# 318 problems



## greenbrair52 (May 12, 2012)

tractor runs great for 30 to 40 mins. then it drops a cylinder and looses power. can park and let it cool down and will be fine till it gets warm and then acts up again


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## jhngardner367 (Apr 5, 2011)

Welcome to the forum! It sounds as if it either loses spark,OR compression,on one cylinder.connect a spark tester between the sparkplug,and the plug wire.Then run it,and see if it is losing spark when it happens.If it still has good spark,try a new plug,and retest. If it still has good spark,and still loses power,it could have a valve problem.


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## greenbrair52 (May 12, 2012)

Just does not seem like it would be a valve, but it might be wouldnt a valve be a problem from startup? It has new plugs not new wires.


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## jhngardner367 (Apr 5, 2011)

It might have a slight out-of -round on a valve face,or even a slight bend in a valve ,that worsens as it warms up,causing a compression loss.
First,though,I'd check the electrics(wires,coil,points,condenser,etc). Also check to see if the battery is holding,as a low charge can kill one side,or both sides,due to weak spark.
When my 317,with a Kohler engine, did this,I found that one side of the coil was bad,and would lose spark,once it got warm.


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## shona13 (Aug 12, 2011)

Hi Greenbriar.
The first thing to do is check the high tension side of the ignition ,the coil ,to check (BE CAREFUL YOU ARE DEALING WITH HIGH VOLTAGE) remove both spark plugs and refit them to the high tension leads earth the body of the plugs to the engine that is make sure the plug body makes contact with the engine good, then crank the engine over,(with the ignition turned on) and at the same time watch the spark plugs they should produce a nice bright BLUE spark,
if not check the condition of the contact points once you have ensured they are good i,e. surfaces are clean ,smooth and parallel and the GAP is correct try checking the spark again if the spark is good refit the plugs and give her a go,if it still does the same thing replace the condenser the condenser when it heats up loses it,s ability to hold power and consequently when it heats up the spark becomes weaker and weaker till it stops ,the reason it will lose a cylinder is the fact that the compression may or will be a little bit higher on one cylinder ,the higher the compression the more resistance to spark so the plug will not ignite the fuel in the cylinder and it will miss .
Happy Days 
Hutch.


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## Mickey (Aug 14, 2010)

Being a 318, it came with an Onan engine. These engines have a single coil and both spark plugs fire together each revolution. In the area of ign system, what affects one cyl affects both. Possible exception is some funky thing with a spark plug. I'd look somewhere else.


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## jhngardner367 (Apr 5, 2011)

Not all 3218s came with an Onan engine. I've seen them with Kohler th18 s engines,as well. If it is an Onan,it could still lose spark,on one side, due to a weak coil,as one cylinder will use the spark,robbing the other,and causing it to drop out.


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## Mickey (Aug 14, 2010)

I'm assuming that was a typo, i.e. 3218. The JD317 came with a Kohler and the 318 came with the Onan. We're talking original and not some engine swap-out.

http://www.tractordata.com/lawn-tractors/000/0/3/35-john-deere-317.html

Not as familiar with the Kohler's that were use during that time period but here's an offering on e-bay offering a coil that says fits 316, 317 & 318.

http://www.ebay.com/itm/JOHN-DEERE-...290?pt=LH_DefaultDomain_0&hash=item231d39fe5a

As can be seen, both plug wires connect to the coil. Both plugs fire at same time. Only one circuit, current flow is in to one plug and out the other.

It might be possible for one of the plug wires to be damaged and in such a position that with time and heat causes that wire to short to ground, thus loosing spark to that cyl.


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## jhngardner367 (Apr 5, 2011)

Yes,it was a typo! I have also been informed,by Paul,the owner,that is a "swap"engine.So, I stand corrected.


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## Mickey (Aug 14, 2010)

No problem. We all get things mixed up from time to time and the freq increases with age.  I know from personal experience. :lmao:


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## jhngardner367 (Apr 5, 2011)

I hope I don't forget how my zipper works...that could be EMBARRASSING! LOL!


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## greenbrair52 (May 12, 2012)

Ok, sorry it took so long to get back here. I changed plugs and wires, and it seemed to fix my problem. I was able to mow for around an hour with no issues. I will be putting it to the test on Saturday. No posts means good news.
Thanks so much to all that gave their input, Kind regards. Chuck.


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