JD 318 mower switch problem

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JD 318 mower switch problem

Frank Gibbs
I have a 88 JD 318 that has been running fine. The other day, I cranked the motor and when I engaged the electric clutch for the mower, it killed the engine. It will now not even turn over, completely dead. What did I do? What do I need to check? Any help will be appreciated.

Dave Frank - The first thing I would do is check the battery. The current draw of the PTO could pull the battery down if it was weak, such that now it's dead. Best pull the battery out and have it checked with a load. A lot of auto parts stores will do that for you.

If the battery is bad, put a new one in. I'd recommend going with a JD Hibernator, but that's your decision. Just make sure it is the proper size and rating.

Once you have a good, fully charged battery in place, give it another try. The problem you have could be caused by the battery, and that's the most obvious and easiest to resolve. If the problem persists, repost and we can go from there. - Dave

Frank Gibbs Dave: Thanks for your quick reply. Have been working on the tractor about all day. I had two problems, one of which I still have. I can get the tractor cranked now. There was a problem with the contact switch on the hydrostatic control arm, and I got this fixed. However, with the tractor running, whenever I engage the PTO, the 20 amp fuse blows and the tractor shuts down. I can replace the fuse now and get the tractor to crank, but, again, just as I throw the PTO switch, the fuse will blow again. I think I have either a bad PTO switch, a short in the wiring somewhere or a bad cluth on the PTO. How do I go about finding out which one it is? Or do you think I may have some other problem. Thanks for your help.
Tim Boisvert Frank

I would disconnect the PTO coil and see if the fuse stills blows when the switch is in the on position (make sure when you disconnect the PTO that the wire connector coming from the switch doesn't short to the tractor frame). If the fuse doesn't blow, you have a short somewhere beyond the PTO connection; most likely the PTO coil has a short in it or is shorted the some metal in the PTO.

If the fuse still blows after disconnecting the PTO, there is a piece of wire that has been pinched after the switch, or has rubbed through the insulation, or the switch may have a short.

I'm not sure which would be easiest to check first, but I'd start at the PTO.

Dave Frank - I think Tim's response pretty much addresses the issue for you. If you are unable to find a short, post back. Good luck. - Dave
Frank Gibbs Tim: Thanks for your reply. I have done exactly as you stated. I disconnected the PTO and fuses continued to blow. I have looked everywhere, traced wireds, etc. and can't find the problem. About to pull my hair out, what there is left of it. Do you know which wires I should trace, or, any other advice will be greatly appreciated. And, thanks for your reply.
Frank Gibbs Tim/Dave: I failed to mention in my recent follow up that I installed a new PTO switch first thing this morning and still had the problem. Then started tracing wires with no results.
Help if you can. Thanks.

Tim Boisvert Frank

Disconnect the wire from the switch that goes to the PTO. If the fuse still blows I suspect something with the wiring for the switch.

I looked at a schematic and the switch has two circuits, one for the PTO and the other has to do with the starter so the motor can't be started when the PTO is on and won't allow the rear PTO (if you have one) to be used when the front PTO is engaged. From the schematic, there are 2 blue wires; one goes to the PTO and the other goes the the PTO light. Have you checked the wire that goes to the PTO light?

The schematic I have is for a 318 sn # 475001 or higher. I think the difference is that the newer 318 has a time delay module. That module also has a PTO solenoid in it. I'll need to see if more information about the module is available. Do you have this module (I beleave the tractor will run for several seconds when the ignition switch is turn off when you have this module)?

Tim Boisvert After looking at the Time Delay Module, I think it may be a delay to prevent the PTO from being turned on too soon after the motor is started and shouldn't have anything to do with your issue.

I'll log onto another site and see I can find out more.

Dave Frank - Here's some informatin from the Tech Manual that may help you out. Take note of the paragraph with a double asterisk (**) at each end.

If the 20-amp fuse blows each time the key switch is turned to the RUN position, there is probably a short in the 20-amp fuse power circuit, neutral start circuit or ignition/hour meter circuit. Isolate the short by using the following method:

1. With the PTO switch in the ON position, turn key switch to
RUN position.


FUSE BLOWS: Short is in the 20-amp fuse power circuit.

2. Put PTO switch at OFF position, hydro lever in NEUTRAL/STOP and engage park brake. Disconnect TDC 8-pin connector, then turn key switch to RUN position.

FUSE BLOWS: Short is in the neutral start circuit.

FUSE DOES NOT BLOW: Short is in TDC module or ignition/hour meter circuit.

If the fuse blows after pulling the light switch to the ON position with key switch in RUN position, then a short is probably in yellow wires between the light switch and lights.

If the fuse blows only after the keyswitch is turned to START position, a short is probably in the purple wire between key switch and starter solenoid.

**If the fuse blows after PTO switch is moved to ON position, the short is either at the PTO clutch or blue wires running between the PTO switch, clutch and lamp. The short is NOT in or before the TDC module.**


Wires routed through panels or between frame and deck.
Wires routed near exhaust manifold or muffler.
Wires routed near the drive shaft.

Frank Gibbs Tim/Dave: Again, thanks for your rapid response. I will check the areas that you mentioned to me tomorrow. Wish me luck. I will keep you posted. Hope I can report good news.
Hope someone is open tomorrow that has some fuses.
I've already thrown away a 5 gallon bucket full...

Frank Gibbs Tim/Dave: Hallelujah... I found the problem first thing this morning thanks to you both. There was a short in the PTO light. That was the first place I looked and it was immediately obvious. Repaired short and tractor purrs like a kitten. Thanks so much for you help.

One more question: Given a 318 and a 332 in basically the same shape, with the exception that the 318 has about 800 hours on it and the 332 has about 1500 on it. Which would you prefer? I know that the 318 is gas and the 332 is diesel. I know everybody has there choice, but was just wondering which one both of you would pick. Unit will be basically used for large lawn mowing only. It will not be used for any other task with the exception of maybe pulling a very small yard trailer. Thanks.

Dave Frank - 1500 hours on a 332 diesel is actually less than 800 hours on a 318 gas. A bit more noise, but more fuel efficient and a lot more torque with the 332. If I had a choice, as much as I love my 318, I'd go with the 332. - Dave
Tim Boisvert Dang Dave!

That's one to print and put in my notes! I don't have a Deere manual, is that what you got the info out of?

Jon Frank,
I own one of each. If you are going to be mowing 2-5 hours a week and can get the 332 for about the same-GO Diesel! The Onan seems to get about 1200hrs on them before things get ugly, the little Yanmars seem to go forever (2500hrs shouldn't be a problem). The fuel consumption difference is amazing.

Frank Gibbs Dave, or anyone: I just bought a JD 318, 1983 model that has points. Where are they located and how do I get to them. ALso, I assume that you set the gap on the high step of the cam, and what is the gap setting? Thanks.
Tim Boisvert So what was the out come?

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