Thermostart function and its components

[Big Horn]

Hey everybody, so I got a 1972 Ford 4000 3 cylinder diesel tractor starting and running good. (I posted awhile back about the no start) I have degreased, and am now fixing a lot of small items. Much easier to see when it’s clean.

So I discovered the intake has a thermostart igniter with the small fuel line going to it supplied by the small reservoir at the return fuel line- right begind the fuel tank. The wire to the thermostart has been disconnected for a long time. I’m not sure my Dad ever had it in working condition all the years that he had it.

I still need to check the ignition switch to see if it has a terminal for the thermostart activation and in what position the key needs to be.

So my questions are;

Now that I have the tractor running I don’t want to clean the return line canister and it’s small line to the thermostart if that’s going to allow air into the system, as it took a long time to bleed all the air out with the distributor injection pump and injectors out….. how much trouble will it be to bleed that?
(I ask because before I tore into it for a “no start”, the fuel filter, lines, distributor injection pump, injectors were all gummed up- All rebuilt now)

Also, I’ve read the tractor manual and can’t find what turns on and off the fuel to the thermostart element- is it built into the element along with heating up or is it something else that allows the fuel drip?

Does the fuel drip onto the hot element before cranking or once the cranking begins?

It’s not something I have to fix right now but is definitely on the things to do list.

I’m currently replacing all senders, oil temp, engine coolant temp, fuel, coolant flush, new thermostat, hoses, and ordered a new seat, a front tire repaired (new tube) and rear tire removed, repair rim (calcium chloride leak) and remount.

The original owners manual seems a little vague so I appreciate the help……

Glenn

 

[Sean in PA]

The thermostart works when you turn the key to the "Heat" position by first heating an electric heating element that is on the end of the thermostart that is inside the intake manifold. As it heats up, a spring loaded valves opens from the heat and that allows some fuel to dribble onto the heating element and the fuel catches fire. That all happens before you turn the key to the start position. You are supposed to hold the key in th e"Heat" position for 30 seconds or so before turning it to the start position.

Nothing turns the fuel to the thermostart unit on or off. It is always there waiting for the spring loaded valve to open.

The thermostart reservoir and line are connected to the excess fuel line that returns excess fuel from the injection pump and injectors to the tank. There is no need to worry about getting air in those lines or the reservoir. When you bleed the air out of the fuel system, you only bleed it to the pump and then from the pump to the injectors. There is no need to bleed the excess fuel line or anything connected to it.

 

[Big Horn]

TY. I suppose I could run the 12V wire from the switch to the thermostart and then this winter use an infrared thermal heat gun to see if it is working by checking the intake temp.

Thanks for the explanation.

 

[Hacke]

 

[Ultradog MN]

I have coolant heaters on both of my tractors.
Either in the lower radiator hose or preferably, in place of a frost plug in the block. In cold temps I plug the heater in for an hour and the engine will start like it's July.

 

[Texasmark]

Different tractors have different methods of energizing the heating coil. Having diesels, I think I recall the '63 4 cylinder engines had a separate button and the '65 3 cylinder has a mid switch position where you start turning the on-off (key operated) switch to the first position and you get oil and gen lights and nothing else....as you keep turning, the lights go out.....when they go out you are in the TS position and just have to hold it there for as long as you feel is right to get the heater up to temp....30 sec. or so.... so that it will unplug the fuel line to drip diesel on the hot coil and set it afire, and then roll the key on over to the start position where the lights come back on until the engine starts. I think the TS is still activated when you move on over to the start position.

 

[Ultradog MN]

Different tractors have different methods of energizing the heating coil. Having diesels, I think I recall the '63 4 cylinder engines had a separate button and the '65 3 cylinder has a mid switch position where you start turning the on-off (key operated) switch to the first position and you get oil and gen lights and nothing else....as you keep turning, the lights go out.....when they go out you are in the TS position and just have to hold it there for as long as you feel is right to get the heater up to temp....30 sec. or so.... so that it will unplug the fuel line to drip diesel on the hot coil and set it afire, and then roll the key on over to the start position where the lights come back on until the engine starts. I think the TS is still activated when you move on over to the start position.

IIRC, the earlier 4 cylinder diesels did not ignite any fuel in the manifold.
They merely heated the air in the air cleaner. I doubt it was as effective as the thermostart on the 3 cyl models but never had to use it to find out.

