This is the vacuum pump. Since it was out already, we might as well test it. Red = +12v; black = ground. One pin is for the motor, the other is for a check valve. This pump works, on the bench, at least.
1995 Range Rover Classic Mini-Overhaul
We're getting down to the fine details now! Is there a 100% working Range Rover Classic still on the road? Is that even possible to attain? I'm not sure, but we're going to try to get close, at least...
Cruise Control
Also like pretty much every other Range Rover Classic, the cruise control in this one is INOP. That's unfortunate. The first order of business is to replace ALL of the vacuum hoses. The worst one is actually the vacuum pump hose. The vacuum pump is buried in the cubby hole underneath the horn. Disregard the manual's instruction to remove the air box - that is not necessary. Simply remove the horn and you can fetch the pump out.
If wholesale vacuum hose replacement is not the cure, it's time to start debugging the system. Many people seem to just replace the ECU, but there are many components involved. The 1995 RRC Electrical Troubleshooting Manual has a whole section on the cruise control (they must have known that it would break). And that section is MUCH more informative than ramblings and summaries found elsewhere on the Internet. Read the manual, skip the Internet commentary.
The cruise control ECU (as well as other relays and the engine ECU) reside behind the glove box. Lift the springs on the side up and the glovebox will lower beyond the fully-open position, dumping the contents on the floor.
That's the cruise control ECU. Take the plug off, get a multimeter, get some spare wire and pins, grab a copy of the Electrical Troubleshooting Manual, and dive in! The pin order is printed on the side of the ECU.