Questions: CIS, cold start, WUR and O2 sensor

[tirwin]

Tony,

You were spot on. Resistance on the WUR was 9.2 Ohms.

[tirwin]

Stupid question... will someone confirm for me that I have these tests right? To check the duty cycle of the FV, red to terminal on fuse panel, black to ground and green to the test port. Duty cycle should be fluctuating on warm engine 65-85%, correct?

I read somewhere that you can use the voltage of the O2 sensor as a proxy for mixture/hydrocarbons. Should be reading .7V for normal mixture at operating temp. Is this correct?

[boyt911sc]

Originally Posted by tirwin

Tony,

You were spot on. Resistance on the WUR was 9.2 Ohms.

tirwin,

Your WUR is out of spec or calibration. Before I put my CIS bench tester back into storage, I could test and calibrate your WUR. I'll be travelling on June 10 and will be away for 4 weeks. This is one of your problems (?).

I'll do the test for FREE just take care of the return postage back to you. The earlier you send it to me, the earlier you would get it back. I like to have a couple of days with your WUR so I could test it and observe its performance. There is nothing wrong with your WUR except its calibration!!!!!

It's a coincidence that I worked and calibrated five (5) WUR-090 last week and you came up with this post. Decide and let me know your decision or PM me for details.

Tony

[tirwin]

I did the FV duty cycle test. I may need some help with interpreting the results.

Comparing the Bentley specs to my digital dwell meter properly is the question. I'm getting a dwell reading of 44 on the 4-cyl scale (30 on 6-cyl scale). Bentley says it should be 45-60%, fluctuating. Referring to page 240-26.

I am a little confused on the dwell/duty cycle conversion. On the previous page, Bentley says "when using a dwell meter, the scale range is 90% and must be converted to correspond to the 100% duty cycle scale. For example, a 50% duty cycle is equivalent to 45% dwell."

Bentley quotes duty cycle. Am I supposed to use the numbers from the 4 or 6 scale? If 4, and I convert from dwell to duty, then my duty cycle was 50% on a 75 F day with the engine at operating temp.

I know how many cylinders I have, but I thought the old analog dwell meters used a 4 or 8 scale and numbers quoted were supposed to be on the 4 scale. Did I get that right?

[tirwin]

Might have answered my own question...

Found this:

Dwell angle divided by (360 divided by number of cylinders)= Duty cycle

So dwell of 30 on 6-cyl scale:

(30/(360/6)) = 50% duty cycle

[tirwin]

Tony,

Missed your post above earlier today. I appreciate the help and will send you a PM.

-T

[marty911sc]

I'm having the same cold start problem. It's very very intermittent. I was told it only happens when its sets up. I check and rechecked. I keep a can of starter fluid handy.

[tirwin]

Marty,

Great to see a fellow Atlantan.

Tell us more about your car. And the rule for first-timers is you have to post pics.

You can get a lot of help here if you're a DIYer.

[marty911sc]

I'll work on the pic. I don't want to hi-jack the thread.
I really lucked out. I bought it from a Doc from Blue-ridge, who bought it brand new after medical school.I have a giant stack of recipts. Rebuilt powerplant, supension, AC. Interior. brakes. All the must do's seemed to be checked off. Its not a trailer queen. Fram Blanz Racing was the mechanic.It runs like a sewing machine.

[tirwin]

Ok, guys, I must've goofed my original test. Maybe I had the valve on the FD side instead of the WUR side.

Anyway, happy to report new numbers from this morning.

Ambient temp in my garage: 75 F (~24 C), 60% humidity on June 1, 2013.

Gauges hooked up in-line between WUR and FD, valve on WUR side.

System pressure, cold engine, valve closed, engine off, FP running: 4.75 bar

Control pressure, cold engine, WUR electrical connection disconnected, valve open, engine off, FP running : .1 bar

Control pressure, cold engine, engine off, FP running, valve open, WUR electrical connected: 3.6 bar

Control pressure, warm engine, engine running, valve open, WUR electrical connected: 3.6 bar

Residual pressure: 1.5 bar after 15 min.

[boyt911sc]

Originally Posted by tirwin

Ok, guys, I must've goofed my original test. Maybe I had the valve on the FD side instead of the WUR side.

Anyway, happy to report new numbers from this morning.

Ambient temp in my garage: 75 F (~24 C), 60% humidity on June 1, 2013.

Gauges hooked up in-line between WUR and FD, valve on WUR side.

System pressure, cold engine, valve closed, engine off, FP running: 4.75 bar

Control pressure, cold engine, WUR electrical connection disconnected, valve open, engine off, FP running : .1 bar

Control pressure, cold engine, engine off, FP running, valve open, WUR electrical connected: 3.6 bar

Control pressure, warm engine, engine running, valve open, WUR electrical connected: 3.6 bar

Residual pressure: 1.5 bar after 15 min.

Tim,

Do you have the data for the cold control fuel pressure versus time? The numbers are good except for the CCP. Did you punch the plug down before? I like the WCP @ 53 psi.

For the benefit of other readers, post the duration (time intervals) for the CCP to stabilize (max.) to 3.6 bar (53 psi.). For example: initial, after 30 sec., 45 sec., 1 min. etc.........till it stabilized. Include your observation about idle speed during warm up process. Thanks.

Tony

[tirwin]

Tony,

Yes I forgot to post that. I took a video so that I could make sure I got the time right. It took 1 min 30 sec give or take a second or two for the control pressure to rise from .1 bar to 3.6 bar.

So, to summarize for those playing along at home.

My WUR is type -090 from an '83 CIS.

Resistance between the electrical terminals on the WUR is out of spec. Currently I'm getting 9.2 Ohms when I should be getting 25-26 Ohms.

Cold control pressure is low. It's .1 bar when it should be ~1 bar.

Since resistance is too low on the WUR bimetallic strip, the plunger is closing too fast and leaning out the engine prematurely.

So there we have the diagnosis to the problem!

Thanks to Tony and everyone else.

Next step: fix the WUR!

PS - I will edit the video and post it later.

[boyt911sc]

Originally Posted by tirwin

Tony,

Yes I forgot to post that. I took a video so that I could make sure I got the time right. It took 1 min 30 sec give or take a second or two for the control pressure to rise from .1 bar to 3.6 bar.

So, to summarize for those playing along at home.

My WUR is type -090 from an '83 CIS.

Resistance between the electrical terminals on the WUR is out of spec. Currently I'm getting 9.2 Ohms when I should be getting 25-26 Ohms.

Cold control pressure is low. It's .1 bar when it should be ~1 bar.

Since resistance is too low on the WUR bimetallic strip, the plunger is closing too fast and leaning out the engine prematurely.

So there we have the diagnosis to the problem!

Thanks to Tony and everyone else.

Next step: fix the WUR!

PS - I will edit the video and post it later.

Tim,

The WUR-090 arrived today via UPS ground with a return sticker. I did some preliminary tests:

cold control fuel pressure @ 5 psi...................adjusted to 18 psi.

heating resistance at Room temp. @ 9.2 Ohms.........adjusted to read 26 Ohms.

I would need to observe and calibrate the switching device to open/close at cold condition. Once it passed the testing parameters, I'll ship it back to you on or before Saturday (June 8).

Tony

[boyt911sc]

Tim,

Did you get a chance to install the WUR back into your car? Any feedback you like to share with us? Thanks.

Tony