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1971 220D
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3 Posts
Discussion Starter #1
My high mileage 71 220D surges at idle when cold (idles fast then slow) & will smooth out when warm but the surge will carry to a higher rpm once warm. (about 1400 rpm) There is no surge once the motor is under a loaded condition. Has anyone experienced this or have any ideas as to what it could be? The car runs fine otherwise, not the fastest thing in the world but guaranteed to get you there. Gas mileage is 24mpg. I've cleaned/adjusted throttle cable, linkage, intake & choke all to no avail. Any help is appreciated, Thanks.
 

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2001 Volvo V40
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2,954 Posts
The vacuum chamber of the governor of the pump is leaky. This will cause this sawing of the engine. Leaks can occur because of:

- leaky diaphragm
- leak around the axle of the poppet cam
- leak of the connection of the vacuum tube
- leak of the gasket between poppet and governor housing

Usually it is the axle, but a diaphragm is also possible.

Read about the working of the governor in the FSM:
07.1 Diesel Injection System - OM616
there 07-010 section A
 

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1971 220D
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3 Posts
Discussion Starter #3
Thanks Govert. It looks like I can get a re-build kit for around $35us. Is this a hard/skilled job? I've re-built many carburators in my time just never a diesel component.
 

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2001 Volvo V40
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2,954 Posts
Replacing the poppet cam house (picture below, 15 is the poppet cam) is easy enough, just use a new gasket and watch for stuff falling out.

Replacing the diaphragm is more complicated, you need a micrometer and it is difficult to connect the diaphragm to the control rod of the pump.

 
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