924Board.org

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

I pulled the dash from my 924 while doing the battery tray repair which is still underway, but I need to move the car and now it won't start.

The engine cranks over just fine, I know the battery is good because it's not 6 months old and has been working great. After being left in a leaky car for a few months, my multimeter seems to have taken a turn for the worse and is reading my battery voltage at 1600 volts. It tells me I'm getting 600 volts at the coil with the ignition switched on. Time for a new multimeter, but shouldn't this read the same voltage as the battery?

I'm going to jump the #15 circuit and starter at the switch and see if this helps. Failing this, is there a better way to do it from under the hood, at the ignition module or something?
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'81 931 in various states of assembly

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

Hmm, this isn't very reassuring, no replies

I have an idea I am going to try however. The starter circuit is working very well, the engine is cranking over with authority and the battery has a great charge. So my notion is to pull some chicanery and power the ignition through a fused switch, directly to the ignition module itself.

I already have the fuel pump running off a fused switch as it is, so I should be able to encorporate it with an extra relay and a small switch in the centre console. I'd have to turn off the switch to shut off the engine, but I have to switch off the pump when I turn off the engine anyways.

Any thoughts, or reasons why I really shouldn't do this? It'd still take the key to start the car, so if someone wanted to steal it they'd have to hotwire it anyways.

Another idea I have going is a master power switch that will disconnect the entire electrical system in case of a fire, or vehicle storage. I would keep an always closed circuit for the clock, stereo, and to power a relay to connect and disconnect the main power of course. How realistic is it to get a 12v relay that will be beefy enough to handle the current drawn at engine start?
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'81 931 in various states of assembly

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

additional thought, I hate wiring.
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'81 931 in various states of assembly

Tigger937 · Posted: Sun Nov 06, 2005 7:05 am Post subject:

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

Tigger937 · Posted: Sun Nov 06, 2005 8:27 am Post subject:

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

Scratch that, I got my multimeter working properly. It tells me my battery is at 16.8 volts

I'm getting that same 16.8 volts at the coil and the plug for the ignition module. The kicker is, when I plug the MP plug into the ignition module, I get nothing at the coil. Not even 6 volts anymore. So this shows my ignition switch and wiring to be good, but points to a bad transistor unit, doesn't it?

If that's the case, I have a spare and I can think of two likely cases that could have cause it. Exposure to water, since the hood was off and it got sprinkled on a bit, and that ludicrously high 16.8 volt battery charge. Can overcharging a battery kill an ignition module?
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'81 931 in various states of assembly

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

Gotta say, a diesel is sounding pretty attractive right now.
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'81 931 in various states of assembly

Joes924Racer · Posted: Sun Nov 06, 2005 10:33 am Post subject:

Thats rough .. goodluck fixin the no start.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

Disregard all of the given voltage measurements here, just checked my multimeter against a wire and plug into a house receptacle and got a fluctuating voltage between 3 and 8 volts. Now call me crazy, but that should be reading 110-115 volts. Good thing Mastercraft has a warranty on all their tools.

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'81 931 in various states of assembly

leadfoot · Posted: Sun Nov 06, 2005 3:35 pm Post subject:

Are you measuring DC current on that appliance, I'd be getting a new multimeter as it seems like yours is malfunctioning or at least checking the battery in it first...
If you are truly getting 16.8V at the battery then this would mean your alternator regulator needs a look at.
Leadfoot
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

Oops, turns out it was set to DC. Checked the 110v outlet again, got readings 160v and 1660v depending on the setting I used. Are teh two different settings for single phase and three phase?

I'll replace the battery, and failing that replace the unit...
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'81 931 in various states of assembly

Tigger937 · Posted: Mon Nov 07, 2005 4:37 am Post subject:

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

Replaced the battery in the multimeter and now it tells me I've got 12 volts. Replaced the ignition module with a spare and it still won't start. Checked at the coil and I'm getting voltages that are ok according to the haynes manual.

One thing I was checking for was the resistance of the coil, I got 1.2 ohms between the coils, but it tells me to check the resistance between the #1 terminal and the #4, which is the lead to the distributor correct? I get no reading on the coil, or on my spare coil which is in a working engine.

Still no start...

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'81 931 in various states of assembly

Smoothie · Posted: Mon Nov 07, 2005 7:59 am Post subject:

Obvious, but I'd be looking for something that got disconnected with the dash removal.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox