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Ignition Pump Shut Off Valve Replacement
 
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Pelican Technical Article:

Ignition Pump Shut Off Valve Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$175

Talent:

**

Tools:

5mm Allen, 10mm socket

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Valve

Hot Tip:

Make sure it is connected correctly

Performance Gain:

Motor shuts off

Complementary Modification:

Diesel Purge

If you are new to diesels engines you should be aware of the fact that they do not run or shut off like a regular gas motor. There are no spark plugs or throttle body as diesel motor speed is controlled by the amount of fuel going into the motor. Unlike a gasoline powered engine that needs spark to run and can be turned off by discontinuing the spark, a diesel motor runs on the compressed air and fuel self-igniting. The only way to stop a diesel motor is to shut off its supply of oxygen or fuel and in extreme cases you can get a "run-away" motor which can be extremely dangerous and destructive. If you own an older diesel engine vehicle please see our article on run-away diesel engines just so you have this information.

The W123 diesel motors are shut off by discontinuing the flow of fuel from the pump and this is controlled by a vacuum injector pump shut off valve. The valve attaches to a shut off lever in the injector pump and when activated cuts off the supply of fuel. If your motor is starting to have a hard time shutting off you should check vacuum pressure and/or replace this valve right way as even though this valve's failure will not cause a run-away motor, it can cause the motor to not shut off. If the engine starts to run away, DO NOT PUT YOUR HAND OVER THE INLET OF THE TURBO. It can suck in your fingers and chew them up by the spinning blades. 

You will be working with diesel fuel so make sure to take the appropriate precautions including working in a well ventilated area, no smoking and wear eye and hand protection.

Over the years your car may have been serviced by multiple people including previous owners and this can lead to parts replaced with different size fasteners and hardware. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches. If something is different on your vehicle please let us know and share your info to help other users. If you have any questions or comments or even a different procedure you would like to share please leave it below and please include your vehicle information.

The shut off valve is located on the rear of the injector pump under the transmission switch over valve (red arrow).
Figure 1

The shut off valve is located on the rear of the injector pump under the transmission switch over valve (red arrow).

You are going to have to move and disconnect several vacuum lines to get access to the valve so make sure to take plenty of pictures and label everything as you go.
Figure 2

You are going to have to move and disconnect several vacuum lines to get access to the valve so make sure to take plenty of pictures and label everything as you go.

Disconnect the vacuum lines to the transmission switch over valve (red arrows) and then use a 5mm Allen to remove the two bolts (yellow arrows) from the switch over valve and set it off to the side.
Figure 3

Disconnect the vacuum lines to the transmission switch over valve (red arrows) and then use a 5mm Allen to remove the two bolts (yellow arrows) from the switch over valve and set it off to the side. The upper yellow points to a lever. On the right side is a round rod that comes up from below that connects to it. 

There is a plastic clip that can break from age, Think it is NLA.

The lower end of the round rod has a ball socket that can be popped off. But as with most of these linkage ball and sockets, they have not been lubed over the years. (I usually try to remove the rod along with the VCV.) 

Use a 1/4 inch drive and remove the four bolts holding the shut off valve and plate to the rear of the pump.
Figure 4

Use a 1/4 inch drive and remove the four bolts holding the shut off valve and plate to the rear of the pump. It is a tight fit but you will be able to work it out if you take your time (red arrow). You may want to get in there with a set of long needle nose pliers to compress the arm if you are having trouble getting clearance to remove the valve. (To remove the shut off valve, I find it is easiest to lay across the engine. I use to use a 1/4" Ratchet and 10mm Socket. But the handle is a bit short to get good leverage.) Removing the 4 bolts on the top cover of the IP will allow you to see exactly where the lever fits in the Pump. Then the new valve lever can be positioned in the right place. 

There are two gaskets and a metal ring that need to be installed on the valve.
Figure 5

There are two gaskets and a metal ring that need to be installed on the valve. The gaskets will go on both side of the ring and you need to reuse the metal ring that was on the old valve so don't throw it away (red arrow). There is a notch in the ring and gaskets and a raised portion on the valve that will be seated in the notch in the bottom of the pump; this insures that the arm of the valve is installed in the correct position (yellow arrow). Installation is the reverse of removal. If you have done it correctly everything will be fine, if you have installed it incorrectly you can cause a run-away motor because the valve can force the pump into the wide open full fuel position. If you are worried get a plastic cap from a spray can of paint and remove the turbo air boot, if the motor starts to run-away place the cap over the inlet on the turbo and this will instantly rob the motor of oxygen, if you don't have a turbo remove the air cleaner and use a piece of wood or cookie sheet to place over the intake manifold--this will starve the motor of oxygen.

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Comments and Suggestions:
charmalu Comments: You may want to make a notation that if the engine starts to run away, DO NOT PUT YOUR HAND OVER THE INLET OF THE TURBO. It can suck in your fingers and chew them up by the spinning blades.
Even the large spray can lids come in various sizes. Make sure the lid fits before starting the project.

Picture #3. the upper yellow points to a lever. On the right side is a round rod that comes up from below that connects to it.
There is a plastic clip that can break from age, Think it is NLA. The lower end of the round rod has a ball socket that can be popped off. But as with most of these linkage ball and sockets, they have not been lubed over the years.

I usually try to remove the rod along with the VCV.

You should make a notation to be careful with the large black plastic vacuum line between the VP and Brake Booster. There is one or two small plastic nipple vac lines plug into. They can be broken off very easily. That line is around $50.

To remove the shut off valve, I find it is easiest to lay across the engine. I use to use a 1/4" Ratchet and 10mm Socket. But the handle is a bit short to get good leverage.
I find this HF 1/4 3/8" double Ratchet works best. it is longer.

http://www.harborfreight.com/14-in-38-in-drive-dual-head-ratchet-67993.html

I use my left hand to hold the Socket on the bolt head. and right to lever the ratchet.

Removing the 4 bolts on the top cover of the IP will allow you to see exactly where the lever fits in the Pump. Then the new valve lever can be positioned in the right place.

Of course, clean off the pump area first so dirt will not fall into the pump.

I have removed over 30 of these in the yards. PNP.
Point the nipple away from you, push in the lever, place finger over nipple. If it holds, its good.
Pointing nipple towards your body, you could get squirted by black engine oil if the diaphragm is compromised.
I had one squirt oil 5 ft.
If you use a Mity-Vac to check one. Use a piece of clear tubing, this way you will se oil coming up the tube and not get it in your MV.

This is just some things I learned, hope it helps.



April 5, 2016
  Followup from the Pelican Staff: Sent your comments to the author for review. Thanks again for taking the time to review and comment on the articles. Much appreciated. - Nick at Pelican Parts  

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