Carb trouble

[lincman 3]

I have a '97 520H that is having a carb issue. It starts up fine, then it runs fine until 20 or so. Then it starts to faulter. Like it shuts off by itself. If I choke it it keeps running until I get it back to the garage. Took the plugs out, and they were fouled. Cleaned them up, put 'em back in. This time it ran for 40 mins no problem until I engage the hydro and start plowing. The horsepower % gauge moves the left (I believe it's a vac gauge). Before the engine dies it smells rich and vapor comes out of the carb. The choke was sticking open, so I put my hand over the the throttle body and it (my hand) smelled of gasoline. Any thoughts and tips would be greatly appreciated. Thank you.

[sorekiwi 761]

Onans are a little notorious for the carbs being sensitive to a little dirt. You probably need to give the carb a good cleaning and make sure you have a good filter on there.

There are quite a few threads on here about Onan carb cleaning. I've only done mine once, as part of an engine overhaul, so I dont know the tricks, but some reading might produce some hints.

PS Welcome to RS.

[lincman 3]

Okay, thank you sorekiwi. I will check around. I am thinking about getting a carb kit for it. It did have a somewhat dirty air filter, and I recently changed the fuel filter as well.

[dennist 139]

Welcome to RS. Like mentioned above, If it is the carb, I had one that was surging bad and I took the top of the carb off and cleaned it real good and then used air on it. I put it back together and it still acted the same. I figured I would be wasting my time, but tried it again and when I started it the second time it ran very smooth and had no issues from that point. I had cleaned the fuel tank, replaced fuel lines and filter prior to the first cleaning. Good luck.

[lincman 3]

Thank you. It's frusterating, but I get it figured out. I am going to take the carb off either tomorrow, Friday, or this weekend. I thinking the float is sticking. Like the problem you had it surges, but I choke it and it runs just well enoug to get back to the garage. Luckily I have a 312-8 as a back up. Thanks again.

[sorekiwi 761]

Have a look at the float and the needle valve and seat, but I think its more likely that there is a little dirt in the jets or the internal passages of the carb.

If the float was sticking down, then probably adding choke would make things worse. The fact that it gets better with a little choke makes me think that there is something causing a little restriction in the passageways.

[lincman 3]

Okay, I will make a note and check that out tomorrow. I miss that hydro something fierce!! LoL

[AMC RULES 37,259]

Keep us posted with your progress :WRS:

[Rollerman 290]

I had similar problems with a 520 I had.

The carb is pretty easy to clean by just pulling the top 4 screws & removeing the upper body.

That will let you clean the float bowl & check the bowl for leaks.

Also take a look in your fuel tank too.

With the cap off, carefully look inside with a flashlight & see if the screen (at the oulet) within the tank is plugged up.

[lincman 3]

Okay, I checked the tank, and there is some debris in it. So I will drain the fuel out and get the junk out, amd tinker with the top portion of the carb when time allows. Then complete tune up; Thank you.

[Sparky-(Admin) 25,592]

As long as the tank is going to be empty you should replace the shutoff valve and the rubber grommet the valve goes in.

Mike.............

[lincman 3]

Alright, thank you Sparrky.

[lincman 3]

It's alive!!!!

Took the top portion of the carb off Thurs, cleaned it with carb cleaner, and some compressed air. Took the float and needle out, cleaned the bowl. Reassembled everything (the spring with a ball bearing was a little tricky figuring out where it went) Then drained/cleaned the tank. The screen was partially plugged. So I went to fire it up, half choke, let the horse run for 20 minutes, ran the hydostatic trans, and lift. Ran like a boss. Now I just have a small fuel leak at the fuel filter. Easy fix. Thank you everbody for the advice, this forum rocks. FYI Autolite plugs are no longer made in the US, they are now made in China. Back to Champion I guess.