 

[sotxbill]

Different tractors have different methods of energizing the heating coil. Having diesels, I think I recall the '63 4 cylinder engines had a separate button and the '65 3 cylinder has a mid switch position where you start turning the on-off (key operated) switch to the first position and you get oil and gen lights and nothing else....as you keep turning, the lights go out.....when they go out you are in the TS position and just have to hold it there for as long as you feel is right to get the heater up to temp....30 sec. or so.... so that it will unplug the fuel line to drip diesel on the hot coil and set it afire, and then roll the key on over to the start position where the lights come back on until the engine starts. I think the TS is still activated when you move on over to the start position.

Some of the early 5000 tractors and others.... you had to turn the switch to the LEFT of off, to get them to heat. Then later models had the newer switch the required you to turn to the right... but only in a certain position to heat... On those switches you turned it to the right, and the first click, the idiot lights came on... The you turn it more JUST until the idiot lights just go off, but not far enough to crank.. ITs in the position that the thermostart starts it heating cycle.. And it can take it 5 seconds or more to get hot enough to start to let the diesel into the heater element,, thus the little flame starts up. Then you must hold it long enough to heat the manifold air up to 300 degrees or more... This means when very very cold, you need to heat longer.. Sometimes YOU need to heat,, try to start, then heat, and try to start, then heat again, and then it starts... as it below freezing.... When it gets even colder, I cant say as it never gets much colder than 32 around here... AND also note, on the newer switches, when ever you crank, the thermostart is activated during the cranking position during the complete crank cycle. As least on the aftermarket switches that I currently getting. After a heat cycle, the manifold should be warm or even hot around the thermostart on the manifold.

 

[Big Horn]

I had the battery disconnected so I removed the rubber hose to the intake, and I ran a light set of jumper cables, battery negative to tractor starter body (ground) and from battery positive to the thermostart coil terminal…..and nothing.

As far as I know the 40 years my Dad had the tractor it was never in operation, so I ordered a new thermostart heater. When I change it out I’ll know if there is fuel in the line, or if it and the reservoir needs to be cleaned out.

It does have the block heater and we have used that for many years….. but I might as well get the thermostart operational again

 

[Big Horn]

I spent the afternoon taking out the ignition switch, headlight switch, testing wires, and comparing my notes with my DVM to the web.

I used my photo app to modify a picture and now I need to verify the key position between run & start with a test light on
Terminal #3. (There is no counter clockwise from Stop) Once I’ve verified I plan to run a small LED indicator lamp next to the gauge panel so that I have a visual of when it’s activated.

 

[Hacke]

If there are five key positions:

 

[Big Horn]

Thanks for the expanded view with the safety switch and starter solenoid

I’m replacing the original cluster with individual analog gauges (already replaced the generator with an alternator)

I know the cluster looks original but I dislike the (idiot) warning lights. I’d rather see feedback of real time.

I’ve upgraded most of the gauges on my ‘02 7.3 PSD and love them. My 68 Chevelle when I was in high school had the red warning lights……. as does my ‘59 Chevy but I’m keeping those original for appearance sake.

 

[Texasmark]

Some of the early 5000 tractors and others.... you had to turn the switch to the LEFT of off, to get them to heat. Then later models had the newer switch the required you to turn to the right... but only in a certain position to heat... On those switches you turned it to the right, and the first click, the idiot lights came on... The you turn it more JUST until the idiot lights just go off, but not far enough to crank.. ITs in the position that the thermostart starts it heating cycle.. And it can take it 5 seconds or more to get hot enough to start to let the diesel into the heater element,, thus the little flame starts up. Then you must hold it long enough to heat the manifold air up to 300 degrees or more... This means when very very cold, you need to heat longer.. Sometimes YOU need to heat,, try to start, then heat, and try to start, then heat again, and then it starts... as it below freezing.... When it gets even colder, I cant say as it never gets much colder than 32 around here... AND also note, on the newer switches, when ever you crank, the thermostart is activated during the cranking position during the complete crank cycle. As least on the aftermarket switches that I currently getting. After a heat cycle, the manifold should be warm or even hot around the thermostart on the manifold.

I had a tractor once that was like your 5000 mention but I think it was a MF 35.

