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Strange non-starting problem


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I am scratching my head on this one! My S3 cut out in a hotel car park, just ticking over, after I had just covered 200 miles up the M6 with no issues. I tried starting it immediately, but it just turned and turned with only 1 cough.

I looked at it the next day and the fuel pump is ok and working and delivering fuel to the carbs. I pulled the coil ht wire off the distributor and cranked the engine, and it is sparking strongly. However when I check the plugs for sparking, there is nothing. So, great I thought, its just the distributor cap or rotor arm but these look absolutely fine with no cracks or tracking marks. It doesnt cough at all now when cranking and I am thinking that somehow the ignition timing has slipped, but the cambelt is nice and tight and the rotor arm cannot be rotated freely so it must be still connected to the toothed wheel. Any ideas anyone? Where should the timing marks be at TDC on the toothed wheels, including the one that does the dizzy. Even if the ignition timing had slipped, I surely should still get a few random sparks out the spark plug leads unless perhaps the rotor arm is firing between the cylinder contacts in the dizzy cap?

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First: (easiest)

Check that the screw holding the points in position has not loosened. If it has and the points don't open, you won't get any spark.

 

Second: (harder)

There should be at least one wire that exits through the dizzy body. Check the rubber where the wire exits the body of the distributor and also check the wire insulation. I had the minutest of marks on the wire on an old car I had and this was the issue with it.

 

Third: (more difficult)

Get someone with another distributor that you can try.

All we know is that when they stop making this, we will be properly, properly sad.Jeremy Clarkson on the Esprit.

Opinions are like armpits. Everyone has them, some just stink more than others.

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On the S3 you would have 3 wires coming from the dizzy, dependant on the type of ignition unit, check the connections where they join onto the wires going to the coil a small plastic plug, mine looked fine but were in fact starting to break down, new terminals and away she went, if you just pull the plug apart you may see that maybe one wire has come adrift, clean the terminals and push it back making sure it is making contact, been there done that with the  same problem.

 

Good luck.

 

John.

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I'm not au fait with the S3. If there aren't points and it's an electronic unit, then I'll go with johnpwalsh.

All we know is that when they stop making this, we will be properly, properly sad.Jeremy Clarkson on the Esprit.

Opinions are like armpits. Everyone has them, some just stink more than others.

For forum issues, please contact one of us Moderators.

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If the coil lead is sparking, then all the ignition system is working; any problem with the 3 wire connector stops all the sparks. Thus the problem lies either with the ignition timing or the distributor cap or rotor arm. The rotor arm is a trick thing with springs on it, designed to cut out the sparks as a rev limiter...this can go wrong and short them out permanently. Turn the engine to TDC on the compression stroke of no. 1 cylinder, take the distributor cap off and see where the rotor arm is pointing...it should be pointing to the no.1 plug lead. If it isn't that's your problem!! The distributor is spring loaded so that, if you loosen the clamp, it tends to move out of the engine and lose drive...but if you have sparks, then it must be rotating. If you do turn the distributor, you have to watch out, though. I have known someone to replace a rotor arm with one that sat a bit too low, and it worked for a while...then the sparks wouldn't get across the larger gap between the rotor and the cap contacts. Have a good look at the bits.....can't be too difficult to sort out!!    

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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If the coil lead is sparking, then all the ignition system is working; any problem with the 3 wire connector stops all the sparks. Thus the problem lies either with the ignition timing or the distributor cap or rotor arm. The rotor arm is a trick thing with springs on it, designed to cut out the sparks as a rev limiter...this can go wrong and short them out permanently. Turn the engine to TDC on the compression stroke of no. 1 cylinder, take the distributor cap off and see where the rotor arm is pointing...it should be pointing to the no.1 plug lead. If it isn't that's your problem!! The distributor is spring loaded so that, if you loosen the clamp, it tends to move out of the engine and lose drive...but if you have sparks, then it must be rotating. If you do turn the distributor, you have to watch out, though. I have known someone to replace a rotor arm with one that sat a bit too low, and it worked for a while...then the sparks wouldn't get across the larger gap between the rotor and the cap contacts. Have a good look at the bits.....can't be too difficult to sort out!!    

Hi, thanks for your help. You are correct in saying that the sparks coming from the coil prove that the electronic points are OK, and it must be the rotor arm or the distro cap. I spoke to Steve at SJ and he seems to think its the rotor arm, so I have ordered one. However I was looking again at the distributor and I have noticed that one vane of the 4 vane disc that passes throught the optical sensor was broken off! I dont think it was me that broke it - while looking at the rotor arm. And since the engine stalled, there was something clearly wrong with the ignition before I even touched the dizzy. There are no firing sounds at all when turning the engine over.

Surely though the car would still have 3 cylinders functioning if one vane was missing? Dont the vanes correspond to each cylinder?

 

Joolz

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 Dont the vanes correspond to each cylinder?

Yeah, that's what I understood & they are working which is why you're getting sparks at the coil HT lead.

 

It's probably the broken rotor arm that's stopping them getting to the plugs.

Cheers,

John W

http://jonwatkins.co.uk

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Unless of course the broken vane part is stuck between the pickup and the remaining vain.

 

Possibly, and is the only logical explanation, but the broken bit wasnt near the pickup to block it, although it may have been when the engine stopped running and only moved later when I was fiddling with the distro.

 

I glued the vane back on with super glue, reassembled with a new rotor arm ( I had to smash the old one off as it was stuck solid) and the car started normally and ran smoothly! There was definitely nothing wrong with the old rotor arm - no cracks and as good as new.

The weird thing was the way the engine stopped before I had all this faff - it stopped like someone had turned the ignition off, and I only heard 1 weak cough from the engine after trying immediately hot and on the following 2 days when cold. There should have been a good spark from the three working cylinders or at least some firing sounds. It defies logic.

 

I have bought a new "chopper" - thats what the plastic thing is called- from SJ and I will fit it tomorrow. The old one had traces of glue near the broken vane so I think a PO had a similar problem. The plastic vanes are very easy to accidentally break if you are trying to lever or force the rotor arm off.

 

Thanks to all for your help, I was stuck 200 miles away from home with no tools trying to fix the S3 in the evenings in the Hotel car park - the car conked out exactly at my destination luckily, almost like it was doing me a favour! I recently drove it to the Alps and back and it didnt miss a beat so I cant complain.

 

Joolz

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