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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14728
Experience:  Certified on Onan and Generac generators
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Small Engine
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Onan generator no spark.

Onan generator no spark. I... Show More

Onan generator no spark. I have this generator out of a motorhome in my shop with no spark. I was asked by the owner to tune it up. when it first came in it would start and run just fine. So I changed the spark plug, fuel filter, cleaned air filter, changed the oil. I ran the generator for 5 minutes, and noticed some residual oil dripping off the bottom. I used brake clean and compressed air to clean out the bottom of the generator. I went to start it and it started and ran. shut it off, then tried to restart and it started and ran a few seconds then shut off. would not restart. I asked the customer again about the generator, and she stated that this is what happened to her. ( she forgot to mention it to beforeI started on it.) I removed the plug and no spark. checked the signal wire to the coil and it has 5.63 v ( A/C scale ) while cranking. Checked primary coil resistance (.8 ohms) checked secondary coil resistance ( 1.111k ohms) I do not have any service information on this unit! Am I checking the ignition out correctly or am I missing something? I do not see a low oil switch on the engine, is there one hidden somewhere? Can you provide a wire diagram and specs on the ignition test that I have done? I feel the coil has failed. Is there a place online that I can get parts without going to a cummins /onan dealer? Thank you in advance Hal.


I have found a service manual in pdf form online that has the coil specifications.primary .5 @75 deg F and 1.100 for the secondary. This manual also shows a low oil switch inside the engine. I have also read online that the oil level switch was discontinued on later models due to failure rate.

I would still like an opinion as to if this model has one, and if you think it may be at fault here. I am going to test the mag per the manual tomorrow.

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Thank you for choosing Just Answer for the solution to your problem.
My name is Hank, and I am going to assist you with this.

Yes, this set has a low oil level switch.
However, it is not going to be the problem, as the start switch bypasses the oil switch for start up.

You are either going to have a bad coil, or a bad magneto.
Since you have already ohmed the coil as good, the magneto is the most likely issue.
If it is not putting out 15-50VAC while cranking, the magneto is bad.
Customer reply replied 5 years ago.

Thanks Hank. Thats what I suspected after I found the specs in the manual. I just wanted a second opinion to make sure . Since I was only getting 5.6 VAC during cranking I had a feeling it was too low. Now I know for sure.

Whats involved in getting to the Magneto on this unit, ( how much time, so I can estimate it to my cust) ?



Sorry for the delay - I work a 12 hour night shift. I got home at 7:30 this morning, and had to get some shut-eye - 60 hours makes for a long week.

To get at the magneto is a major job.
The entire left end of the genset needs to come apart, down to removing the flywheel.
With the genset already out of the coach, it takes me about 2 hours for R&R of the magneto. The flat rate manual lists 0.7 hours.

One word of caution. When removing the flywheel, be very careful not to lose the flywheel key. It is less than 1/4" long, and is easily lost.
Customer reply replied 5 years ago.
Thanks Hank, Thats what I needed to know.
No problem.
Please let me know if you need any more help.
Customer reply replied 5 years ago.
Hank do you have the part number for the mag on this unit? 2.8KV FA261008 serial# H290 481041 and where I can get one from. Thanks Hal
I do - give me 5 minutes to find it for you.
The part number is 160-1358-S0

It can be ordered from any Onan dealer.
To find your nearest Onan dealer, go to and enter your ZIP code.

It can also be ordered online here: