Crank, but no start (and the fix) - Deere 425 AWS.

[mrsilv04]

Just to document this for others...

This spring, bought a used 1997 John Deere 425 AWS with a 60 inch deck. Only 1000 hours. Engine already has the cam update. I already own a 1995 John Deere 425 AWS with a 54 inch deck, with 3000 hours (bought new in 1996).

It developed some odd behavior when starting, almost like a weak battery (cranking was trailing off, the longer it cranked). Battery was 3 years old, so I replaced it.

The odd starting issues continued. Maybe it is the starter or the solenoid. Once I discovered that JD wants $400+ for a new starter and solenoid, I decided to wait in replacing it.

Since I now have a backup unit, and that I can also use to swap out parts on to troubleshoot this, I never "found" the time to work on it.

Then it started occasionally missing on one cylinder when good and hot. Bad coil? Hmmm... this pesky issue seems to be moving around. And add a couple of instances of run-on when trying to shut it down.

After enough of these issues had come and gone, it finally quit running. Dead. No spark at all. Something has finally failed completely.

NOW, I can finally troubleshoot this.

I began by swapping a simple module with about five wires on it, between the two units... and the 425 springs to life. The starter barely engaged, and it was running. This is more like it!

Here's the fix, and it is $20 from any John Deere dealer... and 15 minutes to install.

It is John Deere part number AM128906, Ignition Time Delay Module.

http://www.greenpartstore.com/John-Deere-Time-Delay-Module--AM128906_p_4451.html

 

[bioburner]

So this little module is there to give the fuel pump a bit of time before the starting system engages?

 

[Chris Meutsch]

Feels great to fix stuff for cheap.

 

[mrsilv04]

Originally Posted By: bioburner
So this little module is there to give the fuel pump a bit of time before the starting system engages?


I'm not sure about a delay when it starts, but it does provide an obvious delay shutting down the engine... to allow it to shut down gracefully. That's why I saw "run-on" (dieseling) a couple of times with the engine, when the module was slowly failing.

When everything is right, this engine will run for about 2-3 seconds after you turn the key off.

 

[mrsilv04]

Originally Posted By: Chris Meutsch
Feels great to fix stuff for cheap.


Oh, don't you know it. When that engine roared to life, I was hooting and hollering, I was so happy.

It took me less than 30 minutes to swap the parts, and figure out what the problem was... and about 15 minutes to install the new one that I'd stolen off of the older tractor. Since I have two tractors, I bought the replacement time delay off of eBay, and had the mailman bring it right to me.

This has to be the first part that every John Deere tech replaces, when a dead 425 rolls in through the door.

 

[bchannell]

You would think that when a dealer service tech gets stumped that's what he would do, swap pairs to figure it out, but no they will give it back to you with the same problem it went in with, sometimes.

The fuel pump is is powered off the ignition switch, not the delay. Key on. The delay opens fuel via the solenoid in the carb body when key is on. Key on, fuel pump runs, solenoid opens,and power to ignition module via delay module. When you shut the key off, fuel pump off, solenoid shuts, but ignition module has power for a second or two, so as to burn a little of the remaining fuel in the bowl to stop it from soaking, bubbling into the intake. The delay is nothing more than a latching relay for the power to the ignition module.
How do I know this? I had the same problems, traced it all out, took carb apart, all good, no start & flooding, backfires etc. Pulsars good, delay good, ignition module good, coils good, whaaaat? Wiring good, but wait ...it was a bad ground, cleaned and reattached, hasn't missed a beat since. Woohoo!