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  #16  
Old 10-19-2010, 07:45 AM
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Location: Falls Church, VA
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T-Connector?

You don't need a "T" to do this. You need a gauge with two connections and a shut-off. The gauge is connected between the FD and the WUR with the shut-off on the WUR side. You measure system pressure with the shut-off closed, and control pressure with it open.

You will need to jumper the sockets for 30 to 87 on the fuel pump relay to do the system pressure because the engine won't run with the shut-off closed.

Good luck!

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #17  
Old 10-19-2010, 11:39 AM
Pex Pex is offline
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Join Date: Oct 2010
Location: South of Sweden
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Problem solved
Manage to borrow a fuel pressure gauge and mesured the pressure from the WUR...
Cold motor : 1 bar
"Half warm" motor : started to raise and stopped at 2 bar
Very Hot motor : still 2 bar???

Mesured the electrical connection and there where no 12V.
Removed the rubber-hose which protect the contacts and there was the problem, the +12V cord was broke, fixed the cable and mesured the pressure again and now it went up to 4 bar which is correct due to the book I borrowed from the local Bosch firm.

It's a little strange that the motor didn't manage to warm the WUR enough to raise the pressure since they say "disconnect cable when testing WUR", seems like my WUR need some help from the warmup element to work properly. It could still be something wrong with it but at least I know whats wrong now...

Took it for I ride and what a difference, now I see how quick and fast the car really is. Checked the spark plugs and they look as they should. Thanks for the support everyone, hopefully it will past the swedish "MOT" now so I can get my license-plates...
Attached Thumbnails
82 380SL Frequency valve BUZZING! Among other things!-broke.jpg   82 380SL Frequency valve BUZZING! Among other things!-gauge.jpg  
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  #18  
Old 10-19-2010, 12:51 PM
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Nice wrench!

The WUR works by the bending of a bi-metallic piece of metal to raise the control pressure. It is thicker than you would expect and you proved that it needs the heat from the electric current to bend enough to change the CP.

I don't know why the instructions would be like that.

Now you should be able to get a duty cycle reading and fine-tune your mixture.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #19  
Old 10-21-2010, 01:19 PM
Pex Pex is offline
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Have mesured the system pressure and it was 5.5 Bar, exactly as it should be.

Mesured the signal from the oxygene sensor while driving and it seems like it works, it was alternating between 0.3V to 0.9 and it looks like it's ok...
But I dont get any stable readings from the duty cycle mesure...

Can you confirm which number on the diagnostic plug I should use.

I mesured between number 3 (white cable coming from ECU) and earth and the value was alternating to much to get a decent reading.

I thought I could adjust the mixture to a 50% duty cycle by using the mixture-screw on the fuel-distributor.

Can I ruin anything if I turn the adjustment counter clockwise and lean the mixture until the motor stops then adjust it clockwise until it runs normally?

Last edited by Pex; 10-21-2010 at 01:41 PM.
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  #20  
Old 10-21-2010, 02:26 PM
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You might have better luck with an analog meter - I use an analog dwell meter - 30 degrees would be 50% on a six-cylinder.

That system is definitely after-market. Most of these were added to meet the requirement that the car have an O2 sensor and a lambda system as opposed to actually working to control the mixture. If you can't get a duty cycle reading, use the O2 sensor instead, and adust the hot idle reading to as close as .45V as possible.

Now that the car is running better, I STRONGLY recommend against changing the mixture unless you have some way to measure what is going on.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #21  
Old 10-21-2010, 03:00 PM
Pex Pex is offline
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Location: South of Sweden
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I think I actually have an old analog dwell-meter... I used it to measure the angle when the breaker-points in the distributor should open. Is this the type of meter you refering to?
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  #22  
Old 10-21-2010, 03:34 PM
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Exactly. You connect the wire that would normally go to the points/coil to pin 3 in the socket. You divide 360 by the number of cylinders and then take 50% of that as your desired reading.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #23  
Old 10-22-2010, 12:55 PM
Pex Pex is offline
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Join Date: Oct 2010
Location: South of Sweden
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Finally solved it...

Since I didn't get a proper signal for the duty cycle, I built a voltage regulator handling 0 - 1V, which I connected instead of the oxygen sensor, changed the signal between 0.2 - 0.9V and the frequency valve started to tick as it should... So the oxygen sensor's ECU was ok...

Noticed that oxygen sensor signal was almost constantly 0.9V when the car was idling ...
Adjusted the fuel mixture screw, almost a full turn counter clockwise and then the valve began ticking, the problem was apparently that the mixture was so fat that oxygen sensors circuit was out of range.

Now I can clearly see both the duty cycle and hear the valve working, can hear the idle speed following the duty cycle a little but I will adjust the mixture better with a CO meter, hopefully I can fine tune a little bit more then.

Thanks for the support, always nice to have some feedback... Feel like a K-Jet expert now ...

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