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Ask Hank F. Your Own Question
Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14487
Experience:  Certified on Onan and Generac generators
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Hank F. How are you today?

Customer Question

Hi Hank F. How are you today?
Submitted: 1 year ago.
Category: Small Engine
Customer: replied 1 year ago.
Ran gen out of gas and since will not start. Have checked and is getting fuel. Battery is charged. When attempting to start it turns over until I let off the switch, and it backfires and then nothing. Can you help?
Customer: replied 1 year ago.
It is a Onan 6.5NH 3CR/16004p
Expert:  Hank F. replied 1 year ago.

Check both plugs to see if you are getting spark while the engine is cranking.

Are you?

Customer: replied 1 year ago.
Hi Hank. I have checked one closest and it does not have spart until I let off of start and I only get one spark. Have not checked the other but will first thing in the morning, late here. Also have taken out coil to check it but not sure of resistance measurement.
Expert:  Hank F. replied 1 year ago.

The coil should be 3.87 - 4.73 ohms on the primary, and 12,600 - 15,400 ohms on the secondary.

Customer: replied 1 year ago.
Thanks will check in the morning and let you know.
Expert:  Hank F. replied 1 year ago.

Ok

..

Customer: replied 1 year ago.
Good morning Hank, I did check the coil this morning and I believe it is bad. Between the positive and negitive terminals I read 6.5 ohms. Then I checked between the positive and center holes and there was no reading on any setting. Got the same results from the negitive and center holes. If the coil is bad how do I get the one spark when I let off of the start switch?
Customer: replied 1 year ago.
Good morning Hank, I did check the coil this morning and I believe it is bad. Between the positive and negitive terminals I read 6.5 ohms. Then I checked between the positive and center holes and there was no reading on any setting. Got the same results from the negitive and center holes. If the coil is bad how do I get the one spark when I let off of the start switch?
Customer: replied 1 year ago.
Hi Hank, this morning I checked the primary at 7.5 ohms and the secondary at 15,170 ohms. With these readings I assumed the coil is good and reinstalled it. I then checked both spark plugs for spark by removing them one at a time, connecting th pug wire and grounding the body. When I pushed the start switch there was no spark until I let off of the switch and there was one spark. This occured on both plugs.
Expert:  Hank F. replied 1 year ago.

Sorry for the delay. The rear end went out on my truck, and I spent all day yesterday trying to get my truck fixed.

You are testing the coil wrong. On the secondary, you do not test from igh tension tower to positive or negative - you test from high tension tower to high tension tower.

But the reaidng on the primary is awfully high - I would suspect that this coil is bad.

Even with the resistance being so high, it is possible to get a spark either when it first starts crankng, or when you let off thestart swich, just due to the physics of how a coil works.

Customer: replied 1 year ago.
Sorry to hear a bout your truck! Hope all goes well with it.Will get a coil tomorrow and will get back with you tomorrow afternoon.Thanks!
Expert:  Hank F. replied 1 year ago.

It turned out good - thanks. It is actually moving now.

Let me know how it goes with the coil.

.

Customer: replied 1 year ago.
Sorry, been working. Cummins said that the coil is not too far off, and before buying a new coil to test the points first, so will try that when I get home. They are sent me a manual. Will let you know.
Expert:  Hank F. replied 1 year ago.

Ok