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How to Test Your ABS Pump

Discussion in 'Common Faults and Questions' started by TAKdriver, Jul 15, 2010.

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  1. TAKdriver

    TAKdriver Active Member

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    There is a test to determine whether or not your ABS pump is working before you spend serious money on replacement. The fault might well be in the pressure switch alone.
    Take a length of wire and earth it to the bolt holding down the battery clamp : bare the other end : remove the rubber sleeve from the connector to the pressure pump : jam the other end of the earth wire into the BLACK AND YELLOW wire in the pressure switch connector while it's in place : switch on ignition. If your pump fires up the problem is almost DEFINITELY in the pressure switch.
    There are five wires going into the connector : BY goes back to the relay : BG goes back to the fusebox and is the + for the relay inside the pressure switch : BW goes back to the ECU and doesn't appear to go through the fusebox. The other two are blacks and they go to a common earth.
    When I got the pump running by earthing BY it made me think ( not unreasonably) that the problem was a bad earth somewhere in the system. That resulted in futile weeks of tracking down and checking every earth.
    I wrongly thought that earthing BY triggered the abs relay (17) . BY in fact goes through the fusebox and is in fact power going to the pressure switch which is earthed by one of the relays inside the pressure switch being closed by the pressure from the pump.
    IF YOU EARTH THE BLAck/YELLOW WIRE AND YOUR PUMP RUNS THE PROBLEM IS DEFINITELY IN THE PRESSURE SWITH OR THE CONNECTOR. The connector wires are easily checked.
    I suspect that an awful lot of perfectly functional ABS pumps have been replaced due to a faulty pressure switch. I have now had two out of three pressure switches faulty ( viz my original which went : the replacement which I assumed was OK and thirdly the scrapper which I put in as a last resort.)
    You can also replace the pressure switch in situ by using a jubilee clip round it , tapping, slackening, tightening, tapping. Very little brake fluid comes out because the chamber that the pressure switch is going into is sealed by a diaghram which activates the plunger on the top of the pressure switch.
    There's a million more things I could tell you that I got wrong before arriving here ! DON'T SCRAP YOUR ABS PUMP UNTIL YOU HAVE EARTHED B/Y TO FIND OUT IF THE ACTUAL PUMP PART FUNCTIONS
    Pic 1 shows the abs pump complete
    ABS Pump complete.jpg
    pic 2 shows the pump with pressure sweitch removed and sitting on top
    pressure switch removed.jpg
    pic 3 shows the rear of the connector where earth wire can be inserted.
    abs connector.jpg
     
    Last edited: Jul 15, 2010
    kapilamuni likes this.
  2. TAKdriver

    TAKdriver Active Member

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    All noted and will deal with same : it's like everything else I do : takes me half a dozen tries before I get it right. I'll stick with it and try to improve it with pics. Can I edit in pics ?
     
  3. TAKdriver

    TAKdriver Active Member

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    Text edited as suggested.
    Pics is another matter ! Heading for the camera.
    watch this space.
     
  4. plastic soul

    plastic soul Active Member

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    Is the pump quite audible?
     
  5. wammers

    wammers No longer with us, RIP Donater

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    Yeah and you can hear it as well. :D:D
     
    RangeRoller dt likes this.
  6. plastic soul

    plastic soul Active Member

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    mine looks different to that, mines a 96 disco
     
  7. plastic soul

    plastic soul Active Member

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    i have plenty of power going the the motor, I guess there is a switch inside the modulator?
     
  8. mrrover

    mrrover New Member

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    Do someone know where i can get a new pressure switch? the cable i earth was white and to the right upper side. and the pump run fine.
    But i have a thing i wonder about the reley to abs it is 2 i guess to the left seat. they where the same kind but when i switch them and earth the cable once more the pump didn't start when i switch to the other one it starts fine so i thinking can it be just the relay or did i do something wrong.. but the relay has 86 87 85 30 in numbers two side by side.
     
  9. plastic soul

    plastic soul Active Member

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    abs relay in side of footwell passenger, take the plastic side panel off on th eleft, one of the green ones
     
  10. flyingbanana

    flyingbanana Member

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    I know its an old post but just joined site great information.
    I seem to have a fault with abs.tc braking my mates diagnostic kit says its
    faulty pressure switch which we believe is this switch if I can get it of
    is it sealed and cant be repaired or can you service it.
    if not can you get them and where
    thanks andy
     
  11. ThatchP38

    ThatchP38 Member

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    I know this is 11 years old now but wondering if grounding the BY wire energizes the abs relay on the fuse box and therefore turns on the pump?
     
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