(85 300D) Checked Threads: Still Confused About No Shutoff - PeachParts Mercedes-Benz Forum

rbc · #1 08-01-2012, 05:17 PM

Got an 85 300D (CA version). My guess is someone is going to clear this up easily. Here is the deal ...

Car is not shutting off. There is some engine oil dripping from ignition cylinder. Cylinder is 1 year old (teeth broke; I replaced whole thing).

I put a MityVac on the shutoff valve. Pumped and the car shut off. However, it seemed to need a couple good pumps AND the pump sucked ample amounts of engine oil.

I have reviewed multiple threads but cannot seem to nail this one. Vac trigger of shutoff valve seems to suggest it's vac, not valve. But the valve seems to need to be sucked real hard and the engine oil has me thrown off. I forgot to check how much vac was needed to trigger valve.

Last thing: when it started to not shut off, it happened intermittantly, definitely worse when hot and humid. I know this subject is well covered (hat in hand), but if anyone has an idea I am all ears. Thanks in advance.

Diesel911 · #2 08-01-2012, 05:43 PM

Quote:

Originally Posted by rbc

Got an 85 300D (CA version). My guess is someone is going to clear this up easily. Here is the deal ...

Car is not shutting off. There is some engine oil dripping from ignition cylinder. Cylinder is 1 year old (teeth broke; I replaced whole thing).

I put a MityVac on the shutoff valve. Pumped and the car shut off. However, it seemed to need a couple good pumps AND the pump sucked ample amounts of engine oil.

I have reviewed multiple threads but cannot seem to nail this one. Vac trigger of shutoff valve seems to suggest it's vac, not valve. But the valve seems to need to be sucked real hard and the engine oil has me thrown off. I forgot to check how much vac was needed to trigger valve.

Last thing: when it started to not shut off, it happened intermittantly, definitely worse when hot and humid. I know this subject is well covered (hat in hand), but if anyone has an idea I am all ears. Thanks in advance.

It is not so hard once you break it down and you think about the direction of the vacuum flow (if there is such a thing).

On the very end of the Vacuum Flow for the shutoff system is the Vacuum Shutoff/Valve/Servo. It is the only component of the shutoff system that is exposed to the Engine Oil; the side of the Shutoff Valve Diaphragm that faces the inside of the Fuel Injection Pump Governor (the Fuel Injection Pump is lubricated by the Engine Oil by way of a Plastic tube).

So there must be a significant hole or holes in the Vacuum Shutoff Valve diaphragm to allow that much Oil into the System.

From the Vacuum Shutoff Valve (by way of a Brown Tubing) on the Fuel Injection Pump the Vacuum Flow goes to another Vacuum Shutoff Valve on the Steering Colum. That is likely where the Oil is leaking from.

From that Valve another Brown Tubing (may have a green stripe on it) connects to one of the Rubber Connectors under the Hood that intern connects to the Main Vacuum Line and on back to the Vacuum Pump.

So due to the large amount of Oil getting into the Vacuum System you for sure need to replace the Vacuum Shutoff Valve that is on the Fuel Injection Pump.

The Vacuum Shutoff Valve on the Steering Colum may also need to be replaced.

While you are at it you also should check the Vacuum At the Vacuum Pump itself.

Diesel911 · #3 08-01-2012, 05:48 PM

If you replace the Shutoff Valve you need to be extremely carefull. If you get the Hook on it in the wrong place your Engine will run away; that mean it will shoot up to like 5000 rpm lke right now.

Govert · #4 08-01-2012, 05:55 PM

If you suck oil from the shut-off valve, the valve is leaking. The fact that it works sometimes and with the mityvac would indicate that the leak is small at this stage.

rbc · #5 08-01-2012, 06:07 PM

Thanks guys. It does not work sometimes anymore. And there was a small amount of engine oil in the vac lines when I changed the ignition cylinder last summer. But now it simply does not shut off and the oil is plentiful.

charmalu · #6 08-02-2012, 03:49 AM

Here is how to install the vacuum shutoff valve as posted by "Thegears"

Vacuum Shut off device & pics

Charlie

rbc · #7 08-31-2012, 05:07 PM

ok. finally getting to this. I have the shutoff valve out of the car. But the guidance here suggests the old valve has a metal ring on it and the gaskets go on either side of that. problem is, my old valve seems to just have one gasket seated between it and the housing. the old "reassemble as it was assembled when you took it off" trick is not working. any thoughts?

CONFIRMED. With regard to the valve I just took off, there is the IP housing, gasket, then shut off valve. The old gasket looks just like the new gaskets I just bought. No metal ring or anything. Is the metal ring another vintage? Dont want to do this wrong.