Bouncing tachomter needle and erratic fuel gauge | FerrariChat

Bouncing tachomter needle and erratic fuel gauge

Discussion in 'Mondial' started by 19ken96, Nov 16, 2020.

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  1. 19ken96

    19ken96 Rookie

    Jan 31, 2019
    25
    San Antonio, TX
    Full Name:
    Kenneth Aguilar
    #1 19ken96, Nov 16, 2020
    Good afternoon everyone,

    I hope this message finds y'all well. I am writing to seek your advice regarding the bouncing tachometer and somewhat erratic fuel gauge in my 1991 Mondial T Coupe.

    I am just getting to know my car as I just recently acquired it and immediately sent it for a full service upon its arrival. A full engine out service was performed. After taking delivery I drove the car home for about 1.5 hours, and out to dinner near my home the following evening. The next morning the car started but died in traffic.

    Upon further investigation by the shop, a short near the battery cutoff by the right headlight was discovered. They also cleaned other chassis grounds. Other work was also done to cure a related engine cutting out/surging condition.

    The car now runs beautifully but the tachometer does not mark correctly. It sometimes is marking anywhere from 2 to 4k rpm at idle. It does seem to mark correctly once the car is underway and at a steady cruise, otherwise it is all over the dial. On a recent trip I had a slight scare in traffic as I had started out about an hour before with a 1/2 tank of fuel, but looked at the fuel gauge and it was marking almost empty.

    I immediately began to look for the nearest exit, and kept looking at the gauge, and suddenly it was marking slightly less than 1/2 again.

    Previous to the electrical work the car was experiencing some surging and a cut out condition but the gauges were functioning normally.

    I have been driving the car almost daily to see if it might clear up on its own. The biggest problem with the car is that it has not been driven. It's a 1991 and only had 12k or so kilometers when I bought it a few months ago.

    Any thoughts or help would be greatly appreciated.
     
    paulchua likes this.
  2. 19633500GT

    19633500GT F1 World Champ
    Rossa Subscribed

    Nov 9, 2010
    12,023
    Blueberry
    Full Name:
    Muffin-Tops
    #2 19633500GT, Nov 17, 2020
    From one Ken to another Ken, these issues are simply one of the joys of Mondial (and other era FCars) ownership :)

    (the tach and gas tank readings, not the vehicle dying)

    You're doing it the right way though, these cars NEED to be driven. Italian tune ups daily will help.
     
    paulchua likes this.
  3. 19ken96

    19ken96 Rookie

    Jan 31, 2019
    25
    San Antonio, TX
    Full Name:
    Kenneth Aguilar
    #3 19ken96, Nov 17, 2020

    Thanks Ken, I will continue to drive it and see if it improves. If not I will get the shop to do more investigation later. I just wanted to finally be able to drive it as the weather has been great in Texas.
     
  4. djs308

    djs308 Formula 3
    Silver Subscribed

    Sep 2, 2002
    1,100
    Long Island, NY
    Full Name:
    David S.
    #4 djs308, Nov 18, 2020
    Have a look at the Fusebox itself. Check the contacts and relays. Might be some corrosion in there, especially if it's the original board. My 87 coupe's tach did something similar but cleared up after the fusebox contacts were cleaned up.
    Regarding the fuel gauge, mine is stable while idle but easily starts moving around once I'm underway. It always returns back to the right place when the car is either idle or cruising at speed (straight line). I was advised that they all do that, but if yours is not returning consistently back to where it should be, then it could be the float sensor in the tank needs to be checked out.
     
  5. theunissenguido

    theunissenguido Formula 3
    Owner Silver Subscribed

    Jan 21, 2004
    2,372
    Argent/Brasil
    Full Name:
    Guido
    #5 theunissenguido, Nov 18, 2020
    Tach will freeze when not driven the car. Turning point has some oil that gets hard....open your tach and put a very little drop of fine oil.
     
    paulchua likes this.
  6. 19ken96

    19ken96 Rookie

    Jan 31, 2019
    25
    San Antonio, TX
    Full Name:
    Kenneth Aguilar
    #6 19ken96, Nov 19, 2020
    Thanks, I'll check this out.
     
  7. paulchua

    paulchua Cat Herder
    Lifetime Rossa Owner

    Jul 1, 2013
    16,096
    Menlo Park, CA
    Full Name:
    Paul Chua
    #7 paulchua, Nov 19, 2020
    Hi Ken, two possible culprits in my opinion. 1) bad tach - solution is send to Palo Alto Speedometer for repair about $200. 2) bad sender unit, replace with KIA sender unit $25 ( search site for exact part #)

    as for fuel gauge, use tripometer as a rule (I do it even though mine works) just in case it failed and I don’t know. Again could be the meter or float in tank.
     
  8. paulchua

    paulchua Cat Herder
    Lifetime Rossa Owner

    Jul 1, 2013
    16,096
    Menlo Park, CA
    Full Name:
    Paul Chua
    #8 paulchua, Nov 19, 2020
    Best thing to do for a Ferrari is drive it, and often. Agreed with you 100%
     
  9. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,835
    Isle of man- uk
    #9 mike32, Nov 19, 2020
    Have u fitted a towbar yet for the removal van ?
     
    paulchua likes this.
  10. 88MONDIAL

    88MONDIAL Formula 3

    Apr 13, 2005
    1,052
    Racine, Wisconsin
    Full Name:
    Jim Smith
    #10 88MONDIAL, Nov 25, 2020
    I had a 1982 Mondial 8 I just sold last month - it had the erratic tach. Mine.... Start the car, the tach stays on 0, I had to lightly tap the dash top above it EACH time I'd start it. I had no problem with it, as it was consistent and I found that a bit charming. But the car after a while out at a steady cruise would go all over the tach giving miss readings from 0 - 6,000rpm's. Never found the issue. After my major it went away for well over a month, then came back. I can't help you, other than to give you that little bit of being in the same boat so to speak. They need a weekly drive of at least 25 miles. I did that and other then it's quirks it's always had, it never developed any real problems at all. I stored mine each winter for almost 6 months, but other than that, 1-2x per week 25-30miles out in the country a bit.
     

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