IP lubrication is supplied by engine, no lube oil is needed unless the
pump is removed.

Lambach's post:

Doesn't  apply to Randall's car.

There were 3 types of injector pumps for the diesels in those years.

1. M - with pneumatic governor

2. M/RSF and MW - both with a mechanical governor.

The M-injection pump had a separate oil lubrication system that was
supposed to be serviced at regular intervals.

The other two drew their oil from the engine block.

One way to tell the difference between the M-type and the other two was
that, when you viewed the back of the M-type pump, the bottom of the back
of the pump that faced the firewall was round. The sides of the back end
of the other two types of pumps were straight and parallel with the
corners beveled or rounded off at the  bottom.

For the '75 diesels here are the numbers:

For engine numbers 615.912/913/916 the pump was M-type => 240D's up to 1977

For engine number 617.910 it was MW-type => the '75 300D

Your's is probably an M-type. It has it's own oil and uses the same type
of oil as your engine (although my mechanic put in synthetic oil when he
rebuilt the injector pump).

As you face the injection pump from the driver's side of the car, the
you'll see a check plug on the side of the injection pump housing a little
less than an inch to the right of the manual delivery pump. Unscrew it and
notice what happens when you do. If nothing comes out, the pump's low on
oil. Add oil until it comes up to the check bore.

It's not unusual for fuel to end up in the pump. So more typically,
instead of nothing coming out, you'll notice a fuel/oil mixture coming out
when you unscrew the plug.

There is no drain plug for the pump so I aspirated the oil out of it
whenever it came to changing it's oil (If I recall correctly, the
recommended way was to back off the bolts on the back plate and let the
oil run out. Far too messy and potentially problematical for me).

As far as amount is concerned, I just added oil until it came up to the
check bore. It's less than a quart - probably a lot less.

Sorry I can't be more exact but I think you have enough to work with.

Have fun.

ron

P.S. Randall also later said:

There is no way you can actually see the oil by looking "inside the pump".
It sits at the bottom of the pump and there is a lot of things between the
two of you. Take a thin piece of stiff wire with white insulation and slip
it down the oil port and you'll find it down there - if it's there.