Electrical Problems - anything I can easily check?

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PaulHere
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PaulHere PCGB Member
2018/01/31 01:40:04 (permalink)

Electrical Problems - anything I can easily check?

Hello all
I have a non responsive fuel pump relay, I know I'm asking a simplistic questions but what can I do to unsure that I'm not overlooking anything related to it's operation? For example I'm looking at earthing points around the car to increase the electrical efficiency.
Many thanks.

Paul Hedges
924 2.0 1983MY - 218,850m
Porsche 924 Register Secretary
My Mobile number 07940 441452 (6pm till 10pm)
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    vitesse
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    vitesse PCGB Member
    Re: Electrical Problems - anything I can easily check? 2018/01/31 09:39:04 (permalink)
    Paul,
    Have you read the various posts I have made about relays ( plus many other contributions from other 924 owners)-all the tips are included re bridging the relay contacts etc.
     
    As you have previously posted about your fuel pump ,have you tried running
    a separate supply to it to prove it is OK?

    1986 924S Stone Grey.
    1987 924S Guards Red
    2004 BMW 530D SE Touring Chiaretto Red
    1966 MGB GT B Racing Green.
    scm924s
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    Re: Electrical Problems - anything I can easily check? 2018/01/31 14:28:48 (permalink)
    In addition to bridging the FPR contacts as a check, also check the fuel pump fuse.

    1984 924 n/a Ruby Red Metallic
    1986 924S Guards Red
    1988 924S Guards Red - sold.
    1984 924 n/a Black - sold.
    1980 924 n/a Le Mans.x2-sold
    1977 924 n/a Martini - sold.
    PaulHere
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    Re: Electrical Problems - anything I can easily check? 2018/02/06 16:12:17 (permalink)
    Fuel pump fuse is intact, and indeed the fuel pump does run when operated with a fuel pump bypass switch, it was fitted about 15 years ago to aid with a hot start issue. But there is no action when the ingition key is turned.
     
    I will sit down and have a good read about 924 wiring and see if there is anything I am missing.

    Paul Hedges
    924 2.0 1983MY - 218,850m
    Porsche 924 Register Secretary
    My Mobile number 07940 441452 (6pm till 10pm)
    924@porscheclubgb.com
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    adriandavidson
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    Re: Electrical Problems - anything I can easily check? 2018/02/06 19:20:32 (permalink)
    With the ignition on, when you push open the flap in the fuel distributor with you finger the pump should run. You will hear the injectors. You can also hear the switch on the fuel distributor click.
    vitesse
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    vitesse PCGB Member
    Re: Electrical Problems - anything I can easily check? 2018/02/06 23:47:49 (permalink)
    Paul
    You might want to check the actual switch behind the ignition lock-they are known to fail unannounced.
    One connection can suddenly fail possibly the ignition circuit  in your case.
    I remember that happened on our original 924 Lux

    1986 924S Stone Grey.
    1987 924S Guards Red
    2004 BMW 530D SE Touring Chiaretto Red
    1966 MGB GT B Racing Green.
    russmw
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    Re: Electrical Problems - anything I can easily check? 2018/02/07 09:16:08 (permalink)
    Are you getting a spark? The fuel pump wont run without a spark which was designed as a safety feature in case of a crash. When you bypass the relay does the car run fine?
     
    good luck!
    scm924s
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    Re: Electrical Problems - anything I can easily check? 2018/02/07 18:43:04 (permalink)
    adriandavidson
    With the ignition on, when you push open the flap in the fuel distributor with you finger the pump should run. You will hear the injectors. You can also hear the switch on the fuel distributor click.


    russmw
    Are you getting a spark? The fuel pump wont run without a spark which was designed as a safety feature in case of a crash. When you bypass the relay does the car run fine?
     
    good luck!



    Couple of bits of misinformation there!
     
    Quote 1 only applies to early (77/8 cars)
     
    Quote 2 is not correct, the fpr relies on a pulse from the coil to the electronic ECU, if it doesn't get one after about 1 sec, the fpr stops the live feed assuming car has stopped. Unfortunately that doesn't always guarantee that the rest of the ignition circuit is functioning correctly, providing a spark.

    1984 924 n/a Ruby Red Metallic
    1986 924S Guards Red
    1988 924S Guards Red - sold.
    1984 924 n/a Black - sold.
    1980 924 n/a Le Mans.x2-sold
    1977 924 n/a Martini - sold.
    PaulHere
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    Re: Electrical Problems - anything I can easily check? 2018/02/08 20:41:42 (permalink)
    Thank you everyone, lots to check
     
    Some great points about the coil and switch behind the ignition key!

    Paul Hedges
    924 2.0 1983MY - 218,850m
    Porsche 924 Register Secretary
    My Mobile number 07940 441452 (6pm till 10pm)
    924@porscheclubgb.com
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    scm924s
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    Re: Electrical Problems - anything I can easily check? 2018/02/08 21:52:51 (permalink)
    The ignition switch is easy to check, obtain a new one and remove the multiplug at the back of the switch and plug in the new one using a screwdriver to operate.

    1984 924 n/a Ruby Red Metallic
    1986 924S Guards Red
    1988 924S Guards Red - sold.
    1984 924 n/a Black - sold.
    1980 924 n/a Le Mans.x2-sold
    1977 924 n/a Martini - sold.
    vitesse
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    vitesse PCGB Member
    Re: Electrical Problems - anything I can easily check? 2018/02/08 22:27:31 (permalink)
    Paul,just to expand on Stan's post,the switch is I believe a standard VAG part used on Golfs,Audis before smart keys came along.It is a white round plastic item the size of a large pillbox having the terminals for the loom multiplug at the rear & slotted operating shaft  centrally placed at the front which is why Stan suggests you can fit a replacement to the multiplug & operate it initially using a screwdriver in the slot.
    Your keys stay the same  as they just operate the steering lock & in turn this switch behind.

    1986 924S Stone Grey.
    1987 924S Guards Red
    2004 BMW 530D SE Touring Chiaretto Red
    1966 MGB GT B Racing Green.
    scm924s
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    Re: Electrical Problems - anything I can easily check? 2018/02/09 08:31:58 (permalink)
    They can be found cheaper if you ferret about, they have a habit of cracking internally under contacts arcing.
     
     
    https://www.ebay.co.uk/it...Po5ahJydHSBw1fGpcCPYsw

    1984 924 n/a Ruby Red Metallic
    1986 924S Guards Red
    1988 924S Guards Red - sold.
    1984 924 n/a Black - sold.
    1980 924 n/a Le Mans.x2-sold
    1977 924 n/a Martini - sold.
    PaulHere
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    Re: Electrical Problems - anything I can easily check? 2018/02/25 14:03:42 (permalink)
    Quick update: It turned out that the source of the problem may have been as simple as a bad earth, in this case the one between the rear lights inside the car. I had actually looked at this earth myself and didn't think it looked to bad - which is a sign of how wrong you can be.
     
    I'm no electricial expert but I was told there was 3 to 4 Ohms of resistance at the pump. and only 9 volts reaching it. The car is using the older fuel pump relay, and I suspect the original fuel pump would still be working if I had this looked at earlier.
     
    Well the car is/was running now but just this morning another old problem has re-occured..
    See post "Snapped belt..."

    Paul Hedges
    924 2.0 1983MY - 218,850m
    Porsche 924 Register Secretary
    My Mobile number 07940 441452 (6pm till 10pm)
    924@porscheclubgb.com
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