03-12-2008, 04:55 PM
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Join Date: Sep 2007
Location: Long Beach,CA
Posts: 58,609
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Quote:
Originally Posted by nhdoc
Does anyone really know what the function of the copper crush washer is? It appears to me that it doesn't really get crushed, so calling it a crush washer may be incorrect. It seems more to act as a "bearing" surface between the spring and the DV plunger part. I've always questioned the necessity of replacing the washer since, as I said, it never gets crushed and don't think it will even wear out. I don't even see it pictured in that drawing in post #1 of this thread. I wonder what would happen if it was left out completely?
I always assumed it allowed the plunger piece to rotate if it wanted to since having it be between the bottom of the spring and the top of the plunger allows the plunger to slide against the washer instead of the bottom of the spring - where it could get snagged on the end of the spring wire or the spring itself could wear into the top of the plunger piece if they were in constant contact with one another. I'd love to know if someone actually knows the exact purpose of that copper washer in there.
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(Please see FIG-11 only)-The purpose of the Copper Crush washer is to provide a seal between the top of the Delivery Valve Support-item 5 and the Pressure Valve Holder- item 1. The Copper Crush washer is exposed to the same pressure as the injectors and in fact it is possible for the high pressure to erode the crush washer.
The reason the Crush Washers need to be changed is that in order form a seal the copper compresses conforming to any irregularities between the Pressure Valve Holder and the top of the Delivery Valve Support. Ounce used the Crush Washer is in a sense deformed to fit; and also when squashed down during the torque procedure the Crush Washer becomes work hardened and is no longer as soft as before (meaning if you use it again it may not seal well).
Also I believe that the Crush Washers are some stiffer alloy that is not as soft to begin with as stay the copper washers on your fuel filter banjos. (If you heat these red hot and let them cool they become soft again and can be reused.)
Back to the picture- There are the words “Lapped Surface” with 2 lines pointing to where the lapped surface is. Below that parting line is where the Plunger and Barrel Assembly; the plunger part of this is the part that rotates.
Also the Lapped Surface area if lapped properly dose not need any sort of seal do to a precision fit between the bottom of the Delivery Valve Support and the top of the Plunger and Barrel.
Item number 3 the Delivery Valve Cone; the part that we call the delivery valve dose not rotate it just goes up and down.
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84 300D, 82 Volvo 244Gl Diesel
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