1977 911s - Time to replace coil? Anything else?

[szyzygy]

recently my car cut off while driving on PCH. Lost all power. had it towed to local shop where they fixed the coil wire connection.
I noticed tonight that the connector area is cracked; please see attached picture.


Do I need to replace this? If so, I see a genuine porsche part on here for $300 something vs a Bosche part for $95 IIRC. Please tell me why I shouldn't buy the cheaper part.

Is there anything else I should check with my car as well? Is the coil issue part of a bigger problem?

I wonder why the coil part got broken. Seems like it's not a part that would break like that. It's not like it moves around or anything.

Thanks.

[Dave Colangelo]

There are a few reason why it could have cracked. As you can see it is mounted on the fan shroud so it does see a good deal of vibration from the engine. Something people tend to not realize is that these coils are filled with oil. That being said extreme temperature can cause the oil to heat up and expand which could have caused the crack. Chances are this is not related to anything but an old coil. The plastic simply could have heated up and become brittle and cracked I see no reason not to buy the cheaper Bosch part unless you desire to keep the car all Porsche original. Bosch designed many of the ignition systems for may Porsche's so I would trust there parts for these cars. If it were between a Porsche genuine and a chinesium knock off I would say Porsche, but in this case Bosch is reputable company and I would have no issue with there stuff.

If it is a vibration issue you may want to consider a piece of thin rubber around the coil in side the ring that holds it to the shroud. This will help reduce vibration and should hold it just as well.

Regards
Dave

[szyzygy]

Originally Posted by Dave Colangelo

There are a few reason why it could have cracked. As you can see it is mounted on the fan shroud so it does see a good deal of vibration from the engine. Something people tend to not realize is that these coils are filled with oil. That being said extreme temperature can cause the oil to heat up and expand which could have caused the crack. Chances are this is not related to anything but an old coil. The plastic simply could have heated up and become brittle and cracked I see no reason not to buy the cheaper Bosch part unless you desire to keep the car all Porsche original. Bosch designed many of the ignition systems for may Porsche's so I would trust there parts for these cars. If it were between a Porsche genuine and a chinesium knock off I would say Porsche, but in this case Bosch is reputable company and I would have no issue with there stuff.

If it is a vibration issue you may want to consider a piece of thin rubber around the coil in side the ring that holds it to the shroud. This will help reduce vibration and should hold it just as well.

Regards
Dave

Thanks

I will go for the Bosche part.

This seems like a simple switch out job - am I being overly optimistic?

I like the rubber snuggie idea.

What about the coil boot I see as well for sale here? It appears mine doesn't have that. DO I need one? What does it do?

[szyzygy]

can I just superglue it back together?

[Dave Colangelo]

The coil is very easy to switch, just remove the 2 leads and the main out put wire which just pulls off. Then remove the one bolt that holds that ring on, the coil will come out of the ring, pop the new one in, put all the wires back and you are done. The job should not take more than 20 min at most. The boot looks to be a rubber cover for the connections. I dont have one on my car either, I would not say you need it but by any means, many cars I have seen dont have them. It could serve to keep a spark from accidentally jumping off the leads and grounding to the fan shroud but i doubt that will ever happen. IMO it will most likely be one of those rubber things that gets in the way and always falls out of place. However for 5$ it may be worth a shot just to keep things all capped up and clean.

I would not super glue the coil back together. The oil in the coil is put there when it is made and sealed in, air bubbles can effect the performance and function of the coil. Basically there are 2 winds of wire in there, an outer wind that has many wraps, and in inner wind that has fewer wraps. This is how the spark is transformed from 12V to around 1000V However this is also controlled by the dielectric medium between the winds air and oil have very different properties thus if the oil were to leak out and be replaced with air the coil would not function as it should. The most automotive electronics are relatively safe to play with as a 12 volt spark is usually not dangerous, that being said with enough current 12V can and will kill but the fuses on car electronics usually blow quite fast and the worst you get is a nasty shock. The coil puts out very high voltage and a good deal of current, it can hurt you quite a great deal so I would not try and quick fix it, replacing it is the thing to do.

Regards
Dave

[szyzygy]

Thanks Dave, I just ordered the Bosche part from the site sponsor. It'll be here Tuesday, ground shipping.

