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Impact Bumpers


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About carrpet

  • Rank
    IB Enthusiast

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  • Interests
    Porsche engineering, Salmon Fishing, Golf

Previous Fields

  • Current 911
    1989 930 G50 66 K27 7200, Fabspeed Long Neck Intercooler owner since 1997
  • Daily Driver
    BMW X5
  • Most-played albums in your iPod/CD Changer
    Tarkus - Emerson Lake & Palmer
  • Day Job?
  • Drink?
    Bordeaux, St. Julien, Talbot

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  1. Hi David, Thanks for your response First of all I continued to have an intermittent cold start problem. While my warm pressure was right on specification my cold pressure was always right at the high end limit. I figured from all of the discussion on a range of forums on WUR related cold start problems, that I really ought to be at the mid to bottom end of the Cold Pressure specification if I was experiencing Cold Start problems. I also noticed that every time I cold started the car after breaking into the fuel lines, the car started first time, perfectly. This reinforced my view that I needed to be at the bottom end of the range. So to lower the CP I pushed in the plug but clearly too far. I hadn't realised how sensitive that CP plug position is and I dropped out the end of the working range. I have now made the CP plug adjustable and have extracted it to its original position, then adjusted the plug position to give a CP of 11psi at 7 degrees centigrade with both pumps running, the WUR heater plug disconnected and the airflow switch plug off. Started first time and ran perfectly as I might have expected, the real test is tomorrow morning. Warm pressure solid at 53psi. What freaked me out was that with the plug pushed in by 1mm I was getting no increase in pressure at all due to the bimetallic strip bending and therefore no warm pressure ! All is great now but I did have a minor panic. I got down to it this morning put the CP plug back in its original position then set the cold pressure in-situ by adjusting the plug position. Panic over ! The fuel line mods were to tidy up the connection of my AEM pressure sensor which had previously long unnecessary pipe runs with lots of fittings. That is now fixed with proper hydraulic swivel fittings. Cheers Peter
  2. Hi there I have created a problem of my own making ! I started the day with a hard cold starting / high cold pressure problem which was clearly WUR related. I was getting 20psi at 7.5C. Engine ran fine apart from hard starting with a warm pressure of 53psi. Pulled out the WUR, knocked in the small plug about 1mm. Connected the WUR up again, made some mods to the simplify the fuel pipework where I have a tee piece to accommodate by AEM pressure sensor, and now all I get is about 6-7 psi which is static with the fuel pumps running ie. no apparent pressure increase as the bimetallic strip heater kicks in, but when I turn them off the pressure gauge jumps to about 20-25psi depending upon how long I ran the pumps for. I checked that there are 12 volts for the heater element and the resistance of the heater element is 25 ohms. I can't believe this is down to a 1mm depression of the cold pressure plug ? I haven't yet checked the system pressure. Any ideas as to what may be going on or what I may have unwittingly done and how to get out of the mess ? Peter
  3. Hi David, Mine definitely has the Yellow Relay. You can however replace the yellow relay with a red relay. The yellow relay is alleged to have an extra property which ensures that the fuel pumps don't cut out due to air flow switch "bounce". An excerpt from Rennlist https://rennlist.com/forums/911-turbo-930-forum/315180-what-s-so-special-about-the-magic-yellow-relay-2.html "The answer to "why Porsche put the magic Yellow relay in the fuel pump circuit instead of a regular red relay". For starters the red relay and the yellow relay pin connections are the same so a red relay will work. As you know, in the yellow relay there is a circuit board with diodes and transistors on it. I enlisted the help of a great friend who is an EE to tell me what the circuit board does. Between my understanding of the fuel pump circuit and his understanding of the circuit board I think I have the answer. As many of you know when you have the key in the on position and the engine off, if you push the sensor plate down or disconnect the plug at the plate the pumps will run. This switch on the plate is a very unstable "switch" in the world of electronics being it is mechanical and is prone to transient movements given its enviroment. So, there is potential for the plate to make contact or bounce against the contact and very momentarily cut the fuel pump off if the plate is swung violently up. (high revs,high engine load, quick shift type of scenario). Within the circuitry of the yellow relay there is a de-bounce function on pin 85 which is the ground potential coming from the plate switch to the tune of about 282milisec. What that means is if the plate for some reason is swung up and makes contact with the switch and completes the ground path to pin 85 of the yellow relay while the engine is running there is a delay of aprox 282milisec. (which is about two blinks of the eye) before it completes the circuit and cuts the fuel pump off. This potential for cutting the pump off in a turbo motor even for a short amount of time or if done repeatedly could theoretically be very damaging to the engine as we all know. So, the red relay will work but you run the risk of cutting the fuel pump off momentarily if you use one. Perhaps its a little overkill on Porsches end but very well thought out I think... " As far as the noise is concerned, it did not happen this morning and it started first time, but I am convinced it is the accumulator diaphragm compressing the coil spring which is making the noise. The spring provides stored energy for a period of time, maintaining fuel pressure after the fuel pumps are switched off to ensure that the car warm starts. I haven't seen anything which convinces me that the accumulator has a cold starting benefit. Regards Peter
  4. Hi David The noise is definitely not fuel pump cavitation having stood in my pit under the car while Ian Comerford fired up the fuel pumps. The noise definitely appears to be coming from the Fuel Accumulator - will confirm tomorrow ! On another note I have read that the yellow relay on the LHS of the engine compartment should fire up the fuel pumps (priming ?) for about 1 second when the ignition switch is in the run position and the air flow switch is connected "in-circuit" as normal ? Is this a phenomenon that you are familiar with and does your car do this ? Peter
  5. Thanks David It may just be pump cavitation which is a sound I am familiar with. I will get close to the pumps while I get someone to operate the ignition switch. I would not hear the noise if the engine was cranking over. My AEM Fuel pressure gauge reads 0 after about 6 hours. Perhaps it's nothing to worry about. Peter
  6. When I start the fuel pumps from cold with the air flow switch disconnected, coincident with the start of the fuel pumps there is a noise which lasts for about 2 seconds from the engine bay. After that just the noise of the fuel pumps running. I was wondering if anyone else has experienced this. It only happens first time I start the car during the day with 0 psi fuel pressure It sounds like the noise of a dry moving part. My initial thought was a fuel pump but wondered about the sound of the fuel accumulator diaphragm being pushed back against its spring as the pressure builds? The fuel accumulator is < 500 miles old. The temperature in the garage is 6C and the cold pressure is 12psi. All of my fuel pressures are in specification - cold, warm and system plus the fuel system retains its pressure for much longer than the minimum specification. Would welcome any input on what it might be. Peter
  7. Thanks - are SWF an OEM ?
  8. carrpet

    AFR target ranges

    I have found the conversion table for AFR to CO%
  9. What would you recommend ?
  10. Should the SWF blades be 100% in contact with the screen over full travel, because my existing Bosch blades are not ? Peter
  11. carrpet

    AFR target ranges

    David, I will take a look at your thread. Are you able to convert my AFR of 14.3 to an 0.5% CO level. Is this where you got the 0.5% from ? My 66 engine specification is 1.5 to 2.5% CO. Peter
  12. Which is the wiper blade of choice for our very curved windscreens ?
  13. carrpet

    AFR target ranges

    David, That is very helpful thanks ! Have you set up your idle around an AFR target, a CO target or increasing the mixture until you get hunting then backing off a tad, until it stops or a combination of these ? Peter
  14. carrpet

    AFR target ranges

    And to get 14.7 across all conditions with a high tech WUR is a big ask !
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