Shut off valve - Page 2 - PeachParts Mercedes-Benz Forum

Diesel911 · #1 07-27-2021, 12:29 PM

Quote:

Originally Posted by NZScott

I see this thread has a bit of a terminology problem...
Some reason many people on this forum have "shutoff valve" on the injection pump...
Leads to confusing threads like this (or was it just me...)

So just to clarify, the shutoff valve ("vacuum switch") is on the ignition. The governor has the shut off actuator which the shut off valve controls...

So what I'm reading the issue as, is a leak between the shutoff valve and the shutoff actuator on the engine.

Some sources also call this a servo.

See pelican parts ad in the attached picture.

dsvw · #2 08-07-2021, 05:07 PM

OK, had some time to mess with this today.

The car was sitting for a couple of years before I got hold of it and many of the issues I am working through are attributed to non use.

1. I have determined that the vacuum shut off valve is good. When I apply vacuum to it, the car shuts down immediately. It also holds vacuum.

2. I applied a vacuum gauge to the other side of the line going into the firewall from the shut off valve to the ignition lock vacuum valve and got zero vacuum. I only just realized that the vacuum is actually actuated when you turn off the ignition. That makes perfect sense to me now. When I turn off the ignition, it will come up to a healthy vacuum.

3. The shut off issue seems to be getting better as I drive it but it will occasionally take too much time to shut off.
I have put 200 miles on it since I started to sort it out. All new fluids, filters, belt, diesel purge, etc.

4. My vacuum pump is putting out good vacuum and I have tested all of the lines, even replacing some of them. All locks, trunk work great.

5. Car starts with a bump of the key but does anyone have any idea why I may still be having a shut down issue?

Thanks for the help.

BillGrissom · #3 08-14-2021, 02:52 AM

I know that you can't swap the 2 brown tubes in the engine bay. One is a vacuum source to the key switch and the other goes to the shutdown solenoid (valve). The switch is like an SPDT electrical switch with the tube to the shutdown the "pole". The switch connects it to either full vacuum or the atmosphere. The later is just a bleed at the switch.

If you swapped the tubes, the switch would apply vacuum to the switch when you turn the key to OFF, but would never vent it. If it held vacuum well, you could never start the engine since would always be in the "shutdown" condition. But, you have a different problem. Most likely there is a flow restrictions in the tubing or the switch itself to cause the long delay.