From early on, we’ve had both warnings and suspicions about our Briggs Magneto.

Only just now am I understanding that the sage advice from several magneto mavens should probably have been heeded.

But hey – “It worked on the original car. Why shouldn’t it work now?” Um… there are a host of reasons why not……. but I didn’t want to hear them. And as the car gets more complete and we deal with the OBVIOUS problems, the less glaring flaws assert themselves.  This happens in small bursts with little revelations as we try our car out on the road. Mind you – we are talking about little drives to test stuff.  One mile, three miles, 5 miles was the longest. In these short drives the car has been running on BATTERY – deriving all electrical power from the battery through a 21st Century standard automobile coil

Modern coil in the firewall mounted BRIGGS switch box

(replacing the resin block of wires in the original firewall mounted wooden box)

Original coil encased in some sort of pink resin and lined with mica insulation material.

and then on to an interruptor set of points in the main magneto housing and from there through the distributor section of the magneto to the spark plugs. If you switch it to MAG. (magneto) from BAT. (battery), the engine coughs, sputters and then dies. It ran rough on magneto for a while, but I wouldn’t call it anything approaching nice and smooth. This is after two visits to the magneto guy in Orange, CA. and spending a fairly significant chunk of change with him as well.  Hmmmmm. That is not how things are supposed to go. Perhaps I should have listened to the early warnings regarding our Briggs mag.

So, when I start the car (or TRY to start the car) we’ve seen the front cover of the distributor portion of the mag try to unscrew itself from the rest of the mag. And on a different occasion, the entire distributor cap portion, including the cover, tried to unscrew itself from its mounting position. This is not a good thing.  Not at all.  This sort of unreliability of the component parts of the ignition system necessitates a ritualistic step by step approach to every attempt to start the car. It’s a fairly long list of ways it wants to misbehave electrically. You must:  check the battery, check the switch, check the wires, check the mag cover, check the mag mounting screws, check this, check that, check the other thing. Check everything but the Czech Republic. Um…… as a fancier of horseless carriages, we enjoy the simplicity of these early cars………. up to a point (or a set of points – which, of course, should also be checked.) Oh, and the unscrewing itself trick — this happens while the machine is running.  Performance deteriorates quickly into non-operational stasis.   Bricked. Kaput. Tow it home. BAD MAGNETO — BAD!

So– I’m going to do what I understand most owners of Michigan cars have done over the years. Retire the Briggs and install a Bosch. Yes, that Bosch – makers of home appliances, power tools, modern car electrics, medical devices and probably a host of things I can’t think of right now. Anyway, Bosch has been making automobile ignition systems since about 1897…..and Bosch ignitions have been keeping autos going ever since.  RELIABLY. In the early horseless carriage days, many ignition brands came and went. Eisemann, K-W, Splitdorf, National, Mea, Simms, Heinze, Pittsfield, Kingston, Remy, Herz, Duplex, Connecticut, No-Lag, U & H, and the list goes on. About the only brands that have survived are Bosch and Remy (Delco-Remy).

So I acquired a Bosch magneto setup. For this car, which needs to be able to be started on battery if I am ever to attempt to get the acetylene starter to function, the choice was a period correct Bosch DU-4 DUAL Ignition. “Dual” in the case of this particular version of the Bosch DU-4,  means both a self sufficient magneto (not requiring a battery) AND a separate battery based ignition. Two separate switching positions and two separate sets of interrupter points. The BRIGGS magneto that came with our car was intended to be used this way – but appears to have only one set of points. Generally speaking, you start on battery (requiring MUCH less hand cranking effort) and once the car is running, you flip the switch to magneto – which does not draw down the battery.

My “new” Bosch Dual Ignition magneto and switch. Both somewhat encrusted with 110 year old loveliness.

With the two Bosch components in hand, (magneto and its separate dash mounted switch-coil)  the cleanup began to get them working together as they were intended. The original documentation helped – but proved to be lacking in troubleshooting suggestions. At least ones that I could recognize and deal with.

The full manual is attached below. Click on the description.

Bosch DUAL Coil Manual DU4 & ZR4, click on blue wording to open – it is a BIG file.

Two separate sets of points.

As of the date of this writing, May 18, 2022, my bench testing shows the MAG. side of the ignition works as it should. The BAT. (battery) side does not. So – I may need some expert assistance to get this all working.  With the BRIGGS, only BAT. works. With the BOSCH only the MAG. works.  To know how this feels, play the recording, below.

BUT WAIT!  Good news. For the next several days I went through the entire wiring setup AGAIN. I consulted the fellow that I bought the magneto from. I queried other horseless carriage owners. During such consultations, I was advised to change the wire leads on terminals 3 & 4 from 12 gauge wire to spark plug wire (high voltage insulated).  That was nice and stopped some arcing at the back of the switch – but still no sparks at the plugs when switched to “battery”.  Hmmmmmm.

Testing the Bosch magneto and switch

Better check all the connections again and clean the contacts everywhere. Including both sets of points (interrupters). Lets just check the gap on the interrupter for the battery setup.  It looks like it’s opening and closing but maybe not.  Let’s adjust it open a bit more.  ZAP!  We’ve got SPARK!

PROBLEM SOLVED!  The Bosch DU-4 Dual Ignition works as advertised. This is very good news, indeed.