ArdWrknTrk Posted May 28, 2021 Share Posted May 28, 2021 Is this relay next to the booster for the fuel pump? Just a reminder of the mess. Theres another smaller relay in there, green. But isnt there supposed to be a pump relay and trailer light relay somewhere around here? I'm not sure about '84. The '85 EVTM shows both a pump and a swtching/selector relay. I think the trailer relay only came with the trailer package. Link to comment Share on other sites More sharing options...
grumpin Posted May 28, 2021 Share Posted May 28, 2021 Its been loud for the 2 years Ive had the truck. It never struck me as a good sign, but it always worked so I never questioned it. Previous owner did tell me the pumps were replaced at some point, although I have reason to question the quality of work they did. Im going to order some wire this weekend. The Yellow wire running to that relay has some spots where the insulations melted. Well, that doesn’t sound like it’s going bad like mine, interesting. Link to comment Share on other sites More sharing options...
swampedout Posted May 30, 2021 Author Share Posted May 30, 2021 Its been loud for the 2 years Ive had the truck. It never struck me as a good sign, but it always worked so I never questioned it. Previous owner did tell me the pumps were replaced at some point, although I have reason to question the quality of work they did. Im going to order some wire this weekend. The Yellow wire running to that relay has some spots where the insulations melted. Well, that doesn’t sound like it’s going bad like mine, interesting. So the relay thats clipped into that housing on the firewall is the Fuel Pump Cutoff. With the Pl/bk wire replaced with a yellow wire. Link to comment Share on other sites More sharing options...
swampedout Posted May 30, 2021 Author Share Posted May 30, 2021 Going through the process of elimination, now what is this relay? And where is the other half? The most distinctive wire is Brown with solid Yellow stripe. And White, Black, Black with Gray stripe. And for anyone who notices the wire nut in that picture, I am looking at how to address that. Its got the red ignition wire from my MSD box, the large gauge Yellow wire that replaced the PK/Bk into the Fuel Cutoff Relay, and a section of the old PK/Bk wire going into another relay which I think is the Tank Selector Relay? This is the big black and gray relay in the background of that picture. On that relay, there is also a Orange/Blue striped wire. I used that to search for because it seems uncommon. On the Color Code it says "238 FUEL SUPPLY PUMP RELAY ORANGE/LT BLUE STRIPE", the only Orange/Blue stripe wire that seems like it would make sense to be tied into those other wires. But I'm not seeing "Fuel Pump Supply Relay" in any of the other documents related to these circuits... Link to comment Share on other sites More sharing options...
Gary Lewis Posted May 30, 2021 Share Posted May 30, 2021 Going through the process of elimination, now what is this relay? And where is the other half? The most distinctive wire is Brown with solid Yellow stripe. And White, Black, Black with Gray stripe. And for anyone who notices the wire nut in that picture, I am looking at how to address that. Its got the red ignition wire from my MSD box, the large gauge Yellow wire that replaced the PK/Bk into the Fuel Cutoff Relay, and a section of the old PK/Bk wire going into another relay which I think is the Tank Selector Relay? This is the big black and gray relay in the background of that picture. On that relay, there is also a Orange/Blue striped wire. I used that to search for because it seems uncommon. On the Color Code it says "238 FUEL SUPPLY PUMP RELAY ORANGE/LT BLUE STRIPE", the only Orange/Blue stripe wire that seems like it would make sense to be tied into those other wires. But I'm not seeing "Fuel Pump Supply Relay" in any of the other documents related to these circuits... Well, there are too many questions in that last post for me to get my head around. Let me try to tackle the easy ones first. There is not Fuel Pump Supply Relay on our trucks. Just the Fuel Pump Cutoff Relay, and I guess the thinking was that in an accident it would cut off the pump when the inertia switch "opens on impact". But when you said "Color Code" I'm guessing you meant you'd searched the listing at Documentation/Electrical/Standard Wire & Color Codes. Right? That listing is generic for Ford vehicles of many years and models. But on our trucks O/LB is used in circuit 238 between the Tank Selector Relay and the Rear Fuel Tank Unit, as shown below on the far right. Link to comment Share on other sites More sharing options...
