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mca mca is offline
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Quote:
Originally Posted by holtjv View Post
mca--you mind sharing the item #/model for the gauge and jumper? I'm having the same problem and just looked at the price for a new WUR..yikes. thanks, jack
http://www.jcwhitney.com/autoparts/ItemBrowse/c-10101/s-10101/p-100000160266/mediaCode-ZX/appId-100000160266/Pr-p_CATENTRY_ID:100000160266

If the link doesn't work, the item # is ZX123617U ... at JC Whitney's website.

Very nice product.

For the jumper wire, I simply took my Bentley manual up to a NAPA autoparts and had them find everything for me. You will need 14 gauge wire, toggle switch, wire connectors, and the inline fuse wire.
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Old 09-11-2007, 05:36 AM
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Quote:
Originally Posted by Jim Williams View Post
The next thing to check is the control pressures of the WUR, first cold and then hot. Then compare them against the pressures listed for your WUR. You can find the nominal pressures listed in the little Porsche spec books for your year model or find them here on my website.

http://members.rennlist.com/jimwms/CIS/wur_specs.html

There is also a guide on using the pressure gauges there. Start at

http://members.rennlist.com/jimwms/CIS/CIShome.html and look under Testing (Fuel pressures).

Hope this helps.
Thanks for the info.

http://members.rennlist.com/jimwms/CIS/CIShome.html

Great link! I will follow these instructions and report back.

Thanks for all of your assistance.
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Old 09-11-2007, 09:40 AM
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Quote:
Originally Posted by mca View Post
http://www.jcwhitney.com/autoparts/ItemBrowse/c-10101/s-10101/p-100000160266/mediaCode-ZX/appId-100000160266/Pr-p_CATENTRY_ID:100000160266

If the link doesn't work, the item # is ZX123617U ... at JC Whitney's website.

Very nice product.

For the jumper wire, I simply took my Bentley manual up to a NAPA autoparts and had them find everything for me. You will need 14 gauge wire, toggle switch, wire connectors, and the inline fuse wire.
Thanks, mca.
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Old 09-11-2007, 09:43 AM
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Quote:
Originally Posted by Jim Williams View Post
The next thing to check is the control pressures of the WUR, first cold and then hot. Then compare them against the pressures listed for your WUR. You can find the nominal pressures listed in the little Porsche spec books for your year model or find them here on my website.

http://members.rennlist.com/jimwms/CIS/wur_specs.html

There is also a guide on using the pressure gauges there. Start at

http://members.rennlist.com/jimwms/CIS/CIShome.html and look under Testing (Fuel pressures).

Hope this helps.
COLD ENGINE RESULTS:

System Pressure
69 psi (~4.7 Bar)

WUR Electrical Unplugged
50 psi (~3.5 Bar)
** Note ** pressure quickly rose to 50 psi then quickly dropped to 40 psi and then rose back to 50 psi at a steady rate where it stayed

WUR Electrical Plugged
Pressure slowly rose to 58 psi (~4.0 Bar) probably over the course of 30 seconds (seemed a lot longer)
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Old 09-13-2007, 04:56 AM
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Your ccp seems too high. I don't know @ what ambient temp you did your test. If it was about 25C the ccp should be about 2.5 bar. Even @ 30C it should be about 2.8 bar. Was it hotter than that?
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Old 09-13-2007, 07:15 AM
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Quote:
Originally Posted by Paulporsche View Post
Your ccp seems too high. I don't know @ what ambient temp you did your test. If it was about 25C the ccp should be about 2.5 bar. Even @ 30C it should be about 2.8 bar. Was it hotter than that?

It was about 80 degrees in my garage ... roughly 26C.

For clarification purposes - the Cold Control Pressure is the pressure reading obtained with a cold engine, the gauge connected b/t the distributor and the WUR, the WUR electrics unplugged, the gauge valve is open, and the fuel pump is running.

Is that right?
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Old 09-13-2007, 07:29 AM
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Quote:
Originally Posted by Paulporsche View Post
Your ccp seems too high. Even @ 30C it should be about 2.8 bar
See my note about the pressuring dropping from 50psi to 40psi and then back to 50psi.

It should have stayed at 40psi as that would equate to 2.76 Bar.
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Old 09-13-2007, 07:31 AM
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Sounds like your setup is right. At 26c your ccp should be between 2.35 and 2.8 bar. If you are feeling confident you can try knocking the plug to get it down.
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Old 09-13-2007, 07:49 AM
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Paul -

Any reason why the psi would have hit 50 and then quickly dropped to 40 ... only to rise again to 50?

Is that normal?

Is it possible that I need to bleed the gauge between tests?

