Dennis Wilson

Jon,

The later Mercedes did run without accumulators. Actually, all CIS with O2 sensors have frequency valves which dampen any pressure fluccuations better than the accumulator. Concerning the accumulator holding pressure, since it's capacity is less than 75 ml, that function is best left to the check valve at the pump and the relief valve on the distributor. Actually, considering that they are prone to leak with age, the accumulators are more of a liability than an asset.

Dennis

checkmate1996

Ok. To continue the saga...

I have not received the gauges yet but I have visually confirmed that the accumulator is not leaking or seaping fluid externally. It appears to be completely dry.

I have also confirmed that by pressing on the gas pedal fully, after three igntiion starts with a cold engine, it will kick over rather consistenly.

It also runs great right away, no stumbling.

So are we starting to lean toward cold start, or can the fuel accumulator leak internally?

Optimator

Brad,

From your description of the problem so far, it doesn't really sound like an accumulator problem to me. However, you can verify the leakdown after your gauge and book arrive. The first thing I would check would be the cold start injector. It is relatively easy to access. Also, a malfunction here would fit the description of your problem. The control pressure regulator (WUR) is also a possible cause. It is a simple procedure to check it with the gauge.

To answer your question on the accumulator: There are two types of accumulators used on the early cars. One type has a third hose connection that is a leakage line that directs leakage back to the tank. This type would not neccessarily show any external signs of leakage.The other type simply vents the back side to the diaphram to atmosphere, so a significant leak would show up after running the car for awhile.

jpitman2

My 83 accumulator had NO vent, just a hole at the top plugged with a screw. On removal the screw was wet with fuel, indicating diaphragm failure....replacement cured the warm start problem for me, but YMMV.
jp 83 Euro S AT 50k

checkmate1996

Dumb Question Alert!

Just to be clear, the thermotine (coolant Sensort) switch sits right behind the WUR on the waterbridge. Correct?

If this is correct , I am getting nada!

Please confirm!!!

Optimator

That sounds right. It's located directly under the WUR. Is there no evidence of it switching? IIRC, you have to make sure your test leads are connected right on the first try, otherwise you will have to wait for the switch to cool off again before testing.

jpitman2

Brad, What does 'nada at the thermotime' mean ? Ignition on, one lead should have 12V on it, and when cold, IIRC, it should come out and go to the cold start injector. If this is the three wire , testing is a bit more complicated. DO a search on posts on this by Wally P, I have been here before myself when looking for a similar problem.
jp 83 Euro S AT 50k

hupp

Brad,

The sensor on the top of the bridge, behind the WUR, is the sender for the temp gauge on the dash (wrong thing to check). The thermo-time switch is located on the front, passanger side of the bridge, tucked in by the coolant hoses. You will notice one of the square bosch connectors plugged onto it.

Dennis Wilson

A test light can be used for initial test on the thermotime switch. When cold the test light should show a circuit between the two posts (connector removed). If that shows a circuit then check each post to ground. If either shows a crcuit to ground or no circuit between the two posts the switch is bad.

Dennis

checkmate1996

Guys,

GREAT INPUT! I really appreciate it.

So, based on the embedded diagram, 22A is the correct switch.

hupp

22A is the one! A small amount of coolant will flow out if you remove it for some reason.

checkmate1996

Ok. Quick update:

The good: Switch is operating fine. I tested per Dennis' instructions and everything checks out.
The bad: The electrical connector that goes over the switch is NOT showing any resistance as like the other connectors are. So now what? Fuse? Crack in the wiring harness? Any alternatives?

checkmate1996

So my guess is that, if now power is getting to the switch, the switch obviously doesn't work, of which doesn't kick off the cold start valve. Correct?

jpitman2

Sounds right to me. Here is where I would use a networking type cable tracer - isolate which wire at the switch should have +12V on it, inject a tracing tone on it, and follow the tone with the tracer sensor until it stops somewhere it shouldnt, or it reaches the fuseboard, and there is a problem there. Its a real PITA trying to test this sort of thing with a DVM and long bits of wire all over the car...DIsconnect battery earth please.
jp 83 Euro S AT 50k

Optimator

Resistance? Did you mean to say voltage? I'm not sure that a resistance measurement would tell you anything conclusive. Do you have a copy of the wiring diagram? Take a look to see how the thermoswitch and the injector are connected. Looks to me like with the plug disconnected from the switch, you should be getting voltage between ground and either of the 2 wire terminals when cranking. What are you using - a DMM, analog meter, or test light? With any of these, you should at least get a clear indication of voltage at one of the connector terminals when cranking (terminal "G" on the diagram).