YI think the check valve is most important. It trumps over o-rings. It seems that it is NLA. The pump is very simple, a lot of the time the problem is the check valve, it will pump 'OK'-ish with a cracked disk if it is fully primed. If you run out of fuel then a crack disk will not cut it.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.