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Engine doesnt want to shut down

dawgs

Regular Contributor
86 merc 170....once in a while

86 merc 170....once in a while when i shut the key off the motor starts to "cough" and doesnt seem like it wants to turn off....this goes on for a few seconds then turns off on its own.....any ideas?
 
The condition is known as &#39

The condition is known as 'dieseling'. The idle mixture is too rich.
 
"Had a similar problem a coupl

"Had a similar problem a couple of years ago with my boat, and it turned out to be my voltage regulator was going tits-up. Unhook your excite wire on the regulator and see if it turns off then."
 
"How does a voltage regulator

"How does a voltage regulator problem relate to run-on?
Daniel, I'd bet there's more to your story."
 
"Troy, all I know is that when

"Troy, all I know is that when I couldn't shut the engine down by turning off the key my mechanic told me to unplug the excite wire off the voltage regulator. That killed the engine. Replaced the VR and haven't had a problem since. Beats me??"
 
"Daniel,
Thanks for posting y


"Daniel,
Thanks for posting your experience. I want to try out your theory. My 87 MCM 170 recently started dieseling and it coincides with my VR biting me in the ass. Which wire is the excite wire? I want to try doing what you did and see if it stops the dieseling. If it does this may add one more nail in the coffin of my VR positively taking a dump.

Dan"
 
Looks to be red w/purple strip

Looks to be red w/purple stripe at the VR which comes right from the battery via the starter and then the circuit breaker.
 
"Just recently had this proble

"Just recently had this problem with my 4.3l. I did the timing and haven't had a problem since.

I would start with the gas, it could be bad. If that doesn't work, try changing the plugs. Still no luck, try the timing.

good luck"
 
Sg had the same problem with m

Sg had the same problem with my 4.3l . Had to ease up on that cheap gas. Everytime I forget she likes the good stuff I pay by pinging and running on. Cheers...
 
You have carbon buildup on the

You have carbon buildup on the pistons. Have it cleaned out with mercs. product.
 
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