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Thread: Dirk's Avante

  1. #651
    Quote Originally Posted by Dirk View Post
    There is only one pump which takes fuel from both sides like you say a pic is worth a thousand words this is how it works



    Dirk

    Yes BUT..... There is an electrical connection to the Jet Pump pickup on the other side of the tank... Which if I am reading this forum post correctly means the fuel gauge won't read correctly without it..

    "When the car is running, the fuel pump, which is on the right side, pumps fuel from that part, but as long as the fuel is above the "bridge" between the two sides, the level goes down equally. Once the fuel level drops to the bridge, the pump is drawing fuel from the right side only. However, it delivers more fuel to the engine than is needed, and the extra fuel is sent back to the tank. This returning fuel passes through a jet pump (at the fuel pump assembly). The pump is connected to a fuel pickup on the left side (where the sub-sensor is located) and draws fuel from the left side to the right. This should ensure that all the available fuel in the left side is transferred to the right so that it can be pumped to the engine.

    The fuel level sensors are wired in series. When the tank is empty, the total resistance is around 94 Ohms and this causes the fuel gauge to read at E. When the tank is full, the total resistance of the two sensors is very low, less than 10 Ohms, and this causes the gauge to read at F.

    If, when the tank is filled, the gauge does not go to F, it means that the total resistance of the circuit isn't as low as it should be. This could be because one of the floats isn't moving up as far as it should. If it's stuck in one position, such as mid-way, the gauge will not go to E. If the float cannot go above the sticking point but can go down below, then the fuel gauge readings at the lower end will be correct, and it's not likely only 8 gallons could be added when the gauge reads E."

  2. #652
    Quote Originally Posted by islandman View Post
    Yes BUT..... There is an electrical connection to the Jet Pump pickup on the other side of the tank... Which if I am reading this forum post correctly means the fuel gauge won't read correctly without it..

    "When the car is running, the fuel pump, which is on the right side, pumps fuel from that part, but as long as the fuel is above the "bridge" between the two sides, the level goes down equally. Once the fuel level drops to the bridge, the pump is drawing fuel from the right side only. However, it delivers more fuel to the engine than is needed, and the extra fuel is sent back to the tank. This returning fuel passes through a jet pump (at the fuel pump assembly). The pump is connected to a fuel pickup on the left side (where the sub-sensor is located) and draws fuel from the left side to the right. This should ensure that all the available fuel in the left side is transferred to the right so that it can be pumped to the engine.

    The fuel level sensors are wired in series. When the tank is empty, the total resistance is around 94 Ohms and this causes the fuel gauge to read at E. When the tank is full, the total resistance of the two sensors is very low, less than 10 Ohms, and this causes the gauge to read at F.

    If, when the tank is filled, the gauge does not go to F, it means that the total resistance of the circuit isn't as low as it should be. This could be because one of the floats isn't moving up as far as it should. If it's stuck in one position, such as mid-way, the gauge will not go to E. If the float cannot go above the sticking point but can go down below, then the fuel gauge readings at the lower end will be correct, and it's not likely only 8 gallons could be added when the gauge reads E."
    are you sure there are twin senders?

    I understand the twin pumps, but couldn't it just run with a single sensor on one side of the saddle correctly calibrated?

    On my 996 a very similar tank is fitted to drop over the transmission to the front wheels. When fuel gets low you have to fill £30 or more as otherwise it doesn't register as only fills one section!
    All the best,

    Jim

    Club Nova Member, SDBC Member, GRRC Member, Southern Classics



    Read more about latest Nova developments in Complete Kit Car

  3. #653
    Senior Member
    Join Date
    Mar 2009
    Location
    East Riding
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    1,057
    I think the jet pump is a misnomer, there is only one pump and that one pump delivers fuel to the engine and circulates fuel from one side of the tank to the other. There are however 2 senders and the combined resistance of the 2 senders gives you the correct voltage at the fuel gauge see the pics.





    The original question was

    whether to keep both pumps main and slave to avoid unnecessary fault codes being sent to the ECU

    There is only one pump the ECU does not see the pump or monitor it, it just just grounds the fuel pump relay coil.
    The ECU does monitor the 2 senders and will put out a fault code if the fuel tank gets too low, but so long as it is given a voltage higher than the empty threshold you will not get an error code. David is right by only using one the gauge will be wrong and never show empty. If you are using the Subaru dash you could just use the gizmo that Buffy used and problem solved.

    Dirk

  4. #654
    Senior Member
    Join Date
    Mar 2009
    Location
    East Riding
    Posts
    1,057
    Quote Originally Posted by Peter View Post
    I had the pump below the tank outlet and now it is about 150cm above, not much difference.
    Attachment 2952

    That's OK for a carb engine, but an injection pump should not be allowed to run dry even for a few seconds which is why it should be gravity fed (or in the tank)

    Dirk

  5. #655
    Quote Originally Posted by Dirk View Post

    The original question was

    whether to keep both pumps main and slave to avoid unnecessary fault codes being sent to the ECU

    There is only one pump the ECU does not see the pump or monitor it, it just just grounds the fuel pump relay coil.
    The ECU does monitor the 2 senders and will put out a fault code if the fuel tank gets too low, but so long as it is given a voltage higher than the empty threshold you will not get an error code. David is right by only using one the gauge will be wrong and never show empty. If you are using the Subaru dash you could just use the gizmo that Buffy used and problem solved.

    Dirk
    Well I am using the scooby instruments with a single stock VW sender in my tank and it works fine - low fuel light as it drops to reserve etc, and no fault codes
    All the best,

    Jim

    Club Nova Member, SDBC Member, GRRC Member, Southern Classics



    Read more about latest Nova developments in Complete Kit Car

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