Hooking up a tach and dwell meter

ExSquid

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Greetings from Green Bay,
As a Navy diesel mechanic, we don't use tach and dwell meters or timing lights. It seems that the light is straight forward. Battery power and left plug wire. So where do you hook up the tach and dwell meter? I know on my older cars its the signal from the distributor. Do I have to find "that secret wire"?
 
Red wire goes to the points, black to ground.
 
Personally, I don't use the tach feature much, if at all, but I do use the dwell function all the time. It's the only way I set points gaps now. So yes, hook the meter's red lead to the points set wire (I clip it to the little bolt holding the wire), black to ground (I use a cylinder fin), like so .....

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Be sure the red wire connection is isolated to only the points wire. It can't touch anything else like the rest of the points set, the backing plate, or the housing. You will need to connect it to each points set individually to set each one. Now let's talk about the dwell value. It is given in the shop manual and is 93° ± 5°, or 88°- 98°. Now, this is the 2 cylinder value that you'd read on a 2 cylinder dwell meter, but I've never even seen one of those. Most likely you will be using an automotive type with 4, 6, and 8 cylinder settings. The reading you get will be a little different on those scales and we need to do a little math to figure out what it will be. The lower the scale, the more accurate the reading will be, so use the 4 cylinder scale if you've got it. On the 4 cylinder scale, you divide the 2 cylinder value by 4 (for these dual points). So that means you'll be looking for a reading of between 22° and 24.5°. Now, the reading you get on a dwell meter is inversely related to the points gap size. That means a larger reading indicates a smaller gap, smaller reading a larger gap. I try to set the points as close to the smaller number as possible so I get the largest in-spec gap as possible. As points wear, their gap usually closes up, so I figure they will stay in spec longer if set to the larger gap.
 
Hey sailor... just had a memory jog...... don't you have a TCI iggy? If you do there's no point in checking dwell. It's baked into the electronics.... non-adjustable.
 
Gotcha. Don't worry, you'll develop an ear for the rpm.... ;)
 
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