• hank
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  • From: British Columbia Canada
  • Registered: 2004-03-30
  • Posts: 430

Topic: reading amp draw for compression test

Howdy Gang,
Anybody happen to know about the diagnostic plug used on later air cooled model VWs?
I was told by plugging in with the proper tester the VW techs could get a relative compression reading from how many amps the starter was drawing.
low amp reading would show low compression and high amp  reading would indicate a higher compression.
there must have been a probe to tell #1 cylinder.

Is there any way to rig up a homemade unit to do the same?
just a thought
cheers
hank

'57 bug "BlackBerry"
'58 type261 single cab "Ruf"
'86 vanagon syncro "Syncro da Dr.Mayo"
and way too many project waiting
  • From: somewhere over the rainbow USA
  • Registered: 2006-07-26
  • Posts: 1,889

Re: reading amp draw for compression test

Don't know about the VW diagnostic but on a scope it just shorted out the cylinders to get a balance between them, IIRC
What I do is just pull a plug wire and listen to the engine rpm raise and fall and do my own balance test.
Best thing tho is a leak down test to determine the engines shape.
And yes it had a sensor on #1

burrhead

A wise man makes his own decisions, an ignorant man follows public opinion.
  • From: B.C.Canada
  • Registered: 2005-01-26
  • Posts: 2,610

Re: reading amp draw for compression test

This explains it pretty thoroughly>

http://www.nls.net/mp/volks/htm/plug.htm

jim

'71 SB(DD only 79K(now 84K miles) & '78 FI Westy (project)
PO of '65 Beetle in '69, '70 Crewcab & '70 Ghia in '77
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http://www.openroad.ca/volkswebbin/view … p?id=85915
  • hank
  • Member
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  • From: British Columbia Canada
  • Registered: 2004-03-30
  • Posts: 430

Re: reading amp draw for compression test

thanks guys

'57 bug "BlackBerry"
'58 type261 single cab "Ruf"
'86 vanagon syncro "Syncro da Dr.Mayo"
and way too many project waiting