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Discussion Starter · #1 ·
Hey all,

I have my 500sec at the shop to get the rough cold start figured out, and it seems the WUR is the culprit. My car is an '85 gen1 grey market 500sec, so I just want to make sure the Bosch parts number on the current WUR is the correct one (and that it wasn't meddled with at all when it was imported).

The parts number is : 0438140071

Is this correct? If so, I'll probably end up grabbing a used one from ebay (unless someone here has one they'd sell)

Best regards,
Graham
 

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1991 500SEC 55K mi. 1987 560SEC Now 153K mi. 2020
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Hey Graham,

I just looked it up & it seems the MB number was superseded some time ago.

So here is what I found just now for you.

500 Control Pressure Regulator.png


That's the MB number, but you know that during the day, that Bosch part was used [with variations of course] by every European manufacturer pretty much across the board]... They are a dead simple design as well and lately there has been a cottage industry doing rebuilds of your unit [if need be]... So its a thought..
I just saw a pristine brand new one advertised for some $1100 plus shipping...
You definitely do NOT need to go down THAT particular route....

Hang in there & good luck Graham.

MBL
 

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Discussion Starter · #4 · (Edited)
Thank you! Is this for a gen1 car?

I can find that the number there corresponds to: 0438140101

It seems my car has the wrong WUR then? I don't want to order a new one if it's also the wrong part. But, I can't for the life of me find any mention of 0438140071 with any SEC or m117
 

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1991 500SEC 55K mi. 1987 560SEC Now 153K mi. 2020
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5,393 Posts
Thank you! Is this for a gen1 car?

I can find that the number there corresponds to: 0438140101

It seems my car has the wrong WUR then? I don't want to order a new one if it's also the wrong part. But, I can't for the life of me find any mention of 0438140071 with any SEC or m117
To 9/85


To 9:85.png


Not nessassarilly the wrong part really.

This info I look at has not been updated, likely for years...

Its a good guide...
 

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1991 500SEC 55K mi. 1987 560SEC Now 153K mi. 2020
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Were I you, I would test for resistance across the the electrical pins. There is a electrical heater element inside the control pressure regulator to act upon a bi-metallic strip/spring that responds to temperature, and adjusts therefore according to that OR the underhood/block temperature to affect mixture control at the fuel distributor. 'Less is more' and I'll leave you with that.

If still in doubt, call your dealer with your [[Oh dam, yours is a Euro.. so good luck with getting help...].
You could call MB and ask if there is a supercession to the MB number I just cited?

That would bear fruit I'm sure

M
 

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Discussion Starter · #7 · (Edited)
Hmm, alright. I'll check into that. I just can't find any connection between my part number and any w126 or m117, which leads me to thinking it's wrong. But, I'll try to call MB and see.

Edit: the part number for my WUR seems to be for a BMW 320i. I'm going to confirm with the mechanic that that is indeed the proper part number, but he told me over the phone and read it twice. He also mentioned that it seems to have been fiddled with quite a bit; probably because it isn't even the correct WUR? I have no idea who did the work, although I'm sure I could go through the service records and check, assuming it wasn't in the last few years.
 

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84 500SEL AMG, 90 560SEC AMG, 85 500SEC AMG Widebody
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Just looked at my widebody Euro 500SEC WUR that was recently rebuilt by Larry @ CIS and my # is 0 438 140 101
 

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Discussion Starter · #9 ·
That's what I thought, for the proper one; thank you for the confirmation!. Anyways, after talking to my mechanic (who is a specialist with these cars and CIS systems, being a well-known guy in the area who's worked on these since they were first made), he suggested that I get another of the same (incorrect) part.

My car, when it was federalized, had some interesting stuff modified it seems, with some of the vacuum lines normally going to the WUR removed, and some other stuff added. Obviously, the car ran fine for decades with this WUR in it, and the problem he said definitely seems to be a bad WUR. So, hopefully a new one will solve the rough start it has; otherwise, I'll just need to live with it for a bit, until I decide I want to pay to have whatever federalizations were done, un-done, and the fuel system reverted to an unmodified euro one. He said that, while having a proper WUR with vacuum lines in could obviously be done, he can't really give an estimate on what all would need to be done, until he could figure out exactly what was changed in the federalization process (which he most likely wouldn't be able to tell until disassembling and testing more).

The joys of a grey market car!
 

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Once upon a time when I had my first W126 which my parents bought in 1988 and gave to me as my first car in 2005. I took the car in to a 'Mercedes Specialist' to have some work done. My car was a 500SE. Car came back to me with very bad cold start rough idle and smoke which it never had before.

I went back to them and found that someone at the shop owned a W116 450SEL 6.9 and they had a faulty warm up regulator on their car. So the thought they would swap it out with the one on my car. Not only did the swap make my car run like sh*t but it also didn't work for their car either as the units were different. Long story short he admitted to it and swapped them back. Needless to say... I never when there again
 
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