cant turn engine off

[waterboymvp]

I have a 99 challenger that I was adjusting the idle on the port engine. Got it running smooth at 3000rpm on the hose, I brought it up to 5500rpm and back down to idle a couple of times then all by itself it jumps up to 6500rpm I hit the start/stop button and that didnt shut it off. I had to choke the engin to get it to shut down.
Does anyone know what causes this? Any help would be great

 

[parrothd]

Air leak or fuel issues causing a lean condition. Check the fuel system and carbs

 

[waterboymvp]

Carbs

Thanks,
I made sure the carbs were on nice and tight and gaskets were good. I will remove carbs and go through them and post what I find.
Thanks

 

[parrothd]

Are the low speed adjusters set at 1.5

 

[Dr Honda]

You can't adjust the carbs for a smooth idle out of the water. The pump needs to be loaded to properly tune things.

You probably leaned it out to far, and it finally just jumped. It's called a lean rev.

Set the low needle to the factory spec, and then set the idle to 3000 rpm.

 

[waterboymvp]

low speed screws

parrothd< The low speed screws were at 1.5 turns out
dr honda< When I said running smooth I just meant idling at 3K
I took the carbs off, they were pretty clean, filters had nothing in them at all. Could this be from old gas lossing its octane? I have not had this boat running since last september because the mpem went bad and I just now got one today. Would bad gas make it run lean and rev uncontrolable like that? Should I drain my tank? Or is there a additive I can put in it?

 

[waterboymvp]

Carbon build up?

Just came accross a thread about someone having same issue with engine running with no spark. Someone replied to his post and said carbon build up in cylinders will get hot enough to ignite fuel and will run until it cools enough not to ignite or the choke is pulled. He decarboned the engine with seafoam, is this something I should try also? He said this fixed the problem

 

[Dr Honda]

I don't recommend seafoam. If you want to de-carbon the head... pop it off, and scrap it out. But... once you get it in the water, and run it... you will burn the carbon out to an acceptable level.

Like I said... you can't adjust things on the trailer... and you can't evaluate engine issues either. The hose doesn't cool the engine the same, and you can get hot spots. Also, run away doesn't happen when it's in the water.

Old fuel is never good. Did you put in a fuel stabilizer when it was parked? If not... you should drain the fuel, and put in fresh fuel.

THEN... put the boat in the water, and see how it runs.


It was good to pop the carbs off, but since they are clear... you shouldn't have any issues once it's properly loaded.

 

[kustomkarl]

The seadoo is not under any "load" on the trailer. The water puts a load on the impeller in the water and the rpm's should be about 1500 -+ at idle, under "load" If you need any further fine adjustment do it in the water. Run away is common on a trailer as heat builds up and fuel is present in the engine. Even if you pull the spark plug caps it will keep revving...it's the high temp and fuel causing it. Choking the engine causes cool fresh fuel to enter the engine and stop the high rev condition.

Karl

 

[seadoosnipe]

Runaway....

Outside the points made by others, the main cause of a run away engine is an air leak Either at the split of the casing, or the rotary chamber plate cover. IF you tighten these down to tight, you can warp them. This will allow air to seep by.

Remember, the denisity of air is so minute that it can pass through areas that fuel can't.

Also, like Dr Honda points out, this can't happen in the water. Always pull the choke to use the introduction of cold fuel to cool off your motor....:cheers: