Luis_M

Before dismantling the top side for a planned replacement of lots of old rubber, I was having some trouble during warm-up with my 1981 Euro S. It would start right up, but then die after a few seconds if I didn't keep giving it a little gas, but then it would idle fine again after a couple of minutes. Made me think the AAR might not be open far enough when cold.

I've seen conflicting posts about exactly how far the internal plate is supposed to slide open and closed. Right now, mine is about 1/4 open at 70 degrees, which seems like it's too far shut. Can anyone with a "good" AAR tell me how far open and closed is normal?

Luis
1981 Euro S

Luis_M

Here's a picture of the opening. Measured resistance is 21 ohms. The WSM gives two ranges for acceptable. 24-18 lists 40...75 ohms. Later on 24-118 lists 10...45 ohms in the LH-jet troubleshooting section. This one has the Bosch part # ending in "204"; other cars seem to have "219"; not sure if that makes a difference...

Steve J.

Here's the one from my '78 euro.

Luis_M

Steve J,
Thanks for the pic. Looks about the same as mine. If that was a known good AAR, I guess I'll have to look at the WUR when I put things back together. If you have a chance to measure the resistance across the terminals, please let me know the result. I'll assume yours is stamped "204" based on the year, no?

Luis
81 Euro S 5spd

tailpipe

i have had more luck with adjusting the WUR to cure this prob you will need the guage set to see what its doing usually the presure is to high in the WUR and the mixture is to lean for warm up I modified my WUR but drilling and taping the metal plug on the top and using a screw and nut to bring the plug upward or tapping it with a hammer to adjust it down i think down is richer and up is leaner but you will need guages to see its very touchy make sure there is no crud blocking the screen on the inlet side that may be all thats wrong good luck


Paul

Luis_M

A long over-due follow-up:

The starting issues were due to the fuel system, not the AAR.

During my December 2010 intake refresh, I also cleaned out my WUR which had clogged intake screens, replaced the internal WUR O-ring, removed and thoroughly flushed the fuel distributor (without separating the distributor halves), all the hard fuel lines in the engine bay, the Hot-start valve and the pressure-damper found between the fuel distributor and WUR on my car (not found on all CIS cars) and replaced the fuel injectors with the Mercedes short injectors.

After this, system and control pressures were all in spec and the car now starts immediately and stays running without any issues, cold or hot.

To get back to spec, as measured with a CIS pressure gauge set, I did not have to change the position of the pin in the WUR up or down. As luck would have it, I only needed to clean out the WUR internals and replace the O-ring (which was completely flattened) with a new one of the correct size.

My conclusion is that pics of the size of the opening on my AAR at 70F in my original post are just fine. Note that I did clean the internal AAR passage (without disassembling the AAR) and did verify that the AAR closed fully after a couple of minutes when I applied 12V to the heating element.

jpitman2

Luis, whats size O ring did you use inside the WUR please? Cleaning the filters in there is vital, as is regular use to stop fuel drying and leaving deposits behind!
tks
jp 83 Euro S AT 54k