Can't get fire to plugs

[H80N]

This one...???

http://www.mytractorforum.com/images/reference/Onan_16_18_20_24.pdf

[duaneb55]

I couldn't find where the John-Deere manual covered troubleshooting the ignition module. Just changing it.

The Onan manual I emailed has the troubleshooting steps as well. If you want one too, PM an address.

[dle]

My model number is 903039

[D Auger]

Any luck yet ?

[dle]

not yet, I was told to check the CB4, self set breaker???

[LoganpClayton]

Dle,

Logan here, Firstly, make sure you read the good info supplied by duaneb55

Because the oil pressure switch is open with the engine not running, there will not be any 12VDC at the coil with the ignition switch in the RUN position. However, there should be while cranking as the by-pass diode allows 12VDC(+) to the coil from the START signal at the starter.

If you have 12VDC(+) at the coil while cranking and still no spark at the plugs then I suspect the ignition module behind the flywheel has failed.

PM me an email address and I'll send you the engine Service Manual that covers testing.

Now that you have made 100% sure you read it, any questions?

One note that I would make is that the easy way to do this with no tools and little electrical background is literally take the plug out, lay plug on it's side, on something metal, and see if you get any arcing across the gap. I say this is the easy way but in reality it can be quite tricky. The real "easy" way is to have tools to help you do the job, one that I use as a go-to for no start issues is a spark gap tester, as seen below:


This baby takes the spark plug wire right to it, then you clip the alligator onto the top of your existing plug, you should see spark (if not something is wrong with coil/supply) *these tools are a whopping 4$ on ebay*


To start an engine, as we all probably know, you need Fuel, Air, Spark, and compression. If you have checked off Compression, Fuel, and if there is no obvious blockage stuck in you're intake for air, then it comes down to spark. Here is a detailed diagram for the B48M Onan Engine used on the AEAD welders:



One thing I will note is that the coil pack under the flywheel seems to only be used for the charging system. now, back to the beef and taters:

If you have Voltage at the ignition coil, and it's grounding that primary of the ignition coil properly from the breaker & cap assembly, then either that coil has a bad secondary, or there is an issue from the secondary on (spark plug wires, or plugs them-self).


Let me know how it goes!