348 - Low Fuel Light Flickering but Fuel gauge ok | FerrariChat

348 Low Fuel Light Flickering but Fuel gauge ok

Discussion in '348/355' started by 348Jeff, Jan 16, 2022.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

Page 1 of 2
  1. 348Jeff

    348Jeff Formula 3

    Oct 25, 2011
    1,503
    UK
    Full Name:
    Jeff
    #1 348Jeff, Jan 16, 2022
    Got a bit of a strange problem - my orange low fuel indicator in the binnacle has started flickering almost constantly but the fuel gauge shows what I think is an accurate representation of how much fuel I have.

    Done the basics ie. put plenty of fuel in which is accurately reflected by the fuel gauge but the ow fuel lightst continues to flicker.

    Do they work independently? I'm assuming there's a bad electrical connection but not sure where to start. Should I be looking at the binnacle or is there something underneath round the fuel tank etc. ?
     
  2. Ferrarium

    Ferrarium F1 Veteran
    Rossa Subscribed

    Jul 28, 2018
    5,637
    Central NJ
    Full Name:
    Eric
    #2 Ferrarium, Jan 16, 2022
  3. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    11,555
    Sydney
    Full Name:
    Ian Riddell
    #3 Qavion, Jan 16, 2022
    Yes, there is a separate low fuel switch on the fuel level sender. There may be a sender fault or a short to earth on the pink/black wire. If you disconnect the plug on the sender and the light still illuminates, it means that you have a shorted wire somewhere.

    Wiring diagram here:

    https://www.dropbox.com/t/rTCKINUYTQzwMDid

    Note that this is different from the F355 system.
     
  4. 348Jeff

    348Jeff Formula 3

    Oct 25, 2011
    1,503
    UK
    Full Name:
    Jeff
    #4 348Jeff, Jan 17, 2022
    Thanks guys:

    I think Ill try this first and report back :)
     
    Qavion likes this.
  5. JM280z

    JM280z Formula Junior

    Aug 22, 2020
    706
    Full Name:
    Jake
    #5 JM280z, Jan 17, 2022
    Cleaning grounds, checking for corrosion where the bulb plugs in, checking the wiring harness connectors, etc.
    -Another thought.

    Removing the dash cluster is easy. Just two small phillip screws underneath by the steering column.
     
  6. 348Jeff

    348Jeff Formula 3

    Oct 25, 2011
    1,503
    UK
    Full Name:
    Jeff
    #6 348Jeff, Jan 17, 2022
  7. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    11,555
    Sydney
    Full Name:
    Ian Riddell
    #7 Qavion, Jan 17, 2022
    Last edited: Jan 17, 2022
    Not sure. Supposedly, the purple wire is the sender. They share a common black ground wire. The colours may have faded.

    The sender is on the RH side of the bottom of the tank.

    https://www.eurospares.co.uk/parts/ferrari/348-1993-tb-ts/fuel-system/fuel-tank-23642

    Photos and diagrams show only one plug for all 3 wires. I don’t know how accessible the plug is.

    https://www.ebay.com/itm/233904071470

    If the sender is faulty, the good news is that a superior aftermarket sender has just come on the market.
     
  8. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    11,555
    Sydney
    Full Name:
    Ian Riddell
    #8 Qavion, Jan 17, 2022
    Last edited: Jan 17, 2022
    Sorry, I thought your photo showed two plugs. It's just the odd shape of the plug which makes it look that way. Yes, it looks like the right plug.


    Image Unavailable, Please Login

    If there is a way of safely removing the pink/black wire from the plug (and taping and stowing it temporarily), you could keep your gauge indications during your test period.

    For a new sender, contact your local spares stockist (Eurospares?) or contact Brian on the forum:

    https://www.ferrarichat.com/forum/posts/147388119/
     
  9. 348Jeff

    348Jeff Formula 3

    Oct 25, 2011
    1,503
    UK
    Full Name:
    Jeff
    #9 348Jeff, Jan 17, 2022
    Its a bit late here in UK now (10pm) so Ill investigate further tomorrow :)

    Thanks for the help so far
     
    Qavion likes this.
  10. 348Jeff

    348Jeff Formula 3

    Oct 25, 2011
    1,503
    UK
    Full Name:
    Jeff
    #10 348Jeff, Jan 18, 2022
    Last edited: Jan 18, 2022
    Had another look at this today...

    Was a bit of a faff to untuck the plastic plug connector as it was just in behind the tank support. I didn't want to risk breaking it so sprayed a bit of contact cleaner on it just to act as a lubricant. It is a straight pull apart and couldn't see any clips o anything you need to press - just a tight fit!

