Help! 3.2 with no spark

Fahrvergnuugen · 04-25-2004, 10:12 AM

I just got my car out of storage for the summer. The car is an 82 with a 3.2 from an 86 swapped in. I have a Bentley for the car but not for the engine (its on order...)

I drove it yesterday and a bit this morning for about 30 miles with no problems.

Then all of a sudden, 1 mile from my house, it just died while in gear. No sputtering, coughing or anything.

It cranked over fine, but wouldn't fire.
I had 12v at the coil, so I pulled a plug wire off to test spark... I turned the key and it made spark and fired. So I put the plug wire on and it started up, ran like a top.

50 feet down the road, the engine died again. After sitting for about 20 minutes, I tried it again, and again it fired ran for a few seconds, and then died.

Now there is no spark at all. There is power to the coil but no spark at the plug.
What should I check next?

Fahrvergnuugen · 11:13 AM

How similar are the 3.2 and the 3.0 ignition systems?

I know that the 3.0 SCs have a CDI module, which the bentley shows being mounted inside the driver's side fender - which my 3.2 does not have (the coil is mounted there).
I don't see a pulse wire going to the distributor either.

http://darklotus.dyndns.org/users/fahrvergnuugen/911/Images/28.jpg
http://darklotus.dyndns.org/users/fahrvergnuugen/911/Images/32.jpg

I don't know enough about the 3.2 ignition, so if someone could explain the differences from the 3.0 that would be helpful.

Early_S_Man · 04-25-2004, 11:27 AM

You need a spare DME relay ... do a search on "DME relay" in the subject line ...

No similarity at all between CDI ignitions and DME-controlled ignition!!!

Your DME uses a conventional 12 Volt coil switched by the DME controller box under the seat ... the negative side of the coil primary is switched [to ground] on and off by the DME box. The only function a distributor has in the DME system is to carry spark to the individual spark plugs. The speed and reference sensors on the transaxle bellhousing provide timing signals to the DME.

J Smith · 04-25-2004, 11:37 AM

Sounds like it may be one of the reference senders near the flywheel. Doesn't one control fuel, the other spark?

Fahrvergnuugen · 04-25-2004, 01:22 PM

well, i checked out my DME Relay. When turning the key on, it DOES NOT click though the fuel pump is running, because this is a swap, the fuel pump is turned on by the relay used in the SC model cars.

I took the relay out and ran 12v power through pins 30 and 86. upon touching 85 to ground ONE of the switches inside the relay closes/clicks.

I have continuity between both 87 pins and pin 30 if i manually depress the spring switch.

So... I think the relay is ok. But as I said, it doesnt click when I turn the ignition on, so maybe I have a bad ground or other problem with the harness.

Fahrvergnuugen · 04-25-2004, 08:37 PM

I've got 12volts in the harness for pin 30. I do not however, have 12 volts on pin 86 with the ignition turned on (which, if memory serves me right, 86 is conditional power)

Where does pin 86 connect? I followed it into the mass of wire that goes through the conduit out the back of the car...but once it goes inside the conduit, I lose track of it.

What is it wired to?

Jim Smolka · 04:09 PM

There are two sensors that are mounted together on the back of the motor above the flywheel. One is the reference sensors; it lets the DME brain know where top dead center is. The other is the speed sensors, which tells the DME brain how fast the motor is turning.

However, the fastest check is the DME relay as stated above.

Dan Owens · 04-26-2004, 04:54 AM

When the DME relays go bad they can work intermittently.

Fahrvergnuugen · 04-26-2004, 05:46 AM

right, but as i said, the relay works, however there is no power to pin 86 (which trips the relay) in the wiring harness.

So I need to know what turns the relay on.

armandodiaz · armandodiaz's Garage

Check out my thread on my " no spark" situation. The last page really helped out alot. Also look at my summaries:

no spark

d993 · 05-13-2004, 11:52 PM

If you haven't fixed it yet.......................I had the same issue with my '87 Carrera- no spark. (First, my car started losing power, then it got worse and worse, until it just wouldn't start anymore).
I tried everything I could think of (change the spark plugs, distributor cap and rotor, coil, reference and speed sensors, DME relay, etc.)
I was getting really pissed off after a while.
On this RARE occasion, I took the car to a local Porsche dealer (I know some of the techs there, so it didn't cost me an arm and a leg, although it took them 7 hours to diagnose the problem:
I had 2 bad injectors, which threw off the timing via the reference sensor!
Once the bad injectors were changed, all I had to do was unplug/plug in the DME relay, and the engine ran perfectly.

88911coupe · 05-14-2004, 07:33 AM

My '88 had very similar probs. Turned out to be a broken solder in the DME Unit itself. There are some threads on this if you do a search but basically you'll need to remove and partially disassemble the unit but it's very easy (obviously, since I managed to do it

) Once apart there is a row of pins that are soldered and one of mine had a VERY fine crack in it that could only been seen in very clear sunlight. I just added a tiny dot of solder and it's worked perfectly ever since. I have thought about sending it out to have an expert check all the connections but have not done that yet.
Good Luck

Fahrvergnuugen · 05-14-2004, 10:20 AM

Hi Guys,
Sorry I did not post back sooner. Thanks for all of your help - I did manage to get the car running again.

I jumpered pin 30 (battery) with pin 87 (switched out). The problem is either with the relay itself, or with pin 86 (switched power in). The relay seems to work fine when I hook it up to an external power source, so I'm thinking its the second possibility.

Gotta get a Bentley so I can figure out what pin 86 is wired to!

Thanks again.

Jeff · 05-14-2004, 11:18 AM

Fahr, 86 goes to the anti theft system.

armandodiaz · armandodiaz's Garage

If you connect 86 to +12V you bypass the alarm system.

movin · 05-14-2004, 11:28 AM

I experienced something similar when my DME unit went bad. It developed an intermitent run/no run problem probably due to a broken circuit trace on the circuit board. Try swapping DME units.

Fahrvergnuugen · 05-14-2004, 12:04 PM

Quote:

Originally posted by armandodiaz
If you connect 86 to +12V you bypass the alarm system.

thats a pretty fancy alarm, lol.

i suppose its possible that my car doesn't have the alarm since its a swap. I'll have to investigate... In either case, I'll probably just end up wiring 86 to switched power as was suggested.