280se - new to me, warm stalling!

[raueda1]

I don't recall ever seeing anything like that bottom pic.  In any case, there's a critical order to the setup. Have a look at THIS if you haven't already, page 2 in particular.  My problem turned out to be something else, but it's still good for WUR info.  In outline the process is:

 First is getting hot pressure right with the big cylindical valve body.  The thermoactivator needs to be removed.

 Second is setting cold pressure using the indented plug on the top of the WUR with thermoactivator reinstalled.

 Last, vac enrichment, the bottom one is vacuum enrichment and acts only on the diaphragm in the lower chamber.  I think there's a thread on that.  It's easy to overdo it.  S Class says that doing so will wreck to diaphragm. 

Good luck!  Cheers,

[SteveDuNord]

I don't recall ever seeing anything like that bottom pic.  In any case, there's a critical order to the setup. Have a look at THIS if you haven't already, page 2 in particular.  My problem turned out to be something else, but it's still good for WUR info.  In outline the process is:

 First is getting hot pressure right with the big cylindical valve body.  The thermoactivator needs to be removed.

 Second is setting cold pressure using the indented plug on the top of the WUR with thermoactivator reinstalled.

 Last, vac enrichment, the bottom one is vacuum enrichment and acts only on the diaphragm in the lower chamber.  I think there's a thread on that.  It's easy to overdo it.  S Class says that doing so will wreck to diaphragm. 

Good luck!  Cheers,

Thanks!

I might email kjet.biz and see if I can pick their brains. They advise backing off the Allen key bolt a few turns during a refurb, then, after reassembly, tapping the bottom plug to adjust.

I wonder, though, if the tapping is just another way to achieve the same effect as manipulating the bolt...  Obviously they wouldn't want to be drilling into a customer's bottom plug just to do an adjustment when they can use a non invasive method.
We shall see.

[daantjie]

Here is a video showing the bottom plug mod:

https://www.youtube.com/watch?v=PuELRd3gqgk

[raueda1]

Careful here.  A couple things worth noting.  First, When rebuilding, did you polish the bottom of cylindircal WUR body?  proceed with progressively finer wet paper going from 1000 to 3000 grit.  You want a mirror finish.  This is a must do.  Second, the WUR shown above is a different, later version.  If you don't have that brass button then there's no hex screw inside, so that adjustment won't apply to your unit.  Cheers,

[Feather535]

If you're doing all this to fix the combination of high system pressure and zero control pressure, I think you're on the wrong track.  The vacuum diaphragm only comes into play at wide open throttle, so it shouldn't affect pressures at idle or with the pump running and the engine off...unless you've done something drastic by moving the bottom plug.

I would advise going back to the beginning.  System pressure is set by the primary pressure regulator in the FD?  Is it assembled correctly?  Are all the springs and o-rings in the right places?

Zero control pressure basically means fuel is flowing through the WUR as if it wasn't there.  Is the screen in the inlet in place and intact?  Are the metal diaphragm and the o-ring correctly installed?  There should still be measurable control pressure (maybe 0.5 bar) with only the those components installed, no springs or bimetal strip.

[Feather535]

I would advise going back to the beginning.  System pressure is set by the primary pressure regulator in the FD?  Is it assembled correctly?  Are all the springs and o-rings in the right places?

I should add, check the shims in the regulator, too, and make sure you put them all back where they belong. 

[SteveDuNord]

Yes I'm also concerned that when I fiddled about with the primary fuel reg, something went wrong. I'm not sure exactly how though as all I did was renew a couple of O rings. Had it back out and everything looked fine.

I didn't end up drilling through the bottom plug to access the adjuster because my plug is indeed a different design to the one in the video, looks more solid. That being said, the allen key bolt that sits on the membrane is there. Either way, I shall be knocking it in the old fashioned way.

Going to be an absolute pain because of the m110 WUR location. 

It's all been rebuilt again and the plugs have been knocked out, fuel cell polished etc. Let's see what tomorrow brings.

[SteveDuNord]

Yet more frustration as I attempted to calibrate the WUR. Jumped the wrong pins on the fuel pump relay, smoke, crackles.

Corrected my mistake, pump running but zero system pressure or control pressure showing on the gauge. Figured it could be down to having removed/reconnected a fuel line, so gave it a minute for the fuel to work around the system. Nada.

After a good minute, I swear the relay started to smoke again. Abandoned experiment!

I couldn't be any more peed off with myself and the car at this juncture!