Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Mercedes-Benz SL Discussion Forum

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 10-04-2009, 09:06 PM
Registered User
 
Join Date: Dec 2000
Location: South Dakota
Posts: 310
WUR & CSV

I have looked all around these postings on these subjects and may have missed something but my problem is with a 1976 450. I apologise for bringing up these items again. The usual no start when cold but does when the air flap is depressed--so, I figure the CSV. Then when it gets warm, it coughs and the usual stuttering until revved. Sure, I guess the WUR for that . I want to go through both and am not sure if all the vac. lines are correctly in place. I need a primer in these two things or maybe others so that I can properly go through the system and do it sensibly. There those who will replace everything but that does not always seem smart, dollar-wise. Most of the posts seem to assume some additional understanding of how they work.

I would like it to be placed is some orderly manner ---and maybe the manual is the thing but there are some very informed people here that I may have to owe my sanity to and I plea for some clarity. (Can't seem to get into the 450 manual section on the 116 site.) Seems that this motor will be fine if I can clear these items up. Sorry for the redundancies.

Sparky

Reply With Quote
  #2  
Old 10-04-2009, 09:15 PM
88Black560SL
 
Join Date: Oct 2004
Location: CT
Posts: 3,510
Quote:
Originally Posted by gs sparhawk View Post
I have looked all around these postings on these subjects and may have missed something but my problem is with a 1976 450. I apologise for bringing up these items again. The usual no start when cold but does when the air flap is depressed--so, I figure the CSV. Then when it gets warm, it coughs and the usual stuttering until revved. Sure, I guess the WUR for that . I want to go through both and am not sure if all the vac. lines are correctly in place. I need a primer in these two things or maybe others so that I can properly go through the system and do it sensibly. There those who will replace everything but that does not always seem smart, dollar-wise. Most of the posts seem to assume some additional understanding of how they work.

I would like it to be placed is some orderly manner ---and maybe the manual is the thing but there are some very informed people here that I may have to owe my sanity to and I plea for some clarity. (Can't seem to get into the 450 manual section on the 116 site.) Seems that this motor will be fine if I can clear these items up. Sorry for the redundancies.

Sparky
You should check your air flow plate for centering. Also check your WUR with a pressure gauge. The CSV can be checked by just pulling it out and letting it shoot into a can while someone turns the key to on.

1/4 turn of the mixture adjustment screw, I believe clock wise might get you running but this should be verified with a CO meter and all other things fixed.
__________________
To see my 129 parts for sale visit:
http://stores.ebay.com/The-Mercedes-SL-Store
John Roncallo
Reply With Quote
  #3  
Old 10-04-2009, 11:56 PM
Strife's Avatar
General Purpose Geek
 
Join Date: Apr 2004
Location: KY USA
Posts: 2,238
The WUR is absolutely critical to the proper operation of the car, there's no point in digging any further until you verify that this is working to spec. Too bad it's really expensive, even rebuilt. I got a used one when mine was failing and I modified the failing one to be "adjustable" (Porsche owners do this). But I haven't reinstalled it yet to adjust it to spec. It's difficult for me to fix something that is not broken.

I'd look at the modern electronically controlled unit by Unwired but I'm not all that happy with it's aesthetics!
__________________
86 560SL
With homebrew first gear start!
85 380SL
Daily Driver Project

http://juliepalooza.8m.com/sl/mercedes.htm
Reply With Quote
  #4  
Old 10-05-2009, 12:06 PM
Super Moderator
 
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,318
Here is a thread that discusses an almost identical problem.

Where to go from here?

In this thread, I tried to explain how the WUR works and how to fix its most common problem, a clogged inlet filter. The other problem area is vacuum loss. Be sure that one/both sides of the WUR (I think your car has vacuum on both sides) hold vacuum.
__________________
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
Reply With Quote
  #5  
Old 10-05-2009, 03:25 PM
Registered User
 
Join Date: Dec 2000
Location: South Dakota
Posts: 310
Thank you, gentlemen, for the insight. Chuck, I had read the post you refer to but had forgotten it as I was researching something else. What you said made sense to me since, after reading some of the various posts, I did get a handle on the principles of the operation as described. As you said, the WUR seems to be the first place to look and it serves little to go on until that functionality is determined---and then CSV and others after that. I am impressed from other reading that the CIS K-jet is designed as a sophisticated system and if set up properly can provide a satisfactory performance. This one of mine sat for some time with various degrees of attention---and, as you related, is the prime example of need for service. I made a weak attempt at checking the WUR ( due to the time allowed) and, unfortunately, did not get the filter screen out. Is there a part # for it & can it be obtained new for when I ,most probably, ruin the one in there? I do like to take the most obvious and simple approach to these things and the screen filter seems to be first on the list. ( Why disassemble the whole thing only to find that it is the filter?)

My Air plate functions nicely--no sticking and good sealing. Fuel flows when pressed and makes the thing start --like usual. When warm, it still stumbles and barks back, indicating insufficient fuel. Filter, again. Simple CSV check was discussed and I will try to understand the details of that so I don't ruin it in trying. ( Like I usually do--and how others learn the bitter but indellable lessons)

It is readily apparent that the issue is the fuel supply and that the problem could be one or a combination of several issues from the tank to the injectors. Filters, vacuum supply, sticking and mal-adjusted bits of the several control devices appear to all be in the mix of possibilities. That is why Werner at the dealership gets quiet and studious and approaches his adding machine with respect and dreams of the nice fat bill. Then there are folks like us who dream of figuring it all out for ourselves and trumping the shop.

I do have access to a fully supplied shop w/lift. ( Don't be jealous, some of you folks. I have wrenched in the snow and cold for over 55 years on Fords and Chevys which had no such complications as these.) I should be able to knock together a pressure test for the mentioned units and I'll let you know the outcome---and credit you with the guidance which has been so patiently given this old man. Damn, I love this site.

"Still wrenchin' after all these years."

Sparky

Last edited by gs sparhawk; 10-05-2009 at 03:32 PM.
Reply With Quote
  #6  
Old 10-05-2009, 04:10 PM
Super Moderator
 
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,318
Unfortunately, there is no replacement part for the little screen. The "rebuilt" units come with what looks like brass wool in its place. You can get it out without (much) damage with a really fine pick with a little bend on the end.

There is a replaceable filter in the main inlet to the FD itself, though.

__________________
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
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 08:37 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page