Burning distrbutor rotor

I have now received my replacement Bosch rotor arms and cap, and I have to say the difference in product from the Beru is quite signifcant. The Bosch parts have a glossy finish/coating, and the rotor looks much more substantial. the mounting shaft is much thicker than the Beru. So much so, that when I compared the Bosch side by side with the Beru, I thought the mounting aperture on the Bosch was too small. I checked it with a ruler, and it is exactly the same as the Beru, but the thickness of the shaft makes it look smaller. Like one of those psycholgist's optical illusion drawings.
I will photgraph it when I come to remounting the distributor. Yesterday evening was spent replacing the cylinder block-thermostat coolant hose, and then swearing at the thermostat and housing and trying not to bend it when remounting. ( which I didn't). and then doing the same swearing at the air-slide which I had to remove to get at the coolant hose.
I would recommend an inspection of these hard to get at hoses to all of you. As I already have all the big hoses off and the coolant drained, it would be daft for me not to. I was shocked to see how much oxidation there was on the cylinder block flange . I used my dremel and a brass brush attachment to clean it up. I also reassembled with a smear of silicone grease on the flanges and just inside the hose. and of course new hose clips, mounted so i can undo them easily if needed. It all helps when reassembling., and will hopefully prevent any more oxidation or build up of deposits there. I also used a silicon hose for the replacement. I love new technology...

Guten Feiertagabned freunde,

the quest for truth goes on and on.. I have managed to replace the timing chain and upper guides okay, in fact I am very pleased with the work. My wife saved me a fortune after I manged to let the end of the old chain slip back down the timing cover, she helped me fish it out. Unfortunately, everything else is going to the devil since I recommissioned the moror on Saturday.

on the topic of rotor arms, i fitted my 'spare' Beru cap and rotor arm, just to static time the ignition and in case anything went wrong. The engine has been run for less than an hour, long enough to warm it up for an oil change, and to try the dynamic timing with a strobe lamp.

the picture of this brand new rotor arm says it all. less than an hour's work, less than 100,000 revs, less than a 50km drive. It's burning out.
I have taken it and the Beru cap off, and fitted my new Bosch ones. Ignition timing and rough running are preventing me from driving the car anywhere, but this can't be good. Any ideas gentlemen?

Hi Myros,

when a new rotor arm and distributor cap burns that quickly, I do not believe in just bad quality of Beru parts. I would check pre power resistors and their wiring before ignition module and ignition coil.

Dr Volker, I think I agree with you completely. The 1st beru cap and rotor I fitted lasted 10 years without trouble. I have always liked their spark plugs. I will continue the detective work as much as i can and keep you posted. the engine is running like a schwein and i can't set the timing. something must be out of whack from the chain job ( the chain installation was eventually perfect)

Dr Volker und freunde, here is a picture of the top of the rotor arm. There is a distinct pattern of 8 marks, presumably corresponding to the position of the rotor when firing for each sparking plug. I haven't seen anything like this before.

Hi Myros,

it looks as if you are missing the carbon in the centre of the distributor cap. There is a small spring and pen in the centre pressing on the rotor arm.

Check please that this is present.

it was certainly there when I took it out of the box on Saturday. I will look again later on. Thanks.

Dr Volker, the ( new) distributor cap carbon electrode seems to have a bit of a hotspot. You can make it out in this photo if you zoom in.

Hi Myros,

to be honest, I do not recognize something on that photo. However, it seems you still have higher voltages than normal. What could be the reason?

1. Missing or wrongly connected power resistor. They should be 0.6 and 0.4 Ohm to coil.
2. Wrong ignition coil
3. Wrong spark plugs
4. Gap in secondary cable (4) from ignition coil to distributor.

Why could a gap create such a problem? It would take higher voltage to make the spark jump over. And for sure your burnt rotor arm looks like too high voltage.

Dr Volker, thanks for the reply. It looks like I will have to throw some parts at the problem. i will start with the vacuum hoses and pipes, as they might have reacted badly to all the dismantling and remantling going on when I did the timing chain and guides. the car is running really really rough, and I can't get the dynamic timing to set. So vacuum first, then electrics, although it is probable that the overvoltage would have to be from the failure of the ballast resistor. If the coil is meant to run on 9volts most of the time, but is running on the full start-up 12 volts, then that's a lot more volts than the rotor arm is meant to have continuously. It has to be unlikely that the ignition module causes over voltage, all it does is give signals to fire.

Morning freunde,

I now have all the parts, coil, HT leads, vacuum rubbers, and ballast resistor, ( although I now think my car doesn;t have one).

I will start with the coil, and see if that fixes the rough running. Only time will tell if it fixes the rotor burn out. I will measure the resistances and comapre to the old coil.

then I will change the HT leads, and then the vacuum connectors and piping.

If tha doesn't fix it, ....help.

here are some pictures of the new chain and sprockets showing everything spot on at OTP no1 cylinder.

Hallo SL-freunde. Lots of good news this week. My new coil, ballast resistor (not needed, does anyone here need a new Bosch 0.6 ohm ballast?), and new HT leads arrived. MB also got my rubber elbows and other connectors for the vacuum system. I replaced the coil, the new one has the big resistance of 9.41 k ohms, which is a lot higher than the old one. I checked all the vacuum connections, and found a big one halfway up the inlet manifold was off its pipe. It must have been blown off when the engine backfired through the manifold. I reconnected it,put the filter back on, and started the motor. It fired first turn of the key, as smooth as a glashutte watch. Much smoother than before the chain job, and before was pretty good. I went for a 30km drive, absolutely no hiccups , smooth as silk.
I will hook up my strobe light and do a dynamic timing, but for now, lets hope the new coil has fixed the burning rotor. I tried to work it out logically, and only the coil an produce overvoltage. couple that with less than perfect Beru ( compared with Bosch) rotors, and that could be the problem. Time will tell.

Hi Myros,

Ed from Wheelers Dealers would now say "Job done". And indeed it is well done.

Morgen freunde,

on Friday i had a 250 mile ( 400km) trip on the motorway, at proper germanic speeds. 4 hours travel time, average speed 100km/h ( don't forget there was about 15 miles of city driving in there and lots of traffic getting in the way on the faster roads0 No hiccups, lovely response from the engine, and 25mpg as well, in the 28 deg Celsius heat, with the windows down ( I haven't had chance to get the hardtop off yet). thats about 10.75l/100km in German. I am a happy bunny. I have had better consumption, but only because of speed limited to 80km/h motorways.

Hi Myros,

great, wheather was lovely then. And good to hear your feedback!

Dr Volker, it was my pleasure. andmy thanks to everyone else who pitched in with advice and sympathy. Attached is a picture of my reassembled after timing chain and tensioners engine, if anyone is interested. It took a little finessing to chase out the very small leaks from the coolant hoses, they just needed positioning square and tightening up well, very well, which is easy to do with t-bolt hose clamps. It is also easy to think you have tightened enough, when there is still a long way to go...

Hi Myros,

I would say: "You must be with the fireguards"