Bosch timing / dwell / points

[99ctehan]

Okay... stupid question. Where do I check dwell from? I just bought a dwell meter and the directions say that I should use the coil. Haynes says the distributor. Info:

'71 911 Targa
2.2 CDI Ignition with Bosch dist. and points
Zeniths (no longer a pluming fountain of gasoline)

I hooked the leads up to the + side of the coil and dwell read 45 (I know, real high). I hooked it up to the connection on the outside of the distributor above the capacitor and dwell was 38 (right on!) The car sat 10+ years, points were stuck and then unstuck by yours truly. Spark registers 22,000 volts with stock components. The tiiming marks fluctuate +/- 3-4 degrees.

The porsche backfires like a howitzer... It sent a 5 gallon bucket literally flying across the garage. (I had to laugh). Sometimes I get muffler pops, sometimes intake burps (and high throttle fireballs). Any dwell, point, timing hints?
Thanks

[Gogar]

ground it on the ground side of the coil or the fan housing or something/ and then check dwell using the points connection on the outside of the distributor.

Now that you have your dwell right on, you should check your timing. IIRC, at idle it should be around 5ATDC with the vacuum line on, or 5BTDC with it disconnected, and around 35BTDC with the vacuum line off at high rpms after the distributor has fully (mechanically) advanced.

If it's sat for a long time, I wonder if the innards of the distributor are gunked with old grease, thus causing your timing fluctuation. Maybe the pros can help.

[304065]

Ok, NEVER hook anything up to the positive side of the coil with a Bosch CDI system, you will burn it up.

The dwell meter is properly hooked up to the points connection on the side of the distributor.

Make sure the point gap is correct, close enough works. The dwell doesn't much matter the way it does with an older kettering style ignition, because it doesn't charge the coil, it charges the capacitor in the CDI, which then dumps into the coil which acts as a transformer. That's also why you shouldn't hook anything up to it.

There should not be a capacitor on a Bosch CDI equipped car. What is the part number on your distributor?

Search here under "early_s"man" and "bosch cdi" for a wealth of information about this ignition system. Also, get yourself the little white specifications book.

Be very very careful with those Zeniths if they have leaked in the past. Gas is the most hazardous substance most people encounter.

Good luck!