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Tach trouble 86 Testarossa

Discussion in 'Technical Q&A' started by CRUZINTR, Jan 18, 2005.

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  1. CRUZINTR

    CRUZINTR Rookie

    Jan 18, 2005
    8
    Santa Cruz, CA
    Full Name:
    John DeAngelis
    #1 CRUZINTR, Jan 18, 2005
    Tach stopped working correctly a month or two ago. Now shows idle of 1K, but when rev'ed up, shows maybe as high as 2000 to 2500 RPM when it's turning 4000 to 5000rpm. Once in a while, it does show correct reading, but not often.
    Any ideas about what components I could check, electrical contacts, their physical location, etc.

    It's not good to use the rev limiter as a shift point indicator, a working tach is better.

    Thanks, 86TR
     
  2. ASG 86TR

    ASG 86TR Formula 3

    Aug 23, 2001
    1,474
    New Jersey
    Full Name:
    Adam G
    #2 ASG 86TR, Jan 18, 2005
    Typicaly it is one of the sensors. I replaced mine as well as a few other. I cannot for the life of me rem which sensor it is, but I think it is the one on the flywheel.
     
  3. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    37,288
    Cowboy Capitol of the World
    Full Name:
    Brian Crall
    #3 Rifledriver, Jan 18, 2005

    If those sensors are bad the motor won't run. One is the rpm sensor, the other is the crank position sensor for the Marelli Ignition unit. Either one quits, the motor dies. If the signals are getting to the tach (check them, there is no substitute for good old fashioned diagnosis) it is a bad tach. If the signals are not present go up stream and find out where you lose it. This will require the Testarossa electrical manual. If you do not have one finding electrical faults will be like banging your head against the wall.
     
  4. f355spider

    f355spider F1 World Champ
    Owner Rossa Subscribed

    May 29, 2001
    18,055
    USA
    #4 f355spider, Jan 18, 2005
    All the 3.2 engine cars from the mid/late 1980's had a similar problem. It sounds exactly the same, the tach constantly reads low. I sent the tach from my 1987 328 to Palo Alto Speedometer, and Helmut the owner was well aware of the problem, and turned it around in about 3 or 4 days. $150, worked great from then on...

    http://www.paspeedo.com/

    Apparently there are some components in the tach that commonly fail.
     
  5. CRUZINTR

    CRUZINTR Rookie

    Jan 18, 2005
    8
    Santa Cruz, CA
    Full Name:
    John DeAngelis
    #5 CRUZINTR, Jan 19, 2005
    I went to PASPEEDO at lunch today... Owner(paspeedo) had a TR + many customers with this low reading problem. Got an appointment on Fri to repair....Thanks!!!
     
  6. khayes

    khayes Formula Junior

    Nov 1, 2003
    591
    Austin, TX
    Full Name:
    Kelly Hayes
    #6 khayes, Jan 19, 2005
    There is no rev limiter on my 86 TR. It'll run up as high as you care to push it.
     
  7. f355spider

    f355spider F1 World Champ
    Owner Rossa Subscribed

    May 29, 2001
    18,055
    USA
    #7 f355spider, Jan 19, 2005
    Glad to be of help.

    Regards,
    Dave
     

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