K-Jet Control Pressure Too High

Discussion in 'K-Jetronic OEM injection' started by Pete, Jul 29, 2017.

  1. Pete Forum Member

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    So I have finally got my Mk2 Golf Gti 16v on the road that's running on standard KJet on the original KR engine. It always starts fine cold or hot, but runs a little lumpy during warm up. When up to temp it drives ok, but is a bit sluggish on acceleration and generally feels quite flat.

    Anyhow, I decided to get hold of a KJet Fuel Pressure Test kit and check the fuel pressures, here's the results:

    System Pressure:
    SystemPressure.JPG

    Control Pressure:
    ControlPressure.JPG

    I know that the general rule is to have System pressure at 5bar, and control pressure around 3.4bar (48psi) but as you can see these are both a little high in my tests.

    Would the system pressure being 0.2bar too high cause the control pressure to be so high at 57psi? Has anyone had similar to this before?
     
    Last edited: Aug 1, 2017
  2. notenoughtime

    notenoughtime Moderator Moderator

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    Take the wur off and check to see if it's been drilled on the back
     
  3. notenoughtime

    notenoughtime Moderator Moderator

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    Mine feels flat Eddie said cam timing maybe out so could be worth a check
     
  4. Pete Forum Member

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    I took the WUR off earlier to check and theres no sign of it being drilled. That was my next thought, whether to drill it and adjust the control pressure down but wanted to rule other stuff out first.

    I will check the cam timing to make sure its not out.
     
  5. notenoughtime

    notenoughtime Moderator Moderator

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    Iirc to high pressure results in lean mixture
     
    Last edited: Jul 29, 2017
  6. Pete Forum Member

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    Ok, thanks for the info. That makes sense as high pressure would be more restrictive on the metering head pin and not allowing enough fuel through would it.

    Should I strip the WUR down to check for blockages? I did take the supply line off and the gauze filter didnt look too bad, but I did clean it as best as I could.
     
  7. notenoughtime

    notenoughtime Moderator Moderator

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    Why not drill the brass plug on the back and adjust fuel pressure
     
  8. Pete Forum Member

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    Ok, I will try adjusting the pressure first as you have suggested. Cheers ;)
     
  9. rubjonny

    rubjonny Administrator Staff Member Admin

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    also worth noting the 48psi figure is for a 'wur tuned' unit, the factory figure is just over 50 psi. but still 57 does sound quite a lot higher than it should be. but then it depends what altitude you are at, this would be perfect at around 800meters above sea level :lol:
     
  10. Pete Forum Member

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    Lol! I think we are about 60m above sea level here in Sunny Nottingham :-)

    Ahh.. Ok, so the factory setting is more around 50psi then. Good to know, cheers!
     
  11. Pete Forum Member

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    Something stuck in my mind what Notenoughtime said in an earlier post about cam timing being out could cause flat performance.

    I had changed the timing belt and tensioner a few months back so thought i'd better double check, but it seems ok:-

    Cam_Timing.JPG

    GearBoxTiming.jpg
     
    Last edited: Aug 1, 2017
  12. rubjonny

    rubjonny Administrator Staff Member Admin

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    so yeah I would start with the simple checks, timing, air flap level etc as found in my 16v troubleshooting guide:
    http://www.clubgti.com/showthread.php?195423

    then adjust the shims to sort the system pressure, see if the control pressure comes back closer to where it should be. also check the residual pressure stays over 38psi for at least 10 minures, after shuttign the engine off after its fully warmed up.
     
  13. Pete Forum Member

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    Quick update. I have adjusted my WUR Control Pressure down to around 50psi (System Pressure is still set as before, just over 5bar, with 1 shim installed which looks like the original one).

    I have then set up the CO as close as I can get it as per rubjonny's excellent setup guide and it seems to be running better. I will get it down to an MOT test station when I get chance to check that the CO is at 2% to make sure its spot on.

    Thanks for all the help on this one guys :thumbup:
     
  14. KeithMac Forum Junkie

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    Might be worth investing in a wideband AFR gauge if you do a lot of tinkering..
     

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