Author Topic: Question about WUR testing  (Read 835 times)

1960mog

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Question about WUR testing
« on: 04 June 2016, 09:17 AM »
Hi

I am trying to test the CIS on a 79 6.9.
The engine is not running at the moment, but I can run the fuel pump.
If I apply a small amount of negative pressure to the top vacuum connection on the WUR, the control pressure rises.
I understand that this is part of the full load enrichment.

The question is.
Do I need to have the engine running while checking control pressure on a WUR?
Does the WUR need to 'feel' manifold pressure to reach 3.7 bar during the check on not?

Thanks for your help


78 6.9 #4084
79 6.9 #6669

s class

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Re: Question about WUR testing
« Reply #1 on: 04 June 2016, 10:26 AM »
THe WUR won't know if the engine is running or not.  If there is no vacuum on the top port, then that is the full load enrichment pressure.  Use a vac pump to suck on the top port to simulate normal running.  There are specs in the handbook for how much vac should be applied.  With the correct vac, you should then see around 3.5 - 3.8 bar control pressure. 

I like to set them up with the normal running control pressure around 3.7 to 3.8 ie at the high end of the range to get economy, but then I set the full load enrichment at the bottom end of spec, eg 2.8 bar to get a shot of power under sudden acceleration. 

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

1960mog

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Re: Question about WUR testing
« Reply #2 on: 04 June 2016, 02:21 PM »
Thanks S class

How do you adjust the full load pressure ?
Just by playing with the inner spring?

Thanks


78 6.9 #4084
79 6.9 #6669

s class

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Re: Question about WUR testing
« Reply #3 on: 07 June 2016, 01:02 AM »
The inner coil spring rests on the diaphragm, which in most cases has a threaded adjustment in its centre to adjust the bottoming-out point. 

'76 6.9 Euro, '78 6.9 AMG, '80 280SE, '74 350SE, '82 500SEL euro full hydro, '83 500SEL euro full hydro , '81 500SL

1960mog

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Re: Question about WUR testing
« Reply #4 on: 07 June 2016, 09:39 AM »
I didn't see any possibility of adjustment on mine. I have to check again.
78 6.9 #4084
79 6.9 #6669