Also, is there a time limit as to how long I can run the fuel pump when performing these tests?
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Old 09-13-2007, 08:48 AM
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mca,

You should bleed the gauge between tests. If you didn't maybe that was the cause of the fluctuation.

I saw something interesting in the Bentley. It says to operate the fuel pump w/o the engine running, which is what I think most of the guys do. However the charts quote pressures w/ the engine running. Sounds like that is a mistake.

One thing that does seem good advice is that the ccp should be taken w/ a temp of 20c or less (68F). At 20 you should be between 2 and 2.4 bar.

I didn't see anything in the book regarding a max time limit for operating the pump, although I would do it just for as long as it takes to get the reading, since the pumps don't like to be run dry.

Can you get back to us w/ a reading @ less than 68, after a bleed?
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Old 09-13-2007, 09:05 AM
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Paul -

Retested and got correct numbers.

WUR Electrical Unplugged
2.7 Bar

Doh! Now what?

Does this mean the WUR is functioning correctly?
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Old 09-13-2007, 02:42 PM
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mca,

As Paul says, the variation in control pressure reading could be due to air in the gauge lines, but once the reading has settled out, I wouldn't worry too much about it. The factory manual says to bleed the gauge, but I've never been convinced it is required. In a steady-state situation, pressure in the lines is still pressure whether it is air or fuel, unless of course the engine is running, and the air is behind the injector nozzles or in the fuel distributor. According to the specs, both your cold pressure and the warm pressure seem too high. Knocking the plug will affect the cold control pressure, but I don't think will affect the hot pressure. A restriction in the WUR return line COULD be the cause of a high pressure for both the cold and hot condition, just a possibility.

As far as a time limit on running the fuel pump, I don't see that it is any different running the pump whether the engine is running or not, except that it is drawing from the battery without the battery being charged. Fuel is still passing through the pump in both cases to keep it wet and cool.

Paul,

Tests on the control pressure regulator can be made with or without the engine running, Except when the vacuum controlled WURs need a vacuum and this control pressure is specified to be tested with a vacuum. The vacuum can be obtained from a running engine, Or, with a vacuum tool connected to the WUR such as a Mighty-Vac. The US '82 (mca's engine) WUR won't have a vacuum connection if it is a stock setup.
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Old 09-13-2007, 03:15 PM
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Quote:
Originally Posted by Jim Williams View Post
According to the specs, both your cold pressure and the warm pressure seem too high.
Jim - I never did a warm pressure test.

Which of these cold pressures is off?

System Pressure
69 psi - 4.7 bar

WUR Electrical Unplugged
38 psi - 2.6 bar

WUR Electrical Plugged
58 psi - 4.0 bar
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Old 09-13-2007, 03:33 PM
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A ccp of 2.7 @ 26C is ok. Maybe it's time to go back to the AAR and AAV, which affect cold running and starting.

mca,

I don't remember, do your revs rise at all just after cold start and then gradually settle to 950 or so after a few minutes? Did you ever check those 2 components?

Jim,

Thanks for that info. I will have to remember that if I ever check my pressures. Since I have no Lambda system, I am running an older style, vacuum assisted WUR on my engine.
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Yellow 77 Sunroof Coupe/cork interior; 3.2L '80 SC engine/c10:1/No O2; Carrera Tensioners; 11 Blade Fan; Turbo tie rod ends; Bilstein HDs; 28 tube Cooler; SSI, Dansk; MSD/Blaster; 16x7" Fuchs/205/50 Fuzion ZRi; PCA/UCR, MID9
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Old 09-13-2007, 07:07 PM
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A ccp of 2.7 @ 26C is ok. Maybe it's time to go back to the AAR and AAV, which affect cold running and starting.

mca,

I don't remember, do your revs rise at all just after cold start and then gradually settle to 950 or so after a few minutes? Did you ever check those 2 components?

Jim,

Thanks for that info. I will have to remember that if I ever check my pressures. Since I have no Lambda system, I am running an older style, vacuum assisted WUR on my engine.
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Yellow 77 Sunroof Coupe/cork interior; 3.2L '80 SC engine/c10:1/No O2; Carrera Tensioners; 11 Blade Fan; Turbo tie rod ends; Bilstein HDs; 28 tube Cooler; SSI, Dansk; MSD/Blaster; 16x7" Fuchs/205/50 Fuzion ZRi; PCA/UCR, MID9
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Old 09-13-2007, 07:08 PM
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Quote:
Originally Posted by Paulporsche View Post
I don't remember, do your revs rise at all just after cold start and then gradually settle to 950 or so after a few minutes? Did you ever check those 2 components?
Basically she starts up immediately and revs up like she used to. But then the rpms fall off immediately. More often she will still hang on and not die but the engine is BARELY running ... i mean BARELY ... to the point where the entire car shakes as the engine slowly turns.

