John deere 755 wont stay running

   / John deere 755 wont stay running #1  

richfarrar

New member
Joined
May 15, 2014
Messages
1
Location
Wrentham, MA
Tractor
John deere 755
I have a john deere 755 compact tractor with 1581 hours on it. I purchased it in relatively rough shape not running with an injector issue. The injector pump was junk so I replaced it with a working used one and put all new injectors in also. I timed the pump and bled all the lines and now it starts. My problem is that the tractor will not stay running. The engine will run for several seconds then dies out. Whenever I move the throttle up just a little bit the rpms increase rapidly. Any suggestions would be great. Thank you.
 
   / John deere 755 wont stay running #2  
Sounds like a bubble somewhere. Try bleeding again?
 
   / John deere 755 wont stay running #3  
You sound like you know your way around mechanically to have done the work you already have, so you probably already know this...

Check the electric fuel pump for a steady stream.. I have a 755 and on a recent engine repair,, on first startup I had to bleed several times before engine would start and hold... I only had to bleed up to the pump these times,, not the injector lines..

These tractors use a fuel loop system that returns surplus fuel to the tank. There is a return hose I'm sure you worked with when you changed injectors.. You want to make sure the hose back to the tank is not plugged also..
 
   / John deere 755 wont stay running #4  
I doubt that timing is any part of your problem mind you, but I'm curious as to how you went about setting the timing?
I'm just guessing here, as is everyone else, but my "guess" would involve the condition of your "working used" injection pump. The governor and/or internal linkage that controls, but is not actually part of it may also be suspect based on your described symptoms. I add this only because you apparently have no real knowledge of how the engine behaved when it ran last.
 
   / John deere 755 wont stay running #5  
The timing on these is 13 to 15 degrees btdc... On the tna72 engines,,, .020 worth of shims under the pump is good if the pump is any good at all..

The governors on these tractors are never set correct and that and the radiator placement was the downfall of these tractors... However,, the governor should not affect a startup, and I figured I'd help him with the governor after he reported he got it to run.. Like everyone else, I don't know if or how he timed the pump
 
 
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