318 Slow to Start

[SeventhSojourn]

My 1984 318 (Onan BG43) takes a long time to start up if I haven't used it for several days. The starter turns for 10=15 seconds before the engine kicks in. Once the engine kicks in, it doesn't loose a beat. The tractor is on its 2nd fuel pump, plugs are clean and gapped, fresh fuel and fuel filter, new air filter and pre-filter, etc.

Do these Onans normally do this?

 

[pmsmechanic]

Sounds like the fuel is leaking out of the carburetor and it takes that much cranking for the fuel pump to fill it enough to start. I'm not exactly sure how to check on this. I would lay a piece of Kleenex under the carb to see if it gets stained or not. Maybe you can see it drip. If you take the air cleaner off and pour about a thimbleful of fuel down the carb before cranking and it takes right off then you have found the problem but not what is causing it.

 

[Gator6x4]

The valves guides were bad to accumulate oil coke or shellac in the valve guides binding one or more of the valve in a open or partial open position making the Onan hard to start. Marvel Mystery Oil added to the oil usually would clear such a problem. After the engine has been setting a couple days or a week, pull the spark plugs prior to trying to start. Place a finder in the spark plug hole, have someone crank the engine and see if compression blows the fingers away.

 

[SeventhSojourn]

I usually give it a shot of starter spray and it kicks right in. Not sure about the carb leaking, I would probably be smelling raw gas if it was, but I'll take a closer look.

 

[SeventhSojourn]

Thanks, I'll pick some up and start adding it to see if there's a difference. It just turned 900 hrs. so I guess it might be showing its age a bit. I'll give it a compression test too to get a reading. I think it's supposed to be 100-125 PSI?

 

[pmsmechanic]

Gator6X4 has a good idea. If the engine doesn't blow your finger out of the spark plug hole while you crank it over then there isn't enough compression to start the engine.

 

[kansas john deere]

After you shut the tractor down are you turning off the fuel valve on the tractor? If not then I would look to see if the check valve is defective and it is letting the fuel go back into the tank. Making it have to reprime the line so it will start....................KJD

 

[Napi]

After you shut the tractor down are you turning off the fuel valve on the tractor? If not then I would look to see if the check valve is defective and it is letting the fuel go back into the tank. Making it have to reprime the line so it will start....................KJD

Good advice here. I sold mine, but I had to replace the check valve. If I remember correctly, it was in the tank on the end of the pickup line. Turning the fuel valve off after each use, as Kansas suggests, really helped mine before.

 

[uglyboywith11fingers]

You say with a shot of starter spray it starts right away, instead of cranking for 10-15 seconds ???

If true, your carb is probably leaking gas from the float bowl, as PMSMECHANIC said.
The float bowl barely holds an ounce of gas, if that... so you may not be noticing the leakage.

Pete

 

[BBO]

This extreme cold weather makes lots of engines hard to crank.
It sure is better to put mowers in a garage or at least out of the wind if possible in the winter.