe the 1985/86 E series didn't use it, I know the 1989 E series did as I have dealt with one of those. Here are the two versions I have found, both show a tank selector valve which is probably the big motor operated 6 port the carburated 460 with hot fuel handling package used in the F series. Maybe one of our parts guys can shed some light on the plumbing. Here is what I have found: First the 1986 E150 diagram: Second one identified as 1985-1987 multiple applications. This shows both a tank selector switch and a tank selector valve, I am interpreting that as a one or the other, not both as theay are show as wired in parallel. Bill, Thanks so much! That top diagram matches exactly what I have traced down on the van, including where the grounds are. Since I have yet to find the C134, C135, S108 or S113, I've only been assuming those connections based on wire colors at the switch, valve and tanks. Now that my multitester is working again I'll look harder for all of those connections and doublecheck the grounds but this reaffirms my suspicion that there are really only a couple of possibilities when both the rear pump and sending unit are out - switch not flipping the polarity of the circuit running into the FSV, or FSV solenoid no longer functioning (I guess both wires to the rear tank could be broken but given how the problem started that seems unlikely). Thanks again. Link to comment Share on other sites More sharing options...
85lebaront2 Posted March 6, 2021 Share Posted March 6, 2021 Bill, Thanks so much! That top diagram matches exactly what I have traced down on the van, including where the grounds are. Since I have yet to find the C134, C135, S108 or S113, I've only been assuming those connections based on wire colors at the switch, valve and tanks. Now that my multitester is working again I'll look harder for all of those connections and doublecheck the grounds but this reaffirms my suspicion that there are really only a couple of possibilities when both the rear pump and sending unit are out - switch not flipping the polarity of the circuit running into the FSV, or FSV solenoid no longer functioning (I guess both wires to the rear tank could be broken but given how the problem started that seems unlikely). Thanks again. Ok, I have the list for connectors and splices printed out. C134 - LH side of dash panel near ignition module (underhood) C135 - On rear crossmember S108 - in the harness probably near C134 S113 - probably the same area On the splices, factory they are essentially spot welded. I would unplug C134, C135 and the fuel tank selector valve. Check continuity from C134 Circuits 739 and 808 to the selector valve connector and 739 to C135. 808 will involve unplugging the front tank connector, since it is working I would leave it alone. Circuit 286 is rear tank sender and Gary has a chart (I believe) on the site with resistance values. You might get lucky and find C135 unplugged or just plain dirty. Good luck! Link to comment Share on other sites More sharing options...
L.R.D. Posted March 13, 2021 Author Share Posted March 13, 2021 Ok, I have the list for connectors and splices printed out. C134 - LH side of dash panel near ignition module (underhood) C135 - On rear crossmember S108 - in the harness probably near C134 S113 - probably the same area On the splices, factory they are essentially spot welded. I would unplug C134, C135 and the fuel tank selector valve. Check continuity from C134 Circuits 739 and 808 to the selector valve connector and 739 to C135. 808 will involve unplugging the front tank connector, since it is working I would leave it alone. Circuit 286 is rear tank sender and Gary has a chart (I believe) on the site with resistance values. You might get lucky and find C135 unplugged or just plain dirty. Good luck! I finally had time to get back to this and I think I finally grok these circuits (thanks again, Bill). After all the disconnecting/reconnecting of wiring and cleaning of connections, the original problem that almost left me stranded - neither tank sending unit or pump working - is now gone. Both sending units are working (I added gas to the front tank to make sure it was reading a different level than the rear) and the front pump turns on. The only thing that does not appear to turn on is the rear tank pump. On the 739 circuit (pump) I get 10 V at the tank. The 286 fuel gauge circuit reads 0-4 V pulsating. I disconnected both circuits at the C135 (it was hidden between the tow bar and the bumper) and tested the circuits from there to ground. The pump read 3 ohms and the sending unit read 30 ohms. What should the resistance across the pump be here (C135 to ground)? I can't access the front sending unit connections so I don't know what a working pump should read. I also tested voltage at the FSV connector. When switched to the rear tank, I get 10V on 739 and 0 V on 808 circuits. When in the front position, I get the inverse - 10V on 808 and 0 V on 739. This tells me the dash switch is working properly (I also pulled the switch and tested the connectors in both positions and it behaves correctly). In either switch position, the 673 sending unit circuit from the gauge reads 1-5V pulsating at the FSV connector. That seems correct. The 285 and 675 circuits read 0 V, as expected, because those circuits to the tanks are disconnected when the FSV connector is disconnected. All this tells me the switch and the FSV are working correctly (recall, I can hear when the front pump is running), and the problem is the rear tank pump. When I knew it was working you could definitely hear it. One last test that I still need to do is disconnect the From Tank fuel line at the FSV and confirm that no gas is being pumped when rear tank is switched on. This pump was replaced 4 years and 10K miles ago (its probably only been used for about 6K miles of that though). Am I missing anything else, or did I just get a lousy pump? and, of course, what caused the initial problem is still a mystery, but until that happens again, not sure what I can do about it. I suspect the FSV solenoid got hung up when I switched tanks on that drive since it happened right after that. I may invest in a spare... thanks Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted March 14, 2021 Share Posted March 14, 2021 I finally had time to get back to this and I think I finally grok these circuits (thanks again, Bill). After all the disconnecting/reconnecting of wiring and cleaning of connections, the original problem that almost left me stranded - neither tank sending unit or pump working - is now gone. Both sending units are working (I added gas to the front tank to make sure it was reading a different level than the rear) and the front pump turns on. The only thing that does not appear to turn on is the rear tank pump. On the 739 circuit (pump) I get 10 V at the tank. The 286 fuel gauge circuit reads 0-4 V pulsating. I disconnected both circuits at the C135 (it was hidden between the tow bar and the bumper) and tested the circuits from there to ground. The pump read 3 ohms and the sending unit read 30 ohms. What should the resistance across the pump be here (C135 to ground)? I can't access the front sending unit connections so I don't know what a working pump should read. I also tested voltage at the FSV connector. When switched to the rear tank, I get 10V on 739 and 0 V on 808 circuits. When in the front position, I get the inverse - 10V on 808 and 0 V on 739. This tells me the dash switch is working properly (I also pulled the switch and tested the connectors in both positions and it behaves correctly). In either switch position, the 673 sending unit circuit from the gauge reads 1-5V pulsating at the FSV connector. That seems correct. The 285 and 675 circuits read 0 V, as expected, because those circuits to the tanks are disconnected when the FSV connector is disconnected. All this tells me the switch and the FSV are working correctly (recall, I can hear when the front pump is running), and the problem is the rear tank pump. When I knew it was working you could definitely hear it. One last test that I still need to do is disconnect the From Tank fuel line at the FSV and confirm that no gas is being pumped when rear tank is switched on. This pump was replaced 4 years and 10K miles ago (its probably only been used for about 6K miles of that though). Am I missing anything else, or did I just get a lousy pump? and, of course, what caused the initial problem is still a mystery, but until that happens again, not sure what I can do about it. I suspect the FSV solenoid got hung up when I switched tanks on that drive since it happened right after that. I may invest in a spare... thanks Glad to hear you're getting it figured out! Bummer the rear pump seems to have given up the ghost. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 14, 2021 Share Posted March 14, 2021 Glad to hear you're getting it figured out! Bummer the rear pump seems to have given up the ghost. Yes, so glad you are making progress! Link to comment Share on other sites More sharing options...
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