vaccuum switch for shut-down - PeachParts Mercedes-Benz Forum

ewmROVER · #1 03-29-2007, 04:46 PM

I have to install a vaccuum switch in order to shut down the 616 going in my land rover.

However, I'm not sure of the psi range involved in the mercedes vaccuum system.

What do you think (some switches from McMaster Car)...

Mini Pressure Switches

Repeatability: Not rated
Pressure Sensing Element: Buna-N diaphragm-sealed piston
Single adjustable setpoint with fixed deadband (see table)
Electrical Switch: SPDT, 10 amps at 125/250 VAC
Pressure Connection: 1/8" NPT male, 1/8" BSPP, or 1/8" BSPT brass
Electrical Connection: 1/4" spade
Temperature Range: Ambient and Process: -40° to +250° F
Maximum Pressure: 250 psi
UL listed

Sized just right for tight spots. Please specify pressure connection: NPT male, BSPP (British Standard Pipe Parallel), or BSPT (British Standard Pipe Taper).

Setpoint Range, psi Deadband, psi Each 2-101-23460K11 $19.806-302-43460K13 19.8020-1204-153460K15 19.80

Thanks for any advice on what will work for shut-down.

rrgrassi · #2 03-29-2007, 04:54 PM

Why not use the vacuum pump already on the engine? What ever you use, why not use the same source that feeds your brake booster, making sure the vacuum to the shut off valve is released after the engine stops. Electric is a good way to go also since you will not have to worry about rebuilding it, or catastophic engine damage from a failed pump.

AFAIK the vacuum generated by the engine's vacuum pump is about 20 in/mg. Vacuum is not measured in PSI in this application.

ewmROVER · #3 03-29-2007, 05:09 PM

thanks for the advice rrgrassi.

I'm not too terribly (read: not at all!) knowledgable on the mercedes vaccuum set-up. I took this 616 motor out of a wrecked 240D, leaving everything behind the firewall behind when it got picked up. So, I do not have and am not sure where the "shut-off valve" is. I mean I know what a shut off valve is, but just not the one specific to the mercedes vaccuum set-up.

What I have now is a 616 with a bare fitting on the top of the fuel solenoid shutoff waiting for a vaccuum line to bu plugged on, and a 'tee' off of the main line coming off the vaccuum pump going to the brake booster. I'm not sure how such an electrical switch gets wired up and plumbed up to the vaccuum system. Is there a vac line going in to the switch (from the main booster line), a vac line coming out of the switch (going to the fuel shut off on the IP), and the switch itself having a 12V source?

After not knowing the internal mechanics of the fuel solenoid shut-off on the IP, all in all how do I successfully and simply get to... "making sure the vacuum to the shut off valve is released after the engine stops"

By shut off valve, can that be translated to fuel solenoid shut-ff (as on the back of the IP)? Isn't this vaccuum actuated solenoid shut-off the only thing that actually shuts down the motor by cutting off the fuel supply?

Thansk

rrgrassi · #4 03-29-2007, 05:47 PM

The fuel shut off valve is vacuum/mechanical. Not electrical.

What happens is this. The vacuum pump on the MB 616 is powerd by the engine. It feeds the brake booster, locks, and engine shut off valve. All the vacuum consumers are branched off of the main line that is connected to the brake booster.

The ingition switch aligns the vaccuum ports so that vacuum is pulled to the fuel shut off valve resulting in fuel being cut off. Since this is not hooked up to a vacuum keeper, the vacuum to the cut off valve is bled off since the vacuum pump is no longer working.

Electrically you would need to rig a timer up to shut vacuum pump off after the engine stops. If vacuum is applied to the shutoff valve while the engine is running, it will make it stop. Also, if vacuum is still applied after the engine stops, you will not get it started again until the vacuum is released.

I found that out the hard way by hooking up the cut off valve to the locking system which uses a vacuum keeper.

P.E.Haiges · #5 03-30-2007, 01:31 AM

Rover,

Vacuum can never go above 15 PSI because it is limited by atmospheric pressure. Remember vacuum is atmospheric pressure pushing on the opposide side of the diaphram where the vacuum line is connected.

P E H

TerryS · #6 03-30-2007, 08:33 AM

ewmROVER, The part you show in your first post is a pressure operated micro switch, and not what you want.

