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Join Date: Jun 2008
Location: SE Pa.
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Sorry - I did the standard test with the gauge in-line between the distributor and the WUR.

Engine cold and off, pump relay jumpered to run.

Valve closed (system pressure) 4.5 bar

Valve open (Control pressure) 0.5 Bar. The was 2.5 bar two days ago.

Residual pressure (Pump off, valve open) 1.5 bar.

This is really weird.
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1981 911 SC
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Old 07-25-2019, 07:50 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #41 (permalink)
Hey, nice marmot.
 
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If you’re doing the COLD control pressure test we need to know what the ambient temp is at the time you record those pressures. Engine off, fuel pump jumpered to run with key ON. Also WUR electrical connector disconnected.

Then to get WARM control pressure plug in the electrical connector and record how long it takes to max out.

.5 bar CCP in the summertime would be a rich mixture on cold start. But it should only be that way while the engine is warming up. If your WCP is too low then you’ll be overly rich during normal operation as well.
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Old 07-25-2019, 11:35 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #42 (permalink)
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i would do your restriction tests again .... if it is plugged up again you have contamination in your tank.
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Old 07-25-2019, 12:00 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #43 (permalink)
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I expected it to be plugged up - but it's the opposite. I'm thinking it's the WUR.

Until I found that low control pressure I was scheming how to drain the tank with the idea that I got bad gas.

Now - normal system pressure, low control pressure - I'm looking at the WUR

I plan to run the test again when I get home tonight and do more troubleshooting.
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Old 07-25-2019, 12:21 PM
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Just arrive here in London........

Mike,

I thought I escaped from the searing temperature in Philadelphia. The weather here is as bad as back home and could be hotter tomorrow. Your problem points toward a displaced pin inside the WUR. I sent you a PM and to try. Keep us posted.

Tony
Old 07-25-2019, 03:00 PM
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something similar is happening to me.. Rich then Lean then Rich.. Dr. Jekyll one Day Mr. Hyde the next..

AFR values all over the place.. Lamb DUH Connector???

I wiggled the Lambda connector in the back of the engine bay and I could change the idle and the AFR readings... (See Bob's post #26 too)

Havent done anymore research....
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Old 07-25-2019, 07:25 PM
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Adjusting the pin has no effect - I'm ready to try whatever.

High Life - my issue is pretty clearly the WUR - Tony is the guy to know how to straighten it out.

Lambda in the 81 has an odd single pin connector under the fuel filter that degrades and falls apart. There's a member on here who sell a quality replacement.
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Old 07-25-2019, 07:45 PM
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Quote:
Originally Posted by Porchdog View Post
High Life - my issue is pretty clearly the WUR - Tony is the guy to know how to straighten it out.
Ok - No problem - I was just trying to throw out an alternative - just surprised that both the rebuilt WUR's are giving you the same issue.

Oh well keep us posted - Real curious to know what failed in the WUR (especially since I need to have mine rebuilt at some point)
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Old 07-25-2019, 09:16 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #48 (permalink)
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So while I was thinking about this today I remembered that I have the original WUR - probably swapped out 18 years ago. I even knew where it was.

I checked resistance - 10 Ohms. Low but it's something. I swapped it in.

Control pressure was 1.5 Bar - 22 psi.

The car was a bit reluctant to start and idled rough at first but it smoothed out nicely. I took it for a 20 minute drive - no problems. It's driving nice and idling smooth at just under 1000 RPM.

I will get the "good" WUR back to Tony and let him figure out what happened. In the meantime I can live with rough cold starts.

It's actually amazing to me that the 40 year old device is working as well as it is.
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Old 07-26-2019, 08:17 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #49 (permalink)
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I'm back with continuing problems.
After 10 days or so the car went back to running rich. I got my original WUR back from Tony and plugged that in - no joy (although pressures are good)

I had the PRV out cleaned it and cleaned the lines. I have a new replacement, but system pressure is good.

I have thoroughly checked the Lambda/ FV and find no fault.

I'm assuming that the cold start valve isn't leaking - the system holds rest pressure.

I cleaned out my fuel tank and put in 5 gallons of ethanol free fuel. I also ran a can of fuel injection cleaner, injected at the fuel filter fitting.

The car is rich. adjusting mixture takes it leaner but it seems like very little effect for the amount I turn the screw - I have turned it over a full turn. As I lean the mixture I need to back out the idle screw to maintain idle - like 3 turns now.

After adjusting I reconnect the FV and the exhaust goes leaner - but the FV is at 10% or so and idle drops more.

So what else is left? Pull the fuel distributor?

Thanks!
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Old 08-25-2019, 05:36 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #50 (permalink)
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Once again, Tony has set me right.

After some back and forth with him I disconnected the "narrow band" lead from the AFR to the Lambda ECU and reset the mixture by ear. When it was running "about right" the AFR was reading 11.3. Connect the Lambda lead and the AFR climbs to about 12.3, frequency valve goes to 9% and the engine runs poorly.

Now I am starting to suspect the AFR. I set the mixture so the engine idles smooth and has good throttle response and take it for a drive - no issues.

I contacted AEM (who make the gage) they gave me some simple tests which it failed. I will be sending it back.

Meanwhile, I'm driving the car. It's running fine.
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Old 08-29-2019, 04:02 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #51 (permalink)
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I bought and installed an original single wire O2 sensor. Once warmed up the car ran even better. Lambda frequency was about 30% on the dwell meter. I adjusted mixture to 46%-48% dwell and I have been driving the car for a couple days - it is running great.

I'm going away for the week but I plan to "fine tune" and buy a new AFR after I'm back.
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Old 09-06-2019, 11:22 AM
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