'96 GTI runaway throttle

[Bradley]

As a new member and a hit or miss fix-it type I am all ears for suggestions about how i might solve this problem. After last ride in October, I did the usual startup to clear water from exhaust. The engine kept on accelerating even though the throttle cable was not stuck. I was barely able to shut 'er down. Every time I try to start it (to winterize) the same thing happens. Any suggestions? Friend said it could be a vacuum leak. A dealer i called said that gas lines should be changed. I would love to solve problem myself if possible but it is also 22 degrees in Philly as I write.

Also, hope to tow ski to Florida for a week in March. Can a 99 toyota Sienna be fitted with a hitch and handle the tow with a loaded van?

 

[seadoosnipe]

Runaway engine.....

This is not uncommon for the Rotax engine. It's usually caused from the heat of the engine getting so hot, that after the engine power is killed, it'll continue to run like a diesel engine.

There are some conditions that cause this like running the engine lean or running hotter spark plugs than normal.

It shouldn't have much to do with your fuel lines.

Look in some of my stickies. I did a little bit of research on this last year. I think it's in my "snipes korner" thread..........

If it happens, pull the choke and hold it out till the engine dies. By doing this, your flooding the engine with fuel, which will cool it off and choke it to a stop (lack of air for combustion).

 

[timmyboy76]

reach down to the carb, and check to see if the throttle/butterfly is sticking?

 

[Bradley]

The runaway first happened (and subsequently on every attempted startup)after the engine was cool so I don't think it is dieseling. I will remember the trick of pulling out the choke to kill it.

Have taken off the cover to the carbs to see that the butterfly is not the problem.

So I guess I will check the plugs but I am still puzzled. ANy other ideas? What do you think of the vac leak idea?

Hard to do a water test with ice every where

Thanks friends,

Brad

 

[coach mike]

I had the same thing happen to me on my '96 SPX. I was also winterizing at the time and engine was fairly cool. Pulled the lanyard and tried the stop button but it kept going. Sucker was screaming and scared the hell out of me. Using recommended plugs and they are new. I have not been able to address either due to cold in Chicago. :chillpill:

I also since bought new fuel lines and plan to check the carbs for filter build-up, etc. I would also be interested in other thoughts. :cheers:

Regards,

Mike

 

[scooper77515]

Snipe is right, it is a dieseling effect. Engine does not have to be hot, though. I have had it happen twice on cool engines.

It does not happen when the boat is in the water, since there is pressure being placed on the engine via the impeller. When on the hose or out of the water, the engine can spin freely, and even if you pull the key off it will still race to over redline speeds. The only way to stop it is to choke it or give it gas, oddly enough. Choking it is safer and quicker.

It has nothing to do with your carbs or fuel system, and cannot be fixed. It can only be anticipated and your hand needs to stay close to the choke when running out of the water.

Also, try not to rev the engine when out of the water as this will start the chain of events that often make it take off.

 

[Dennis]

Runaway

I totally disagree with you SCOOPER. SNIPE is correct.
It has EVERYTHING to do with the fuel system, is not normal and and is a TOTAL indication that there is a big problem with the air/fuel ratio being delivered to the engine. The carb/s isn't supplying enough fuel or the engine has a major air leak. Usually it is a problem with the carb/s. That's where I would start looking for the reason the engine is running lean.
DAWG

 

[scooper77515]

I meant that the fuel system--carbs, fuel lines, possibly filters, would not necessarily contribute to it, but a lean system could. Lean mixture is not a faulty carb, but a poor adjustment.

I DO agree that running lean could lead to this, but running lean is not a "faulty fuel system". It could be a perfectly built and running fuel system needing to be fine tuned.

I guess I was out of line saying "It has nothing to do with your carbs or fuel system, and cannot be fixed" when what I meant was there may not necessarily be anything "broken". Nothing needs to be "fixed" but possibly adjusted.

I am happy to stand corrected :boxing_smiley:

 

[Dennis]

Adjustments

And I am happy to have been the one who corrected you!!!! LOL LOL !!!
You give out a great deal of great advice but thought this time it sounded a bit fishy. Keep up the good work!!
DAWG

 

[scooper77515]

Sometimes, I just get on here and make stuff up. You gotta keep an eye on me :reddevil:

So, if this isn't a relatively normal occurrence, then what is wrong with my boat that causes this?

I can't believe it is running lean since I tend to run rich and my plugs foul out after only 6-8 hours before I need to swap them.

 

[Dennis]

Runaway

Usually, runaway is due to a problem with the low speed fuel circuit in the carb. Dirty or incorrect (too small) low jet or improperly adjusted low speed mixture screw. I say this assuming that your engine is not modified (does not have excessive compression) and there are no major air leaks. I've been told that excessive oil in the premix can also lead to runaway. This might explain your runaway and plug fouling if you are premixing.
In general, runaway is a sign of a lean fuel mixture. Alot of people like to turn off their fuel valve and then run their engine until it's out of gas so there isn't any fuel left in the carb when not in use. I never recommend this. These people are just BEGGING for a runaway situation. Runaway is NEVER a good thing and can cause engine damage. If your engine has a habit of runaway I strongly suggest you look into it.
DAWG

 

[scooper77515]

Alot of people like to turn off their fuel valve and then run their engine until it's out of gas so there isn't any fuel left in the carb when not in use.

EUREKA!!!

That is EXACTLY what I was doing both times!!!:hurray::hurray::hurray: