FormerBigDaddy Posted February 12, 2020 Author Share Posted February 12, 2020 Ok, let me see if I can help. What Bill suggested is brilliant, and that's exactly why we have a forum - someone has an idea and someone else has a better one. The drawing below shows your fuel pump control circuit. In the upper left you'll see "Hot In Start or Run", and below that a red wire with a yellow hash mark (R/Y H) that goes from Fuse 18 to the Oil Pressure Switch. That means that when the key is either in Start or Run there is power provided to the oil pressure switch via the fuse and that wire. As shown the switch is "open", meaning there's no connection between the terminal on the top and the one on the bottom. But there's a note that says "Closed with engine running", and that means that battery voltage will flow across the switch to the Fuel Pump Cutoff Relay when the engine is running. And that will close the contacts on that relay and power the fuel pump. But, I've drawn a red arrow and added "Choke". If you tap into the red/yellow hash wire after the oil pressure switch you can run that wire directly to the choke and it will get battery voltage when the engine is running, and only when the engine is running. So, where are these components? The oil pressure switch is on the back of the engine, right in front of the firewall and behind the carb. If you need I can get pics of the one from Big Blue, but you should be able to find it easily, and it'll have two wires to it, and both are R/Y H. So, which one do you tap into? The one that goes to the fuel pump cutoff relay, and it is between the master cylinder and the driver's fender on the firewall. I've put an illustration below that shows what it looks like. So, are you ok with doing that wiring? Do you need suggestions on how to do that? (Please don't tell me you are going to use an insulation displacement connector to tap into the R/Y H wire and are going to use a cheap wire crimper to crimp the terminals. ) Ok I can follow this... a picture would be nice. That being said, I'm not sure what i have is a stock setup. I know i have a electric fuel pump, but the truck didn't originally so I'm not so sure about having a fuel pump cutoff relay in a stock location. Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 12, 2020 Share Posted February 12, 2020 Ok I can follow this... a picture would be nice. That being said, I'm not sure what i have is a stock setup. I know i have a electric fuel pump, but the truck didn't originally so I'm not so sure about having a fuel pump cutoff relay in a stock location. Ok, good point. If it didn't originally have an electric pump you may not have all of the other bits, like the oil pressure switch and the cutoff relay. I have a meeting at church in a bit, but can take pics when I get home of the switch and the relay. But, are you ok to do the wiring? Do you have wire, connectors, and either a ratcheting crimper or a soldering gun? Link to comment Share on other sites More sharing options...
FormerBigDaddy Posted February 12, 2020 Author Share Posted February 12, 2020 Ok, good point. If it didn't originally have an electric pump you may not have all of the other bits, like the oil pressure switch and the cutoff relay. I have a meeting at church in a bit, but can take pics when I get home of the switch and the relay. But, are you ok to do the wiring? Do you have wire, connectors, and either a ratcheting crimper or a soldering gun? If I have that wire and can locate it I can definitely do the wiring. Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 12, 2020 Share Posted February 12, 2020 If I have that wire and can locate it I can definitely do the wiring. Ok, glad you can do the wiring. Personally, I solder all connections and use adhesive-lined heat shrink tubing to protect the connections. Anyway, I looked for my pics on doing the work on Big Blue in the area we are talking about, and it turns out that it was done before I started this forum, so was while I was on FTE. Unfortunately FTE doesn't allow copying the link to a picture there and placing it here, so all I can offer you is this URL. If you go there you'll see an illustration of where the oil pressure switch is, and if you scroll down you'll see my pics showing the switch I used. And when I get home I can take a pic of where the fuel pump relay is on Big Blue. Link to comment Share on other sites More sharing options...
85lebaront2 Posted February 12, 2020 Share Posted February 12, 2020 Ford used a 3 terminal oil pressure sender just like Chrysler... It was commonly used to turn the electric fuel pumps on 460 trucks off if oil pressure was lost. I think the easiest would to be to use one as suggested above, or wire in a relay to control power to the choke. If you use a Bosch style relay, 7 volts is enough to hold the coil in. Use the stator wire on the control side of the relay, then use the load side of the relay to power your choke. However you wire it, make sure you only have power in RUN, and not ACC! I have never seen a 3 terminal used on a Ford, the oil pressure switch on the 460s with the hot fuel hanling package are two small pins in a weatherproof connector. Here is where it sits: Since the 1984 models used the 12V ignition switched power through that switch makes it easy to get 12V for the choke, FWIW, the 7 volts from the alternator is enough to close a Bosch relay I used it to give me a charging circuit for my 5th wheel trailer batteries. Link to comment Share on other sites More sharing options...
myrl883 Posted February 12, 2020 Share Posted February 12, 2020 I have never seen a 3 terminal used on a Ford, the oil pressure switch on the 460s with the hot fuel hanling package are two small pins in a weatherproof connector. Here is where it sits: Since the 1984 models used the 12V ignition switched power through that switch makes it easy to get 12V for the choke, FWIW, the 7 volts from the alternator is enough to close a Bosch relay I used it to give me a charging circuit for my 5th wheel trailer batteries. My '81 F100's 302 used that same oil pressure sender. I can't for the life of me remember why, but it had to do with California emissions. It was a EEC-III truck. Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 12, 2020 Share Posted February 12, 2020 Ok I can follow this... a picture would be nice. That being said, I'm not sure what i have is a stock setup. I know i have a electric fuel pump, but the truck didn't originally so I'm not so sure about having a fuel pump cutoff relay in a stock location. Here's a pic of the relays on Big Blue. I've circled three since I've seen the fuel pump relay in both the 9C392 housing as well as by itself on the firewall. But look for the red/yellow wire going in as well as yellow, black, and pink/black hash wires. Link to comment Share on other sites More sharing options...
FormerBigDaddy Posted February 12, 2020 Author Share Posted February 12, 2020 Here's a pic of the relays on Big Blue. I've circled three since I've seen the fuel pump relay in both the 9C392 housing as well as by itself on the firewall. But look for the red/yellow wire going in as well as yellow, black, and pink/black hash wires. Ok i'll take a look in there today. I assume this red/yellow wire goes to the largest black box in the pic? Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 12, 2020 Share Posted February 12, 2020 Ok i'll take a look in there today. I assume this red/yellow wire goes to the largest black box in the pic? The black box is just a housing that holds the relays. The red/yellow wire goes into a plug, like the black plug on the right that connects to the green thing, which is the relay. In that black housing there are two relays. The fuel pressure relay is supposed to be in there, but is sometimes on the firewall like the one on the right in the circle. Link to comment Share on other sites More sharing options...
FormerBigDaddy Posted February 12, 2020 Author Share Posted February 12, 2020 The black box is just a housing that holds the relays. The red/yellow wire goes into a plug, like the black plug on the right that connects to the green thing, which is the relay. In that black housing there are two relays. The fuel pressure relay is supposed to be in there, but is sometimes on the firewall like the one on the right in the circle. Couldn’t locate an oil pressure sensor on the back of the engine. Honestly not sure if I found the relay either. I have a ton of relays on the driver side fender. I did find a red/yellow wire but it was going to this unused plug. Link to comment Share on other sites More sharing options...
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