1969 Ford 4500 key switch

mikewood869

Well-known Member
When looking at the thermostat on the ford 4500 (the tractors wiring harness is a C), I noticed on the 5 position key switch, the key switch has; heat, off, on, and crank, but doesn't have a heat-crank (the key won't turn to 9 o'clock). I need to re-look at the lines going from the thermostat. It looks like someone rigged the return line going to a "T" (from the injectors to the fuel tank). I can see smoke from the intake manifold and the thermostat glowing. It seems like the tractor would need to be cranking with the thermostat glowing (& smoking). Where does the fuel come from to supply to the thermostat? In the first picture with the hand, the hand is pointing to the line for the thermostat with one of the ends being for the return line for the fuel tank and one of the others being for the thermostat..
mvphoto33298.jpg
 

Mike, the ThermoSTART, not the thermostat, does in fact use the return line fuel to preheat the manifold. Early models had a reservoir, and your picture does show the reservoir right behind where your pointing. Later models just used a common tee at about the same location. The return line sends fuel back to the tank when running and the tee or reservoir/tee fills the little line up coming back to the thermoSTART with fuel. This is plenty of fuel to run the little thermoSTART long enough to get a cold start.

Looks like you have an earlier/orig switch with the heat on the left side of OFF... replacement switches have it on the right side of off.

Good luck with the tractor.
 

When the tractor is off and sits, does that line fill up for the thermostart (sorry not thermostat) fill up with fuel and when the tractor is running the fuel goes to the fuel tank. if so, the line might be clogged and I'll blow out the line. Where the old reservoir for the thermostart is, it seems like there were lines cut, so I wasn't sure if that was factory or if someone add that later (since the torque converter is leaking a pump was install to catch the fluid and to pump it back in).
 
The line should always have fuel in it as it is tee'd to the return line which should always have fuel in it. The "heat" position on the key switch provides electric power to an electric heating element in the thermostart. When it heats up a valve inside the thermostart should open from the heat and allow some fuel to dribble into the manifold and onto the hot element and the fuel should catch fire. If you see the glow from the hot element and no flame, then no fuel is getting through. It might be because the line is clogged or it might be because the valve is faulty and not opening. Disconnect the fuel line from the thermostart with the key off. If fuel does not dribble out then the line is clogged. If it does dribble out then the valve is likely not opening.
 
(quoted from post at 16:12:16 03/22/19) The line should always have fuel in it as it is tee'd to the return line which should always have fuel in it. The "heat" position on the key switch provides electric power to an electric heating element in the thermostart. When it heats up a valve inside the thermostart should open from the heat and allow some fuel to dribble into the manifold and onto the hot element and the fuel should catch fire. If you see the glow from the hot element and no flame, then no fuel is getting through. It might be because the line is clogged or it might be because the valve is faulty and not opening. Disconnect the fuel line from the thermostart with the key off. If fuel does not dribble out then the line is clogged. If it does dribble out then the valve is likely not opening.
This is how that valve operates:
https://www.youtube.com/watch?v=NeDvCVS38hk
 
Are you saying that yours is working the same as in that video? If so, then it is working properly. In a prior post you said that you saw it glow and that you saw smoke, but you did not mention any flame.
 
(quoted from post at 07:40:21 03/23/19) Are you saying that yours is working the same as in that video? If so, then it is working properly. In a prior post you said that you saw it glow and that you saw smoke, but you did not mention any flame.
The line was either clogged or broke in a spot. I ended up pulling the line out and cutting it in half and putting on a external tank with diesel in it and the tractor fired up (also had to put the battery charger on the tractor).

Tractor without the battery charger:
https://www.youtube.com/watch?v=jcW3_7VjvRo

Tractor with the battery charger:
https://www.youtube.com/watch?v=0pQxdJRcgf8

The old reservoir broke. We might try to make a new reservoir that you would have to fill every once and a while, if not, we'll just re-t and put the t up higher.
Regarding to the last post, I wasn't sure if that is how the thermostart was suppose to work. Now onto charging issue it seems.
 
(quoted from post at 14:03:29 03/23/19)
(quoted from post at 16:05:43 03/23/19) Would that line going to the thermostart need to be bled?

Shouldn't need to be as far as I know.

Okay, going to try to re-cut the lines and put the back together tomorrow. Seems like the old line was fixed in 5 different spots.
 
Okay, going to try to re-cut the lines and put the back together tomorrow. Seems like the old line was fixed in 5 different spots.
 

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