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View Full Version : Sluggist revisited



drnittler
03-31-2007, 07:42 PM
In reference to my 61 Lark 6cyl, which I mentioned was sluggish. Now it doesn't start, just cranks and tries to fire. Looking at the plugs I think some are not even foreing. Any thoughts?

David G. Nittler

John Kirchhoff
03-31-2007, 09:22 PM
There's a difference between a plug not firing because it's not getting any spark and not firing because it's getting spark but a wet or dirty plug is letting the juice dribble away before it can ever make a spark. One way to begin the process of elimination is to first see if after trying to start it, are the plugs wet or dry? If wet with gas, clean them and dry them off, crank the engine over with the plugs out to dry the cylinders out. While doing this, attach the plugs to the wires and lay them on the block and see if they fire. If they all throw a nice, fat blue spark, replace them and try again. If it still won't start, look at the plugs again. If they're wet with gas, the carb must be flooding out. If they're dry, you may not be getting any gas at all. If dry, squirt a little starting fluid in the carb while someone cranks it and if it tries to run, then it's time to start looking for fuel problems. If it doesn't fire, then it's likely electrical. Sometimes a plug will throw a spark while laying on the block but it's too weak to jump the gap when under compression. For a while I had a '61 6cyl in my Hawk and if it cranked the least bit slow, it wouldn't fire a lick. Not really slow, but just slightly slow. If I hooked up the jumper cables, it cranked over happily and started up in a heartbeat. Ends up the rear bushing on the starter was worn as well as the shaft. After I swapped starters that ended that problem. So, were it me, I'd first try to narrow the problem down to fuel, ignition or cranking speed. Once you find the problem area, you can then go to searching for the culprit.

Tom B
03-31-2007, 09:28 PM
Uh...cranking the engine with the plugs connected to see if they spark. Keep them well away from the spark plug holes, the cylinders might fire too and that is an experience not to have.

[img=left]http://www.alink.com/personal/tbredehoft/Bothcars.jpg[/img=left]
Tom Bredehoft
'53 Commander Coupe
'60 Lark VI
'05 Legacy Ltd Wagon
All three Indiana built OD cars

John Kirchhoff
04-01-2007, 01:25 PM
Tom, are you talking from experience? If so, that sounds like an interesting story!

It's funny how the cranking speed affects different engines. I have a Oliver gas tractor that regardless of how cold it is, if you can see the fan blade crank over, even with short jerky movements between dead spots, it'll start. My Lark engine and Chrysler combine engine could crank over evenly and steadily, but if the least bit slow, no-go. All the above engines are points and coil, so that's not the deal. I don't know if it's just a matter of the carburation being absolutely perfect or just slightly off, size of the intake runners or manifold affecting velocity, atomization and condensation, combustion chamber design or just the correct alignment of the moon and stars.