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Diagnostic Plug

Discussion in 'Fuel System & Electrics' started by Bay_Buddha, Oct 31, 2007.

  1. Bay_Buddha

    Bay_Buddha Member

    Messages:
    395
    Location:
    Berowra Heights,North of Sydney
    Hey Kids...

    I have just been reading this article by Jim Mais about the diagnostic plug found in the engine bay.

    [​IMG]

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

    I have known that it was used by VW techs to diagnose electrical faults but I was surprised to note that it was also used to analyse engine compression and ignition timing too.

    I'm curious as to whether the plugs are still useful to us or were special analysing gizmos needed to read the data from the plug.

    Phill.
     
  2. Jehd

    Jehd New Member

    Messages:
    192
    Location:
    Brisbane West Side
    interesting. Alot of cars don't have them anymore. Mine is still there. If i had known it had links to the brake lights and indicators, it would of been a better place to hook up the trailer light plug!
     
  3. Bay_Buddha

    Bay_Buddha Member

    Messages:
    395
    Location:
    Berowra Heights,North of Sydney
    Jehd- Good idea for the trailer plug... You gave me an idea, hook up some lights to the ignition point on the socket and you could have a strobe setup happening! (Probably too weak a current though!)

    (When I get a chance)... I'm thinking it might be interesting to test out the pins and see if they are still registering any current.

    Does anyone know any more about the compression sensor? I'm wondering how the current mentioned in the article is generated for the reading through the pin in the socket.
     
  4. The Duke

    The Duke New Member

    Messages:
    27
    Location:
    Caloundra,sunshine coast
    cylinder balance test?

    The only way i can see that the "compression" is checked is through a cylinder balance test.Basically the analyzer cut`s one cylinder at a time (via the coil)then calculates the rpm drop and so gives a cylinder efficiency in a percentage.
     
  5. Schmoburger

    Schmoburger Active Member

    Messages:
    4,381
    Location:
    Nowra/Jervis Bay area, NSW.
    Mmmmmm... I reckon the DUke is probably onto something there.... tis the only way I can see that compression could be checked "electrically"... I still reckon nothing beats a good old fashioned compression tester. :cool:

    I still have the plug there, but have never used it for anything...
     
  6. ttmck

    ttmck Super Moderator Staff Member

    Messages:
    2,769
    Location:
    Hallett Cove STH AUS
    correct i have seen the tester and its ancient i know of one vw repairer that has one here in sth aus , it does not even have an osciliscope. but yes it will cut the cyls to check the balance out rather than doing a compression test but any tune up machine will do this and whole lot more . tis pretty useless machine . just an ornament in his work shop !
     
  7. Schmoburger

    Schmoburger Active Member

    Messages:
    4,381
    Location:
    Nowra/Jervis Bay area, NSW.
    Heheh... gimme a compression tester, a synchrometer, a dwell tachometer, a multimeter, and a testlight, and I'm ready to conquer the world! :cool:
     
  8. Bay_Buddha

    Bay_Buddha Member

    Messages:
    395
    Location:
    Berowra Heights,North of Sydney
    Hey Tom, Schmo!

    I agree on the diagnosis point of view. There are more reliable ways.

    I was however thinking along Jehd's line of anyones different uses for the points in the socket. I can't really think of anything though.
     
  9. GoblinSA

    GoblinSA New Member

    Messages:
    1,931
    Location:
    Adelaide Hills
    Where abouts in the engine bay is this thing found??
     
  10. Schmoburger

    Schmoburger Active Member

    Messages:
    4,381
    Location:
    Nowra/Jervis Bay area, NSW.
    on the right hand side as you look towards the firewall, mounted on the engine bay ceiling closish to the engine lid... it is plastic and may be covered by a rectangle cap with the Audi rings on it if the cap hasnt fallen off. :cool:

    As mentioned tho, a lot of Kombis have had em pulled off.
     
  11. syncro

    syncro Well-Known Member

    Messages:
    9,638
    Location:
    Southern Highlands

    Urban myth.

    The mechanics used to colour in the compression test cards with a pencil.

    The "computer" consisted of a lot of empty blue and grey boxes.
     

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