Primer Pump location on 1975 300d?

Just picked up a W115 300d which should translate into more orders for MercedesSource! Where is the primer pump on the 75 car? Does not appear to have one?

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Diesel Engine Specific Aid

Chassis Model Number

W115

Located on inlet to main fuel filter.

Look for black plastic knob. Those 300Ds did not have them on injection pump. You will note no room down there to reach. Don't be surprised if previous owner removed it. Kent

Re: W115 300d primer pump

So if removed, I assume I fill secondary filter and prime via lift pump? Or add electric pump by tank or? Were these troublesome which is why they were removed by some owners? Do you sell a replacement pump for my '75? Thanks!