My SC just died...

cashflyer · 04-07-2006, 12:45 PM

Well, I drove the 911 to work today. It ran fine getting here, but not so much now.

It started just fine, and I backed out of my spot. I placed it in 1st and started cruising across the parking lot and ... it just quit. And will not refire.

I can hear the fuel pump running as usual, and the starter spins like a champ - but no "vroom-vroom".

My wife is on her way down here to help trouble-shoot (one person to crank, the other to check items in the engine bay) and to give me a lift if needed.

I will check the usual no-vroom items, like coil output and fuel flow. But I wanted to see if anyone here had any "check this first" advice.

Thanks

btw: car is a 1978 911sc, with CIS.

curlesw · curlesw's Garage

A rookie guess...pop-off value? This happened to me once and the pop-off value had come off. But a loud backfire occured as well.

Good luck

v/r
Wayne C.

cashflyer · 04-07-2006, 01:09 PM

No backfire at all, but that was one of the first things I did check. Pulled the filter off and checked to make sure that the PoV was properly seated.

Thanks. Hopefully some others will chime in.

Harvey

AFJuvat · 04-07-2006, 01:18 PM

Is the sensor plate bound up?

Does the sensor plate move with some resistance (implying good fuel pressure)

Got an extra spark plug about so you can see if you have spark? (always a good glove box addition)

Fuel pump fuse, fuel pump relay.

all I can think of at the moment..

AFJ

tcar · 04-07-2006, 01:30 PM

My 79 SC did the same thing. Drove it into the garage, next morning, cranked till hell won't have it. No fire.

PO valve fine, fuel pump fine-smelled gas after cranking.

Anyway, 27 year old ignition module failed. Just had MSD installed.

johnnyo · 04-07-2006, 01:30 PM

DME relay?

aigel · aigel's Garage

Must be ignition. Check for spark. Install spare module - you have one in the trunk, right?

George

cashflyer · 04-07-2006, 01:49 PM

Okay, some checking has been done now and here are the results:
Fule pump fuse and relay are good. Fule pump is running. I am going to open a line and check for flow, but have no real way to check for pressure...

My next task it to check for spark.

DME relay?? What and where is it??

Thanks again.

At least being stuck in the parking lot doesn't suck as bad as being stuck on the side of the road.

scottb · 04-07-2006, 01:51 PM

Don't quote me on this, but I don't think the SC has a DME relay. The first year the cars had them was 1984, in the Carrera (I think).

slodave · slodave's Garage

SC's do not have the DME or relay. Don't bother looking.

cashflyer · 04-07-2006, 02:00 PM

Okay... the problem must be that the DME is completely missing...

Fuel flow is good.

Spark, not so good. In fact, I have no spark.

Now, I have to admit that I know NOTHING about trouble shooting the ignition module. Any suggestions?

aigel · aigel's Garage

Your ignition module is in the LH side of the engine compartment. It is either a Bosch or Permatune (aftermarket). My bet is that it died and that you will need to replace it. There isn't much else you can do. It helps to have a spare or have a friend that will lend you his for troubleshooting.

George

tcar · 04-07-2006, 02:30 PM

Yep, that's often it when it just dies.

I've heard Permatune does not have a good reliability record. Opted for MSD.

aigel · aigel's Garage

My permatune has held up for 5 years now. (knock on wood). I heard the same - that they are not very reliable. I should get a spare for long trips ...

G

cashflyer · 04-07-2006, 02:51 PM

My SC has Bosch.

I have a junk 1970 that has a Permatune unit on it. Would this be a direct swap in?

Also, is the MSD a direct swap in?

Thanks again.

Grady Clay · 04-07-2006, 03:12 PM

OK, so there is no spark. Do you have a 12V test light?
I have a ’78 Factory wiring diagram in front of me.

There are several possibilities:
1) the CDI may not be getting power for some reason.
Does it normally make noise “sing”? Is it now?

2) The CDI could have failed internally (not “sing” dependent).

3) An electrical connection in the system decided to be on
the failed side of intermittent. That is good because you
can find it. Every device needs good connections for power
supply, intermediate, and grounds.

4) The connection at the distributor is always suspected.
Carefully reposition the wires going into the distributor.
I suppose there could be a problem with the distributor
magnetic sensor but I understand that would be unusual.

5) Always keep your eyes open on the fuel issue. Don’t
flood the engine raising the sensor plate too much.

Now for a plan.

If you don’t (can’t) get an indication that the CDI is working,
take a test light and check the #15 connection to the CDI
has 12V power with the key in the “ON” position and the
“Start” position. The number is marked on the 6-pin connector.

The connection at the distributor (red arrow) apparently
commonly suffers a failure in the wires at this point. If
so, a slight repositioning if the cable might get you a
temporary connection.
IMG IgnDist78b.jpg "

"
© Dr. Ing h.c. F. Porsche A.G.

If the above don’t solve the problem, swapping in a known
good CDI is usually the next step. No, the 3-pin earlier CDI
isn’t a direct exchange.

Let me know how I can help.

Best,
Grady

Superman · 04-07-2006, 03:43 PM

Grady is offering good advice. Again. If you determine that the CDI box is getting voltage at Terminal 15 and you still have no spark, then you can crank the engine and see if the Hall Sender is doing its job. Configure your test meter to recognize a really really wimpy signal....find the terminals on the square plug that attaches to the CDI box, and see if these terminals are getting a tiny alternating signal (the alternating part will not show up on your meter, but some tiny microvolt signal will be seen there.

At any rate, if the CDI is getting a signal, and if the CDI box is getting 12 volts, then your problem is the CDI box or the "coi," and even if it is the coil, it has probably killed our CDI box. You should always carry a spare CDI box. Permatunes are not reliable. MSD units do not work perfectly on SC's often times, but they work okay on earlier cars. Go figure. For my money, the Bosch CD box is by far the best and most reliable.

adigati · 04-07-2006, 05:06 PM

OK this EXACT same thing happened to my 83 SC, only I was on the freeway.

It was the coil so I would check that before spending any more money. I chased that one for awhile as well. Apparently Bosch had a batch of bad coils about 3 years ago. Mine was basically brand new when it failed (200 miles). "It COULDN"T be the coil it's new" (many wasted hours after saying that).

BTW, MSD 6A (nothing trick base cheap model no rev limiters) works absolutely perfect in a 911SC, tach and all. Easy one hour install. I've been carrying around my original well working CD box in case of emergency (MSD failure) for three years now..........probably its now broke from laying around! MSD rocks and also fits under the stock cover........it even mounted pretty much in the same location. For around $120 (if memory serves me @ Summitt) what a deal.

Good luck.

Anthony
www.racerloans.com
83 911SC

Kirk911SC · 04-07-2006, 05:11 PM

I had 3(!!) Bosch coils fail within a 18 months on my SC. Cheapo Brazilian made ones that leaked the oil out the top and fried. I replaced mine with an MSD Hi-Vibration Blaster coil (1/2 the price of Bosch) using the stock CDI box, and no problems since.

Symptoms were identical.

Kirk

snbush67 · snbush67's Garage

Check the rotor, if it was raining and your plug wires were wet and not grounded they could have cross arced and fried your rotor. Its a 10 dollar part at best and a 20 second fix. Ask me how I know.