John Deere Gator 855d Hard To HelloStart

[jdcellar]

Hello- I have been having a problem with my 2012 855D Gator. It has become hard to start when it is cold, it will start but it takes about 5 seconds before it starts, after it has run for a while it starts just fine. I have changed he fuel filter,drained and replaced the fuel, and checked for a blown fuse. Thought I may have gotten some bad fuel but doing that didn't help the problem any. I'm thinking it is either a glow plug or the glow plug relay. Any ideas would be appreciated or if it could be something else that I've not thought of. Thanks for the help

[campoman]

I had the same problem with my 825i , which is a totally different engine but the symptoms are the same , it endeded up being the coolant sensor , took care of the problem starts fine when cold now, hope this helps . Campoman

[sapper94]

I also have a 2012 855D with starting problems - replaced the starter (was wearing out after multiple start attempts over a few months, replace from bottom is best).

The coolant sensor I am looking at possibly replacing is mounted on the water pump assembly (right side of gator, single post electrical connection CH15516). Any suggestions on continuity of sensor when cold/hot/bad?

Also checking the battery power - this is the same battery from when I purchased the 855D new in 2012, may be weak on CCA. Made one attempt to start after installing the new starter and noted the battery voltage dropped significantly when cranking. Hit the charger to give extra amperage boost and got it to start. Will post more - "cooling" engine down now (outside temp 30F) and will attempt to start without block heater on.

[sapper94]

At 0900: 27 degrees F overnight and no continuity at the coolant sensor listed in my previous post. Turned ignition on and wire connected to sensor tested at 12V. Plugged in block heater for 30 minutes and retested, sensor still had no continuity. Waited for glow plug light to turn off and engine fired right up. Disconnected coolant sensor wire while engine running and no change.

Not sure if this is the same sensor "campoman" was referring to. There is another sensor on the lower right backside of radiator though this appears to be only for turning on/off the electric radiator fan.

Just for historical purposes - I have a 2012 855D XUV two-seater (serial number before 06000) with 910 hrs; changed both primary and secondary air filters, oil and oil filter, cleaned fuel sediment bowl and filter/strainer, cleaned battery posts and ensured battery fluid levels were good. This gator is used multiple times every day and has plowed a 1/3 mile driveway every winter with a Boss XTV plow since it was purchased, also why it has a deluxe cab with heater (poly cab is a bad design and did not hold up in cold winters). It is a work horse, not used to play out on the sand dunes, etc.

[200mph]

Perhaps you fixed your 855D by now.

The 855D uses two temperature sensors, but they have different functions. One puts out a variable resistance based on coolant temperature.

The other temperature sensor is a switch. It's either on or off and is used to control when the cooling fan is activated.

You'll find very detailed information on how the glow plugs function and corresponding wiring schematics in the work shop manual. If you plan on repairing your gator, the manual can be a valuable tool.

Added in Edit

Reviewing the manual. It states an ambient temperature sensor located in the VCU to calculate how long the GP's are activated.

Fuse F6 supplies power to the GP