Mondial Fuel Pump Blowing Fuse | Page 2 | FerrariChat

Mondial Fuel Pump Blowing Fuse

Discussion in 'Mondial' started by freelapl, Jun 13, 2022.

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  1. M. Brandon Motorcars

    Sponsor

    Sep 4, 2007
    1,759
    Houston, TX
    Full Name:
    Michael Foertsch
    This is a very common problem on the Mondial. Usually starts because of something blocked in the fuel delivery system, causing the pump to work harder, increasing current through the relay circuit, and then ultimately frying the fuse/relay circuit board, connector, etc.

    Even if your fuel delivery system is now clear, the damage remains to the fuel pump relay circuit.

    There are two fixes. One is to replace the fuse box with one of the new designs. The other is to take the fuel pump relay circuit off of the fuse box (bypass it). There are many threads here on FChat on how to do this.
     
  2. freelapl

    freelapl Karting

    May 8, 2006
    88
    Los Angeles, CA, USA
    Full Name:
    Pete Freeland
    Today I did a test drive to see if t'he improvements have worked....unfortunately they didnt work. I got about 2 miles from the house when the fuel pump fuse went. After letting car cool down for about 10 min I tried again and the fuse went right away. This repeated 5 more times and so was obvious car would not start. The relays didnt seem particularly hot, and there was no burning on the W connector. I had the car towed home and now trying to figure out what to do next......any suggestions? I've put in new fuse board, fuses, relays, W connector & splices, fuel pump, fuel filter, fuel accumulator, and verified all fuel ports and screens are clean. What else am missing?
     
  3. theunissenguido

    theunissenguido Formula 3
    Owner Silver Subscribed

    Jan 21, 2004
    2,371
    Argent/Brasil
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    Guido
    Must be a short in the fuel pump circuit. Did you check the connections on the pump itself ? A fuse board that can handle the current that is needed is an other option. Those little connectors on the W plug are not big enough for that current.
     
  4. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,828
    Isle of man- uk
    Connect a voltmeter to the fuel pump itself and earth- what volts are you getting when pump is running ? If you are getting a reduced voltage then you will be drawing more amps which will blow the fuse. You need to ensure 12 volts at the pump electrical terminal. The car has connection strips where one wire connects to the next, you might have one wire run which is in bad condition
     
  5. freelapl

    freelapl Karting

    May 8, 2006
    88
    Los Angeles, CA, USA
    Full Name:
    Pete Freeland
    Hi, I wanted to do a follow-up on this thread. I inspected the wiring and could not find any obvious wiring problems. I next looked to the other two items on the same power circuit including the warm up regulator and the aux air valve. I didn't see any issues on the warm up regulator but the aux air valve had some corrosion on the right terminal of the AAV connector, and the air intake tube has a bend in it that looks like it reduces the airflow. I disconnected the AAV connector from the car and it started up fine but after a few min began to idle a little rough, telling me that I probably should not try to drive the car with it disconnected.

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    Could this be the source of my fuse blowing issue? How does a AAV typically fail? It makes sense that I was seeing my problems after a few min of the car running, and with the AAV mounted directly under the expansion tank it would be about the time it would start getting warm there.... Should I plan to replace the AAV unit or is it safe to drive it without it connected?

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  6. freelapl

    freelapl Karting

    May 8, 2006
    88
    Los Angeles, CA, USA
    Full Name:
    Pete Freeland
    Looks like I finally found my problem. After replacing and checking everything else it seems my warm up regulator is the culprit. Shortly after the engine gets to temperature it begins buzzing VERY loud, and within seconds of that the fuse blows for the 15A circuit. When I touch the unit I can actually feel it vibrating, so will look to either replace or rebuild it.

    Is this a common problem with teh 3.0 QV Mondials or in general?
     
  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)
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    Steve Magnusson
    I'd say "no" -- can't recall any other time that this issue with the WUR was reported. Many problems reported with WURs, but not causing the fuse to blow.
     
  8. freelapl

    freelapl Karting

    May 8, 2006
    88
    Los Angeles, CA, USA
    Full Name:
    Pete Freeland
    Is there any way I can test my WUR to confirm if it is causing the problem? If not the WUR could it be the AAV failing? Ideally would like to be able to confirm which of these units is causing my power draw since everything else in the circuits for fuel including the fuseboard have been replaced.....
     
  9. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
    25,040
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    Steve Magnusson
    See post #19 -- you can just unplug both the AAV and WUR (they'll heat up more slowly, but they will still heat up). If the fuse still blows = it's not them causing the problem. Then plug them in one at a time to see if either is causing the fuse to blow.
     
    freelapl likes this.
  10. freelapl

    freelapl Karting

    May 8, 2006
    88
    Los Angeles, CA, USA
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    Pete Freeland
    OK sounds good, I wasnt sure if I could safely drive the car with those unplugged but will try that and see if the problem continues then plug each in to see what fails. Thanks!
     
  11. theunissenguido

    theunissenguido Formula 3
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    Jan 21, 2004
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    Guido
    Only way to make sure WUR is ok...you have to open it.
     
