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Need some advice on a Onan engine

D

Dutchman

Well-known Member

It's been awhile I needed help finding parts for my skidloader with a Onan engine in it ... I know I save the site that I got the parts from.... put I can't find it .. must be getting old ...
Anyway heres what I have , it starts up good { when it's cold } it runs for 30 to 45 mintues and DIES ... no poping or anything .. JUST dies ... you have to wait till it cools off around a hour to get it to restart .. { try to start it sooner and all it does is crank over with the starter }
ANY IDEAS ??? I should say I replace the plugs, wiring, and condenser and points..
is it posible I got some bad parts ??? any ideas on what I need to do , will be GREATLY appreacted
I'm missing something ?/ what ???

THANKS ... mark
 
When it dies, get a spark tester on there quickly.
If you have no spark, it's probably a bad coil.
A bad condenser is less likely but possible.
 
When it's not starting you have to determine if its a fuel or an ignition problem. The ignition is easy just see if the coil and plugs are firing or not. If so, maybe its fuel related.. Is there an electric fuel pump and is it working and filling the carb bowl??? I have had Onans with bad elec fuel pumps and ALSO check any in line fuel filter. If it has an elec fuel pump insure its getting power and often you can hear to tell if they are running or not. I have (be safe) pulled the line from pump output to carb to see if its on and pumping or not..CHECK THAT FUEL FILTER

If its an elec problem (no spark) I have had a bad coil or condensor go bad once warmed up

Fuel or Ignition ???????????

John T
 
A plugged up vent in the fuel tank can cause that issue.
If it is 12v make sure the coil is for 12 volts with no resistor required, or that it has a resistor and needs one. Jim
 
Do some diagnostics before making any more assumptions.

Be ready to check the spark as soon as it fails.

If it has spark, give it a squirt of gas in the carb, see if it fires, if only for a second.

That will tell if it is spark or fuel.

If you do find loss of spark, diagnose the loss step by step, voltage to the coil, points making connection, etc.

Did you get the correct coil? A proper coil will be about the same temperature as the surrounding components. If it is hot to the touch something is wrong.
 
I have onan NHC in a skid steer. The original engine had a fuel pump on top of the block which was prone to vapor lock in the summer months. Pour a quart of water on the fuel pump and it would start immediately. Onan apparently knew that there was a problem because the short block had no provision for a mechanical fuel pump. The instructions that came with the short block said essentially that it was up to you to figure out how to get the gas to the carb. Havent had any more trouble since installing electric pump.
 
You may already know this, if so then just a friendly reminder for you. These 2 cylinder opposed Onan engines are fired in a waste spark pattern. That means both cylinders fire at the same time with one on the power stroke while the other cylinder is on the exhaust stroke. When you check these engines for a spark by letting it jump to the engine outside you must have both of the plug wires connected to something so it can fire both sides if you don't there is a possibility of damaging the coil and that can be fatal to the coil as well as expensive for you.

Gene Davis Tennille, Ga.
 
Need to know the model of the engine. Some have electronic ignition some have points and that changes advice you may get.

The advice to check for spark and fuel when it dies is solid, no matter which ignition you have.

FYI, I wouldn't plan to change the coil as a troubleshooting technique. You won't want to either once you price that two tower, waste spark thing.
 
(quoted from post at 20:20:38 06/24/22) What model do you have.

Onan tech since 1980.
Click to expand...

I'm trying to get some info for a friend repairing a mil surplus Onan 2 cylinder generator. Are you familiar with older Onan engines and willing to discuss them? If so, how do we start a separate conversation?
 
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