She remains at extremely low rpms and then will finally make it to a normal idle after a couple of minutes. I think the video demonstrates this pretty well.

I check the AAR last night with a cold engine and I could see that the valve is open. Tomorrow morning I am going to put her back together and start her up. If she dies, I am going to check the AAR valve to see if it is closing too fast.
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Old 09-14-2007, 07:09 AM
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I think poster mystery train had some threads on the AAR. IIRC he rewired his so the resistance was different, allowing it to stay open longer.

As mentioned earlier, did you check for vacuum leaks? Did you ever try richening your mixture? What is your warm idle speed?

If you have a Bentley manual. there are some tests for the AAR in section 240-21.
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Old 09-14-2007, 11:03 AM
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Quote:
Originally Posted by Paulporsche View Post
As mentioned earlier, did you check for vacuum leaks? Did you ever try richening your mixture? What is your warm idle speed?
I am still unsure as to how to check for vacuum leaks. If I had leaks, would this affect normal performance when warm or are there specific vacuum lines that are relevant during cold starts?

The mixture is right on. Adjusted last weekend - was running lean.

Warm idle speed is perfect - 950ish.

I do have the Bentley and I have been reading it over and over and over.

I am still wondering if my WUR test results show that it is operating correctly.

Sorry that this is dragging on ... thanks again for the continued support.
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Old 09-14-2007, 11:14 AM
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Alright, we know it's hot in SC this time of year, and the best test for ccp is done when it is below 68F.. It seems that it hasn't been that low there for a while. I would like to see your ccp just a little lower but it seems that it is within range, albeit @ the top.

Since you richened your mixture, have you tried restarting the car when" cold " w/ the same results?

I would try checking the height of your sensor plate in the mixture control unit. See p 240-19/20.

If you search here you will find various procedures for checking for leaks. Quite often, there are old, porous hoses, a cracked airbox, a popoff valve not seating properly, or a bad decel valve. Often these minor leaks "repair" themselves once components warm up.

Since I don't have these on my car I can't help you w/things like the O2 sensor, the throttle position switches and the frequency valve, but I would go over everything.
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Old 09-14-2007, 11:34 AM
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Craig wrote,

Basically she starts up immediately and revs up like she used to. But then the rpms fall off immediately. More often she will still hang on and not die but the engine is BARELY running ... i mean BARELY ... to the point where the entire car shakes as the engine slowly turns.

She remains at extremely low rpms and then will finally make it to a normal idle after a couple of minutes. I think the video demonstrates this pretty well.


Hello Craig,

The 82 lambda version of CIS has a few quirks that can cause your symptoms, even if the pressures are spot on. Poor running after a cold start usually is a result of a too lean mixture and retarded spark timing. The first thing to check is the operation of the lambda system, if the frequency valve is not operating, no adjustment to pressure or replacing a WUR will solve the problem. The basic settings are lean so that the lambda brain can dither the mixture past stoich for the cat operation. Open the plastic cover on the left side of the engine compartment and find the test plug. Connect an analog dwell meter to the green/ white stripe wire and start the car. You should get around 58 dwell, cold closed loop. After a few minutes, the system should go closed loop and the neddle should fluctuate between 40-58. These specs are for a new engine with ideal compression and most engines cold start much better with the mixture set so that the needle fluctuates between 30-40. You are only adjusting the open loop mixture, the system will bring it back during light cruise and emission testing. There is a temperature switch on the right timing cover that is closed below 59F for cold starts, but this is too low for some climates and there is a replacement Bosch switch that is closed at 78 degrees. If your garage never gets below 59, the replacement switch may help. The other problem that causes initial stumble on cold starts is the vacuum retard that was used soley to meet the curb idle emissions test. Try this test, unplug the gray vacuum line at the back of the distributor and plug it. Start the car, the idle will be higher and you will need to bring it back down to 950 rpm with the large bypass screw on the TB. Then check you timing at 950 rpm with both vacuum lines blocked and set it to 5 BTDC. Most lambda CIS 911's I've worked on cold start best with the vacuum retard capped and the open loop mixture set to 30-40 dwell.

You shouild also check for vacuum leaks at the injector sleeves with an unlit propane torch. Porsche chose an inferior method of mounting the injectors on the 911 and the orings on the sleeves bake with age. The basic problem is that the CIS calibration relies on vacuum to lift the senosr plate to supply more fuel and as the engine ages and leaks develop, there is less vacuum on the plate at idle, resulting in less fuel delivery.

Paul
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