Hello there,
At the end of my last update I expected to have completed the loom, instruments and the engine start. Miracle of miracles, I have almost achieved this, once again work has interrupted progress (but then again, it does earn money that allows me to build the Brooklands).
The 2CV loom went in pretty easily although I did replace the toy fusebox with something a little "safer". A number of you appear to have made up your own looms but I decided to continue with the loom I had, but to remake all of the connectors with ones of a higher quality. It also allowed me to swap multiple bullet connectors for multi-block ones.
At the same time I also connected in the engine loom, which was fun as there are a number of electronic components that need to be sited close to the engine. Now, the front of the Brooklands is a wasteland of convenient places to put these kind of items, so I had to think a little laterally.
The BMW voltage regulator is bolted to the underside of the top cover, the Ignition Control Unit ( a black box with a large metal heatsink and a seven way flat plug) attached to the engine mount and the coil pack mounts upside down on the underside of the bonnet support strap. Note that the BMW is wasted spark i.e. it sparks both plugs at once, one of which will be at the top of the exhaust stroke so it achieves nothing so you can swap the ignition leads over. Also note the dire warnings in the Haynes manual - you must always be sure that the body of the spark plug is earthed when running any tests.
And then the fun began. I "rang out" the loom (which means I tested each of the circuits with a multi-meter) looking for poor connections which showed no problems. I then connected the battery and lo and behold, the fuel pump sprang into life. Reading this, you will all doubtless be extremely impressed, except that the ignition key was in my pocket! With my razor sharp grasp of all things electrical I deduced that something wasn't quite right………..
It took ages to find the problem. What had happened was that because the alternator is enclosed in the BMW engine, I didn't need the 2CV alternator wires. I am by nature a hoarder, so the thought "I don't need these" was rapidly followed by "but I'll keep them just in case" and I wrapped them into the loom. What I hadn't done first is to isolate the connectors (something I blame on my wife, or the kids, or that chap walking his dog at the end of the street - anyone but myself of course) which created a circuit between +ve and -ve.
Once that was solved we could go for the main event - engine start. I was expecting problems here as there is no overall wiring diagram (except see below). The wiring diagram for the BMW is complicated (no wonder the bikes weigh a ton with all that wire!) and the 2CV one is as much use an…er….unhelpful wiring diagram.
I wasn't getting any sparks at the plugs. This tends to be a problem when starting an engine and holding a lighted match to the spark plug hole didn't seem to work either, so I had to fix it. This is where the complexity of the BMW diagram makes life hard. It turned out I needed to connect a wire to 12V, the problem was that wire ran through three switches on the bike (ignition, stop switch, stand down switch) and you had to visualise switch positions to work out what state the wire should be in.
But after all of this I was able to fill the engine with oil, remove the plugs and turn the engine over on the starter until the oil pressure light extinguished. Removing the plug allows the engine to turn over faster, thus getting oil pressure up, and therefore around the oil galleries, sooner.
Once the plugs were refitted, a bit more cranking and the engine fired up. I mean this literally as I don't yet have the exhausts fitted and a foot long jet of flame flickered out of each exhaust port. Fortunately a friend who was videoing the engine start, is fit and could move quickly…………
As it stands, the car can move under its own steam, I have made up the (full width) dash and fitted most of the instruments. I have the wheels and tyres (more on that next time) so I can't really put off the bodywork any longer. This is the bit I am dreading as any mistake will be very visible. Wish me luck……….
I scratched my head a lot when mating the engine loom to the 2CV loom. So what I have done is made up a wiring diagram of what connects to where to make it easier for anyone else - this set-up works on my car. I haven't included any parts of the loom that aren't connected to the BMW bits, but remember to isolate the 2CV alternator cables (unlike me!).
Konrod Pistonslap .
Konrad had included a wiring diagram to compliment the text, but due to the vagaries of modern technology, I could do nothing with the copy in the time remaining to include it in this issue. I am sure that if people who are building BMW engined Brookland's would like a copy, please contact me and I will arrange thro' Konrad to issue a copy of the diagram. It should be fully sorted by then as well - Algernon
| Previous page | Back to archive index | Next page |