I believe DuBois requested his page be removed from jag-lovers, but he may not have been the originator of the scheme, it may have come from the vintage MG folks, who passed it on to the Classic Jaguar Association in 1989.
There have been a few updates over the years, and the latest version available from Burlen has a printed circuit board and eliminates the points.
I have done about 12 of these in this manner.
In my pictures the brown blobs are RTV sealant covering solder joints.
Parts you need:
one transistor…for negative ground get a TIP 32 PNP
…for positive ground get a TIP 31 NPN
one diode = 200V 1A microminiature type 1N4003…same for either ground (or an alternative diode 1N4002 can be used)
one resistor = 1 K Ohm
one resistor = 100 Ohm
one capacitor = .1 uF
First disconnect the one coil wire from the blade contact point small fixing screw, and remove the capacitor if yours has one. The pump in my 1950 Mark V didn’t, so it really arced something fierce. The other coil wire is your 12V input, and stays as is.
The transistor has a mounting tab, which I drilled out to fit on one of the two existing large mounting screws for the bakelite bridge. Use either one you like, since you won’t be reinstalling the old capacitor.
Note the transistor has an emitter, a base, and a collector. Regardless of whether you are doing a PNP for negative ground or an NPN for positive ground, the connections are the same.
The collector is also the mounting tab, which is thus grounded to the coil body, as is the wire from the flipover contact points.
The base terminal is soldered to a wire, which connects to the small screw which holds the blade contacts.
The emitter is soldered to the coil wire that was removed from the small screw above.
The 1000 Ohm resistor is soldered to connect the input wire and the base.
The 100 Ohm resistor and .1 mf capacitor are soldered in series connecting the base terminal and ground.
Now for the diode: For both positive and negative ground the diode is soldered between the emitter-to-coil joint and the input terminal, but in opposite directions. The forward direction looks like an arrow running into a wall.
For positive ground (earth): the diode forward direction is from the negative input terminal to the emitter.
For negative ground: the diode forward direction is from the emitter to the positive input terminal.
Be sure to ream out the hole in the mounting tab on the transistor big enough so the screw head will not damage the transistor before cutting off the excess. I found it easier to put spade connectors on the screws and then soldering the wires to the connectors in place, rather than trying to solder to loose connectors or wrap wires around screws. All the capacitors and resistors come with wire ends way too long. Stick them through the connectors with the excess hanging out, solder, then cut off the excess. For soldering to the transistor terminals, load a bit of solder on the terminal and the wire end separately first, then touch them together and its a quick job to solder them together. The center collector pin terminal is not used so I break it off completely.
For joining the capacitor and resistor, twist the ends fairly close together, solder the joint, then cut off the long excess. One of the wires coming up from the coil is too short, so you have to add an extension wire to it to reach over to the transistor. A lot of this job is figuring out how to do it with only two hands, and the rest is packaging, figuring out how to fit it all inside the cap without any crossed wires. Insulate any potential short circuits with a dab of RTV and let it dry before closing it up. I always make a paper label to stick on the outside of the pump, indicating whether it is positive or negative ground.
The result is a pump that rattles away with not a bit of visible arcing and sparking at the points. An added bonus for those who care is the mod is completely hidden from concours judges by the plastic cap.
Piece of cake, right?