WUR lower chamber investigation...

rbtoj · #1 06-24-2017, 08:24 PM

So I have been fixing my 1978 280slc fuel system for a while now, chasing a rich mixture problem.
I have now turned my attention to the warm up regulator and determined that it cannot provide the correct pressure to the system (wur pressure is too low, explaining the rich mixture).
Since I never saw any pictures on the web of the lower part of the WUR (and I heve the damn thing apart now), I'd thought I'd share some.

If any one needs to change that green-ish gasket, it looks to be totally doable.
The material feels like a very soft rubber, like latex (I know it isn't latex). I imagine it should be easy to find some gasket material similar to that.
The metal part in the middle is screwed in place with a 4mm allen.
And that's pretty much it. Noting else there...
Come to think of it, that's probably why I never saw any pictures of it posted online...

BTW, the model number on this WUR is 0438140057.

Cheers.

Frank Reiner · #2 06-24-2017, 08:58 PM

Quote:

Originally Posted by rbtoj

So I have been fixing my 1978 280slc fuel system for a while now, chasing a rich mixture problem.
I have now turned my attention to the warm up regulator and determined that it cannot provide the correct pressure to the system (wur pressure is too low, explaining the rich mixture).
Since I never saw any pictures on the web of the lower part of the WUR (and I heve the damn thing apart now), I'd thought I'd share some.

If any one needs to change that green-ish gasket, it looks to be totally doable.
The material feels like a very soft rubber, like latex (I know it isn't latex). I imagine it should be easy to find some gasket material similar to that.
The metal part in the middle is screwed in place with a 4mm allen.
And that's pretty much it. Noting else there...
Come to think of it, that's probably why I never saw any pictures of it posted online...

BTW, the model number on this WUR is 0438140057.

Cheers.

Can you provide a picture of the whole regulator, and also specify how the two vacuum and/or vent fittings have been connected.

rbtoj · #3 06-24-2017, 09:47 PM

So I'm not the only one befuddled by the vacuum hoses on the M110

One goes to the under side of the intake manifold on the back (closest to the firewall). I marked this one "to manifold" on the picture.
The other, can be vented to the atmosphere (as far as I understand). On my car it was connected to one of the hoses under the idle air adjustment screw.

The one that goes to the intake manifold is the important one. If it is disconnected, you will run rich.

280EZRider · #4 07-03-2017, 02:52 PM

Thanks for posting the pics. I´ve been meaning to replace the cracked hose to manifold for a while on my M110 and you just reminded me.

Do you know the inside hose diameter / outside fitting diameter?

As I understand it, once the engine is at op temp the WUR has no function, so is it possible that this is not the source of your rich running?

97 SL320 · #5 07-03-2017, 06:03 PM

Between the electrical plug and the word Germany is a circle. This is a pin that holds the bimetallic strip / heater. Tapping this is a slight bit will richen the fuel mixture, someone may have done this to fix a cold start issue. The circle can be drilled / tapped and a jack bolt / washer installed to pull things lean while assembled.

From what I've found taking one of these apart before, the regulator control surfaces are finely ground. Wear causes these surfaces not to seal reducing pressure / making for a rich mixture.

The soft gasket is likely silicone. ( molded not formed in place from a tube )

rbtoj · #6 07-05-2017, 04:24 PM

Quote:

Originally Posted by 280EZRider

Thanks for posting the pics. I´ve been meaning to replace the cracked hose to manifold for a while on my M110 and you just reminded me.

Do you know the inside hose diameter / outside fitting diameter?

As I understand it, once the engine is at op temp the WUR has no function, so is it possible that this is not the source of your rich running?

Unfortunately I already reinstalled the WUR, but I'd say a 8mm ID hose should do the job. You might need a zip tie though.

rbtoj · #7 07-05-2017, 04:29 PM

Quote:

Originally Posted by 97 SL320

Between the electrical plug and the word Germany is a circle. This is a pin that holds the bimetallic strip / heater. Tapping this is a slight bit will richen the fuel mixture, someone may have done this to fix a cold start issue. The circle can be drilled / tapped and a jack bolt / washer installed to pull things lean while assembled.

From what I've found taking one of these apart before, the regulator control surfaces are finely ground. Wear causes these surfaces not to seal reducing pressure / making for a rich mixture.

The soft gasket is likely silicone. ( molded not formed in place from a tube )

Thanks for the info.
It turned out it was a much more deceiving problem: The top of the surface where the fuel distributor attaches was bent downwards, causing the control plunger to be slightly depressed when installed. Adding some copper shims around the screws under the fuel distributor fixed the problem.

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