    350HPMondial likes this.
  12. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,828
    Isle of man- uk
    Just seen this - not like you to be splashing money about !!
     
  13. 350HPMondial

    350HPMondial F1 Veteran
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    Feb 1, 2002
    5,187
    18 mi from the surf,, close to Pismo, CA
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    Edwardo
    I also performed this circuitboard mod.
    ( worked out good.)
     
  14. 350HPMondial

    350HPMondial F1 Veteran
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    Feb 1, 2002
    5,187
    18 mi from the surf,, close to Pismo, CA
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    Edwardo
    Or,, you can fabricate a gauge to measure “Control Pressure.” ( recommended)
    Note, photo shows my test gauge at cold start injector position, for measurement of primary fuel pressure.
     

    Attached Files:

  15. theunissenguido

    theunissenguido Formula 3
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    Jan 21, 2004
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    Guido
    I dont see why there can be a buzzing sound comming from the WUR other than clogged fuel entrence.
     
  16. 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)
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    Steve Magnusson
    Agree that it seems a strange symptom for a WUR. I'm having a vague recollection that some WUR have 2 bimetallic elements inside -- the main one to alter the control pressure and a second one that actuates a switch to turn off one of the heating element coils -- i.e., a lot of heat is applied quickly to the main bimetallic element by two heating coils, then the switch opens and less heat is applied to the main bimetallic element by only a single heating coil. Maybe some of the bimetallic stuff is rattling around. Thought I had saved a picture of this more complicated bimetallic/heater arrangement, but can't find it (or didn't save it).
     
    350HPMondial likes this.
  17. greatscott73

    greatscott73 Formula Junior

    Sep 1, 2017
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    Eastern Tennessee
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    Howard Scott
  18. theunissenguido

    theunissenguido Formula 3
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    Jan 21, 2004
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    Guido
    Here is a file I started some time ago....
    https://www.ferrarichat.com/forum/threads/wur-woes-and-repair.631806/
     
  19. 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
    Thanks Guido and Howard -- that's the WUR style with the adjustable internal switch and two heating coils! (Although, since the fixed resistor values are different, those must be different WUR part numbers.) Good to know that my memory isn't completely faulty ;). Now I am going to save those pictures!
     
  20. freelapl

    freelapl Karting

    May 8, 2006
    88
    Los Angeles, CA, USA
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    Pete Freeland
    Today we finally had a break in the weather and was able to do another test drive. I disconnected the AAV and WUR, then drove the car for about 10 minutes before the fuse blew again. I did go a longer time than prior before it finally went, but looks like I cannot confirm that it is one of the other units.

    So back to square one. I do have another new fuel pump that I can install, but still not sure what else to do.....it must be something in the fuel pump circuit. With a new fuseboard and wiring connectors I'm not sure what else to test or check.
     
  21. 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
    You can use something like this "Fuse Buddy" to measure the current that your fuel pump is drawing to see if it's excessive or not:

    https://www.amazon.com/esi-306b-fuse-buddy-tester/dp/b0014ddk5o?tag=namespacebran246-20

    It should be something like 9A~11A on the stock F CIS Fuel pump (but some of the F part suppliers have been supplying a lesser capacity CIS fuel pump that might be in the 7A~9A range).

    However, your report that it takes some time to blow the fuse makes me think that you might have a poor connection between the female terminals on the fuse relay panel and the male terminals on the fuse, and you are just getting a lot of I^2*R heating at that connection which melts the fuse (a very small resistance makes for a lot of heat because the current is large). If the fuel pump current measures something reasonable, but the fuse still blows = you'd need to inspect/clean/tighten those connection to the fuse itself.
     
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  22. freelapl

    freelapl Karting

    May 8, 2006
    88
    Los Angeles, CA, USA
    Full Name:
    Pete Freeland
    I ordered the fuse tester (very cool!!!) and will check the fuse holder connections also. Thanks!!
     
  23. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,828
    Isle of man- uk
    Now that is a neat bit of kits, never seen that before
     
  24. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,828
    Isle of man- uk
    According to my European copy of the wiring diagram, there is a connection block C1 on the left hand side of the instrument panel, see if you have a bad connection. It then goes straight to the fuse box.
     
  25. freelapl

    freelapl Karting

    May 8, 2006
    88
    Los Angeles, CA, USA
    Full Name:
    Pete Freeland
    A quick update - I got the fuse buddy and tested it, showing current around 9.5 to 10.4 amps. Tested it with the car running for 30 min, in both high rpm and idle. Everything seemed stable so I took it out for a test drive and only got 3 blocks down the road before the fuse blew again. Replaced it with other 15A, then a 20A, finally took a 30A to get the car home. Really not sure what to do next. I've inspected all the wiring I could access and no obvious shorts that I can see. All new fuel parts including fuel pump x 2, fuel filter, accumulator, and new fuseboard from GT Car Parts. Replaced main connector on fuseboard to fuel pump and disconnected the AAV and WUR temporarily but that had no effect.

    Truly lost at what to do next ....
     

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