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1983 512 BBi Burning Fuses

Discussion in 'Technical Q&A' started by petec, Dec 4, 2003.

  1. petec

    petec Rookie

    Nov 16, 2003
    8
    Kansas City, MO
    Full Name:
    Peter Cipolla
    The fuses for my fuel pumps are overheating causing a burning type smell. I of course stopped driving the car but would like anyones opinion as to what may be causing it. The fuel pumps are operating but something is pulling too much juice but not enough to blow the fuse. Ideas please.
     
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  3. tbakowsky

    tbakowsky F1 World Champ
    Professional Ferrari Technician Consultant

    Sep 18, 2002
    15,292
    The Cold North
    Full Name:
    Tom
    The fuel pump fuses in these cars are notorious for getting hot. But if your fuel pumps are old,and getting to the point where they'er not as efficiant as they once were,they may be staring to draw more current. This will cause the fuses to over heat..but not blow. They fuse will protect only in a case of excessive amperage. High current draw will create heat. I would check the pump draw with an ameter around the wires that connect to the fuel pumps. I would start there and see if it leads you in the right direction. Oh..if it does turn out to be the pump(s) don't go to Ferrari to get them. Remove the old pump and get the Bosch number off it and then just call your local jobber and tell them to order it. Much cheaper.
    HTH

    Tom
     
  4. tbakowsky

    tbakowsky F1 World Champ
    Professional Ferrari Technician Consultant

    Sep 18, 2002
    15,292
    The Cold North
    Full Name:
    Tom
    Hie pete..I just got your e-mail but for some reason it won't let my reply go through. I have a BB512i in the shop right now. I will put it up on the lift and snap a couple of pics of the pump location so you know excatly were they are located.
     
  5. jselevan

    jselevan Formula 3

    Nov 2, 2003
    1,856
    Petec - the culprit is likely in the fuse block, and not the pumps. No doubt the pumps can become less efficient, but I would first perform some first-aid on the fuse block.

    First - make sure that the fuel pump fuse block (separate with two fuses) is mounted correctly. During the past 20 years, someone may have removed the fuse block and reinstalled it upside down. Don't ask how I know. The upper aspect should have a shunt bar on the back of the plastic block that connects the two tops of the fuses together electrically. If it is turned upside down, then you have a problem.

    Second - remove the fuse block (FIRST DISCONNECT THE BATTERY), making sure to write down all the wires coming and going. Get a dremel with wire brush and clean the fuse contact points and the tabs that the wires connect to.

    Third - gently squeeze the female ends of the tabs to tighten them (using a needle nose pliers).

    Fourth - and here is the most important - remove the SINGLE red lead supplying both pump fuses. Make up another lead that has 1-into-2, that is, you want to distribute the current going to the pump fuse block between BOTH tabs on the upper end. As designed, the current all goes into ONE tab, and then is distributed by the shunt bar (in back) to the other fuse. This represents a poor design, as 1) all the current must enter through one tab connector (high resistance) and 2), the rivets loosen, creating a high resistance path to the other fuse. I had to cut the red wire to remove the female tab, and then crimped the red wire from the wiring harness with two wires going to each tab of the fuse block. After crimping, I soldered the connection to insure good contact.

    The net result is that prior to this surgery I could not touch the red wire or fuses without suffering 3rd degree burns of my finger. After surgery, the wire is cool to the touch. This suggests that the problem is ALL in contact resistance, and not related to the pumps!

    If you need pictures or more help, let me know.

    Jim S.
     
  6. boxerboy

    boxerboy Karting

    Dec 4, 2003
    89
    jselevan is correct. Just had the same corrective work done to the fuseblock on my 1981 BB512.
     
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  8. petec

    petec Rookie

    Nov 16, 2003
    8
    Kansas City, MO
    Full Name:
    Peter Cipolla
    Thanks everyone. I will try the surgery as soon as I can get to it and hopefully that will work. The problem comes and goes mostly comes however. Will let you know. Thanks again.
     
  9. simonc

    simonc Formula Junior

    Nov 1, 2003
    851
    Herfordshire, UK
    Full Name:
    Simon Campbell
    Jim S

    Could you post pictures of that mod please.

    Simon
     
  10. jselevan

    jselevan Formula 3

    Nov 2, 2003
    1,856
    #8 jselevan, Dec 8, 2003
    Last edited by a moderator: Sep 7, 2017
    Simple modification. The stock configuration is for the red wire to plug onto one of the tabs. I simply spliced two blue wires to the red wire, and plug onto both tabs of the fuel pump fuse block. The splice is a non-insulated aluminum connector that was crimped, then soldered. I then wrapped with black electrical tape.

    Hope this helps.

    Jim S.
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  11. jselevan

    jselevan Formula 3

    Nov 2, 2003
    1,856
    #9 jselevan, Dec 8, 2003
    Last edited by a moderator: Sep 7, 2017
    Here is the mod plugged in. I did the same thing with the radiator fan fuses, which supplied 3 fuses with one power conductor (plugged into one tab). As the rivets loosen, the resistance to each of the tabs increases. By routing power to each tab individually, the common conductor (bus) in the back of the fuse block becomes superfluous. It is this common conductor, electrically connected by rivets, that is the culprit. Of course, tighten and clean the fuse tabs themselves, and clean the ends of the fuses.
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