IP control rod/shutoff link-need help!
 

I have checked the operation of the vacuum shutoff on my 82 300SD(617.951). I can pull 24" vacuum on it and it holds for hours. It develops quite a force. I know that the hooked end engages the control rod inside, and I can get it there pretty easily. What I can't do is get it to move the external linkage. I sure don't want the experience that Larry Bible so graciously shared about having the engine runaway. With the shutoff loose against the IP and vacuum on, I can still have it hooked on what I think must be the control rod inside and move that rod back against a spring force that it is held by. I can do the same with the shutoff removed and reaching my finger in and hooking it. It does not move the stop lever on the external linkage down against the valve cover. Should it really? The functional diagrams in the FSM show that the vacuum shutoff can pull back on the CONTROL ROD, but not necessarily all of the linkage I've read conflicting info on this. Can any of you shed some light on this?:confused:

BTW, when I had the other engine in the car, I had the shutoff out once, and it was the same way. I put it in just making sure it hooked the control rod, and it always worked OK

The vacuum shutoff device does not always move the external linkage. It depends on the year and model of the pump - some do and some don't. My 240D is one that doesn't.

If you're confident that it is hooked in correctly, then go ahead and start. Have a 17mm wrench handy (in your hand!) to loosen the nuts on the injector lines in case it runs away.

Yes, and then share the results with us afterwards, good or bad.

If you follow Ricks advice including the wrench in hand, worst case you will have a little adrenlin rush while you're loosening the injector lines.

Let us know and good luck,

Thanks guys, I'll be sure to let you know what happens!

oops, talk about slow on the draw! Well, what I finally determined is that the shutoff does not move the external linkage, but does move the control rack that meters the fuel. Do your best to be positive that the shutoff engages properly and be ready with wrenches just in case. Mine was OK, but boy, was I ready in case it wasn't!

why should one be ready with a wrench? and what is meant by runaway?

runaway
 

a diesel will keep running as long as it gets fuel and air - your MB has a vacuum line to shut off fuel inside the Injector Pump thus killing the engine (no electricity needed). If you can't shut off the engine with the external linkage and don't want to wait for it to run out of fuel, an alternative is loosening the injector lines with a 17mm wrench thus cutting the fuel supply.

john

The engine might not last long enough to run out of fuel. An improperly installed shut-off valve can cause out-of-control fuel delivery. Engine rpm can not be controlled.

I want to add to this post since I just replaced my IP (injection pump) shutoff valve.

This information is for a 617 motor, I have a 82 300TD.

If the shutoff valve is not properly installed the shutoff rack in the IP is not controlled and this situation will allow a runaway engine upon startup. ( A runaway is when full fuels is provided to the cylinders, like full throttle, and the engine will accelerate to its maximum RPM with no control of the IP. So the engine will run at max RPM until it fails.

Talking to two of the more experienced mechanics at the local dealer as well as reading the posts here I want to make the following post and pointers for the job.

When purchasing the injection pump shutoff valve, make sure you purchase 2 gaskets. One for either side of the shutoff valve washer.
Also consider the following
New vacuum lines and connectors, if old.
Mounts for the air cleaner, since you will remove it for a safety test.
Rubber hose for the Turbo, broke mine it was so old and hard and your there.
Inline filters for the vacuum system to look for oil.
Vacuum pump rebuild kit, if lots of oil in the tube to the pump
Ignition key shutoff valve is oil in there too.


The Valve

http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1S91C0VJ61S91C126B&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1982&product=D2020-11537&application=000004567

The Gasket

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1S91C0VJ61S91C126B&year=1982&make=MB&model=300-TDT-001&category=D&part=Shut+Off+Valve+Gasket

Take a picture of all your vacuum connections,3 ways and 4 ways, it makes it easier to install them when you know where they go. You will have to remove some of the vacuum lines for the job.

I removed the fuel lines to each injector. It made access to the rear of the IP easier.

I also removed the IP vacuum control valve by unbolting the 2 bolts and disconnecting the ball socket at the lower arm of the IP. Don't want to break this, it expensive.

The Vacuum control valve

http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1S91C0VJ61S91C126B&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1982&product=D2032-15990&application=000004530

To remove the shutoff valve there are 4 bolts holding a square bracket on. I used a combination of a close box end ratchet, a 1/4 drive ratchet and a normal closed box end wrench. Its a tight squeeze on the 617, more room on the 616. Unbolt the 4 bolts and to remove the unit. I found the only avenue usable, due to its size, was to move it along the block towards the rear of the engine, between the oil filter housing and the block. On the 616 this is not a problem.

Once you have the unit out, don't push on the lever, If you had an oil leak it will squirt the oil out through the small hole. It goes everywhere.

