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Engine won't shut off right away.....

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Gettin'her warmed up for a ride.
Nighthawk Hull
Nighthawk Hull
1000369
100_1602
AIR-IN IT OUT
is timing right? is right fuel being used? were you talking about right after some hard running? lots of variables on this but somebody will help with answers instead of just questions that is what makes this a great place to hang out
 
If your running regular gas, it may be as simple as changing to High Test. I have seen cheep water injection systems stop the dieseling as well. I would say an electrical fuel shutoff at the carb instead of just killing the switch. If it wants to act like a diesel, kill it like a diesel. Aircraft engines are normally shut down by leaning the mixture til the engine stops, then shutting off the electrical switches.

I'm sure there may be some additives that claim they clean out carbon from the combustion chambers. I never believed their tale but, hey, mighht give some a shot. Local auto parts should have several. Just read the lables.

If your problem is carbon, whats happening is your compression ratio is high enough now it needs either high test or an additive to prevent the dieseling. Does it detonate at any point during operation, heavy loads, full throttle accleration. Thats an indication of carbon build up assuming your timing is right.

Consider all of Country's variables.

Scotty
 
Basket your right on there. Thats the normal way to shut down both aircraft and diesel engines.

Scotty
 
I'm using the highest octaine that I can get at the pump. I don't feel that I have ran my engine "hard" but I have seen folks let their engines idle a while before shutting them down.

It does not diesel all the time but when it does it just makes me feel something is gonna get damaged.
 
I am runing 93 octane with my GPU and have the same problem when I shut it down especially when it is hotter then normal. The timing is probably a little advanced and I should get it checked, but in the mean time I have learned to hold the gas pedal all the way down after I kill the engine. It chokes the engine and shuts it right off.
 
I'll try letting the engine idle for a few minutes and then shut off the mag and mash the gas, I'll see how that works...

Thanks to all responses.
 
Yes, idle it down when hot. The oil circulation helps cool the jugs.
It took me about 4 dropped jugs/valves on my GPU before I became "educated."
 
I think the cleanest way is a combination of what WB and Country suggested. Let the engine idle down for a minute or so then interupt the fuel supply until the motor stops. If you experience a long turn over period before firing the next tme you go to start the engine try running your electronic fuel pump for 3 to 5 seconds to re-prime the carb in the future.
 
Cumbustion chamber "hot" spots usually cause dieseling...try a colder heat range plug.....maybe D-14 or equall......cut the fuel as well.....idle down more.....520 rpm's..or untill the impluse starts to hit up in the mags...run a couple bottles of carb cleaner thru your system, could have a carbon build up.
 
I had the same trouble with my 0540. I installed a lean rich cable to my carb. I just lean it and it shuts down and than I turn my mags off.
 
The lean rich cable is the ticket, I tried everything from av gas, idle, crossing my fingers, and everything else. Installed the cable and it shuts down immediatly.
 
sorry didnt see you had a gpu, cable may not work like an aircraft carb, electric solnoid may be better.
 
I hade that probem with my small block. Mine was simple add 5 gallons of 110 octain per tank brings me up to 96 octain boat runs better starts easyer. I buy that at the gas station Hwy 50 & 13 before the race track
 
First off, don't even consider mixing methods from car-motor boats. It's a GPU, not a SBC.

Second, if you ABSOLUTELY cannot get 100LL Avgas, use an octane booster (like 1 bottle per 15 gallons of 93 octane, or whatever.) Also, with the 100LL, your engine will run cooler.

Third, NGK AB-6 spark plugs have by far outperformed the others in my 220.

Last, letting the boat idle is key, but if you run the right fuel through the thing in the first place, little problems like that tend to correct themselves.



Bob
 
Here's another octane booster, and I've hesitated to post this because this is NOT one of those things where "If a little bit is good, a little more should be better".

Acetone is 150 octane. When mixed in SMALL amounts with gasoline, it greatly improves the burning in a cylinder and at the same time works as a constant fuel system cleaner.

The correct ratio is 3oz. acetone to 10 gallons of gas. That's all .... in bigger quantities it's going to start eroding the O-rings and seals.

I use it in everything around here from my wifes car to the lawnmower. My pickup starts and runs like the day I drove it home, and I picked up a couple of miles per gallon to boot because of the complete burning. If you run a diesel truck, the ratio is 4oz. to ten gallons.

Use a good funnel, and don't get it on your paint ..... a gallon can from the paint dept. at Home Depot will last you a long time.

BF
 
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