924Board.org

[FASTdan]

Hi Guys,

another question regarding my troublesome 924! The car wont start, its turning over (though rather slowly) but just wont quite fire. the spark looks weak when tested (plug gaps at 0.6mm).
My first question is what should the voltage be reading at the coil with ignition turned on? my reckoning is it should be 12-13v? it only reads 6.5v (7.5 if meter is earthed to car body).

Also, the haynes manual talks about testing the primary coil resistance by connecting the meter to terminals 1 + 15. when i do this there is 0 resistance! but then its the same on my working ford fiesta?? Then it talks about testing the secondary resistance but the procedure is identical, terminals 1 + 15??

dizzy cap and rotor are good and the car WAS running until i did a compression test, since then it hasnt started.

Possibly an earthing problem? I know the technical bit of 924.org talks about replacing earth straps - is this necessary if the strap is solid (though old)?

Any ideas? cheers
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1980 924LUX

[Mike924]

Hi, Dan.

0.6 mm is a little on the low side for the plug gap. I think it ought to be closer to 0.7 mm IIRC.

The primary winding resistance of the coil is of the order of 0.5 ohms. Unless you've got a very good meter, most will show this as zero.

I don't know for sure what the resistance of the secondary winding ought to be, but typically it's about 1000 - 2000 ohms on most cars. It should be measured between one of the terminals (I can't remember which, but there are only two!) and the connector for the HT lead.

Most ignition coils actually run off 6 V. There is usually a resistor, or length of resistance wire in series with the coil to drop the 12 V down to 6 V. During starting, the resistance is switched out to compensate for the voltage drop when the battery's working hard to turn the engine over.

Are you sure you put the HT leads back on the right plugs after doing the compression test?
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[FASTdan]

LOL no i actually didnt to start with, i got them mixed up. but im 99% sure im right now as i worked it out from a photo of the engine bay (damn haynes should have a diagram for this but doesnt).

Am i right in thinking no1 is nearest passenger side? then as the dizzy rotates clockwise as you look at the end (from passenger side), ive got it as:

4

3 2

1

I hope this is right otherwise I'll look mighty stupid lol.
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1980 924LUX

[Smoothie]

That's correct - #1 toward the rear-left of the car (rear-right if looking at it from the front) and firing order 1-3-4-2 clockwise.
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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

[FASTdan]

hmm thats interesting as it appears to be front left (pass side) on mine?? wonder if I've somehow got them 90deg out of phase! worth a try lol. although i suppose this is dependent on timing setting and if my fiesta is anything to go by, dizzys can vary a bit too.
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1980 924LUX

[Smoothie]

Yeah the way I described is how they were originally put together, but the distributor could have been removed and reinstalled in any number of different ways, so #1 isn't always at rear-left after it's been messed with. As long as the rotor points to the dist cap post for #1 with the crank and cams' TDC marks lined-up, you're ok. The firing order always follows the same sequence 1-3-4-2 regardless of how the distributor was installed.
_________________
"..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