1971 220D "breathing"

[tointexas]

My 1971 220D did something yesterday that has never happened before. I was stopped, with the clutch pedal pressed to the floor, and noticed that the car was ideling much higher than it ever had. I drove back to the house, and by the time I got home, the car was ideling even higher. Then, when just sitting, the car will rev up and then slow down, rev up slow down--just like it was breathing. What would cause the car to all of a sudden change its idle settings. All of the threaded linkages are in the same place with nothing moved. Could it be the vacuum pump or is it the seals on the pneumatic govenor? Any help will be greatly appreciated.

[pch2021]

todd, i posted under diesle discussions about this symptom. However, read my stuf fin the thread about vacuum pumps, and maybe that will crack the code!

[tointexas]

Pierre:

I pulled the two lines that go to the manifold: the larger line that comes from the pump to the intake manifold had a light coating of oil on the threads, but the one going from the intake manifold to the injection pump had a lot more oil on it. The engine would rev very high, but I found that if I put my finger over the small hole on the air intake side of the mainfold (removed rubber duct work), the car returned to its normal idel and stopped the constant up and down revving that had been going on. Does this still sound like a pump issue or is it the injector pump that is acting up?

[catfish]

i just rebuilt my vacuum pump and it was dead easy. before i didthere was quite a bit of oil in the line out of the pump to the intake manifold. after replacing the vacuum pump's diphragm i no longer see oil in the line.

i'd say it takes about an hour or two to replace the diaphragm and the prices range from $14 to $65 for the parts to do it. it is not too bad. from my understanding, oil in that outgoing line to the manifold means a busted diaphragm. this leads to a wealth of other issues if not fixed promptly.

[pch2021]

toodd...i suggest you do the same. you just descreibed a severe tear in the diaphragm!

[tointexas]

Thanks. The parts will be here Monday. Will let you know what happens.

[catfish]

some of the kits i found didn't supply Lock-Tite for the center allen bolt. i went with the Mercedes kit (a whoppin $45) that included the thread lock, and i am sure they put it in there for a reason. if you want, i can drop the remaining tube in the mail, as postage would be pennies, if you do not get a tube of your own.

[tointexas]

Thanks, Cody. I have lock tite from some of my other repairs of different vehicles. My parts kit arrived today so I should get around to putting it on sometime this weekend. It was very simple to remove, and really, not much to it. I will let you know how it runs afters the rebuild.

[pch2021]

its not a rebuild! (:...but let us know!! (:

[tointexas]

Pierre:

Removed the vacuum pump front section and there is no tear and no oil in the front cover. The parts are to be in on Monday and I will replace the diaphram and the front two check valves. The two check valves seemed to be stuck. Took quite a while to get them to release and allow air through them. Maybe that was where the problem was. I will let you know if I have the same problem after the new parts go in.

[catfish]

i was able to blow air through the two valves very easily with only human power, and not my compressor. and even though my vaccum pump had no evidence of a tear in the diaphragm, after the replacement it is not getting any oil up the pipe to the intake any longer.

[tointexas]

Replaced the diaphram and the check valves and still have the high idle problem. So, I removed the linkage to the tickler shaft and the start/stop cable, removed the govenor cover and the leather diaphram has a hole the size of my pinky at the bottom and several small holes around the edges of the diaphram. So my next question is--how do you change the injection pump diaphram. Any help would be of great assistance.

[pch2021]

OK, ready, Todd? Here we go!

the pump SHOULD BE REMOVED. Have you confirmed that there is a hole in the diaphragm or that it is worn? the diaphragm isa held in by a number of shims, but first, lets remove the pump.

step one: determine your start of delivery! this can be done by rmeoving line number one from the pump, and then turning the engine over by hand [BY HAND!]. Start of delivery should be between 24-27 degrees, on the little pointer on your crank. Leave the engine IN THIS POSITION before removing the pump!

if timing is otherwise, set the engine to 24 degrees, and then remove the pump. 24 degrees IS the factory setting on a 220D!

next, the pump has a retaining bracket on its behind, holding it to the engine block. 2 10mm screws,

remove the primer pump. your life will now be a lot easier.

oh, and make sure that the engine is on its INTAKE cylce when the timing is set, so do it with the valve cover OFF! you dont want the fuel being injected when the exhaust valve opens!

Remove the THREE13MM nuts. the bottom one is quite trickey. a strong 1/4 inch breaker bar, short 13mm socket and 2 swivel joins with 1.25 feet of extension should do it. REMOVE IT FROM UNDER THE CAR!

then, undo the other 2.


when finished, after disconecting all fuel lines [mark the position of the fuel lines on the filter housing] , slide the IP out!

the back of the pup must be rmeoved [you said you did this already]. Now slide the diaphragm backwards by hand. you will need:

a wire hook
a good pair of tweezers
a pair of needle nose pliers, a dial gauge to check for play.

a MB ORIGINAL MUST BE USED! No other diaphragm will work!

draw a sketch to note the position of all the shims that retian the diaphragm. another good tool to ge tis th fit is perfect and flush.

bolt the pump in place. use some spray lithium glue to hold that lower retaining nut in palce and try to screw it on by hand, using the extension, then tighten, but not oo much, as you may have to advance or retard your pump a bit. After ITEMS ARE REATTACHED [i'm assuming you know how to do this] purge the system of air with the vbleeder screw and primerpump, and tighten the two accesible retaining nuts. Then, crank the engine until it runs. purging may tkae a while, but if your timing is correct, it WILL run.

AT 175F, observe how the car runs. White smoke indicates the need for a slight advanc eof 1.5 degrees. There is a large metering nut on the bottom of the pump [19mm]. You may have to adjsut the metering to cut any blakc smoke, if there is any at all. a half turn counter clockwise increases fuel rate. a 1/2 turn clockwise reduces it. be discrepant about adjusting it. Mkae sure, also, that fuel is being delivered right before the numbe rone intkae valve opens. to detemrine this, turning it ove rby hand might be helpful. Anyhow, get it runnign again, and then report back to me!