924Board.org

harnishclan · Joined: 10 Dec 2005 Posts: 30 Location: San Diego

My 82 924 has no spark from the coil. So far, replaced coil, ECU, Ignition control module, and DITC. Any suggestions?
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Current: 81 924T, 82 924T, 87 944, 97 993, 04 Cayenne S.
Past: 83 944, 81 911SC Targa, 86 944.

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

Try checking the solder joints on the L shaped pins that plug into the DITC. Also, IIRC, a bad overboost switch or connection cn kill the ignition.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

924RACR · Posted: Sun Jan 01, 2006 1:10 am Post subject:

Have we verified that you're getting a good signal from the crank pickup? Not sure exactly how this is done, but...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

harnishclan · Joined: 10 Dec 2005 Posts: 30 Location: San Diego

thanks for the tips, solder joints look rugged, but they ring out with a meter. What is IIRC? I did the resistance check on the sensor and is within spec. Discovered the aftermarket plug wires from previous owner have a lot less resistance than OEM, and that there is scarring on rotor and distributor cap tips. Plan on replacing those parts next... My pin 1 of coil is reading battery voltage, this according to manual is wrong. Says it should be no more than 2 volts. I swapped both DITC and Ign Cont Mod, and got the same voltage. Is this normal or should I pursue this one a little further?
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Current: 81 924T, 82 924T, 87 944, 97 993, 04 Cayenne S.
Past: 83 944, 81 911SC Targa, 86 944.

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

IIRC means "if I remeber correctly". The lesser resistance on the sparkplug wires would not be causing a miss but did you check them for cracked or burnt areas? Are they still flexible or stiff? During cranking you should get between 9 and 12 volts at the 15 post of the coil. Are you checking for ohms or volts? If you are getting 12 volts at post 1, the wires are reversed or the coil is bad.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

harnishclan · Joined: 10 Dec 2005 Posts: 30 Location: San Diego

Dennis, thanks! I was thinking IIRC was a part (oops). I have been mostly checking for continuity in the wires. But the coil numbers are voltage. I have battery voltage on both sides of the coil. Haven't tried cranking on 15 yet though. I bought this car in Nov, in a non-running condition. As for plug wires, they are probably less than 6 months old. Coil was new Bosch OEM in August according to receipts.
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Current: 81 924T, 82 924T, 87 944, 97 993, 04 Cayenne S.
Past: 83 944, 81 911SC Targa, 86 944.

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

If you are getting 12 volts on both sides with the ignition switch at the on position, someone has bypassed the resistor or resistor wire and the coil has shorted. With the switch on you should be getting about 6 volts and 9 volts during cranking. Anything more will ultimately ruin the coil.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

John Brown · Joined: 07 Nov 2002 Posts: 903 Location: Leesburg VA

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

John.

Good catch. I was reading the #15 and #1 wire sizes in the Haynes manual as ohm values. Agree there should be 12volts from the #15 blue/black wire from the ignition switch.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

harnishclan · Joined: 10 Dec 2005 Posts: 30 Location: San Diego

Did continuity check on green #1 wire and it checks good. Also checked both factory and Haynes. They both say that the wires have 1-1.5 ohms of resistance built in to the wires in lieu of resistors found on older models. My resistance is only .2 ohms, so does that mean bad and replace? Seems like that is awful close tolerance to go from normal ignition to no spark at all.
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Current: 81 924T, 82 924T, 87 944, 97 993, 04 Cayenne S.
Past: 83 944, 81 911SC Targa, 86 944.

Smoothie · Posted: Thu Jan 05, 2006 7:40 am Post subject:

I was suspecting that those 1.5 and 1.0 ohm values don't apply to the DITC ignition setup, so took some readings -

I get 0.2 ohm on the wire from coil #1 to ICU #1 (green) measured out of circuit.
The coil #15 to ICU #4 (black) measures 0.3 ohm (0.4 ohm with it taken further out of circuit by also disconnecting the "A" connector from the back of the fuse-relay panel)
Coil #15 to fuse panel connector A12 (black/blue wire) measures 0.2 ohms (again, completely out of circuit).

Several reasons why the resistances given in the manuals don't apply to the series 2 931 are
1- My car's running fine with the very different readings given above
2- The 1.5 ohm value given in the manuals applies to a coil #15 to starter #16 (or 15a), but that connection isn't wired on the s2 931
3- Haynes pg.263 shows resistances right on the s1 931 wiring diagram, while the s2 931 diagram on pg.291 doesn't
4- The manuals are known (at least to me) to not always leave it obvious which information applies to s1 931 and 924, but not to the s2 931
5- resistance values should if anything increase over time, but 0.2 and 0.4 ohm are lower than the values shown in the manuals
6-

harnishclan · Joined: 10 Dec 2005 Posts: 30 Location: San Diego

Smoothie, thanks. I will double check those numbers with what I am having. Earlier today I did some voltage checks. Both sides of the coil to ground are same as battery with ign on. Zero volts across 1-15 terminal, 10 volts while cranking on both sides. The beat goes on...
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Current: 81 924T, 82 924T, 87 944, 97 993, 04 Cayenne S.
Past: 83 944, 81 911SC Targa, 86 944.

Paul · Posted: Thu Jan 05, 2006 3:06 pm Post subject:

Let's go back to the beginning of this problem. What happened or what else was done before you started replacing things?
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
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Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

harnishclan · Joined: 10 Dec 2005 Posts: 30 Location: San Diego

From the beginning. I bought the car locally with a no spark condition. Previous owner was having troubles above 3K RPM range and cleaned connectors which seemed to fix car. He then used the car for a PCA AX and broke ring and pinion gear. Then had a friend put a new transmission in the car. Car was driven home about 20 miles and then he took it out later and it ran "until I closed the door." Since then, no spark out of the coil. I then bought it thinking "how hard could no spark be?" Using Haynes and Porsche Manual, did resistance checks and found all of the checks I did to be okay. Checked flywheel sensor resistance, then started replacing parts. Tried the brain, Igntion Control Module, then DITC in that order with no luck. The following parts are new from previous owner: Coil, Ignition Wires, Plugs. The very first thing I did was swap the coil with a known good coil. Same condition applied. I placed the 931 coil in my 944 NA and it fired right up, so coil was eliminated. So that is how I ended up here with no spark (still!).
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Current: 81 924T, 82 924T, 87 944, 97 993, 04 Cayenne S.
Past: 83 944, 81 911SC Targa, 86 944.

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

Distributor cap? Did you check for spark at the coil or at the sparkplugs? If none at the coil, then the problem appears to be a bad connection or short in the wiring loom. Still not sure why you are getting a constant 12 volts at the #1 coil post. That is supposed to be a trigger signal to fire the coil. Could any of the wiring connections be reversed?

Sorry for having questions instead of answers.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black