John Deere 120C Won't Start

[Outdoorsman]

I have a John Deere 120C Excavator that stopped running while working on the farm. The engine turns over but will not crank, I thought it was a fuel issue, so first I changed the filter, then next the little priming pump with the little leaver was changed. Then bought a new Injection pump and replaced. thinking that was it. I installed to all specs with timing the engine with the injection pump to 1st cylinder TDC. fuel is coming out the injection lines, so I'm pretty sure I have the system primed. but will not crank unless a little Starting fluid is sprayed in, if I spray the engine with starting fluid it will crank right up and run fine until I stop shooting bursts of starting fluid to it.
if I shut the key all the way off where I can remove it, then crank the engine it will have a little want to crank and acts like it for about 5 seconds then goes right back to just turning over. (without using starting fluid of course). If I do not turn the key all the way off where I can remove the key just to the point that it kills the engine, then try to start again, it just turns over and over without any want to crank.
Any thoughts of what I could do next to get it to crank and stay running!?
Please Help
Thanks

 

[Diesel Dave]

Welcome to HEF Outdoorsman
Complete Serial number ?

 

[Outdoorsman]

FF120CX034206 I think

 

[Diesel Dave]

That is an ECU controlled injection pump.
Check the fuses in the cab fuse box.
There are also 2 fuses in the area of the ECU.
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https://partscatalog.deere.com/jdrc/sidebyside/equipment/388662/referrer/search/pgId/544951120

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[Diesel Dave]

Also pay very close attention to the electrical connections on the wire harness to the back of the injection pump.

 

[Outdoorsman]

Okay thanks, fuel is coming through injection lines so I'm assuming, that is good, and its an electrical issue from ecu? or from ecu to the pump?! so I will check these and will get back with you! Thank You!

 

[Outdoorsman]

You were Right Diesel Dave,
It was an Electrical connection issue, frayed wires touching each other, fired right up and purred like a kitten after fixed. Ran it for an hour filling in a hole, then started moving it about 300 yards up by the shop and it died about 150 yards after walking. Straight up died, won't crank up, just spins over. Hooked the computer up to it again and it said "Crank Position input pattern error". I went and bought a new OEM crank sensor and replaced. Still doing same thing and throwing same code! What else could that be now? Thanks for the help

 

[Diesel Dave]

So of course I want to say check wiring and or connectors.
Check the Crankshaft tone wheel for being loose.
It can become loose over time and eventually spinning on the crank.

 

[Outdoorsman]

how do you check the crankshaft tone wheel to see if it's loose? and or if something we're missing. checked wiring. jumped wires from computer directly to sensor. and still throwing same code.

 

[Diesel Dave]

Use a small screwdriver and feel if the wheel moves as you pry lightly and try and turn it