workinonit
Elite Member
Interesting you found that. On my old JD 5310 I had the same issue and found the device was a thermister. I lifted that wire at the injector pump and ran the tractor for a couple of years without it.
Cranks but won't start. Injection pump needs electrical power?
- Thread starter slimcity9
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Ok, it's the "cold start advance sensor". Found the name in this video describing the same problem. Theory of operation described here. Sounds like the short to ground occurs in the sensor itself.
jonsstihl
Veteran Member
I was going to say it looks like some kind of temp sensor shut off safety device for when it gets too hot but sounds like you found the problem can you test the resistance of the sensor. the shop manual may have the specs. and double and triple check the wiring.
The resistance measurement was misleading, greater than 10 ohms, which wouldn't blow the fuse. It takes a higher current source to demonstrate the issue. The definitive check will be to disconnect the sensor and apply variable power to one of the leads. If there's current to ground then that's it for sure.
workinonit
Elite Member
That's exactly what mine was and since I'm in SC I don't need it. Mine was only one lead so evidenyly it was shorted to ground.
I'm managing to drag this repair out pretty long. To remove a defective cold start advance sensor you need to remove the bypass tube from the thermostat cover, a procedure briefly mentioned in the workshop manual for the JD 3029 engine. The attached diagram is the important part. My question is: What kind of fitting attaches the bypass tube to the thermostat cover (location B)? Is it just a press fit? I've loosened the hose clamps at the other end and removed the hold-down screw. I've applied modest pulling force, but so far the bypass tube won't budge. I'd like a little reassurance that this is the right approach before I figure out how to get more leverage.
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Finally put this one to bed. I had a guy come over with a skinnier closed-end wrench and a willingness to apply more force to squeeze the wrench between the by-pass tube and the sensor. After that he was able to remove the sensor without removing the by-pass tube. Back in business at last.