Help with B&S engine electrical issue

May be off subject if so let me know where else to post I have an Ariens ZTR 1742 mower with a 17 HP B&S engine that has been afterfiring ( After ingnition is turned off raw gas collects in the muffler and explodes) since I got it .This destroys the muffler and I need replace another $90 one so I thought I'd look into why its happening. When I checked into it there is an afterfire solenoid on the carb that is supposed to shut off the fuel supply when the ignition is turned off. Ariens didn't do this and as a result the solenoid which is powered from the alternator does not disengage until the alternator ( and engine ) has almost stopped so I get feul in the muffler.

When I called Ariens they admited to the problem and sent me a new ignition switch that is supposed to fix the problem. When I got it it was clear that this would not switch teh solenoid power and when I called again I was told that the fix was internal to the switch and did not need any cabling.

When I pressed for how it was done teh engineer told me that rather than switch off the solenoid they simply shorted it to ground when teh ignition was turned off. While I agree this will fix the afterfire it does so by applying a short across the alternator while its still at speed.

So my question is am I trading a annual muffler replacement for a much more expensive Alternator problem down the road Thanks in Advance Bob

Reply to
bob
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Is the fuel exploding because there is a spark that causes it, or is it just the fuel accumulation in the hot exhaust system. If it is anything electrical, you should keep the ignition off/ shorted out until the engine stopsrotating.

H. R. (Bob) Hofmann

Reply to
hrhofmann

muffler

Ariens

almost

ignition

that

told

more

I own an ancient Hayterette with a B&S engine. Not prone to back/misfires but to stop it I just pull the HT cap off the spark plug. As originally a bare metal cap I adapted an old bakelite knob to cover it. I've always the opposite problem - starting , as usual with these mowers, to start - its always take off the airfilter cover and teaspoon of petrol in the inlet chmber. Apparently something to do with a carburetor that can be taken up and down slopes without playing up.

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Reply to
N Cook

This is a different issue caused by fuel in the muffler. If I pull the plug cap it still happens because even without the spark the engine continues to pull fuel/Air into the cylinder and then sends it out to th emuffler where its ignited by the hot muffler.The issue is that the mechanism to shut down teh fuel is delayed by the bad design which I believe just got worst by the "fix" which shouts out the alternator output Bob

Reply to
bob

"bob" wrote in news:Iz9qi.9193$XL4.3626@trndny04:

The older B & S engines had a low current self limiting alternator, it had only a fuse for circuit protection. Those would not fail if shorted with the engine running, they only put out about 2A charging current.

Some larger engines had a voltage regulator those would fail if shorted while the engine was running. Theese put out about 10A charging current.

R!

Reply to
R!

Solenoids were not installed until a few years ago and engines have been around for much longer than that. On the lawnmower I use the book calls it a SAFETY solenoid and it is connect to various limit switches (along with the ignition switch) which shut the engine off if you do something prohibited. I have had several lawnmowers with the same type of engine and no solenoid that performed extremely well and had no afterfiring problems. Perhaps you should look further into the problem.

Reply to
sparky

Put a switch on the wire to the solenoid and turn it off that way.

H. R. (Bob) Hofmann

Reply to
hrhofmann

Reply to
bob

It's possible that the engine is dieseling, that can happen with some carbon buildup in the combustion chamber. It could also be running very rich and accumulating excess fuel in the exhaust.

Reply to
James Sweet

I considered that but don't believe thats the case I pulled the heads last year and there was minimal carbon which I removed.Also if it was dieseling wouldn' the fuel ignite while in teh power stroke with the exhaust valve closed ? I also considered all the fuel wasn't being burnt but assume that would cause afterfire randomly not only when I turned teh ignition off Bob

Reply to
bob

Dieseling in a low compression small engine also seems less likely.

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Reply to
Sam Goldwasser

The 13hp Kohler Commander on my John Deer tractor diesels once in a great while but I would have to agree. Especially motors with minimal sized flywheel.

Reply to
Meat Plow

It's rare, but it happens, and with a weird problem like this one can't rule out the rare just because it's uncommon. This does sound like something else though.

Reply to
James Sweet

The B&S manual actually descriobes this problem if the afterfire solenoid is tied to the alternator which is a 9 amp unit . Their fix is to switch teh solenoid . Ariens decided to short out teh alternator instead If anyone wants to see the diagram I can post it or email it BOb

Reply to
bob

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