330GTC Electrical Question | FerrariChat

330GTC Electrical Question

Discussion in 'Vintage (thru 365 GTC4)' started by Tinbender, Sep 4, 2022.

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  1. Tinbender

    Tinbender Formula Junior
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    Mar 13, 2004
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    Terry W. Phillips
    #1 Tinbender, Sep 4, 2022
    All this started as my electric fuel pump would not operate. I have around 10 volts at the pump, so I start checking around. I have around 10 volts at the fuse for the pump and around 10 volts at the dash switch for the pump. I have seen the suggestion to clean the 4 way connection on the fuse board, so I do this and I have 12.8 volts at this junction and I have 12.8 volts at the ignition switch on the wire that feeds the ignition switch coming from this 4 way. I check the wires coming out of the ignition switch and all of them that are hot have around 10 volts. So I think the contacts in the ignition switch are bad. But then I happen to check the wire feeding the ignition switch while the switch is turned on and it only has around 10 volts now where it has 12.8 with the ignition switch turned off. I check back at the 4 way junction and the wires here only have around 10 volts when the ignition switch is turned on and 12.8 when the switch is turned off. The battery has 12.8 volts with the ignition switch off and falls to 11.8 volts with the ignition switch on. I check for draw and have 9 amps of draw with the ignition switch turned on (about .25 with it off) so I start pulling fuses and the ignition fuse is drawing about 5 amps and the regulator fuse is drawing about 3.5 amps. Could this draw be causing the voltage drop?
    Any ideas?
     
  2. TTR

    TTR F1 Veteran
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    Timo
    #2 TTR, Sep 4, 2022
    Couple of thoughts:
    - Are you measuring all Voltage readings with engine & charging system running or not ?
    - Have you checked the grounding* of each and every component in related system(s) ?

    * In my experience (40+ years of working on them) & according to many others, insufficient ground is the most common contributor to all electrical problems in vintage cars.
     
    christc likes this.
  3. DWR46

    DWR46 Formula 3
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    #3 DWR46, Sep 4, 2022
    Timo has excellent recommendations. Follow his guidance.
     
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  4. enio45

    enio45 Formula 3
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    Ed
    #4 enio45, Sep 4, 2022
    Ck that ground strap at the battery box to the engine etc and the gnd cable that bolts up to the same point.
     
  5. gcalex

    gcalex Formula Junior
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    Alex
    #5 gcalex, Sep 5, 2022
    So my vintage-car experience is limited to my own vehicles, but I am an "electronics" guy, and yeah, either your gnds are "all over the place", or something is pretty "off";

    A fully charged battery should not be showing a full volt of voltage droop at 10amps; maybe at 50+amps, but not 10...

    Are you measuring battery voltage directly across the battery terminals? If so, then I would guess that the battery itself in part of the problem. If not, then you definitely need to check the resistance between the gnd-point you are using for your meter, and the battery negative terminal.

    You really should not be pulling a lot of amps through the regulator unless the car is running, so Timo's question about whether the car is running when you take these readings is apropos, but...

    The readings you are getting would be even more strange if the car were running, so my guess is that they were taking with the engine not turning. If this is right, then it does seem likely that the gnd to the regulator is floating or something...
     
  6. Tinbender

    Tinbender Formula Junior
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    Terry W. Phillips
    #6 Tinbender, Sep 6, 2022
    I am testing with the engine off. In searching the internet (I know. I know) I am finding that coils should draw 3-4 amps each, but I am not finding if that is true with the engine not running. If this is true weather the engine is running or not, then that draw is normal. I have cleaned up the main ground and cleaned the 4 way junction and the fuse connections. I have moved the fuel pump feed wire to the fuse for left power window motor as this is hot without the key being on. This will give me 12.8 volts to the pump and allow me to fill up the carbs and get the car started. Once I get it running I will see what the voltage is with the alternator providing power.
     

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