Clean the washer and mounting surface on the IP block Install the 2 new gaskets on either side of the washer, install the washer on the shutoff valve and slide it along the block to position it in the hole. Now install the clamping base over the shutoff valve to position it. The sharp edge goes towards the IP block

Installing it correctly---- the 90 degree bend in the shaft goes towards the engine block. The vacuum hose hole is on the top. Here is a good way to insure that it is connected correctly. Sweep the lever from the drivers fender towards the block as you are seating the base of the valve onto the IP block. To check to see if it is correctly attached to the rack, use your Mityvac ( you should have a Mityvac if you own a Mercedes diesel) to apply vacuum to the shutoff valve. Once you apply the vacuum, try to pull back on the shutoff valve and see it if will separate form the IP block. If it does not then you have installed it correctly, if it does, then try it again. LEAVE the mityvac applied to the shutoff valve, it will hold the valve in position. Install your 4 bolts. The bolts have sealant on the treads due to the oil in the IP.

Now for a couple of tests to see if it working before you install everything you took off.

Since the IP lines are removed form the IP pump to the injectors you can crank the motor and not much can happen (won't start). I used a Plexiglas shield over the top of the IP output and had the wife crank the engine with both the shutoff valve in the off position ( Mityvac with vacuum applied) and the on position. In the on position the outlets will spit at you. Very low volume but high pressure. The shield helps. When off the amount was decreased by about 80%, Not completely off, but reduced. Try this test just in case you have to reinstall it. It's a pain with everything reinstalled.

Reassemble everything and remove the air intake and 180degree tube from the air filter to the turbo input. Have a piece of wood that you can place over the turbo inlet to shut off the engine, just in case you messed up the installation and might have a runaway engine. Also have a 17 MM wrench available to loosen the Injector lines if the board will not shut it down completely. The board will control the RPM due to lack of air, but a complete shutdown may only be achieved by the loosening of the injector lines. ( not sure about this theory, my installation was correct so I did not have to test it. But with the board over the intake the engine RPM will be low or 0)

Another approach I had. when ready to test the engine, apply vacuum to the shutoff valve. Have your wife/friend/etc start the engine (don't forget the glow cycle). With the vacuum applied it should not start, If it does your standing right next to the turbo. Apply the board and if that does not shut it down then loosen the Injector lines. Doing it this way your attacking the engine at a low RPM and stopping the air right away not while it at 6000RPM.

After the test above start the engine without the vacuum applied. It should run normally since it did not start and run away on the previous test.

Additional notes.

The correct wrench is helpful with the injector lines ( of course I used a regular open end wrench, I will order one of these).

This wrench, scroll down to H4550

http://www.peachparts.com/diy/mb_tools/mb_tools.php

Make sure you run the engine to make sure the injector lines are not leaking. If your rough on the injector overflow rubber lines, they may leak. If you have lots of rubber then try cutting new ends, if not then replace them.


This job was not as bad as I had made it out to be in my mind. Using the Mityvac to make sure the unit has made the correct connection allows you to do this job without worrying about a runaway engine. I would do it again without a second thought.

If the valve has leaked oil into the system you will need to disconnect the lines at various point to see how far it has progressed. If it got into the vacuum pump, the manual recommends rebuilding it, the same for the booster and all the other components. Determine how much oil has progressed through the system and figure out what you want to do.

Dave

PS
When you install the valve correctly, the "STOP" lever wil not move while applying vacuum to the shutoff valve. Moving the "STOP" lever to test the installation is not a valid test. I move the lever with both vacuum applied and not applied and could tell no difference in the action of the STOP lever. This applies to the 617in the 82 300TD.

Runaway engine!
 

Man I wish I had seen your posts before I replaced my vacuum control unit. I only had one or two gaskets and did install it twice as the first time it would still not shut the engine off and the old unit would not hold vacuum. When I installed it the 2nd time, I did have resistance pulling and pushing the connecting rod on the unit before I bolted it back...though I didn't run any further vacuum tests. The bad news, when I started it, the engine ran full blast until out of desperation, I loosened the injector line to a cylinder and it shut down. At the time I didn't actually know to do this, just did this out shear terror. Not sure if the engine blew before it ran out of fuel.

I guess if the vacuum unit control rod is not attached to IP control rod, it allows the IP rod to move further into the pump releasing the fuel? Or is there a possibilty that my incorrect vacuum lines caused the runaway engine?

Until I saw your posts, I suspected the vacuum lines were not reinstalled correctly and, in fact, I believe I failed to reconnect the top line on the vacuum control valve on top of the IP that goes to the transmission...now I can't find that line.

The white plastic locking clip attaching the linkage to the lever on the vacuum control valve has also broken, and as a result, that linkage was not connected upon examination after my the runaway experience.

I am afraid to restart until I recheck the vacuum control unit and verify my vacuum lines. Can't seem to find a good schematic matching my engine that accurately reflects the correct vacuum line connections, and not sure how to determine whether the engine is blown on my 1981 300SD (has no ALDA) before stupid waste any more time.

Any suggestions would be appreciated.

Bob Brown
San Antonio, TX
wk> 210 208-6629
hm>210-497-7717