425 Running Problem

[NCMau]

My 425 is not running smoothly. It is pulsating. Gas is three months old. There is good fuel stream out of the fuel filter. There is a spark from both plugs, but I am not sure if it's a healthy spark. It looks little weak. I will get new plugs tomorrow.
When I was testing the plugs out of the hole, I noticed that the engine with one plug in was actually running smoother, although not perfect. I don't know if this could be a clue.
I know that could be several things causing this problem, but I need to start somewhere.Your suggestions will be welcome.

 

[xer]

I know gas is high now a days, but drain it and get fresh gas. More than likely if the mower has been setting a whike the carb needs to be cleaned. You can take the bowl off and check if there is a brownish film in it. This would be sediments. Take some carb. cleaner and spray in the bowl and remove the needle valve and float and spray it with carb cleaner also. Never hurts to have new plugs and make sure they are gaped correctly.
Hope this helps

 

[beenthere]

NCMau
I agree with xer, and suggest fresh gas and new plugs for starters.

That is a long time setting during the summer months of lawn mowing.

 

[NCMau]

Thanks guys for the reply. I understand that gas, spark plugs and carburetor cleaning would be the logical place to start, and I will do it shortly. I am wondering, however, the symptom of running better with one plug out, got me stumped. Usually you take one plug out, any engine would run rougher.
This 425 is not a simple machine, it's just like a modern car. There is no comparison with the older tractors and simple lawnmowers that I'm used to.
This is a nightmare. I guess I have crack the book and get seriously involved.

 

[beenthere]

Do yourself a favor and get the CD tech manual (or hard copy), especially since it sounds like you are interested in doing the fix and repair work yourself.

If one plug out slightly improved the "running", then maybe that cylinder has a problem. With the plug out, the other cylinder didn't have to drag this one along as a load. At least, makes sense to me.

 

[jd3x]

Check both spark plugs. If one has moisture probably there is a leaky head gasket, or intake gasket, with engine coolant getting into cylinder.

If this isn't the problem, possibly the ignition module may be the culprit.

Good Luck.

 

[98ramtough]

I have a 425 that was running really strange, I bought a new ignition timed delay module for $18 and life is good now... Might try it. I hear they fail often!

 

[beenthere]

98ramtough
Can you describe for us what "running really strange" means? And how the new module would have corrected the "strange" part? Thanks, it will be helpful.

 

[98ramtough]

My mower had been intermittently cutting out. Sometimes it would run fine, sometimes it would start sputtering right after startup. I tried new gas, cleaned the carb, tried bypassing the seat sensor. Then I ran across many many threads talking about the timed delay module on the 425 going out and causing all sorts of "STRANGE" running issues. So I figured what the ****. For less than $30 I will try it. And all my problems are solved and my machine runs like new.

JOHN DEERE 425 WONT STAY RUNNING

John Deere Time Delay Module - AM128906

Small Engine Technical Forum :: View topic - Kawasaki won't start when hot

http://www.smokstak.com/forum/showthread.php?p=668997



Try a google search from John Deere 425 time delay module. Its worth a shot. It took me about 3.5 minutes to replace mine.