3.2 into 72' chassis issues - need help
 

I have a couple of issues with the retro-fitted 84’ 3.2 into my 72 chassis. The first one is with not knowing for sure if the alternator is charging. The orange light on the dash worked with the old engine, but does not come on now when the key is turned on before starting the engine. I am using a correct (for the 84’ engine year) alternator with internal regulator. When I bought it with the fan and fan housing, the seller said it was working. To add to that prospect, I ran the car for 20-25 minutes yesterday including a short ride around my neighborhood (first outing with new engine) and the battery reflects a full 12 volts on the ohmmeter this morning. Is there any certain (but quick) way to verify the alternator is putting out? The reason I wonder (besides the dash light) is that it cranks over very slowly and does not act like it’s getting enough voltage to start without assistance from the battery charger. I have a new ground strap, but very old starter. It turned over slowly with the old engine too, but would start sooner or later. Also, I am running a little more initial advance than the 5 degrees the book calls for. My old engine had 8.5:1 compression and the new one has 9.8:1, so the compression increase is modest, but my be slowing down the old starter to the point it can’t spin it over fast enough.

The second issue is not as ominous, but a little embarrassing considering I just built this engine pretty much from the case out and should have been able to resolve this already. My tach is not registering (because I haven’t connected it correctly…I do know it works) and I need it to complete the dialing in of the MSD timing computer. MSD sold me a tach adapter for this application (MSD6AL box and 8981 timing computer), but several people I’ve spoken to say this is not necessary and I haven’t opened the adapter package in hopes to return it if I can get the tach to work without it. I have read the Porsche factory service manual wiring diagram, but am unsure on my 72’ which wire in the harness needs to be run to the MSD box. There was (and still is in the engine compartment) a wire that attached to the bottom of the old CDI triggering box. I am wondering if this is the wire I need to connect.

Any help will be appreciated.

Jack McAllister

Jack,

It sounds like your alternator isn't connected to the Blue #61 wire to the dash lamp, and isn't putting out anything! 12 Volts isn't a fully-charged battery ... hence the slow cranking.

You have probably had the 14-pin connectors apart already ... but #61 Blue is present at both connectors -- one pin offset, and depends on the 'multiple' at the old Voltage regulator location for a good connection. You could run a new Blue wire directly from one 14-pin connector to the engine to the other 14-pin connector to the dash wiring ... to eliminate any corrosion or 'loose' connection issue with the old regulator wiring!

As far as the tach wire goes ... the forward 14-pin connector has a Black/Violet wire that goes directly to the tach, and that is the one that needs the signal from the MSD-unit.

Warren,
Thanks...I'll be on it in a little while. I'll keep you posted.

Jack

Re: 3.2 into 72' chassis issues - need help
 

Jack,
For a quick test, first, measure the voltage of your battery without the engine running (which you have already done). Then measure the battery voltage with the engine running. If the alternator is charging you should see a higher voltage with the engine running, on the order of 14.5 volts...definitely in excess of 14 volts.

Well thanks everyone. Warren, I did find the black and violet wire in the forward 14 pin connection. Jumped it straight to the MSD and as you will know, the tach worked perfectly. I looked at the blue wire for the charging light on the dash...it seemed to be a clean connection and I buttoned it back up planning to open up the wiring harness another day. I had pushed the car out of the garage this morning early (too early to risk waking neighbors). But when I got in it to start it to pull it back in, the charging light was working and I put the ohmmeter on the battery and viola! The battery was definitely getting plenty of juice.

Thanks again...Saved by Pelicans once more.

Jack McAllister

Geeez, answer in an hour, fixed by end of day. Nice work :D

Jumped it straight to the MSD and as you will know, the tach worked perfectly.

I really hope that this thread comes up next time people search for MSD tach adaptor. I assume you connected the black purple from a standard '72 tach to the MSD tach output on the end of the unit? No tach adaptor required.

Cam,
Yes...black/purple to the tach output on the 6AL.
Jack