Thermostart Interchange

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ScottUSA
Posts: 89
Joined: Mon Mar 26, 2018 1:59 pm
Location: North Carolina

Thermostart Interchange

Post by ScottUSA » Thu Feb 20, 2020 6:22 pm

I have a recalcitrant 885 that is a reluctant starter in cold weather in spite of a new thermostart. According to what I have read in another forum - Ford, Massey-Ferguson, David Brown and maybe others used a thermostart to preheat their diesel engines. The various examples are supposed to be interchangeable but have different heat producing capabilities. If any of this is true which version is considered to be the hottest?

Full disclosure: Engine compression is borderline and is waiting for an opportune time to receive an in-frame.

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ollek
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Re: Thermostart Interchange

Post by ollek » Fri Feb 21, 2020 5:42 am

I have been working with David Brown tractors fo 45 years and I have never heard or seen any different Thermostarts. To me they are all the same. Many of the comments on different forums are made by people with little or no real understanding about topics they are commenting on. Remember that you have to keep the pre-heatinhg on for at least 30 seconds in cold weather in order to get enough heat into the inlet manifold. Have a look at the clock when you are pre-heating, 30 seconds is a long time. Also, it takes a long time for the fuel valve to open and the flame to start burning. You can hear a pop if you are listening carefuly when the valve opens and no heat will be generated before the valve is open. And then, the flame that heats the inlet air can not be hotter or colder. The temperature for a diesel fuel burning flame is always the same. It is posiible that different units use more or less fuel, giving a smaller or bigger flame, but this does not effect the temperature of the flame itself and I have never come across thermostarts with different size fuel supply passages. You just have to keep the pre-heating on for a longer time if the unit have a smaller flame. This is all basic fysics. Diesel engines do not start as quick as a petrol engine. It takes longer cranking time and a battery in good condition for diesel engines to start in cold climate. If the engine starts to fire but do not start, stop cranking and pre-heat for a further 20 seconds before you start cranking again. When the engine starts, do not increase the engine speed but let the engine run at low idle until it cleans up.

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cobbadog
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Re: Thermostart Interchange

Post by cobbadog » Fri Feb 21, 2020 10:59 am

What determines the length of time that the flame will burn for? Is it the length and or bore size of the fuel line that feeds the thermostart?
The reason I asked was I just read about a restoration on a 4 cylinder SMC engine in a Ferguson which were never the best starters and the restorer put a section of copper tubing that was bigger in bore size to act as a larger capacity for the fuel supply and the extra burn time helped him with his bad cold starts.
Not ever had to play with one I don't know what is right or wrong but the theory sounded good.

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ollek
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Re: Thermostart Interchange

Post by ollek » Fri Feb 21, 2020 11:36 am

The time for the flame to burn is determined by the operator and the piping has nothing to do with this. The flame will burn for as long as the driver keeps the igniotion key in pre-heat position. The piping size and the size of the reservoir together must be big enough to be able to hold fuel for at least two normal pre-heat operations. Putting in more or larger copper pipes enlargens the reserrvoir and fuel is available for a longer time. There is a possibility that the thermostart will run out of fuel if the amount of fuel available is too small and thereby stop the flame from burning but this happens because of poor design of the thermostart system. This is exactly the same as with the fuel tank, you can drive a longer distance if the fuel tank is bigger and the engine will stop if you run out of fuel. All David Brown tractors have originally been designed with a system that holds enough fuel to supply the thermostart. I thougt this simple fact was clear to all but have now learn that it was not.

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cobbadog
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Location: beautiful Coopernook NSW. near Taree. NSW. Australia

Re: Thermostart Interchange

Post by cobbadog » Sun Feb 23, 2020 10:14 am

That was not something I knew about the volume of fuel held or for how long or many time it would burn for and is why I asked, so thanks for the reply.

ScottUSA
Posts: 89
Joined: Mon Mar 26, 2018 1:59 pm
Location: North Carolina

Re: Thermostart Interchange

Post by ScottUSA » Sun Feb 23, 2020 3:29 pm

Ollek, according to the owners manual I have, the throttle should be in the wide-open or full throttle position when cranking a cold engine no matter the ambient temperature. In your opinion is this correct? Recently, I found the engine exhaust clears-up more quickly after starting if the half throttle position is used. On average, the engine starts as well one way as the other. This is probably due to a short snort of starting fluid being required if it is to start at all.

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ollek
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Re: Thermostart Interchange

Post by ollek » Sun Feb 23, 2020 4:16 pm

Well, you can have the throttle wide open when you crank the engine, but you must reduce the engine revs as soon as the engine starts. Having the engine idling will make it possible to keep the thermostat working during the engine low idle. The flame will die if you increase the engine revs above low idle, the air drawn in to the engine will do that. Keep the engine at low idle with the thermostart in operatin for at least 30 seconds after the engine has started, this will clear the exhaust as quickly as is possible. A long cranking time does not help as this can cool down the air in the cylinders and emptying the battery. The most important thing is the voltage supply to the starter motor and the condition of the starter motor. Slow cranking is the most common reason for slow starting. Many engines have been destroid by using starter fluid as a ower dose can brake the piston rings and then the engine will be even more difficult to start. Pre-heat a second time if the engine will not start within 15 to 20 seconds from start to crank the first time after pre-heat and forget the starter fluid. We try not to use any starter fluid in the cold country I live but we have block heaters in all engines.

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