[szyzygy]

So glad I took the time today to inspect my engine. Visual inspection saves $$$$

[Dave Colangelo]

If this is the first time you are looking at your engine/ the car is new to you, you may also want to replace the distributor cap, rotor, spark plugs, wires, air filter, fuel filter, and oil filter, fan belt (dont forget the shims) and shifter bushings. All these jobs can be done by the home mechanic and will cost under 100$ in total if done by your self. They will in turn make a huge difference in the performance and operation of the car. If you dont have it the 101 projects for your 911 book written by the guy that owns this site, get it, its a great book, as is the haynes manual or the bently, they are good for reference when it comes to things like nut torques etc.

Regards
Dave

[szyzygy]

Originally Posted by Dave Colangelo

If this is the first time you are looking at your engine/ the car is new to you, you may also want to replace the distributor cap, rotor, spark plugs, wires, air filter, fuel filter, and oil filter, fan belt (dont forget the shims) and shifter bushings. All these jobs can be done by the home mechanic and will cost under 100$ in total if done by your self. They will in turn make a huge difference in the performance and operation of the car. If you dont have it the 101 projects for your 911 book written by the guy that owns this site, get it, its a great book, as is the haynes manual or the bently, they are good for reference when it comes to things like nut torques etc.

Regards
Dave

No, I look under the hood at least once a week. I'm a car newb but have been studying hard. I just got the carr 3 months ago.
I have the Haynes book already. Good stuff.
I already replaced the fan belt and shims because they broke on me while driving. I fixed it myself thanks to this website and the members. Cost about $15 for the parts.
I would like to check the spark plugs because they can tell you alot about engine problems if you know the symptoms.
Given that the oil in the car was terrible when I bought it, I'd like to change the spark plugs.
The wires and distributor look ok upon initial inspection.

[Dave Colangelo]

The plugs on these cars can be such a hassle but it is with out a doubt worth it. I had a terrible miss fire that I was worried was something major. 15$ and some choice words as well as a good selection of socket extensions later I had the new plugs in and the problem was solved.

[szyzygy]

Originally Posted by Dave Colangelo

The plugs on these cars can be such a hassle but it is with out a doubt worth it. I had a terrible miss fire that I was worried was something major. 15$ and some choice words as well as a good selection of socket extensions later I had the new plugs in and the problem was solved.

The passenger side plugs seem easy to get to, drivers side looks like a challenge.

[szyzygy]

Mission accomplished. Got the new part and put it on in about 45min.

Another benefit: the car started right up on the first try, without giving it gas. Rarely does this happen.
It still idled very low, about 400-800rpm. I'll check the fuel mixture setting this weekend. If you guys think of anything else I should check, please let me know.

I love living so close to pelicanparts.

Thanks everyone!

[Dave Colangelo]

The idle can also be adjusted on the throttle mechanistic its self. I have not explored that system specifically but there should be a set screw in there some where. If your engine runs fine otherwise I would not play with the mixture. The set screw should allow you to adjust the idle it may take some plying with but you will be able to get it.

Regards
Dave

[szyzygy]

Originally Posted by Dave Colangelo

The idle can also be adjusted on the throttle mechanistic its self. I have not explored that system specifically but there should be a set screw in there some where. If your engine runs fine otherwise I would not play with the mixture. The set screw should allow you to adjust the idle it may take some plying with but you will be able to get it.

Regards
Dave

ok, the set screw....I will mess with it.

[Dave Colangelo]

If im not mistaken the 77 had CIS

Pelican Technical Article: Tuning and Adjusting CIS Fuel Injection - 911 (1974-83) - 930 Turbo (1975-89)

figure one shows the screw I think you are looking for

Regards
Dave

[szyzygy]

Originally Posted by Dave Colangelo

If im not mistaken the 77 had CIS

Pelican Technical Article: Tuning and Adjusting CIS Fuel Injection - 911 (1974-83) - 930 Turbo (1975-89)

figure one shows the screw I think you are looking for

Regards
Dave

Thanks, Dave!

wrt to fig 1, could you narrow down the location of that area in my engine compartment please?

[Dave Colangelo]

not totally sure as I have never adjusted this screw but logically it should be either some where on the injection mechanism (the thing with the 6 hoses coming out of it on the passenger side) or somewhere behind the air box. taking the air box cover off would be a good place to start and frees up a lot of access to that area. Dont worry about running the engine with out it, just make sure to leave the air filter in place.

regards
Dave