ONAN 20HP Problems

[ezeastside 93]

Hi guys, I finally signed up although I've been reading your posts for some time now. There is alot of knowledge within this group and I finally need to tap into it further.

I have a 520H 1991 with the Onan P220. When I bought this tractor 2 years ago it was not running and I had the same exact problem I am having now. The fix last time was the ignition module so I was told. I can not get spark. The coil checks out to specs, The module works as the service maual describes. I have jumped the coil directly to the battery with no luck. I have torn the fly wheel off to visual check the module etc.. and all looks good. Before I spend 500.00 on all new electrical componets I was hopeing for some ideas from you guys.

This tractor ran all summer for me very strong although it had a fuel problem and some times started hard ( I thought was no fuel) it always started.

If it is the module again why would it fail after 1 year? High voltage? Grounds are all good. HELP

Thanks alot,

Ed in CT :thumbs:

[Duff 206]

Hi, Ed!

Don't know anything about the Onan motors, but someone will be along shortly who will, I am sure.

Glad you joined us!

Duff :thumbs:

[Rideawaysenior 25]

Doubtful that your putting out too much voltage or so much that you would cook the module. Do you have an inline spark tester? How about the contacts on the mag behind the flywheel? Are they clean? Although it is possible but unlikely, you could have bought a bad unit replacement coil...

[ezeastside 93]

Thankyou Ride,

I do have and use a spark tester, I don't beleive this unit utillizes contacts as the electronic ignition module takes their place behind the flywheel. it gets its signal from the ignition rotor on the main shaft

The stator and magnets also resides there and are in order and fairly clean. The coil and all other parts of the ignition are original to the machine.

As I mentioned earlier, the coil rings out within Onan specs.

:thumbs:

[jaysmith801 0]

Hve you checked the reluctor ring behind the flywheel?

[Daveycrocket 1]

Dose the engine turn over, does it crank?

[Daveycrocket 1]

Another thing I have been told you cant test spark in the conventional manner on these onans, they have resistive spark plug wires, dont put any thing else but those in the onan.

[ezeastside 93]

The motor turns over very well. The spark plug wires are the resistive type (look to be original). I pulled the flywheel to visi check the module. The stator is in good shape and clean. The magnets on the flywheel are all there and tight.

This is why I am so confused. Every test comes out favorable but yet there is no spark.

[nylyon-(Admin) 7,121]

On MTF, there is a fella named Onanparts.com (they're in our links section as well). Anyway, I have seen some of his posts on MTF and he seems to know his Onans. I sent him a PM on MTF to see if he'd be interested in joining here, to add some extra Onan help.

[Don1977 604]

The graphite resistor wires do break down, have you replaced the wires.

[can whlvr 991]

could it be the pto safty,or the seat safty?

[ezeastside 93]

I have not replaced the wires but have tried the spark tester in both wires seperatly with no luck.

I checked the safty circuits and all operate but to bypass I have given the coil positive voltage directly from the battery without any luck.

I think at this point I will purchase new:

Ignition Module

Ignition Rotor

Voltage Regulator

Wires

And start there. At least I won't have to pull the Flywheel of again and I can reassemble the motor tins.

In the mean time if someone comes up with any Ideas I would be very greatfull as I am with all the help so far!!

ED :thumbs:

[KB9LOR 4]

I am checking the Onan technical Manual for any help to your problem.....

*******UPDATE*******

Well so much for that! the Manual tells you how to tear it down and put back together, but nothing on diagnosing the electrical problem per se; will tell you how to remove test starter, etc..... Sorry!

[baerpath 517]

How did you make out ?

My 520 is doing the same thing Except mine will run for a while and then quit. If you leave it for a while and come back it will start right back up. My thought is to replace the ignition module and see what that does.

Duane

[Save Old Iron 1,563]

Some quick checks

Coil Check >>

Spark Check - confirms 12 volts to coil

[04fxdwgi 0]

I have not replaced the wires but have tried the spark tester in both wires seperatly with no luck.

I checked the safty circuits and all operate but to bypass I have given the coil positive voltage directly from the battery without any luck.

I think at this point I will purchase new:

Ignition Module

Ignition Rotor

Voltage Regulator

Wires

And start there. At least I won't have to pull the Flywheel of again and I can reassemble the motor tins.

In the mean time if someone comes up with any Ideas I would be very greatfull as I am with all the help so far!!

ED

No one has mentioned the condenser (capacitor). A bad one will prevent firing.....

I would lean toward the module or the condenser if everything else checks good. If 12 vdc is applied at the B+ on the ignition coil and she won't run, then I would look at module or condenser first.

PS. When unit runs for a while and quits, then won't restart till it's cooled off, then 99% of the time it's the module that is about to completely let go. Something in the module electronics is heat sensitive and is just waiting to completely fail.

[refracman 166]

Your on the right track, its usually the pickup that causes a no spark situation with onans. I allways change both pickup and rotor cause its a pain if the rotor is bad too. A little pricey but worth it.

[baerpath 517]

I should have put in that we did check the coil, it has checked out okay' Even put a spare one on as a test.Also tried a new condensor

By watching the tach you can tell when it's gonna quit as it will drop to zero just before it shuts down. If I read it right thats where the tach gets it's input from the pickup

Duane

[TT-(Moderator) 1,127]

If I read it right thats where the tach gets it's input from the pickup

Duane

I'm pretty sure the tach gets it signal from the piggy-backed connector on the one A.C. terminal on the rectifier/regulator.

[Save Old Iron 1,563]

Jumping the + side of the coil to the battery is only one side of troubleshooting no power to the engine -

Don't forget the ground wire too.

Maybe place a temporary jumper from the engine ground to the battery ground before you tear out the ignition module.

[baerpath 517]

Ya got me there, didn't check the ground side' I have had to run a seperate ground on ones with shaker mounts before(C125)

Dunae

[ezeastside 93]

Hi Guys,

Thanks for coming back to the thread.

I have been working 7 days a week and haven't had a minute to work on the machine.

Too bad really as we have been getting a bunch of snow and the 520 is sitting in the garage with the Snowthrower on it without a pulse.

I see some real great info recently and it confirms my belief that the Module has quit.

The only thing I didn't try was the condensor this time although a year ago when I had the same issue I did get a new one from a dealer ( The dealer told me it was only for rfi on this unit) which didn't do it.

The big question is why would the module quit after only 1 year of operation and why would it perform to the test specifications but not fire the engine?

I will be ordering the new parts this week .

Has anyone used Onanparts.com , They seem to have the best prices on this equipment.

Until then I appreciate and welcome all of this awesome advice!

[Operator 7]

I've had those modules go from the epoxy filling cracking then moisture getting in there. The fuse block is another bad spot, the contacts corode [use dilectric grease], and I've had the plug under the battery try go bad and loose the connection too. Even a simple thing like the main fuse blowing has caused me problems in finding why it wouldn't fire up.

Good luck here, you'll get it figured out.

Randy