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Fuel pump replaced on 2.5tdi now wont pull diesel up

Discussion in 'A4/S4 forum(B5 Chassis)' started by cobrascim, Jan 21, 2010.

  1. cobrascim
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    cobrascim Member

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    [Jan 21, 2010]
    I replaced the in tank fuel pump on my 1998 A4 2.5TDi avant quattro as it wasn't feeding fuel up to the filter. Now when false feeding the pump on the plug at the tank end I cant get the new pump to even throw some diesel out. Starting to think the old pump was OK as I could hear it running but no fuel was being sent up the pipe.
    Anyone know why it wont feed fuel? I have correct polarity on pump socket and plenty of diesel in the tank.
    John.
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  3. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Jan 21, 2010]
    There was a thread before that claimed the fuel pump in the tank on a 2.5tdi is only there to move fuel from the various "cavities" in the tank into the main area.

    Apparently, the main fuel pickup occurs by the VP44 on the engine actually sucking the fuel up itself.

    Since you've seen the pipe work, are you sure the in tank pump actually connects to the fuel lines?
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  4. diffas
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    diffas Member

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    [Jan 22, 2010]
    Aragorn is right. VP44 has internal lift pump which sucks from the tank. If the fuel lines are empty you need suck it manually through the filter until it is full of diesel.
    Replace your fuel filter in case it leaks air.
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  5. cobrascim
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    cobrascim Member

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    [Jan 22, 2010]
    Thanks guys,
    My worry here is you may be right. The fuel pump hose goes into the return piping connectors within the tank.
    I will try a suction pump to prime the system and as you say put a new filter on and hopefully that might work. My fear here is that when the feed hose was dry I automatically thought the fuel pump in the tank wasn't providing the low pressure side of the diesel.
    My original fault code was 01318 which tells me the "control module for injection pump". Back to the drawing board then.
    John.
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  6. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Jan 22, 2010]
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  7. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Jan 22, 2010]
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  8. cobrascim
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    cobrascim Member

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    [Jan 22, 2010]
    Thanks. Have just sent them an email.
    Not looking good is it? Ouch. Think the pumps are over £1,000.
    Going to do some more digging. I will let you know if I get it going or scrap the whole bl00dy thing.
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  9. diffas
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    diffas Member

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    [Jan 22, 2010]
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  10. adamss24
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    adamss24 Well-Known Member

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    [Jan 23, 2010]
    I would get in touch with dieselbob and send the pump to him to refurbish. He will fit new cam plate, rebuild the rotor head, new bearings and will fit a Brand New control unit toghether with new stop solenoid and advance solenoids for £600 + VAT... You cannot get any better than that really ! All this and a full year warranty does it for me as i really dont trust no one to tinker with a delicate "die cast" state of the art electronics...no matter how good they are ! Also, 380 euros isnt cheap at all for a half job...
    #9
  11. diffas
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    diffas Member

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    [Jan 23, 2010]
    Riight. :D
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  12. jonnycraig
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    jonnycraig Member

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    [Jan 28, 2010]
    Similar thing on mine, turned out to be the nonreturn valve next to the hand primer, 5 mins fixed it, now starts everytime

    J
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  13. Neutech
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    Neutech New Member

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    [Jan 28, 2010]
    Patterson Up in Fife will refurb your Vp44 for better price, theyve just done one for me nd they are bosch agents

    100% top job

    Alrite big J ;-)
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  14. cobrascim
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    cobrascim Member

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    [Jan 30, 2010]
    I found a fix for this on another forum. Turns out most of the failures on this pump are down to failure of a transistor inside the EDC unit attached to the pump. There is an online video that shows you how to remove the EDC with the pump still on the car to send it away for testing and repair if faulty. It can then be re-installed at a lot less cost than buying a full new unit at over £1,000. I shall post up how I get on with my repair.
    John.
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  15. andybnwc
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    andybnwc Member

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    [Jan 30, 2010]
    Just a stupid question but does it have immo on the pumps ?
    #14
  16. adamss24
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    adamss24 Well-Known Member

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    [Jan 31, 2010]
    I cannot stress how delicate these things are, you will most likely damage the the ribon cable from the speed sensor or drop a screw inside wich you wont be able to take it out ! You still wanna get it done cheap ! Spend 600-700 pounds and have it done properly with a new brain/Control Unit. I have oppened a few of these and as much as i would love to say i fixed one, there is no way you can do-it. You cannot fit a second hand one as well as its calibrated to the pump, thats were the labour money goes in to-4 hours on the test bench adjusting the output...
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  17. cobrascim
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    cobrascim Member

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    [Jan 31, 2010]
    Yep. I understand what you are saying but I got it started after the "fix". Then it died after about a minute. The transistor that I replaced was overheating. I think this drives the fuel quantity spooling solenoid on the side which might mean the solenoid is faulty as well. I've messed about with the EDC unit while it is still on the car so I dont have a problem with dropping the T10 torx screws into the pump. I'm committed to trying to get this working as it will now require a new/reconditioned pump as you have said.
    John.
    #16

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