Newbie engine cut-out problem

CraigH · 08-27-2004, 05:33 PM

Hello All,

I am a newbie owner. I just bought a 1979 911 SC Targa. It is a fun car (not a daily driver) that is in decent overall shape but definetely a bit of a project. I am excited as I have wanted a 911 as long as I can remember.

Now the bad news. When driving, the engine simply cuts out at various speeds, etc. It definetly is more frequent at low speeds, but happens throughout the gears and rpm levels. The car generally immediately starts back up either via the key or popping the clutch, and most often I dont even need to pull off the road. Obviously it is something I want to fix as soon as possible. In looking through the records I got with car, it seems this has been an issue for a while and the previous owner has had most of the ignition system replaced. I am admittedly an amateur to the 911 engine, but I am still thinking ignition system, most likely the ignition coil. Any thoughts?

I have only driven it once (from pickup to my house), but I did notice an overheat smell right before the engine cut out some of the time. All of the guages showed normal conditions, and the car does not leak any fluids for what its worth.

Any opinions are appreciated.

Craig

930 Guy · 08-27-2004, 06:00 PM

Check the connections to the coil. Pull the cap off the distrib. See if you have much play both in a circle both ways, and tip rotor end to end. had a similar prob. went away after replacing coil, but did a few other things as well. get ready, lots of others will respond with tips to follow.

CraigH · 08-30-2004, 04:05 PM

Thanks for the response 930guy. I did some poking around and do not notice anything obvious. Any other ideas before I just go ahead and get a new coil?

thanks

MetricWrenches · 08-30-2004, 04:10 PM

Quote:

Originally posted by 930 Guy
Check the connections to the coil. Pull the cap off the distrib. See if you have much play both in a circle both ways, and tip rotor end to end. had a similar prob. went away after replacing coil, but did a few other things as well. get ready, lots of others will respond with tips to follow.

Look for a relay under the right front seat. This is called the Lambda relay and due to its location, tends to turn to dust over 25 years.

Hladun · 08-30-2004, 04:30 PM

Quote:

Originally posted by MetricWrenches
Look for a relay under the right front seat. This is called the Lambda relay and due to its location, tends to turn to dust over 25 years.

Don't bother looking, 79's don't have Lambda system. What is happening when engine dies; are you shifting, accelerating or what?

gsxrken · gsxrken's Garage

Craig, welcome to the club. The first thing to learn about porsche ownership is that you'll go broke if you start throwing parts at it without some homework first. There are so many things that could be causing your symptoms that throwing a coil at it is almost amusing. Loose/overaged relays, little green wires on your distributor, faulty CDI box, bad ignition switch, loose grounds, etc. The search functions in the upper right hand of the screen is your best friend here. Generally there is a test for everything. The coil should have certain resistatnce to it across the 2 little posts, and from one of the posts to the center winding. Good luck!

john walker's workshop · 08-30-2004, 04:53 PM

look in the area of the driver's side hood hinge mount on the body, and you will see a 3x3x1 black relay with a white plug on the bottom, bolted to the side of the cowl. unplug the relay and see if that fixes the cut-out problem. it's the over-rev fuel pump cut-off relay. they seem to be going bad a lot after 25 years. also visible thru the gas gauge hole (gauge out of course).

930 Guy · 08-30-2004, 05:02 PM

GSXRKen is spot on. Before you buy a new everything, maybe a local guy could loan a part for testing. Testing, testing, testing is the key. John Walkers advise is always good. I read a post he made on the delayed ign cutoff connection. It fixed one of my problems, and he doesn't even know it. Thanks JW. PM me if you still need sunroof tubes.

MetricWrenches · 08-30-2004, 05:03 PM

Quote:

Originally posted by Hladun
Don't bother looking, 79's don't have Lambda system. What is happening when engine dies; are you shifting, accelerating or what?

Sorry if I made you go looking under the seat there Craig. Hladun is Correctomundo!!!

