W113 Pagoda SL Group > Drive train, fuel, suspension, steering & brakes
WRD and cold idle
wwheeler:
You bring up a good point about screw and nut on the WRD. Since that rod acts directly on the air valve, it would change both the air and fuel. When you change the length of the rod, it alters the timing of the WRD, or in other words, when it shuts off at a certain engine temperature. Later thermo bulbs that do not have this adjustment, use small round shims on top of the piston. That is what I have.
The only mixture adjustment available on the WRD that I know of, is the oval shims. I just can't think of anything else that would make the mixture more rich only during the engine warm up phase. All the other mixture altering devices are primarily when the engine is cranking or they affect at all temps. You state that when you changed the number of oval shims, there is no effect on the mixture. I guess that sounds like we are fishing in the wrong pond. Maybe ignition is at fault? I am afraid this is beyond my knowledge level and the big guns need to step in.
Benz Dr.:
Please note: the 7 - 8 mm I stated in an earlier post is just a guess on my part and it could be more or less than that amount. 1.1 mm on the earlier IP is an accurate amount and everyone should be safe following that.
Keep in mind that your ignition system will be challenged during warm up. If something is amiss you will likely see more problems during that phase of the warm up cycle.
If you remove a spark plug and carefully inspect it you should look at the ground electrode and the center tip. If the very end of either, or both, have a small clean area it's a sign of low voltage going to the spark plug. In an over rich environment the spark will only ignite some of the fuel and a lot will exit as black smoke. Low voltage only makes this condition worse.
Inspect all of your high tension wires and replace anything that has carbon core. I also remove all resistors from the system leaving only 1 K ohm spark plug terminals. Your ignition system has to be in perfect working condition before you look at fuel systems.
FresnoBob:
I'm sorry if I gave the impression that the oval shims had no effect. The car clearly ran worse the more shims were installed. What seems a bit strange is the large amount of air going through the WRD air filter. With the filter removed, there is clearly a lot of air sucking through the 20 mm opening.
I have new copper spark plug wires and I've tried various sets of spark plugs. My wires are:
http://www.karlynsti.com/Folders/Karlyn_STI_Ignition_Wire_Sets.htm
I agree that ignition issues could be causing a weak system to not operate well when cold. My points are less than a year old and I haven't changed any ignition adjustments since the car ran well (but never cold).
I'm going to adjust the valves as I haven't done this yet and have no idea as to their gaps.
Cees Klumper:
The number/combined thickness of the shims only affect the length of time that the WRD enrichens the mixture, but not the degree of richness, I believe. If that's correct, then adding or taking out shims does not affect how rich or lean the engine runs during warm-up.
wwheeler:
Cees, I think you are referring to the small round shims that are stacked on the air valve in the WRD. Those in effect change the length of the thermo bulb rod by moving both the air valve piston and the rod below the piston that changes the fuel in the IP. That does change the timing when it shuts off.
The larger oval shims we are referring to are for the WRD housing and only moves the rod that changes the fuel in the IP. So those oval shims should alter the cold mixture.
Navigation
[0] Message Index
[*] Previous page
Go to full version