520H onan dies when it gets hot

[biggun2869]

This engine runs great fo 1/2hr to 1hr then just dies like you turned off the key. Will start right back up but only run a few minutes and die again. Any suggestions as to the problem?

 

[DanD78]

I had an older onan engine once that about every two years you had to replace the condensor because it would quit working after it got hot. After it dies do some trouble shooting and see if the spark went away or it is out of gas at the carb. You may have electronic ignigion. Not sure which engine that is.


And Welcome to TBN

Dan

 

[biggun2869]

Thanks Dan,I may just try repacing the condenser. It would be very hard to do any testing on the thing because it'll start right back up.

 

[Rick_CT]

Possibly you have a vented gas cap that has a clogged vent. Try loosening the gas cap after it stalls, then re-start and see if it will continue to run. If it runs, then you found the problem, if it stalls, then you know it is not the cap. Good luck.

 

[546cowboy]

I had that same problem on a 520 and it was the ignition trigger. After I replaced it with a used one off Ebay it ran fine for a while and then the same thing happened. I bought a new one and it has run perfect ever since.

The new one was pricey but it sure beats having to disassemble and replace the trigger over and over again. This is the cure if you have no spark when it dies and won't start. After the engine cools down it would start again,

 

[KubieTwo]

I had an older onan engine once that about every two years you had to replace the condensor because it would quit working after it got hot. After it dies do some trouble shooting and see if the spark went away or it is out of gas at the carb. You may have electronic ignigion. Not sure which engine that is.


And Welcome to TBN

Dan

It the OP ever found a solution it is not evident. If the Onan does not have electronic ignition, it will have a condensor, but it will also have ignition points which generally wear faster than the condensor. They are most often changed as a set. Secondly, point gap should be adjusted more often than once every two years if indeed it has points and condensor ignition.

It is not likely a fuel cap vent or a fuel problem if it runs an hour before it stalls, unless the fuel pump is already weak and fails to pump sufficient volume when the whole engine heats up enough.

The electronic ignition module is the more likely candidate.

 

[DHD]

I agree with 546cowboy on the solution.
I had the same shut down problem on a Wheel Horse 416H with the 16 HP Onan.
I first changed out the coil (expensive but easy to change) shut down when hot problem still continued.
Then I changed out the ignition trigger under the flywheel.
Not so easy to change out as the coil, but problem now solved.
I found that even though the ignition parts were expensive, they were allot cheaper through Onan than through Wheel Horse.

 

[veteranchuck]

Don't know if the 520H Onan has a hot engine cutout switch, but I do know it is important to blow out the cooling fins on both sides of the engine with compressed air after every use. This is especially important for the rear cylinder because it is a common problem in this cylinder to overheat causing the valve seat to come loose and prevent adequate compression. Also, make sure you use the spark plugs recommended in the users manual. The spark plugs listed in the manufacturers manuals list a hotter plug for the Onan engine and not the one recommended by Toro.