    Image Unavailable, Please Login

    Image Unavailable, Please Login

    I superglued a piece of sandpaper to a peg to clean up the terminals which were looking a bit green then sprayed with contact cleaner. Did a visual inspection for damaged wiring (couldn't see anything) and did a quick electrical test for continuity.

    Image Unavailable, Please Login

    Now this may be my poor electrical skills but I got continuity between the black wire and each of the the other pegs (I'm assuming one for sender and one for low level fuel light??? not sure) and both had continuity (green and yellow lines). However, what I didn't expect was continuity between the 2 non black wires between each other - shouldn't they not have continuity?????? (orange line)

    I also repeated the test on the other side of the plug and this did the same (with ignition off) so am wondering whether I'm doing the test wrong - tried to take a pic but ran out of hands. Does anyone have one of teh new ones they could test for me so I can compare???

    Image Unavailable, Please Login
     
  11. Ferrarium

    Ferrarium F1 Veteran
    Rossa Subscribed

    Jul 28, 2018
    5,637
    Central NJ
    Full Name:
    Eric
    #11 Ferrarium, Jan 18, 2022
    I'd try Deoxit D100 as well before mechanical removal of corrosion.
     
  12. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    11,555
    Sydney
    Full Name:
    Ian Riddell
    #12 Qavion, Jan 18, 2022
    A high resistance on the pins due to corrosion shouldn't cause the light to come on. Only a short to ground would do this. I suppose if the inside of the plug was damp and dirty, you might get some conductivity, but I doubt it would be enough to turn on the light.

    Here's the circuit but I'm not 100% sure of the wire colours on the sender side of the plug.

    Image Unavailable, Please Login


    It would be great if you could tell me which pins have which colours. I usually draw my plug graphics showing the metal contact side (not the wire side). I see what looks like red and yellow in your photo, but I can't be sure.

    By getting continuity between pin 2 (red?) and any of the other pins with a non-empty tank basically proves you have faulty sender. I was thinking your problem was so intermittent, I didn't think you'd find the problem with an ohmmeter.

    (EDIT: If you shake the sender wiring, do you get any changes to the ohmmeter readings. I suppose if the wiring was damaged, it might cause the light to come on. Repairing wiring would certainly be cheaper than a new sender)
     
  13. 348Jeff

    348Jeff Formula 3

    Oct 25, 2011
    1,503
    UK
    Full Name:
    Jeff
    #13 348Jeff, Jan 18, 2022
    I've just looked through my pics and I cant find a good clear one so I'll try again tomorrow. (I put everything back together and then went for a drive in the car).

    I shall double check but pretty sure I was getting continuity between pin 2 and either of the other 2 pins. Really hope its not the sender as even the aftermarket one is quite expensive.
     
  14. 348Jeff

    348Jeff Formula 3

    Oct 25, 2011
    1,503
    UK
    Full Name:
    Jeff
    #14 348Jeff, Jan 18, 2022
  15. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    11,555
    Sydney
    Full Name:
    Ian Riddell
    #15 Qavion, Jan 18, 2022
    Don't worry. I think I have figured it out from your pics and other online pics. I'll add this detail to my wiring diagrams. Thanks!
     
  16. 348Jeff

    348Jeff Formula 3

    Oct 25, 2011
    1,503
    UK
    Full Name:
    Jeff
    #16 348Jeff, Jan 18, 2022
    Tomorrow I'm going to:

    1) Just unplug the connector to make sure that the fuel gauge registers empty and the light goes out (rule out a short on the gauge side)

    2) short the wires from the black to the 2 other wires (one at a time) to make sure fuel gauge goes to full and light stays on permanently (currently it flickers).

    I think if the above both do what I am expecting I'll have to resign myself to the sender is faulty. Certainly wont be shelling out 2k for a new one so wil either attempt a repair or buy either Brians aftermarket one or SuperPerformance do one for £64.95 UK

    https://www.superformance.co.uk/348/fuel.html

    Anyone whose already done this job interested in selling their old tool?
     
  17. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    11,555
    Sydney
    Full Name:
    Ian Riddell
    #17 Qavion, Jan 18, 2022
    Just found this thread on gauges.

    https://www.ferrarichat.com/forum/threads/how-to-deal-with-a-gas-guage-problem.492687/#post-144045488

    Not sure what shorting the sender gauge wire (purplish-brown?) to earth would do on your car. Full or empty? Anyway, it will be full scale one way or the other.
     
