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Munchkin Boiler, Spark Plug Gap - the manual is in error.

PostPosted: Tue Dec 29, 2015 10:25 pm
by jpcallan
Several places in the various Munchkin manuals, like under error F09 as an example, the manual says: "If there is no spark, check the spark electrode for the proper 1/4” gap by holding two quarters together and sliding them through the gap." The manual specifies the wrong gap in the same sentence. Two quarters sandwiched are just a shade over 1/8", not 1/4".

I have yet to find a spark gap set to 1/4" from the factory on a new plug, like the 7250P-058 or the superseding plug 7350P-020. The message goes on to say "holding two quarters together and sliding them through the gap." If you take two U.S. Quarters (Washington's profile, State, or Bicentennial) and sandwich them together in a caliper you will find they measure .135" to .137". An eighth inch is .125", a quarter inch is .250", way more! I spoke with Nick at HTP tech support today and he confirmed the the two-quarters (.135") gap is the correct gap size.

I've adjusted the gap in years past to the specified 1/4", only to see F09 errors or a noticeable increase in the volume of the WOOF sound when the gas ignites. Until this past week, I never question the accuracy of the gap specification in the manual. Nick said the shorter gap causes a hotter spark.

Also... the spark plug electrodes are made from a very hard, brittle metal alloy. I have broken off the electrode I was trying to bend while trying to adjust the gap. Out of fear of damaging the porcelain, I usually bend the ground electrode. If you must reset the gap, heat the ground electrode with torch to red hot before trying to adjust it.

Pencil the corrected gap setting into your Munchkin manuals. It appears in several places.