K-Jet holding pressure high

Discussion in 'K-Jetronic OEM injection' started by Dans2382, Jan 22, 2021.

  1. Dans2382 New Member

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    Hi all.

    After 12 years sitting in the garage I decided to put my mk1 Golf Convertible GTi 1.8 Rivage back on the road. Small overhaul of brakes and rubber and MOT is passed.

    It always had a minor issue of rough cold idle and hot start problem which never bothered me too much but I’ve decided to get it running sweet. System and control pressures were high at 5.8 & 4.4 bar respectively. No apparent blockages so I removed the shim from the regulator, pressures now bang on at 5.2 & 3.4bar (cold pressure 0.8bar). AAV and cold injector fine. A tweak of the CO and idle screws and idle is good.

    Trouble is when I switch off the holding pressure rises to 4bar. It will hold there for a good half hour or so. Has anyone seen this before or know what might cause this and if it will affect hot starting?!

    Many thanks in advance.
     
  2. Rustbuster Forum Member

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    Not sure that there is an upper limit for residual pressure after switching off the engine. Figure I have in mind is that pressure must remain above 2.6 bar for at least 10 mins. Don’t see why 4 bar would be a problem. If anything it should reduce any hot start problems by reducing the possibility of vapour lock and shows your check valve/accumulator are fighting fit.
     
  3. Dans2382 New Member

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    My only thought was maybe this high pressure was enough to make the injectors let a bit through!?
     
  4. Rustbuster Forum Member

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    It may do, just for a fraction of a second but that would be into a hot cylinder so fuel will instantly vaporise. Don’t forget too that the instant you’re switching off the air flow plate will drop to a sub idle position so the plunger will then isolate the injector circuit so the pressure your measuring between the metering head and WUR won’t be the same as that at the injectors. That’s my understanding but I could be wrong. When it’s hot does it start ok?
     
  5. Dans2382 New Member

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    Yeah starts fine up until about 15mins after. Interestingly though today it held 4bar, I looked after half hour and it was 0. I had seen it hold above 2 overnight. Might be something intermittent.
     

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