Thanks for the correction Hladun. I was thinking CIS-E. Thought maybe his Frequency Valve was coming and going.

vash · vash's Garage

your are just driving along and it dies?

are you on the gas? mid shift? coming to a stop? like others have said, start with JW's advice first. you dont know how many times i have just poked my head into my perfectly running car just to see what the hell he is talking about. now let me go and look at the lil black box he is mentioning.

cliff

CraigH · 08-30-2004, 06:22 PM

Thanks for all the suggestions. I will again start checking some things this weekend. There does not seem to be any consistency to the cut-out. It happens at all rpm levels when on the gas or not. The only strange thing is that there is sometimes a slight overheat smell right before the cut-out. Not major like burning parts, but a smell nonetheless. I guess the only other thing I did not mention is that it is a Euro model.

Thanks for the tip about searching for part test methods. I did search the board for similar problems without much luck, but searching for test methods will hopefully help me narrow down any part issues.

tsuter · 08-30-2004, 06:26 PM

Just for kicks I might try turning off the lights, opening the rear deck, and rev the car up and down a bit and look for blue sparks.

And some of you think I'm kidding!!!

Hladun · 08-31-2004, 06:10 AM

Could be your ignition switch overheating. Do you have a million watt stereo you're not telling us about?

konish · 08-31-2004, 07:34 AM

my permatune CDI box would cut out if it got hot. Worked great through the fall and winter. IN the spring, I tried my AC and it manifested itself for the first time as a quick ignition faillure followed by a HUGE backfire. As the summer wore on, it grew progressively worse until I could not drive the car more than about 20 mins before it would die completely...

R/
Dustin

bbt1237 · 09-11-2004, 03:50 AM

Craig,

I have an '83 911SC recently having the same problems EXACTLY as you have described. I puchased it almost 3 years ago and it came with a Permatune already installed. About 2 years ago, the car died in PA and I was forced to have it towed to a dealer who determined the coil was bad. I am now wondering if the coil they supplied(used off an '84) does not meet Permatune specs. Please post any resolutions to your woes and I will do the same.

Bob T.

Mysterytrain · 09-11-2004, 04:43 AM

This is going to ruin your sleep for awhile...I had the same problem with my 78 sc. The car rean well and then would just cut out yet always start back up. Long story short one day it didn't start back up and I needed to be towed home. The distributor seized, sheared the drive gear off and dropped it down onto the intermediate shaft gear where it punched a hole in the case. Have someone take a look at your distributor. The bearings or advance weights may be going bad. I've spent big $$$$ on a rebuild so try to save yourself. I had also replaced, fuel pump, relay, removed the rev limit relay, ignition switch..be careful and don't wait!

Paulporsche · 09-11-2004, 07:24 AM

Besides all the other suggestions, do you have a lot of keys on your fob? Had a friend who wore out his ignition switch from the weight. The inertia of the swinging keys would cut out the ignition.

Also check the circular black plugs under the dash below the steering wheel.

Check connections in the fusebox and grounds.

Spread the pins apart on the fuel pump relay.

Early_S_Man · 09-11-2004, 10:32 AM

Craig,

The ROW SC engines used a rev-limiter rotor rather than a fuel pump cutout relay.

The 'smell' you detect ocassionally may be a good clue that the electrical portion of the ignition switch is failing.

You need to monitor the system Voltage, and see if a Voltage dropout occurs at the same time as the engine stutters. A DMM that logs to a laptop would be a great aid to the troubleshooting.

If it isn't a sytem-wide electrical problem ... you need to move to the engine electrical system. Here is a thread with some general recommendations for cleaning the electrical system connections:

Ignition Troubleshooting??????

The panel on the left sde of the engine compartment is where the CDI unit is mounted, and you can test the pickup coil in the distributor and green coax at the 6-pin connector for the CDI unit. Terminals #7 and #31d should measure 600 Ohms +/- 10% at room temperature. An 'open' ... (no continuity) indicates a problem with the coax, which should be green, not brown or cracked.

This hand-colored wiring diagram isn't correct for your year [or for ROW model] but uses the same CDI unit as ALL SCs ... so CDI wiring portion is relevant: