OnanEngine

[Fixityourself]

How is the best way to turn over an Onan engine 18hp twin cylinder that has not been run for 16 years I would like to get it running . Any advise is appreciated THANK YOU !

 

[Scrubcadet10]

I assume it has no electric starter or pull rope?

 

[Rivets]

This is what I would recommend, others may disagree. I’m assuming it has electric start.
1. Check the oil, level and condition. If it is not black, proceed. If black, change using straight 30W.
2. Remove plugs and ground spark plug wires.
3. Remove and plug fuel line before the pump. If you can’t remove, clamp it off.
4. Remove air filter and housing so you can see top of carb.
5. Make sure throttle and choke shafts move freely. If they don’t you should fix before proceeding.
6. If you cannot get them to move freely, you will have to decide if you want to go through the expense to remove and rebuild the carb down the road.
7. Spray a small amount of engine oil into each cylinder.
8. With a good battery, click the starter switch a couple of times to see if the starter will engage the flywheel.
9. Turn the engine over for about 5 seconds.

If everything above works as it should, if you have decided to repair the carb if needed.

10. Reinstall plugs and connect plug wires.
11. Using carb cleaner, spray it directly into the carb.
12. Try starting the engine to see if it will fire. If you cannot get it to fire you will need to check for spark. No spark means you will have to check the points.
13. If you get it to fire you can now reattach the fuel line and using carb cleaner as your fuel and fresh fuel in the tank, see if you can get fuel to pump from the tank to the carb. If you have a rubber fuel line installing an inline clear fuel filter will allow you to see if fuel is moving.
14. While doing this you will start fogging for mosquitoes, due to the oil you put in the cylinders, it will clear up.
15. After you get it running I recommend a full tuneup, probably replacing everything.
16. If no fuel flow, you will need to check pump operation and/or carb problems.

If you have any more questions, please remember to include all engine numbers so we have an idea of what engine you have.

 

[hlw49]

This is what I would recommend, others may disagree. I’m assuming it has electric start.
1. Check the oil, level and condition. If it is not black, proceed. If black, change using straight 30W.
2. Remove plugs and ground spark plug wires.
3. Remove and plug fuel line before the pump. If you can’t remove, clamp it off.
4. Remove air filter and housing so you can see top of carb.
5. Make sure throttle and choke shafts move freely. If they don’t you should fix before proceeding.
6. If you cannot get them to move freely, you will have to decide if you want to go through the expense to remove and rebuild the carb down the road.
7. Spray a small amount of engine oil into each cylinder.
8. With a good battery, click the starter switch a couple of times to see if the starter will engage the flywheel.
9. Turn the engine over for about 5 seconds.

If everything above works as it should, if you have decided to repair the carb if needed.

10. Reinstall plugs and connect plug wires.
11. Using carb cleaner, spray it directly into the carb.
12. Try starting the engine to see if it will fire. If you cannot get it to fire you will need to check for spark. No spark means you will have to check the points.
13. If you get it to fire you can now reattach the fuel line and using carb cleaner as your fuel and fresh fuel in the tank, see if you can get fuel to pump from the tank to the carb. If you have a rubber fuel line installing an inline clear fuel filter will allow you to see if fuel is moving.
14. While doing this you will start fogging for mosquitoes, due to the oil you put in the cylinders, it will clear up.
15. After you get it running I recommend a full tuneup, probably replacing everything.
16. If no fuel flow, you will need to check pump operation and/or carb problems.

If you have any more questions, please remember to include all engine numbers so we have an idea of what engine you have.

Sounds good I would probably use fogging oil and spray it into the cylinders. It is made especially for this purpose as it will coat the cylinder all around and not just on the bottom side. Good luck.

 

[SamB]

Sounds good I would probably use fogging oil and spray it into the cylinders. It is made especially for this purpose as it will coat the cylinder all around and not just on the bottom side. Good luck.

Original Onans( from 16 years ago is a plus) were fine engines and to me,junking one would be a very last resort.

 

[Joj]

What's a good replacement for a Onan for a 446 Case mower . I think it's 16 horse ? Parts are to hard find an get worked on . Thanks