Oil & Fuel 4720 erratic no-start condition

[AcreageGuy]

I have a 4720 that I bought new in 2006. It has a little over 1000 hours on it, because its only been used for personal use on my home acreage, as well as occasional grass seeding or spraying on some commercial properties and a farm. It always had a problem with occasional situations where it won't fire at all until I turn the key on, try to start it, and repeat (sometimes several times) if it doesn't immediately start. I talked to the dealer about it when it was new, and they said they'd take a look at it, but it was then so erratic (could go days or weeks without it happening) that I figured they might not be able to find it and never took it in to them.

It has gotten noticeably worse in the last couple of years, to the point that most of the time I try to start it, I have to make repeated tries until it fires. I thought maybe that something was hanging up in the run/stop solenoid, so this summer, I removed the small cover on the front of the engine that covers the internal throttle and fuel stop linkage that the solenoid operates. Here's what I found.

1. The solenoid always pulls up fully when the key is switched on.
2. The solenoid operates an L-shaped lever that pivots on the throttle shaft.
3. The L-shaped lever lets a spring loaded plunger move forward, out of the cylinder head, when the solenoid operates when the key is turned on.
4. The spring loaded plunger doesn't always extend out of the head when the key is turned on, and is thus the cause of inability to start when this happens.

Looking at Deere's parts book, it looks like the plunger is the fuel rack. When the solenoid is de-energized by turning the key off, it must push the fuel rack back far enough to shut off all fuel to the injectors. If it doesn't pop out under its spring load when the key is turned on, the engine won't start for lack of fuel. To me, it looks like it would be a major job to get the fuel rack out of the engine and replace it and the spring that pushes it out of the block. I've got the technical manual, but it just talks about the fuel rack in terms of a major repair operation.

It must have always had something wrong that caused it to operate harder than it should. Without ever having seen the part and how tight a fit it is in the head, I don't know if being bowed might cause the problem. Or maybe one of the injectors that it operates turns harder than it should? One simple thing that I might try is a fuel additive that is claimed to improve lubricity.

Has anyone else experienced this type of problem with a 4024 type or similar Deere engine?

Any suggestions on what I might do to further investigate or to fix?

 

[beenthere]

Does the intake heater come on when you turn the key on, and you wait until the light goes off? or do you need to energize the heater by pushing down on the key when turning it on, for a few seconds to get the intake chamber warmed up?

Didn't read that was part of your start-up method.

:welcome: to TBN

 

[beenthere]

Start procedure according to operators manual. Assume you are doing this.

9. For cold weather starting, use the intake air heater system. Activate the intake air heater system by pushing in the ignition key switch with the key, and holding it there for the required time:

• 10 - 15 seconds for temperatures as low as -18°C (0°F).

• 15 - 30 seconds for temperatures below -18°C (0°F).

 

[AcreageGuy]

This problem has always occurred year round. It has nothing to do with cold weather. Its a matter of fuel versus no fuel at all. I've concluded that there is no fuel to the injectors when the fuel rack does not move under the force of the spring that tries to push it forward in the head when the start solenoid moves the lever that should allow the rack to move forward and allow fuel flow.