There are a couple ways of doing what you need.
One would be to get a manual, lever operated valve, with connections suitable for the tubing size. Operating the lever (or however it is operated, could be a button, but I haven't seen a button operated valve) opens the port, allowing vacuum to go to the fuel pump shutoff valve.

The second way to do it, with the key is to get a 12VDC solenoid operated valve. These are usually NO/NC like a spdt switch. When the key is turned on, the solenoid closes the ports you want to be connected to.
When the key is turned off, the solenoid is de-energized, and the port then opens, allowing engine vacuum to go to the pump shut off.
Connect the vacuum supply to the NO (normally open) port, and the line to the pump to the common port. This will ensure that you're not sucking air when the key is on.

What Landie are you puting the engine in? We're also into them, and are now down to 7 of them. Did you get one of Jim Young's adapters? I'm toying with a 300 turbo into my 109. I'm getting ready to put a 200Tdi into the 88. I love the 4.2 I built too much to change engines in the 110(#103).
Terry
.

ewmROVER · #7 04-01-2007, 08:28 PM

TerryS,

Thanks for the info! I am using one of Jim's adapters to fit a 616 in my 1967 88. After this works out, I'm tooling with the idea of putting a 617 in my dead 1994 5 speed disco. It's just begging for a diesel transplant!

Any leads where to get such a solenoid operated valve? Sounds like exactly what I need. Jim recommended some kind of switch from McMaster Car, and I thought that's what he might be talking about... he's using some kind of switch on his 88 set-up. I'll get with him again and get some more details.

Thanks again

kerry · #8 04-01-2007, 08:48 PM

Why not just hook up a choke style cable to the manual shut off lever?

yellit · #9 04-01-2007, 10:07 PM

It only takes about 4-6 inches of vac to pull the engine shut off on the 240D...

greazmunky · #10 04-01-2007, 10:21 PM

Seems to me there is an electic operated vacuum switch in the W123 series cars.
I think I found it in Fastland parts. It could be key operated to close off vacuum when running and open vacuum to the IP shutoff solenoid when the key (and power) is off.
I'll be using one to keep the engine running until purged in a vegoil system I've installed in my '82 240D.

Jim
San Antonio TX
'82 240D 4sp with proto vegoil system
'83 240D 4sp 86K too nice to experiment with

kerry · #11 04-01-2007, 10:35 PM

Quote:

Originally Posted by greazmunky

Seems to me there is an electic operated vacuum switch in the W123 series cars.
I think I found it in Fastland parts. It could be key operated to close off vacuum when running and open vacuum to the IP shutoff solenoid when the key (and power) is off.
I'll be using one to keep the engine running until purged in a vegoil system I've installed in my '82 240D.

Jim
San Antonio TX
'82 240D 4sp with proto vegoil system
'83 240D 4sp 86K too nice to experiment with

Could that be a switchover valve from the climate control system?

greazmunky · #12 04-02-2007, 10:37 AM

Me thinks so. It's square, electrical connection and three ports which I figure are feed, NC and NO.

Jim

bgkast · #13 04-02-2007, 03:28 PM

The stock valve could work. It is a push button arrangement. I'm not sure if the valve is open or closed when the button is pushed though. I'll check my spare tonight. If the valve is open when the button is pressed you could just mount it under the dash and press it to shut the car off.

Nevermind...pushing closes the valve.

300SD81 · #14 04-02-2007, 05:57 PM

I use a alda switchover valve (new square design) on my remote start alarm, works great, I think its the same as the ones used for the climate control? Not sure on that. Just put it between the vac source and the shutoff, and connect it so that its powered while the key is in.

ewmROVER · #15 04-02-2007, 07:47 PM

Someone has used this great little switch on their similar project with great success...

part # 62475K22 from McMaster Carr (what I was looking for the first time, NOT the mini switch)Hand-Operated Miniature Air Control Valve Spring Return, 3-Way, 1/8" NPT Fem Inlet, Push ButtonIn stock at $16.93 Each

I think I'll go this direction. I stopped at the fitting shop today to inquire about vaccuum tubing at fittings to connect to the valve switch. A couple easy compression fittings and it's all plumbed up. Push button... vac to fuel shut-off.