Car mechanics question
 

Thought I'd post this on here as you are all a knowledgable bunch!

I have just been servicing my gf's '76 230 Merc and it was in dire need to new ignition parts (points, rotor arm, cap, leads, plugs etc.) I have done this a 100 times before and have alwasy set the points gap with a feeler gauge and have never had any problems!

This time, I set the points gap as per the book (feeler) - car runs well, job done. However, since I have a new fancy schmancy multimeter, I check the dwell angle (a new thing for me) and it is about 6 degrees too low indicating a too wide points gap. I recheck the gap with the feeler and it's spot on. So I start decreasing the gap to try and get an accurate dwell angle, but it gets to the point where the car stalls (presumably from a too smaller gap) and I still can get the specified dwell angle.

In the end, I went back to the old school, used the feeler and now the car runs great again!

I'm taking the dwell reading of the negative point on the ignition coild and the ground of the battery.

What else could be affecting the dwell angle if not the points gap? I have just bought the multimeter, so I don't think that is faulty.

Thanks for any insight
Luke

Re: Car mechanics question
 

Ignore the dwell angle thing. It's determined basically by the shape of the contact breaker cam lobes, just set the gap and timing.

Where did the value for the dwell come from, Haynes?

Re: Car mechanics question
 

I know nothing, but a google search came up with:

1) Connect the dwell meter as per its manufacturer's instructions: Generally one of two leads is connected to the positive terminal of the battery and the other lead to the negative terminal of the coil.

But, of course, if your meter is telling you to do it differently then....

Re: Car mechanics question
 

Yep - gap + dwell from Haynes

Re: Car mechanics question
 

I can double check that, but i'm 99.9% the instructions with the multimeter says negative battery or any good ground