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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14543
Experience:  Certified on Onan and Generac generators
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I have a 520-H Wheel Horse. The engine will turn over but wont

Resolved Question:

I have a 520-H Wheel Horse. The engine will turn over but won't start. It is getting gas, but no fire to the plugs. The only diagnosis I knew to do is jiggle the wires from the switch. It did run for a few minutes, then backfired and shut off. It seemed to be running very hot too, before this happened. is there any way and how can I check the electrical system?
Submitted: 6 years ago.
Category: Small Engine
Expert:  PK. replied 6 years ago.
Hi, which engine does this have?
Customer: replied 6 years ago.
a 20 hp Onan
Expert:  PK. replied 6 years ago.
Hi, I'm going to opt out and send this to our best Onan Expert as I don't have any Onan books at home and can't look up your particular engine. Someone should be back with you shortly. Thanks, PK.
Expert:  Hank F. replied 6 years ago.

Hello,

What is the full model number of your engine?

Onan made a couple different models, and the testing procedures are not the same.

 

Customer: replied 6 years ago.
a 20 hp Onan P220G-I/10540B
Expert:  Hank F. replied 6 years ago.

There will be a small black wire coming out from under the shroud over the flywheel.

 

If the engine connector on your tractor is a 4-pin, this black wire will go to an inline connector before it gets to the 4-pin connector. Disconnect this single connector.

 

If your engine connector is a 6-pin, this black wire will go to a relay. Disconnect this wire from the relay.

 

Recheck for spark. If the engine happens to start while checking for spark, you will need to ground this black wire out to shut the engine off.

 

Do you get spark to either plug with the black wire disconnected?

 

Customer: replied 6 years ago.
I can't find the black wire, it did start momentarily, but now it turns over but no soark to either plug
Expert:  Hank F. replied 6 years ago.

Does your engine connector have a 4 or 6 pin plug?

 

Customer: replied 6 years ago.
where is the pin plug located? there are 6 wires coming from the switch plugged into 4 slots
Expert:  Hank F. replied 6 years ago.

That will be the 4-pin connector.

 

Mounted to the left side of the engine, right above the starter, you will see an aluminum box with 'fins' and 3 wires attached to it.

Just below the starter, there as another, smaller black or gray box with 3 wires going to it. 2 of those wires go under the shroud, and the other has a bullet connector. Disconnect this bullet connector and recheck for spark.

 

Customer: replied 6 years ago.
no spark
Expert:  Hank F. replied 6 years ago.

This black wire is the kill wire. If you have it disconnected, but still have no spark, there are only a few possibilities.

 

1. Both coils are bad. (Not very likely)

2. One of the 2 wires going under the shroud is shorted to ground under the shroud. (Most likely)

3. The magnet in the flywheel is either rusted, weak or missing.

 

You are going to need to pull the shroud off and inspect the wiring for damage and inspect the flywheel.

 

 

Hank F., Technician
Category: Small Engine
Satisfied Customers: 14543
Experience: Certified on Onan and Generac generators
Hank F. and other Small Engine Specialists are ready to help you