JD 318

M Neely · Sep 12, 2014

I need help fixing my 318 mower. It will start and run 10 minutes then stop with no spark. It has a twin Onan engine. I can not find any # or tag on it. It has the small square coil. I do not know if it has points or not. Any help in troubleshooting is much welcomed. If I let it set and cool off completely it will start and run 10 more minutes.

Cas · Sep 12, 2014

It kind of sounds like the ignition module you mentioned. When it stops I would make sure you are getting voltage to the + side of the coil. The 2 little wires go to the the spark module down by crankshaft.
There is a guy on ebay that sells new modules for $120. The module by the crankshaft is either a go or no go. Kind of a simple system to work on. I knew a guy that made one up to work, but he had a lot of time in it.

Scott in SC · Sep 12, 2014

Try asking here:
Weekend Freedom Machines Hydo Tractors

T.R.K. · Sep 12, 2014

It is probably the trigger under the flywheel. To test it, when it stops, take a test light hooked to battery ground and check for power on the small post on the coil. (It should light)

Then check for power on the larger post on the coil. (It should light-unless the magnet on the crank is directly over the trigger)

Then turn key to start while holding the test light to the larger post. If the trigger is working, the light should blink while the starter is cranking the engine over. If it blinks:

Switch over to a volt meter between battery - and the large post on the coil. rotate the crankshaft by hand with the switch on. At one point the voltage should drop from over 9v to under 2 volts.

If you don't see it blink, the trigger is not trying to work at all.

I had one Onan on a Toro that I had to check several times before I caught the trigger not working. Sometimes with that one, It would start right back up.

M Neely · Sep 13, 2014

Checked terms at coil,no pulse on the large post when cranking. Where is the crank sensor located?

Cas · Sep 13, 2014

You have to pull the flywheel and it is right over the white ring with the magnet. The voltmeter test is kind of tough to analyze. If you do it, make sure to do it several times. When you are sick of doing it do it one more time.
If you determine it is the sensor, Onanparts.com had aftermarket ones for sale for about $80. Also, you usually can catch a good one on ebay for about $60. I change about a half dozen each year.
I used to fiddle around and to do every test possible. Now, I keep extra sensors and modules on hand. It is easier to just get to it.

Charlie M · Sep 16, 2014

There was an updated coil available for a 318 - I had to install one a few years ago on mine. I forget the details but it had a special bracket for installing it.

Lee Richards · Sep 19, 2014

(quoted from post at 17:46:03 09/12/14) I need help fixing my 318 mower. It will start and run 10 minutes then stop with no spark. It has a twin Onan engine. I can not find any # or tag on it. It has the small square coil. I do not know if it has points or not. Any help in troubleshooting is much welcomed. If I let it set and cool off completely it will start and run 10 more minutes.

I agree with Charlie m on the coil but also, follow the electrical [battery side of coil], the wires on the ignition switch and sometimes the switch itself will get dirty and cause the heat[resistance] to the coil to make a tractor coil stop running. I had electric juice at the battery side of my coil but no spark at the plug. Also the points are located under a tin cover by the carb. and this has a allen-head bolt holding it tight. The newer 318's had the electrical ignition module.

JD 318

M Neely

New User

Cas

Well-known Member

Scott in SC

Member

T.R.K.

Well-known Member

M Neely

New User

Cas

Well-known Member

Charlie M

Well-known Member

Lee Richards

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