Mercedes-Benz Ponton
Distributor Maintenance

Henry Magno / / September 5, 2001

This article originally appeared in the International Ponton Owners Group (IPOG) archives on September 5, 2001. Henry Magno runs a Mercedes-Benz restoration shop and mechanical service garage in Massachusetts. See Links for details.

Question from an IPOG Member

The dwell angle seems to vary over 5° when I rev. the engine in my Mercedes-Benz Ponton. Is this due to a worn distributor or faulty mechanical advance?

Henry Magno's Reply

Distributor rebuilding is not mysterious. A change in dwell would be one symptom indicating a problem, but I do not see how the cause would be the mechanical advance, but most likely it is play in the shaft or wear in the breaker plate. So, without tearing one down, the symptoms could be: misfiring, variable dwell, not meeting specs on advance.

Centrifugal advance can be tested with the strobe and tachometer with the vacuum advance disconnected, but testing the vacuum advance I think a distributor bench tester would be needed because you need to measure advance as a function of vacuum, and in the car, you are reading the sum of the vacuum and centrifugal advance on the timing scale. So you would need to have a vacuum meter attached and do some calculations.

For practical purposes, you can disconnect the vacuum line to the diaphragm and apply vacuum from a hand pump, or suck on it to see if the breaker plate moves. If the adjustments on the pull rod have not been tampered with and the diaphragm is OK, this is good enough.

Even if you have no symptoms, it is a good idea to take your distributor apart and clean it up and lube where necessary. It probably has not been done in ages, if ever. First, take it out of the car. Then after taking the points and the bolt for the wiring connections out, remove the vacuum rod then the breaker plate. Then remove the cam section by carefully detaching the advance springs from the pins on the base plate attached to the shaft. Keep track of all the various fiber and shim washers.

Things to Check

- Henry Magno

Created: November 30, 2002 / Jeff Miller

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