Bullnose Gator Posted July 24 Share Posted July 24 I replaced the solenoid and noticed the "i" terminal is smaller than the original, so the wire doesn't connect well (the one circled yellow in the pic below). However, with that wire completely off of the terminal, the truck idles perfectly. I've done my best to dig through the forums and documentation here, and my best interpretation is that this wire is Fuse Link T (highlighted yellow in the wiring diagram below), that should effect the electric fuel pump, or carb circuit, but I haven't learned how to read wiring diagrams properly yet. First, am I right about that? The tank selector valve (or something related) hasn't worked since I got the truck, and I've never looked into it. I'm guessing the prior owner could have spliced up the related wiring to circumvent it somehow, but wanted to make sure I'm not headed down the wrong path. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted July 25 Share Posted July 25 Hi Jeremy, In earlier Hot Fuel Handling systems the (I) wire provides full current directly to the fuel pumps (prime while cranking) This is because there's not yet any oil pressure to pull the safety relay closed Also, while running the pumps get power through a* resistor. Whether this effects pressure or volume or both I'm not sure, because my truck has a mechanical pump. But I do know that delivered volume is supposed to be a quart in 15 seconds (60 gph) Link to comment Share on other sites More sharing options...
Bullnose Gator Posted July 25 Author Share Posted July 25 Hi Jeremy, In earlier Hot Fuel Handling systems the (I) wire provides full current directly to the fuel pumps (prime while cranking) This is because there's not yet any oil pressure to pull the safety relay closed Also, while running the pumps get power through a* resistor. Whether this effects pressure or volume or both I'm not sure, because my truck has a mechanical pump. But I do know that delivered volume is supposed to be a quart in 15 seconds (60 gph) Thanks, Jim. So this wire being disconnected wouldn't necessarily prevent it from starting/running, but, the pump may not be getting all the juice it's intended to get, am I following that correctly? Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted July 25 Share Posted July 25 Thanks, Jim. So this wire being disconnected wouldn't necessarily prevent it from starting/running, but, the pump may not be getting all the juice it's intended to get, am I following that correctly? Here's that fuselink 'T' on the right. You can see power from the 'I' terminal bypasses the 'resistor in run' part of the circuit that is completed when the oil pressure switch back by the firewall closes, feeding the selector switch on the climate control through a resistor. The switch valve and pumps are shown with the senders With that wire disconnected the pumps won't run to prime the carburetor, and if it doesn't built enough oil pressure while cranking to close the switch they won't ever run. You can (A) Prime the carb yourself through the vent tubes front and rear of the carb throat. (B) Jumper the oil pressure switch that is adjacent to the sender, behind the EGR valve, close to the firewall. I hope this helps. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted July 25 Share Posted July 25 Here's that fuselink 'T' on the right. You can see power from the 'I' terminal bypasses the 'resistor in run' part of the circuit that is completed when the oil pressure switch back by the firewall closes, feeding the selector switch on the climate control through a resistor. The switch valve and pumps are shown with the senders With that wire disconnected the pumps won't run to prime the carburetor, and if it doesn't built enough oil pressure while cranking to close the switch they won't ever run. You can (A) Prime the carb yourself through the vent tubes front and rear of the carb throat. (B) Jumper the oil pressure switch that is adjacent to the sender, behind the EGR valve, close to the firewall. I hope this helps. Fuse 18 provides the power to pull in the oil pressure switch It also powers the carburetor bowl vent solenoids... See the grey box lower right.... What Im saying is that while the starter is engaged (and 'I' is energized) the fuel pump has 'turbo' mode to quickly fill the carburetor bowls, if the truck has been sitting and the fuel evaporated. One of the tricky things about reading the EVTM's is that it only shows you the circuit being discussed. There may be other circuits in a certain connector, but only wire '123' is shown. Link to comment Share on other sites More sharing options...
Bullnose Gator Posted July 25 Author Share Posted July 25 Fuse 18 provides the power to pull in the oil pressure switch It also powers the carburetor bowl vent solenoids... See the grey box lower right.... What Im saying is that while the starter is engaged (and 'I' is energized) the fuel pump has 'turbo' mode to quickly fill the carburetor bowls, if the truck has been sitting and the fuel evaporated. One of the tricky things about reading the EVTM's is that it only shows you the circuit being discussed. There may be other circuits in a certain connector, but only wire '123' is shown. Ok, I think I'm slowly getting it (still need to study up on reading wiring diagrams), you've dumbed it down almost enough for me . Sounds like finding either another solenoid that has the same size terminal "i" as the original so the wire can connect nice and snug, or some kind of adapter for the smaller terminal that's on there now is the easiest way to keep the system functioning as designed. Really appreciate your help, Jim! Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted July 25 Share Posted July 25 Ok, I think I'm slowly getting it (still need to study up on reading wiring diagrams), you've dumbed it down almost enough for me . Sounds like finding either another solenoid that has the same size terminal "i" as the original so the wire can connect nice and snug, or some kind of adapter for the smaller terminal that's on there now is the easiest way to keep the system functioning as designed. Really appreciate your help, Jim! Just squeeze the boot with a pair of pliers. It's not that much current that the smaller stud can't provide. I'm still wondering why it runs weird when connected. You might check that it isn't stuck on in "Run" I'm not sure HOW that could happen, but if it did the pumps (in turbo mode) might be overwhelming the float valves in the carb and causing it to run too rich. ??? (This is only conjecture. Diagnosis over the Internet is all but impossible) Link to comment Share on other sites More sharing options...
Bullnose Gator Posted July 25 Author Share Posted July 25 Just squeeze the boot with a pair of pliers. It's not that much current that the smaller stud can't provide. I'm still wondering why it runs weird when connected. You might check that it isn't stuck on in "Run" I'm not sure HOW that could happen, but if it did the pumps (in turbo mode) might be overwhelming the float valves in the carb and causing it to run too rich. ??? (This is only conjecture. Diagnosis over the Internet is all but impossible) I see how I confused you...I wasn't saying it runs weird with the wire on. It starts/runs the same weather the wire is on or off, at least as far as I can see/hear, no perceptible difference. So that made me wonder what it is supposed to do, and it was working properly before the new solenoid. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted July 25 Share Posted July 25 I see how I confused you...I wasn't saying it runs weird with the wire on. It starts/runs the same weather the wire is on or off, at least as far as I can see/hear, no perceptible difference. So that made me wonder what it is supposed to do, and it was working properly before the new solenoid. Sorry if I didn't quite understand. I was more focused on getting you the right diagrams to help you with the Hot Fuel Handling system Some people miss the fact that it changed over time. Earlier systems had the selector switch controlling a SPDT relay that drove the switching valve back & forth Did I leave you confused? Is there anything you still aren't clear on? Link to comment Share on other sites More sharing options...
Bullnose Gator Posted July 25 Author Share Posted July 25 Sorry if I didn't quite understand. I was more focused on getting you the right diagrams to help you with the Hot Fuel Handling system Some people miss the fact that it changed over time. Earlier systems had the selector switch controlling a SPDT relay that drove the switching valve back & forth Did I leave you confused? Is there anything you still aren't clear on? All good now. The boot has been pinched, and wire securely reattached. Thanks again for taking the time. you can consider this ticket closed! Link to comment Share on other sites More sharing options...
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