1969 L46 350 - Engine Won't Stop!
Thread Starter
Intermediate
Joined: Mar 2011
Posts: 38
Likes: 5
1969 L46 350 - Engine Won't Stop!
Hi everyone. I have a 69' with the original 350/350 engine. Everything works great except for one embarrassing problem. When I turn the key to shut it off, the engine keeps running and chugging for 5-20 seconds. I've was told it's called "dieseling". Regardless, it's somewhat humbling to roll up in a cool car and then it sputters for awhile before shutting off. Anyone know what could be causing this or if there is a simple fix? I'm not experienced in working on engines, but I'm sure I can make most simple adjustments. Thanks!
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
If your not running enough timing at idle, then the idle screw on the carb could have been adjusted to compensate for the reduced idle speed.
With the throttle open more the chances of dieseling go up.
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
Go to the main vacuum tap on the back of the intake manifold, disconnect all the vacuum lines and cap off all the vacuum ports there, then start it and see if the idle picks up noticeably over where it was before. If it does and you can get it to idle smoothly at 650-700 rpm by turning down the idle speed screw, and then shut off without dieseling you've narrowed the problem down to somewhere in the vacuum system. I had the same issue with mine years ago; there are a hundred places where this system can leak vacuum which allows air to continue leaking into the intake system when the car is shut off. Once I had plugged the leaks I was able to turn the idle speed screw down far enough to prevent the engine from running on after I had shut it off. Later smogmobiles also have an idle stop solenoid which closes the throttle plate after shutoff since their retarded ignition timing requires excessive throttle openings at idle.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
before you check or reset timing ... do inspect mechanical advance ... ensure it is articulating fully & smoothly ... and that it returns to full-retard properly... then check timing.
do likewise with vacuum advance ... then check timing.
do likewise with vacuum advance ... then check timing.
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Safety Car
Joined: Jan 2009
Posts: 3,736
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From: anchorage ak
This usually seems to be the case for me, but not on the plugs but in areas of the combustion chamber. As i know that this will draw laughter and critisim ( I can handle it, I have enormous shoulders) I start the car let it run for 15 minutes with out the air cleaner on. i take about a half quart of water and slowly start to dribble the water into the venturi of the carberator while accelerating by hand as you do this the engine will want to die and when it dose stop dribbling the water down the carb, and feather the throttle with your other hand in order to keep the engine running. I continue this process untill the half quart is gone. the higher the compression the slower you want to dribble the water. This knocks the carbon off that cause the hot spots. Just what works for me.
Thread Starter
Intermediate
Joined: Mar 2011
Posts: 38
Likes: 5
Thank you everyone for the help. I made some adjustments to the timing and carb, they did the trick with the dieseling.
I decide to take the car out for a bit of an extended drive tonight, 50 miles, speeds up to 80 mph. After getting off the highway I noticed the oil pressure gage go to zero at the stop light. Once I got going it went back up to the mid range, 35. At ever stop the gage would go to 0 then go back up!
I gently drove her back home hoping the oil pump has not went out. Has anyone else ran into this happen after driving on the highway for 20-30 minutes?
Once again - thank you everyone for the help - it makes problems like this much easier to deal with with a great community like this!
I decide to take the car out for a bit of an extended drive tonight, 50 miles, speeds up to 80 mph. After getting off the highway I noticed the oil pressure gage go to zero at the stop light. Once I got going it went back up to the mid range, 35. At ever stop the gage would go to 0 then go back up!
I gently drove her back home hoping the oil pump has not went out. Has anyone else ran into this happen after driving on the highway for 20-30 minutes?
Once again - thank you everyone for the help - it makes problems like this much easier to deal with with a great community like this!