 

[Big Horn]

Now I’m wondering if I shouldn’t install the new thermostart I bought and continue using the block heater, and leave good enough alone.

I looked into the throat of the intake and there’s a thick, dark, oily residue inside on the walls of the runner.
I wouldn’t want to get a fire started inside the intake from the fire thats generated by the thermostarts’ heat coil and diesel fuel operation.

The tractor doesn’t smoke at all after running a bit (other than a cold start) and has good power.

I know I need to clean the oil bath / filter ….. I have no idea when it was done last. I would definitely appreciate your thoughts about any danger of the putting the thermostart back in use after all these years.

The block heater when plugged in during cold weather does work well, as some have mentioned in above posts.

Thank you, Glenn (Big Horn)

 

[Texasmark]

In verifying my TS systems are working, I temporarily remove the intake manifold air inlet hose and look at the TS operation. When the coil gets hot enough and opens the fuel plug, the fuel that drops onto the orange (hot) coil ignite and drop down into the air inlet.....since the engine is rolling over, those "Great Balls of Fire" (Jerry Lee Lewis) are sucked into the combustion chamber and light off the diesel spray mist. Great sport.

 

[Big Horn]

Thanks for the reply. From what I’ve read it’s been recommended to hold the TS engaged for 30 seconds before cranking.

During that time (30seconds) is my concern. I drilled and tapped a 1/8” npt to install a temperature probe, in cleaning out the shavings with a small vacuum hose is when I discovered how oily (greasy) thr intake is. Here’s a picture that might better explain my concern.


After Dilling

After vacuuming shavings…..light shining through hole from troublelight.

If I decide the risk for fire is too great I will simply remove EGT probe and install a 1/8” npt plug.

I noticed the greasy mess when sliding the vacuum tubing in and removing. During a search I found several threads where an OP reported similar buildup and the consensus was for an older diesel with lots of hours, Thats it wasn’t uncommon.

Just not sure about starting a fire inside

 

[Ultradog MN]

Thanks for the reply. From what I’ve read it’s been recommended to hold the TS engaged for 30 seconds before cranking.

During that time (30seconds) is my concern. I drilled and tapped a 1/8” npt to install a temperature probe, in cleaning out the shavings with a small vacuum hose is when I discovered how oily (greasy) thr intake is. Here’s a picture that might better explain my concern.


After Dilling
View attachment 132600

After vacuuming shavings…..light shining through hole from troublelight.
View attachment 132602

If I decide the risk for fire is too great I will simply remove EGT probe and install a 1/8” npt plug.

View attachment 132605

I noticed the greasy mess when sliding the vacuum tubing in and removing. During a search I found several threads where an OP reported similar buildup and the consensus was for an older diesel with lots of hours, Thats it wasn’t uncommon.

Just not sure about starting a fire inside

If you are concerned about it you could wash/brush/clean all the gunk out of it.
Pretty simple job to pull the manifold on a diesel and have at it. I think you could leave the filter and all the fuel lines just hang there.
Not like a 3 cylinder gasser anyway where you'd have to drain the radiator down and mess with carb, throttle linkages and fuel lines.
You might even gain half a horsepower by eliminating the crud and making it a smoother airflow into the engine.

 

[Destroked 450]

What’s the EGR probe in the intake for

 

[Big Horn]

My ears are no good…… thr past 35 years working in a casting foundry. I want to be able to see temps rising on the gauge when TS is activated. I also plan to activate it through a momentary switch and relay. I checked the ignition switch with a DVM and find that the halfway position is very clumsy.

With the momentary switch the TS can never accidentally be left on. While the probe will not be exposed to no where near the heat of an exhaust manifold (like I have on my 7.3 PSD) it shouldn’t have a problem showing temp increase on the intake, and it will be interesting to see the varied temps of different time interval durations and first time starts at different ambient temps.

At least thats the plan…….and Im working on the new gauge display (no warning lights) , all live gauges, and managed to make it all fit:

 

[Dieseltech]

All the Thermostarts I have I use my watch to time them before cranking engine by heat/start switch, 15 seconds heat THEN start cranking. Be aware too if engine has an oil bath air cleaner like my SOS 5000 diesel, TOO LONG heat WILL blow oil back out the air cleaner inlet. CAV makes Thermostarts in LO, Medium and Hi flow models, and both 12 and 24 volts.