Thermo Start Heater

Does anybody know how those Thermo Start manifold heaters work? Does something open up inside them and let the fuel
in when they reach a certain temperature or something? There's no wire to the little fuel reservoir, there's fuel
to the nozzle/heater unit all the time.

I had one quit working three weeks or so ago, so I ordered a new one. Meanwhile, I discovered the old one popped
(ignited) after 30 seconds or so. It used to after about 15 seconds. The new one got here, so I went ahead and put
it in, figuring it would pop after 15 seconds or so like it used to. It didn't. In fact, in the two weeks or so
since I put it in, I've only heard it pop once, and that was after 30 seconds or more.

It's been relatively warm, so I've just been holding it for 30 seconds and it been starting. I figure it must have
just been getting enough heat from the electrical coil to give it the little help it needed. This morning it was 16
degrees. I finally got the tractor started, but it took a while. I felt the unit and about burned my finger from
the electrical coil being so hot, but it never popped. I've had the T off, blew through it, blew air up the fuel
hose all the way to the tank, and still no pop.

I'd put the old one back in and try it again, but the old one had a spade fitting for the wire and the new one has
a screw, so I had to cut it off and put a new one on it for the screw. I don't have any new spades that big. I'd
have to go to town and get one. I hate to keep cutting that wire back, it's none too long now. I could clamp it
with Vice Grips I suppose, but I'm not going to run it that way.

Perhaps your battery voltage isn't up to par (check it while the heater is activated) or excess resistance has developed in the wiring, connections, or switch dropping some of the voltage that should be getting to the heater. (The suspect connections or the switch would be heating up.)

If the heater isn't getting it's designed voltage it will be slow to heat up enough to activate the thermal valve that admits fuel.

Dunno what you got as a replacement unit, I had a new aftermarket one some years ago that acted like yours, and another that drizzled fuel all the time, causing an engine knock.

I can check, but it activates right off the starter switch. You turn it one way to start the engine without the
heater, turn it the other way about 45 degrees and hold it until it pops then turn it farther to start. I can't
figure how the vlotage would drop or rise just turning the switch another 10 degrees. I'm going to hook a jumper
wire right from the battery post on the solenoid directly to the heater in a few minutes when I go back out and see
if it pops then. If there's something causing a drop, that should bypass it.

The CAV Thermostarts come in low, medium, and high flow rates, 12 or 24 volts, spade or screw lug, non turbo and turbo use, and two manifold thread sizes. They have two coils, the first heats up to ignite the fuel that the second valve coil opens after about 15 seconds. The two I have you can hear a poof after 14 seconds and I begin cranking engine at 18/20 seconds to draw the warm air in. The FASTEST way to damage one is to use it with NO fuel at the inlet. The early Ford 5000 will actually blow oil backward out the air cleaner if not cranked over fast enough.

undo the fuel line and be sure fuel is getting all the way down, sometimes sediment, rust, and such will settle in the line and restrict the fuel. As stated, the element has to heat to a preset point, then it releases the fuel to burn on the element. I have removed the rubber hose just before it and had another operate the switch to besure everything is working as it shoud. it usually takes about 25-45 seconds to operate on my old 345C.

I did that right from the start. Just did it again. Blew everything out with air, took the T off and blew that out. I give up. I'll order another one. I hooked a jumper wire to it and left it until it started smoking and it didn't pop. That second coil must be burned up.

I got it from Rick's Ag Parts. He specialized in parts for those foreign built Olivers, so I'm confident it's the right one. Something went wrong right out of the box.

Here's a link that shows a parts breakdown with an explanation in how it works.
https://www.hoyetractor.com/thermostart.htm

Thanks for that. I appreciate it more than you know. The part about bleeding it will probably keep me from burning up another new one. I wish there had been some instructions with the last one.

Here's an easier link to it.
Link

We have a 2001 JD4600 that has a Yanmar engine, and we just love it. I'm pretty sure it doesn't have the intake fuel injector, just the heater. If it's even close to 0 F I plug in the block heater, so it's never been started cold. If it's below 32 F I use the glow plug, it seems to reduce the smoking by a lot, so I know it works, even though it barely smokes at all.

I've got two with thermo start and two with just the electric coils. The thermo start heats up faster and holds heat while you're cranking on it. They don't use near the battery power either. They just use a hot wire. The ones with electric coils use a solenoid with a heavy battery cable running to them and a small wire to activate the coil.

(quoted from post at 08:53:36 03/15/23) We have a 2001 JD4600 that has a Yanmar engine, and we just love it. I'm pretty sure it doesn't have the intake fuel injector, just the heater. If it's even close to 0 F I plug in the block heater, so it's never been started cold. If it's below 32 F I use the glow plug, it seems to reduce the smoking by a lot, so I know it works, even though it barely smokes at all.

Click to expand...

Yep, your Yanmar/Deere has a simple ''grid heater''.