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bgsengineclinic, Small Engine Technician
Category: Small Engine
Satisfied Customers: 220
Experience:  Over 20 years of experience in Small engine repair, Kohler Certified Expert Technician, Self-Employed in my own dealership.
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I have a John Deere 750 compact tractor with a Yanmar diesel

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I have a John Deere 750 compact tractor with a Yanmar diesel engine and I think there are glow plugs on it but am not abe to find them, can you help me?

bgsengineclinic :

Hi. this should be a thermostart system , there is just one glow plug, if equipped.

Part number CH15593 Thermostart glow plug, it will be located in-line near the intake manifold, look for a bracket holding a small tank that appears to be a fuel filter with 3 nipples on it, 2 hoses hooked to it, follow the bottom hose down to the thermostart glow plug which will have one wire attached to it. should be in the vicinity of the intake manifold on the left side of tractor near top of engine.
Customer: replied 5 years ago.
would that keep it from starting and running during cold weather?
It will make it very difficult to start, yes. If the weather is cold enough, diesel fuel can gel if you are using summer blend, but that usually only happens when temperatures get down to the single digits or below zero.

All it does is warm the air in the intake manifold, an d if it started fine last year in cold weather, it is quite possible the thermostart is bad.

Are you activating it before start up? Sometimes if you turn key backwards from off position (opposite direction of turning to start and run) it activates the glow plug system, if that does turn that direction and you see a light come on in the dash, you can hold it there for 10 to 20 seconds to preheat the glow plug and then go to start it. Another trick that has been used with these is to pull out the electric PTO clutch switch which prevents starter from engaging, and turn key to start for 15 seconds or so, then key off, pto switch in, and crank to start.

Not all machines have the glow plug system, cannot really tell from info provided, but if it does have the system, it is thermostart.
Customer: replied 5 years ago.
I just got the fuel pump back from being rebuilt and the shop brought it home and had trouble starting it and the next day I ran a new battery down trying to start it. Last winter it started great with the key to on position but not start and a lightning bolt light on on the dash for a minute or two, if not a small shot of deissl starting fluid would start it and it would run great. now it doesn't, it went once for about 10 seconds then died and never went again. I have white exhaust, am I in the right direction with the start system or not?
ouch fuel pump rebuilt and you installed it? did you bleed the injectors? Air in the fuel injector lines will cause this problem - white exhaust is indicative of moisture or unburned fuel, and if it isn't getting enough fuel due to air in an injector line, then you'll have a hard time getting it started until the lines are bled.

Sounds like your thermostart is working (the lightning bolt lights up to indicate glow plug is preheating)
Customer: replied 5 years ago.
No the shop did, but I have some questions on their knowledge of this motor which is why I am speaking to you. If the cyclinders arre not getting enough fuel it will act like this, correct?
It can, yes if they are lean, or unclean fuel pump rebuild was done (dirt in lines or injectors) , or too much fuel (broken or leaking injector nozzles) if you get white puffs of smoke while cranking it is usually fuel that is atomized but not burning or only slightly burning -

If a shot of ether does not get it to fire though (you'd get some black smoke with the white) then I would be wondering if there is not water in the fuel or injection timing is off.

You indicated it started and ran once for 10 seconds, I'd also be wondering about the fuel return lines - plugged return lines can also cause this problem (excessive fuel)

But it sounds like a fuel problem in one direction or the other, it's hard to tell for me without having it at hand to work with - Ive worked on some Yanmar, but the majority of my diesel experience has been with Caterpillar, Mack, International, John Deere, Detroit Diesel, etc. (heavy truck and equipment) but the principles are all pretty much the same. It does sound very much like a fuel problem , unlikely to be compression troubles (unless they did something to the valves) so I'd be suspicious of water in the fuel, dirty fuel lines, or plugged return lines, or injector issues. Check the return lines that chain up between the injectors and see if any are "pinched off" or kinked. Can also unhook the return line from the fuel tank while cranking and see if you have fuel flow coming back to the tank.

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