Engine runs when key is switched to off

[j442w30]

Hi everyone,

I've got a 1992 Mercury 40 hp outboard that runs for about 15 seconds after the key has been turned off. This past winter I replaced the ignition switch because the old one had become sticky when moving between start and run and I only had one key from the previous owner. The stator was also changed to a new CDI unit.

When I first started the engine this past weekend I let it run for about ten minutes and then I switched the key to off and it kept running. I even moved it between run and off several times with no effects then after I left it in the off position it stopped about 15 seconds later.

I started it up again and it did the same thing. Anyone have any ideas?

Also, I had to remove the oil injection tank to get at the carbs and when I reconnected it and filled it with oil I just ran the engine on a 50:1 premix and didn't bleed out the oil pump. Will the pump bleed itself out over time?

Thanks

 

[crashnburn63]

Re: Engine runs when key is switched to off

Is it really running, or is it "dieseling", meaning firing over w/o a spark from the spark plugs? Old car engines would do that if they got a heavy build up of carbon in the cylinder heads, the carbon would get very hot and also raise the effective compression ratio enough to keep igniting the fuel/air mix even after the spark was turned off. Dieseling will be very rough and can quickly damage the engine...

Another possibility is, *if* this engine has magneto ignition (I have no idea if it does or not) - magnetos are always on unless grounded off. Magnetos are common in light aircraft engines, which is why the prop must always be treated as "live". Also most lawn mowers and 2 stroke yard tools. I've got a 2 stroke weed wacker right now with an obviously busted ground wire, I have to pull the spark plug lead off it to get it to stop. If this is the case for you, the engine would run smoothly until something else (like you cutting off the fuel supply) brought it to a halt.

-dm

 

[j442w30]

Re: Engine runs when key is switched to off

Thanks for the reply

It's not dieseling, it sounds exactly the same as idling and then it just shuts off, not sputtering at all like running out of gas. It's not magneto ignition either, I think thats on the much older engines.

My guess is its some loose connection but I cannot figure out why it would keep running for 15 seconds each time and then shutting off.