W116.org

koan, are you saying you can get gasket sealant in a spray can?  Damn that must be useful. 

Well, this is an interesting topic, right up my alley. 

I'm not sure about the variance of the o-ring for the base of the fuel distributors. I have not seen any reference of come across any variation on the round profile single o-ring, even on the W126s.

Nutz, are you sure it's not just that a round profile o-ring has swolen and taken the form of a square profile ring over time? If this is not the case, then my apologies and I stand to be corrected.

Could someone kingly enlighten me on this difference, ie. with a picture of some sort.

The o-rings inside the unit are easily to work with, as the hold thier position without trouble.

A very interesting point is that there is NO gasket material used from the factory. It is merely a very tight tolerance between the machining of the halves and the metal diaphragm sheet between. I can't imagine that it would even leak after a tear down and rebuild, so I would prefer not to use the gasket material if possible.

Tim

Example I dug up, but of course shallower.

Gee, that does indeed look like a square cross section. 

Yes, do a search for Hylomar and see it in cans. Expensive and a can doesn't go very far - but maybe I put too much on.

koan

Well I talked to Larry Fletcher at CIS Flow Tech. The guy is full of knowledge! He said he would only trust 2 other guys in the world to rebuild these besides himself. Some guy in England and another in Australia. I inquired about the Australian guy for everyone here that is down under. Here is the information he gave me.

Peter Bower
bowerpower@bigpond.com
Bower Power Auto Tech in Sydney
phone 61294530035

He also said I probably do not have a bad fuel distributor but wants my mechanic to check my air flow sensor plate rest postion and sent me the following pdf.

sensor plate

Did some internet digging

Bower Power Auto Tech
3B Cook Street, Forestville NSW 2087
T 02 9453 0035
F 02 9453 0038
bowerpowerautotech@bigpond.com

Thankyou for going to the trouble of providing that address Zedster.

Bill

Larry also pointed out to me that my sensor plate zero position was too high. I measured it and it was 3.5 mm too high and the tolerance is only .5 mm. I adjusted it and it made a big difference. If you think through how the system works if the sensor plate zero or rest position is off your entire air/fuel is going to be off through the range. You can adjust the idle CO and control pressures all you want and the engine will still be too lean or too rich in places.

How do I know this? I replaced everything in the fuel system except the air metering housing and throttle plate but the car still didn't run right. I've know about that throttle plate spec and adjustment for a long time but I did not really understand the criticality until Larry stressed it to me.

WUR stands for Warm Up Regulator which is a misnomer. It controls your air fuel mixture throughout the range and can be thought of as the brains of your CIS system although it is crude by modern standards. It also manages the warm up cycle but that is actually a small part of what it does. It's my personal belief that the vast majority of Mercedes CIS systems are not setup and calibrated correctly.

Just the 6.9's have the WUR right?

All K-Jetronic cars have a WUR or Control Pressure Regulator. It is the "roughly box-shaped" device with two fuel lines, an electrical connector and two vacuum connections terminating at it. It is positioned at the front of the engine on the RHS, relative to the driver.

Tim

Mine have K Jet? 79 450SEL

K-Jetronic rest position is a visual adjustment and what I've read about it from practical sources it isn't all that critical. If it is a fraction high, provided it pulls down when cranked hot (high control pressure) it's not a problem. if the plate is too low though, it does need correcting.

I can't agree with your analysis of the effects of sensor plate rest position. Provided it pulls down as described above it will be OK.

What difference does it make where the sensor plate is with engine off?

koan

Is suppose this is heading towards an off topic debate, but I have not read anywhere about the rest position, only ensuring that the plate is centralised.

Actually, I originally thought that the mixture screw adjusted the rest position, but was told otherwise.

Perhaps it's time I pulled apart an airflow meter to sus it out.

Despite what some people have said, the plate will always deflect downwards with the engine running, even when idling.

The square section o-ring is interesting. I have no idea what fuel distributor that would fit.

Tim