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Thread: Petrol Gauge Not Working - Wiring? Gauge? Sender?

  1. #1
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    Petrol Gauge Not Working - Wiring? Gauge? Sender?

    Hi all. Today I filled up the petrol tank with about £25 worth of super unleaded, not just to have a load in there in order to start and run the engine every now and then but mainly to see if the needle will move on the gauge. Unfortunately it didn't even flinch.

    The gauge is brand new, albeit 10 years old unused.
    The wiring hasn't been touched since it worked last time.
    The sender is the original one. I've never touched it.

    My bet would be that the sender isn't working. I don't know anything about petrol tank senders having never replaced one. Can they easily go wrong after being laid up for 15 years? Can they get stuck? Can they be repaired or is it better to get a new one? etc...

    Could someone please help me with a series of instructions, in process of elimination order, for me to work out what the problem is? For example, first how to test the wiring. If it comes down to being the sender, how I best remove it. I'm pretty sure that it won't come out very easily as the rear bulkhead overhang is in the way but if it can be taken out at an angle then maybe it's possible. Here's a photo. Thanks for any help about this.




    The fiberglass you can see above the tank overhangs the sender almost exactly.

  2. #2

    Re: Petrol Gauge Not Working - Wiring? Gauge? Sender?

    The sender is just a vairable resistor with sender and earth connectors. The gauge just related that resistance to movment via a coil, it should have (apart from light option) earth, ignition 12v, sender.
    Check for 12v (with ignition on) at gauge + terminal, If dead check fuses/wiring.
    If OK then disconect the sender wire from gauge and flick an earth wire across the sender terminal on back of gauge, the needle should flick across, if not gauge is duff/stuck.
    If gauge is OK then disconnect sender unit wires and check for reading on a meter across unit terminals, no? Then no good, remove and check.
    If thats OK check wiring.



    The opinions expressed in my posts may not be made in a sound mind and should be taken in the spirit intended, Jack Daniels is fine.
    Some people see things as they are and ask why? I dream things that never were and ask, why not?” JFK

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  3. #3

    Re: Petrol Gauge Not Working - Wiring? Gauge? Sender?

    £25 worth probably isn't enough fuel to register on the gauge!

    It looks like you've got an earth connection to your sender - it's worth checking whether your nice fresh paint is insulating it though, as that's a really common head-scratching fault on rebuilds!
    It's a 50 year old car and everything works, just not always at the same time.......and it's probably about to get jealous!
    *Donate to Euro-Nova today!*

  4. #4

    Re: Petrol Gauge Not Working - Wiring? Gauge? Sender?

    £25 not enough that's over 22 litres, oh, I forgot, UK prices.



    The opinions expressed in my posts may not be made in a sound mind and should be taken in the spirit intended, Jack Daniels is fine.
    Some people see things as they are and ask why? I dream things that never were and ask, why not?” JFK

    http://ukhozi.page.tl

  5. #5
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    Re: Petrol Gauge Not Working - Wiring? Gauge? Sender?

    Thanks Peter. I'll try your suggestions. I'm pretty sure that £25 worth of fuel is enough for the float to register. That's 15 litres.

  6. #6

    Re: Petrol Gauge Not Working - Wiring? Gauge? Sender?

    Quote Originally Posted by NovaF4
    Thanks Peter. I'll try your suggestions. I'm pretty sure that £25 worth of fuel is enough for the float to register. That's 15 litres.
    That's 2.1€ a litre, SH*T! we pay 1.38€ (£1.1) and even less in Gibralter, I think 98p. I know the Yanks will chip in with 20c a gallon but with their consumption they need cheap gas.



    The opinions expressed in my posts may not be made in a sound mind and should be taken in the spirit intended, Jack Daniels is fine.
    Some people see things as they are and ask why? I dream things that never were and ask, why not?” JFK

    http://ukhozi.page.tl

  7. #7
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    Re: Petrol Gauge Not Working - Wiring? Gauge? Sender?

    Tell me about it. Daylight robbery. That's Super Unleaded.

  8. #8
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    Re: Petrol Gauge Not Working - Wiring? Gauge? Sender?

    If gauge is OK then disconnect sender unit wires and check for reading on a meter across unit terminals, no? Then no good, remove and check.
    Thanks Peter, I've just got round to checking this. The gauge is working fine. I've put the multimeter across the sender but don't get any reading. I'd like to know that I'm doing it right though. My multimeter has 5 different ohms to select from. I'm using 200. I put the red probe onto the sender terminal where the feed to the guage would go and the black probe onto the ring terminal that is still screwed to the sender. No reading. Am I doing it right?

    Cheers for anyone's help
    Giles

  9. #9

    Re: Petrol Gauge Not Working - Wiring? Gauge? Sender?

    Can't quite picture that, but you need to be testing between the gauge sender terminal and earth......
    It's a 50 year old car and everything works, just not always at the same time.......and it's probably about to get jealous!
    *Donate to Euro-Nova today!*

  10. #10
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    Re: Petrol Gauge Not Working - Wiring? Gauge? Sender?

    I'll explain with a closer photo as I'm still not 100% clear as to how to test the sender.

    Here is the sender top close up. The terminal in the center is where the cable to the gauge goes (I've pulled it off). There's another cable clamped down underneath the screw, as shown.

    Now, what do I do again please?


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