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mort

Onan 16 hp engine

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mort

What are the reasons an Onan engine will not ignite the gas that you pour into the carburetor?

I put in brand new spark plugs and checked continuity on the spark plug wires.

The engine cranks but will not start.

Is it a bad distributor cap?

Is it a bad capacitor?

I don't mind buying a bunch of parts and start swapping them out but want to make sure I buy the proper parts that could be bad.

 

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oldredrider

Basics: you need fuel, air, fire and compression. 

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lynnmor

:text-welcomeconfetti:

 

There is no distributor cap, just a coil that fires both spark plugs at the same time.  First thing to test is to pull a spark plug wire and stick it on a plug, ground the plug hex against a metal engine part and see if there is spark while cranking.

 

Download the Onan manual for information about testing the coil, and other parts.  You should have voltage at the coil and the ignition module will switch as the engine is rotated, the manual covers that.

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Stepney

Mine wound up having a bad key switch. First thing I would check is if you always are getting 12v to the + side of the coil when cranking or in the run position. 

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mort

This engine is very frustrating! I have a 1983 310-8 and I have never had a problem with it at all. I have two 416-8 and one is hard to start unless I use it every week and this is the other one. So I have some good news and some frustrating news on the testing I did. First of all I tested the spark plug wires by grounding them and I was really surprised I had spark on both of them. I figured since I had spark I should be able ignite some gas in the spark plug chamber. WOW I was surprised again. The gas actually ignited. That is a first with this tractor!Then I tried it again and it didn't work but I did put a little gas in the carburetor too. I thought maybe it got flooded? I doubt it as I am only using a cap full at a time I waited 30 minutes and tried it again. It didn't work. I thought I would try putting gas in by the spark plug chambers again and then it worked. I tried it several times yesterday and today putting gas in the chamber and it won't ignite the gas. I thought I would check for spark again and it will not spark. I used a trouble light on the coil test and I do not see it pulsing (bright to dim). I think this means it is the ignition module based upon this test. What causes the spark plugs to spark? The coil? As I mentioned before I don't mind buying a bunch of parts and slowly swapping them out as time is money. Also what voltage regulator does this Onan use (20 or 35 amp)?

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lynnmor

A marine squeeze bulb or an electric fuel pump in the supply line from the tank will fix the excessive cranking after a long period of non use.

 

Did you have 12 volt power to the coil when there was no spark?

 

Do the test in the Onan manual to test the ignition module.

 

The ignition module turns on and off as the magnets pass it.  When the power is switched off the collapse of the magnetic field in the coil which causes the high voltage spark.

 

I believe that you have the 20 AMP system.

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mort

I did buy an electric fuel pump and a one way check valve months back.

I was going to install the one way check valve in the other horse but I got side tracked.

Do I install it right before the fuel pump and fuel filter?

 

 Yes I have 12 volts to the coil and there was no spark.

I did the ignition module test and it always read 12+ volts.

So does that confirm 100% that it is only the ignition module that is bad or could it still be the coil too?

I am asking because I did the coil ohm test at different settings and I saw no reading.

Thank you!

Gary

 

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mort

I take that back on the coil test. I just tried it again.

Actually on the primary resistance (terminals) I was getting 3.4-3.6 ohms.

 

At the secondary resistance I was getting 13,000-16,000 ohms but just briefly.

 

Every single time I did the test I got a quick display of 13,000-16,000 ohms and then it went to no reading.

I tried everything to get it to display but it wouldn't.

There is nothing wrong with my meter and nothing wrong with my hands/fingers.LOL!

 

Thanks,

Gary

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mort

One more thing............I was looking on line and someone said this below............

Could the rotor (not the ignition module) be giving me that constant battery voltage of 12+ and not the 1-1.5 volts I should be getting with the ignition test?

Onan 166-0785 Ignition Module

 

PLEASE CHECK YOUR IGNITION ROTOR BEFORE ORDERING THIS AS IT IS ALMOST ALWAYS THE ISSUE.

MICE LOVE TO GET IN BEHIND THE STATOR AND BUILD A NEST. AS SOON AS YOU TURN THE GEN OVER, IT BREAKS THE IGNITION ROTOR WHICH CAUSES NO FIRE TO THE PLUGS.

ONCE YOU INSTALL THIS PART, IT IS YOURS. SO PLEASE VERIFY FIRST.

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lynnmor

A check valve would go between the fuel pump and the carburetor.

 

If you did the ignition module test correctly, then it is not switching.  I believe they are aging out.

 

If the condenser (mounted on the air filter support) is still attached to the coil, that would explain the brief reading, so disconnect it.

 

The older black ignition trigger rotors did fail, but the newer gray ones are very reliable.  Of course a mouse can destroy most anything.

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