Diesel tractor hard to start cold: glow plugs
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Applies to: Diesel tractors (Kubota, John Deere, Massey Ferguson), All years
Symptoms
- Long cranking on cold mornings
- White smoke then rough running
- Starts fine when warm
Why it happens
One or more failed glow plugs, or a bad glow relay or timer, leaves cylinders too cold to fire.
How to fix it
- Hold the glow position longer and see if it helps.
- Check for voltage at the glow plug bus bar with key in glow.
- Remove the bus bar and test each plug's resistance.
- Replace failed plugs; test the relay if no voltage.
Tools and parts
- Multimeter
- Glow plugs
- Deep socket
What the factory service manual covers
Electrical: glow plug test values, preheat circuit. The full procedure, specs and wiring diagrams are in the factory service manual for your machine.