308 fuel pump fuse blown | FerrariChat

308 fuel pump fuse blown

Discussion in '308/328' started by Octonion, Mar 21, 2022.

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  1. Octonion

    Octonion Formula Junior

    Dec 30, 2020
    309
    USA
    Picture for attention. I took my 308 out yesterday to celebrate the BahrainGP win and about 10 minutes into the drive, it blew the fuel pump fuse. It took me a while to figure it out while parked on the side of the road. Is this a symptom of a fuel pump that is on its way out? cause for concern?
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  2. JuLiTrO

    JuLiTrO Formula Junior

    Nov 2, 2017
    383
    Full Name:
    Julio Saiz
    Did you check whether the fuse is Red Bull's design?
    (sorry for the joke)
     
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  3. Dave Bertrand

    Dave Bertrand Formula Junior
    Rossa Subscribed

    Dec 24, 2005
    770
    Castle Rock, CO
    A blown fuse is the result of too much current flowing in the circuit (exceeds the fuse rating). This could have occurred due to the fuel pump momentarily encountering resistance in the fuel flow, causing it to pull too much current. Before losing sleep over it, replace the fuse and see if it happens again. If it does, then you've got a problem to diagnose and fix. Maybe it's the pump, or just an associated relay. But if the new fuse doesn't blow then just note the incident for future reference.
     
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  4. Jonny Law

    Jonny Law F1 Rookie
    Silver Subscribed

    May 6, 2008
    3,173
    Over yonder.
    Full Name:
    IT Guy
    Make sure it is a 15 amp fuse. I once mistakenly swapped it for a 7.5 amp and got just about 10 minutes as well.
     
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  5. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    A slightly bad connection (like just a few tens of milliOhms of resistance) to the fuse ends, or from the rivets to the fuse ends, can add extra heating that will cause the fuse element to melt at a current below its rated value. What is the status of your fuse blocks? Stock, stock but soldered, updated to something else?
     
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  6. Octonion

    Octonion Formula Junior

    Dec 30, 2020
    309
    USA
    The car still has the original stock fuse block. I prefer originality so the birdman fuse option is currently a no-go for me. I do have contact enhancer (Deoxit) that I am going to apply to all the fuse contact points.
     
  7. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    Understood, but you can solder the stock fuse block plate-to-rivet connections on both sides and improve their reliability a lot. Also. inspect them for any plastic melting/discoloration/deformation -- typically, the plastic between the front and rear metal plates softens, gets squeezed out a little, and reduces the clamp load of the rivets. +1 on the DeoxIT -- never hurts and cleans well.
     
  8. Dave Bertrand

    Dave Bertrand Formula Junior
    Rossa Subscribed

    Dec 24, 2005
    770
    Castle Rock, CO
    While you're at it, double check to make sure every fuse in the block is the proper rating according to the fuse schematic. If any fuse is rated above what it should be, it isn't protecting its assigned circuit and is a fire danger.
     
  9. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    12,661
    San Carlos, CA
    Full Name:
    Mitchell Le
    It will get to the point where the fuse box will not make any more contact and your car will die. If you really want to preserve the original fusebox, remove it and save it. Put in Turtlefarmer fuseboards and drive care-free.
     
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  10. Octonion

    Octonion Formula Junior

    Dec 30, 2020
    309
    USA
    Sending a PM to @TurtleFarmer to see if he still has one to sell. Thanks for the info.
     
  11. Octonion

    Octonion Formula Junior

    Dec 30, 2020
    309
    USA
    So, thanks to @TurtleFarmer, I got the beautifully made fuse box replacement which I installed this week.

    But the problem persists. Fuse #1 gets blown if I try to use the left blinker. So atleast I think I have a clue. I just printed the circuit diagram to debug this. Any pointers appreciated.

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  12. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    Are you changing horses in the middle of the stream on us? ;) You originally posted that the fuel pump fuse #3 had blown -- it's now fuse #1? If so, are you saying it works OK when you use the right blinker, but, when you use the left blinker, fuse #1 blows?
     
  13. thorn

    thorn F1 Rookie
    Silver Subscribed

    Aug 7, 2012
    3,322
    Tallahassee, FL
    Test the amperage draw of the fuel pump, at the pump.

    Wait, strike that. It was the fuel pump fuse previously, now it's another fuse? Ditto to Steve's question - do both blinkers kill the fuse, or just left? Does having the wiper or stop lights on make any difference? If all answers are "just the left blinker", i'd start pondering a short starting at the left bulb and going upstream.
     
  14. Octonion

    Octonion Formula Junior

    Dec 30, 2020
    309
    USA
    I am sorry. It was my fault. I meant Fuse #1 originally too as it is driving the relay to the fuel pump. I believe the left blinker use is what is blowing fuse #1.
     
  15. Octonion

    Octonion Formula Junior

    Dec 30, 2020
    309
    USA
    I will go through this sequence and update.
     
  16. Octonion

    Octonion Formula Junior

    Dec 30, 2020
    309
    USA
    So here’s the update: Fuse #1 gets blown only when I try to use the left blinker . If I use the Hazard lights, Fuse #6 blows.

    I disconnected blinker bulbs from left rear and left front and problem persists. Tried to replace the blinker relay from NAPA but it did nothing so I returned it. Probable that pins are different. At this point I suspect the blinker relay but not sure. Going to need the original replacement blinker relay. Any pointers welcome.

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  17. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #17 Steve Magnusson, Apr 19, 2022
    Last edited: Apr 19, 2022
    The blinker relay is used for both left and right so I wouldn't suspect the blinker relay is the issue if right works OK, but left blows the fuse.

    This would still just indicate that you have a short somewhere in the wiring for the left turn signal bulbs. Fuse #1 supplies the turn signal system, and Fuse #6 supplies the Hazard system

    What year and version is your 308i?
     
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  18. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,040
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    Forgot to add that one (fairly easy, I think) thing to try would be to unplug the hazard light switch from the harness and see if using the left blinker still blows fuse #1, or not.

    If you have a 1981-2 US 308i, you just need to unplug the AN (light blue-black) wire from the hazard light switch for this test. (Would also give you a chance to see if something is wrongly touching the terminal with the AN wire. The center tunnel area is a bit of a wiring/cable rat's nest.)
     

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