  18. 348Jeff

    348Jeff Formula 3

    Oct 25, 2011
    1,503
    UK
    Full Name:
    Jeff
    #18 348Jeff, Jan 19, 2022
    Right a bit more investigation and hopefully better pictures. I think it proves it is the sender and gauges and their associated wiring are just fine.


    First of all I made myself a little test wire and tested the test wire - last thing I want is to add to the confusion with a faulty test wire!!!!

    Image Unavailable, Please Login

    So looking at the pictures you have:

    Black Sender connects to Black

    Red Sender connects to Pink/Black Stripe (Low Fuel Warning)

    Yellow Sender connects to Purple (Fuel Gauge)


    Image Unavailable, Please Login

    Image Unavailable, Please Login

    Image Unavailable, Please Login
     
    Qavion likes this.
  19. 348Jeff

    348Jeff Formula 3

    Oct 25, 2011
    1,503
    UK
    Full Name:
    Jeff
    #19 348Jeff, Jan 19, 2022
    Last edited: Jan 19, 2022
    On the gauge side (not sender) if I short the black to the purple wire the fuel gauge registers full but the orange warning lamp doesn't light even for start-up checks so the purple is the fuel gauge.

    Image Unavailable, Please Login

    Image Unavailable, Please Login

    Image Unavailable, Please Login


    On the gauge side (not sender) if I short the black to the pink/black striped wire the fuel gauge registers empty but the orange warning lamp lights up brightly (more so than my flickering fuel light scenario) so the pink/black stripe is the low fuel warning light.

    Image Unavailable, Please Login

    Image Unavailable, Please Login

    View attachment 820461

    So my conclusion from this is that there's nothing wrong on the main harness/gauge side and my problem will be on the sender side.

    BTW With nothing shorted neither the fuel gauge or the low fuel light warning light work.
     

    Attached Files:

    bjwhite and Qavion like this.
  20. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    11,555
    Sydney
    Full Name:
    Ian Riddell
    #20 Qavion, Jan 19, 2022
    Thanks for the confirmation, Jeff.

    I see the wire colours are much easier to identify after they were cleaned :D

    Now the hard part... emptying the tank and finding a tool. Brian offers a tool, but I don't know if it's available only as part of a kit (?)
     
  21. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    11,555
    Sydney
    Full Name:
    Ian Riddell
    #21 Qavion, Jan 19, 2022
  22. 348Jeff

    348Jeff Formula 3

    Oct 25, 2011
    1,503
    UK
    Full Name:
    Jeff
    #22 348Jeff, Jan 22, 2022
    After my fiddling about he low level light stopped illuminating altogether so decided to investigate a little more. Decided to undo the tiny plastic screw on the bottom of the sender and prise out the end cap.

    I was expecting to see corroded wires or a clear break but TBH it looks in good condition.

    After doing this the light worked again but not as bright as shorting it. Beginning to suspect thee might be a break in the wire.


    Image Unavailable, Please Login

    Image Unavailable, Please Login

    Image Unavailable, Please Login
     
    Qavion likes this.
  23. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    11,555
    Sydney
    Full Name:
    Ian Riddell
    #23 Qavion, Jan 22, 2022
    A break in the wiring should not not cause the light to go on. An earth on the red wire is the only thing which can cause the light to come on (or the sender internal "switch" being activated, allowing the red wire to be earthed)

    A break in the insulation on more than two wires in the sender harness may cause an issue. Can you feel any irregularites in the wiring in the sender harness under the black plastic sheath or is it too thick?
     
  24. 348Jeff

    348Jeff Formula 3

    Oct 25, 2011
    1,503
    UK
    Full Name:
    Jeff
    #24 348Jeff, Jan 22, 2022
    I haven't checked yet but I was going to just feel and flex the wire along its length to see if can change its status from either off to on or vice versa. The problem is being able to mess with the wire and still see my dash.

    NB Don't forget that when you first switch the ignition the low level light comes on for a period as a self test and it had stopped doing that. I want to mess with wire whilst that is happening to see if i can get it to come on.
     
  25. Qavion

    Qavion F1 World Champ
    Silver Subscribed

    Feb 20, 2015
    11,555
    Sydney
    Full Name:
    Ian Riddell
    #25 Qavion, Jan 22, 2022
    Interesting. The wiring diagrams (even the later 2.7 diagrams) don't show a circuit which would put on the light during startup. There must be some kind of test module associated with the fuel system on some cars.
     
Page 1 of 2

Share This Page