Ask the Mechanic
Where Is the Ground?
STEVE: This month's column includes a real ghost story in the work world of a mechanic. A strange problem on a machine that is difficult to diagnose is code-named a "ghost." Like an actual ghost, you never know when it will appear, but usually it's just about the time you get back to the shop from the field.
Many ghosts like to cause electrical issues, and the problem is often finally found with the ground. This part (see the photo accompanying this article) had a ghost in it. The owner had installed a new aftermarket distributor on this late-model 8N Ford tractor. The points, coil and condenser were new.
The tractor had been converted to a 12-volt system and had the correct internal resistor coil. It would run fine at idle and half speed. But, when you throttled up, it would miss, spit and sputter. I have had a bad condenser cause this problem before, but it did not fix this one. Yep, it was getting plenty of fuel.
It's rare, but since a distributor must be grounded, and if it is losing its ground on the engine, it will cause this problem. I have seen it on older trucks.
In the photo you will notice a little blue wire that I installed from the base screw of the points to the base of the distributor. This wire fixed the problem. The points must ground to the distributor before the distributor can ground to the engine block. Some older original distributors came with this ground wire for the points.
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-- Email Steve Thompson at mechanic@progressivefarmer.com, and be sure to include your contact information and phone number.
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