Newbie(mechanical) Questions

daepp · 07-20-2006, 06:45 AM

I need to check the points gap on my 72 2.4. This produces the following questions:

1) How do you remove the air intake (horn) from the engine (it contains a flapper)? Is it removed from behind?

2) I can hardly see the points. By removing #1 above do you gain better access?

3) Should I be able to "see" the points opening with the naked eye. I have rotated the engine several times, but I can neither see them opening nor have I been able to insert a .014" feeler guage. Or am I missing something here?

This work was necessitated when my recently rebuilt engine died instantly last weekend while I was going about 20 mph. I think the neg. ground strap on my battery came a little loose. When I wiggled it, every thing began to work again, but now I have no spark. I pulled a plug wire loose and held it near the chassis while my son cranked the engine, but there was no spark whatsoever. I believe the problem is in the CDI as it is not buzzing (however I have never heard it buzz) but I was advised to check the point nonetheless. The dizzy is new and recently set-up, but I still wanted to check it out before getting the new CDI.

And advise?

daepp · 07-20-2006, 07:26 AM

Anyone?

BK911 · BK911's Garage

I wouldn't worry about the points until you verify the cd box operation. Check to see if you're getting 12V's to the cd box. Also verify the ground at the box. There's a m/f connection on the red wire feeding the box. Connect a voltmeter there and to the groundstrap. Turn on the ignition. If you get 12v's, clean ALL connections see if the box humms. If no 12v's try a different ground. If you get 12v's with a different ground, there's your problem. Clean the ground and try again. If it's a stock cd box it should hum with 12v's.

daepp · 07-20-2006, 08:15 AM

Good advise, I am sure. However, the CD was working fine before all went dead simultaneously.

BK911 · BK911's Garage

I've never seen a stock CD box work that didn't humm. If it were my car, it's the first thing I would check. I've been down that road MANY times.

Rot 911 · 07-20-2006, 08:36 AM

Quote:

Originally posted by daepp
However, the CD was working fine before all went dead simultaneously.

Hmmm, perhaps the CD went bad?

Like BK said, check the CD box first. If it is a stock Bosch box it should buzz or hum.

ruf-porsche · ruf-porsche's Garage

If you can't see a gap when the point is at the highest lobe, than you not gonna start the engine. When the points open, it signal the cd box to shoot a charge to the spark plugs.

JGalt · 07-20-2006, 04:49 PM

There are three bolts (10mm head) on the left side near the #1 intake pipe. Remove those bolts, loosen the hose clamp on the hot air hose on the bottom and remove the flapper. Now you can look at the distributor.

Early_S_Man · 07-21-2006, 03:02 AM

daepp,

I suggest reading the following threads:

distributor lube...

72 911 T all the sudden no spark

Perma-tune CD or Bosch CD?

History of Bosch CDI ... toubleshooting info, parts list changes, and schematics ...

Quicksilver · 07-21-2006, 06:42 AM

Quote:

Originally posted by daepp
Good advise, I am sure. However, the CD was working fine before all went dead simultaneously.

Things always work fine right up until the point where they break.

Check the CD. Does it hum?

daepp · 07-21-2006, 07:47 AM

Well, I replaced the CDI with a borrowed, known-to-be-good unit, and the car fired up IMMEDIATLEY.

Lessons learned:

1) Check and double check all ground straps on your 911. The evidently are very prone to malfunction with poor grounds, esp. after 34 years.

2) If you lose the battery ground while the engine is running, you very clearly run the risk of losing your CDI.

3) New ground straps are available from our host and even the dealerships for a reasonable price.

4) I don't think I could own a 34 year old complex sportscar like mine if not for this BBS.

Thanks everyone.

David

daepp · 07-21-2006, 07:56 AM

One finaly question: When you service the CDI, does everyone remove the entire "motherboard" of electronics in the left rear wheel well? Since the nuts holding the CDI are not captive, I can't see any other way to hold them when reinstalling the CDI.

daepp · 07-21-2006, 11:17 AM

Now that I've gotten my fingernails dirty, I'm curious - do all of you have sets of allen style sockets? If so, what's the most useful size drive and range of sockets?

ruf-porsche · ruf-porsche's Garage

Quote:

Originally posted by daepp
Well, I replaced the CDI with a borrowed, known-to-be-good unit, and the car fired up IMMEDIATLEY.

Lessons learned:

4) I don't think I could own a 34 year old complex sportscar like mine if not for this BBS.

Thanks everyone.

David

Your Porsche isn't that comples. It has a points
that trigger the Capacitive discharge system. The new car that is control by a chip is a lot more complex.

Eagledriver · 07-21-2006, 07:57 PM

You should still set the points. As the block on the points wears against the cam, the gap gets smaller and smaller. Eventually the points will not open and you'll be stuck on the side of the road.

-Andy

Paulporsche · 07-22-2006, 08:15 AM

The best way to set the points is w/ a dwell meter. Then you can set the gap more precisely, and even allow for the fact that the rub block wears down over time, decreasing the gap and increasing the dwell angle. Make sure to grease the rub block to make it last longer. I like to set new points @ 35 or 36 degrees. Then, when the wear down to 42, replace them. If you search you will see info on this.