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911SC - Cold Start Valve; Company that Cleans or Supplies in Berkshire Area?

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NeilH
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NeilH PCGB Member
2019/09/28 12:12:37 (permalink)

911SC - Cold Start Valve; Company that Cleans or Supplies in Berkshire Area?

Hi All
 
I'm struggling to find a company in Berkshire (Reading) area to initially test and clean Cold Start Valve = Bosch 0 280 170 409.
I can't test in my car as it uses steel rigid fuel line!
 
I've got the valve out on my bench and with a crude test (adapting length of rubber fuel hose, filling with white spirit, connecting and pressurising to only about 20PSI with a plant sprayer!) I get a jet\flame of fuel and not an atomised mist. Not sure if my test is valid though - hence needing someone to initially test it correctly before moving on by testing Control Pressure etc.
 
CONCLUSION\REASONING
Car performs and drives beautifully at ALL other times - during warm-up, it fast idles for 2-3mins perfectly and even extreme (for UK) hot starting is all 100%.
 
It is only ever cold cranking that's the issue - no hint of firing until about 7-8 cranks - if left idle more than a day or two.
Lifting the metering\airflow disc for 7seconds instead (light as a feather initially, then immediately pushed back by control pressure the moment the fuel pump fires - so good and strong pump?) it then fires immediately and beautifully!
 
Hence suspecting Cold Start Valve.
 
Thermo time switch all checks 100% as well as wire continuity and 12VDC to thermo switch on cranking.
 
I'm trying to eliminate if the spray pattern is the issue - assume the jet may just hit the back of the air box and sits in a pool rather drawn in to cylinders? 
 
 
Best regards,
Neil    
 
 

4 Replies Related Threads

    hotfrog1
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    hotfrog1 PCGB Member
    Re: 911SC - Cold Start Valve; Company that Cleans or Supplies in Berkshire Area? 2019/09/28 14:46:11 (permalink)
    Sorry but I am not an expert on these systems but I have solved some problems myself using a Bosch book that I downloaded.  It does not specifically mention CSV spray pattern but it gives detail about the thermotime switch and how to check its functionality.    The book is an easy read and with some improvisations it is possible to do realistic testing with simple equipment.   I found this book a while ago when it seemed to be opensource.   You can try yourself, the book is titled : "Workshop Manual Porsche K-Jetronic" published by Robert Bosch.   You can get it at this download FOC: http://www.type17.ch/downloads/Injection/Bosch%20-%20K-Jet%20-%20Workshop%20Manual.pdf.  For me the book is gold dust.
    NeilH
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    NeilH PCGB Member
    Re: 911SC - Cold Start Valve; Company that Cleans or Supplies in Berkshire Area? 2019/09/30 08:15:01 (permalink)
    Hi hotfrog 
     
     
    Yes, already have this Bosch K jetronic pdf. It is superb and I've used to help me diagnose the issue to the cold valve - so far.
     
    Used in collaboration with a couple of other good docs and a bosch workshop manual I had for my old golf gti.
     
     
    Best regards
    Neil
     
    hotfrog1
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    hotfrog1 PCGB Member
    Re: 911SC - Cold Start Valve; Company that Cleans or Supplies in Berkshire Area? 2019/09/30 08:50:00 (permalink)
    About 10 years ago I took the injectors in for testing at a Bosch fuel injection specialist.  After some tooth sucking he dug out a machine from his back room and tested them.   I guess you just need to find a Bosch dealer who still has this sort of kit.   I have KMI for a recon fuel distributor, cold start valve and warm up regulator.  He was reliable and his work has stood the test of time:  http://www.kmipetrolinjection.co.uk/
    NeilH
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    NeilH PCGB Member
    Re: 911SC - Cold Start Valve; Company that Cleans or Supplies in Berkshire Area? 2019/10/04 19:53:25 (permalink)
    hotfrog1
    About 10 years ago I took the injectors in for testing at a Bosch fuel injection specialist.  After some tooth sucking he dug out a machine from his back room and tested them.   I guess you just need to find a Bosch dealer who still has this sort of kit.   I have KMI for a recon fuel distributor, cold start valve and warm up regulator.  He was reliable and his work has stood the test of time:  http://www.kmipetrolinjection.co.uk/


    Hi hotfrog



    Yes, I've been getting the same responses from any fuel injection companies I can find, even classic 911 ones. None of them have the kit anymore to clean or test them, preferring just buying new. This doesn't seem to be an option for the cold start injector though. Can only see one or two second-hand on ebay from the US.
     
    One company advised to put mine back in the car as it's not likely to be the problem and to check the control pressure - which I'm attempting to do. But with cold, warm-up and hot running all being 100% solid - and only the cranking\firing from cold being the issue - I'm not sure. 
    Would be good to have a good to injector just to eliminate it.
     
     
    Best regards,
    Neil 
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