swampedout Posted May 30, 2021 Author Share Posted May 30, 2021 Well, there are too many questions in that last post for me to get my head around. Let me try to tackle the easy ones first. There is not Fuel Pump Supply Relay on our trucks. Just the Fuel Pump Cutoff Relay, and I guess the thinking was that in an accident it would cut off the pump when the inertia switch "opens on impact". But when you said "Color Code" I'm guessing you meant you'd searched the listing at Documentation/Electrical/Standard Wire & Color Codes. Right? That listing is generic for Ford vehicles of many years and models. But on our trucks O/LB is used in circuit 238 between the Tank Selector Relay and the Rear Fuel Tank Unit, as shown below on the far right. Ah ok. That makes sense. I didnt realize the Color Code Chart was a generic list. I guess it pays to read closely. I think you answered 1 of 2 big questions in terms of identifying relays. So the Selector relay and Cutoff Relay are the only relays in the fuel circuit? My last bit of detective work is identifying the green half relay in the picture above Link to comment Share on other sites More sharing options...
Gary Lewis Posted May 30, 2021 Share Posted May 30, 2021 Going through the process of elimination, now what is this relay? And where is the other half? The most distinctive wire is Brown with solid Yellow stripe. And White, Black, Black with Gray stripe. And for anyone who notices the wire nut in that picture, I am looking at how to address that. Its got the red ignition wire from my MSD box, the large gauge Yellow wire that replaced the PK/Bk into the Fuel Cutoff Relay, and a section of the old PK/Bk wire going into another relay which I think is the Tank Selector Relay? This is the big black and gray relay in the background of that picture. On that relay, there is also a Orange/Blue striped wire. I used that to search for because it seems uncommon. On the Color Code it says "238 FUEL SUPPLY PUMP RELAY ORANGE/LT BLUE STRIPE", the only Orange/Blue stripe wire that seems like it would make sense to be tied into those other wires. But I'm not seeing "Fuel Pump Supply Relay" in any of the other documents related to these circuits... Trailer Lamps Relay? You said "Brown with solid Yellow stripe. And White, Black, Black with Gray stripe" but it should be Brown, White w/red dots, Black, and Black w/a White stripe. Link to comment Share on other sites More sharing options...
swampedout Posted May 31, 2021 Author Share Posted May 31, 2021 Trailer Lamps Relay? You said "Brown with solid Yellow stripe. And White, Black, Black with Gray stripe" but it should be Brown, White w/red dots, Black, and Black w/a White stripe. Well Gary, not at all surprising, I think you nailed this one too. The colors do match up, except for an extra wire in there which is Brwn/yellow solid stripe. Could this extra wire be for fog lamps or something? Link to comment Share on other sites More sharing options...
Gary Lewis Posted May 31, 2021 Share Posted May 31, 2021 Well Gary, not at all surprising, I think you nailed this one too. The colors do match up, except for an extra wire in there which is Brwn/yellow solid stripe. Could this extra wire be for fog lamps or something? It is possible it is for a fog light. I don't see the wire color shown in the master parts catalog. But it could be Br/Y. Link to comment Share on other sites More sharing options...
swampedout Posted May 31, 2021 Author Share Posted May 31, 2021 It is possible it is for a fog light. I don't see the wire color shown in the master parts catalog. But it could be Br/Y. I was noticing in the relay chart there were different options for fog lights and I did remove some really old fog lights that were mounted under the front bumper. I assumed they were aftermarket but who knows.. Thanks for your help, Gary. In my research Ive seen so many threads of people asking you "whats this relay." Im sure it gets old, but it really is incredibly helpful. Link to comment Share on other sites More sharing options...
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