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Grn rider
Grn rider, Technician
Category: Small Engine
Satisfied Customers: 282
Experience:  12+Yrs experience trouble shooting and repairs
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3 cyl diesel yanmar engine in john deere model 750 turn over

Customer Question

3 cyl diesel yanmar engine in john deere model 750 turn over no start
Submitted: 6 years ago.
Category: Small Engine
Expert:  Grn rider replied 6 years ago.
Hello,Customer,do you have serial# XXXXX for this tractor?
Customer: replied 6 years ago.
ser#385029005599

model#3tna72uj

john deere

this is what happened wife was out using the brush hog unit and she hit dirt mound shutting down the motor instantly has not started since
Expert:  Grn rider replied 6 years ago.
does this unit have glow plugs? or just one Thermostart heater unit. Black wire off r1 terminal of key switch goes direct to heater element.
Customer: replied 6 years ago.
the unit has glow plugs, I had checked to see if they had power and no volts at glow plugs I have power to the relay on the firewall but nothing out of the relay.I took it to a local diesel service ctr and he was saying I did not need the glow plugs?
Expert:  Grn rider replied 6 years ago.
Remove relay and make short jumper wire,turn key switch on, touch gray wire on relay socket to ground, your lamp should come on. Yes you need glow plugs in lower temperatures.
Expert:  Grn rider replied 6 years ago.
Also the 3TNA engine should have fuel shut off solenoid, make sure that is energized when key turned on.
Customer: replied 6 years ago.
ok what your telling me to do is jump out the relay. ? should I have power to the glow plugs when I turn the key, this tractor starts hard. in the past I had to use ether to get it running.do you think the relay could be the issue?
Expert:  Grn rider replied 6 years ago.
Could also be preheat controller, Glow plug cycle depends on engine temperature.It's possible your relay is bad, if you had to use ether, I suspect your compression is low. I would get that checked.Check all wire connections, also check fuse link from starter to control module. I'll check back with you later
Customer: replied 6 years ago.
I'm pretty sure this unit does not have a preheat unit it's an 1988 20hp john deere 750 with yanmar engine, will try your suggestions
Expert:  Grn rider replied 6 years ago.
My manual doesn't list a 750 having glow plugs, thats why I mentioned later model system. Do you have power on only one terminal of relay? How about when key is moved counterclockwise?
Customer: replied 6 years ago.
power on 2 point at the relay 1 comes from the starter which is hot all the time and the other from what looks like the key switch
Expert:  Grn rider replied 6 years ago.
Sounds like your relay is faulty, if you have good on one terminal and power on two.What is the current temp of your engine?
Customer: replied 6 years ago.
cold