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Bosch Rotor Button Failure

Started by hanra , Feb 19 2012 03:37 PM

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13 replies to this topic

#1 hanra

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Posted 19 February 2012 - 03:37 PM

I have been having some issues with one of my other cars over the last 12mths which I have only driven 5 times.... each time out it has failed...

Everything had been good for the past 9yrs, until I decided to fit a MSD blaster coil without thinking if the Pertronix Ign Module could handle the low primary resistance coil. It couldnt and luckily it fried the Pertronix module just as I got home from a small drive... Ok so replace the Pertronix module and fit the correct Pertronix Flamethrower coil.

Second instance, the car stopped dead at a set of traffic lights, would not re-start (no spark) and needed to be pushed off the rd. Popped the bonnet had a squiz, kicked it over, away it went for the rest of the drive... hmmmm

Third instance, forgot my keys to lock the car on a club run. Decided to just pull the rotor button out for safe keeping. Come time to re-fit the rotor button found that the dizzy cap would not fit back on, in my frustration I jammed it on and damaged the rotor button/dizzy cap. Problem was found to be the 2 piece dizzy shaft had moved outwards, got it back in place, re-fitted damaged rotor button just to get me home. Remove dizzy at home, found an advance weight spring broken and dizzy shaft loose. Send away for repairs. Fit new dizzy cap and new rotor button.

Fourth instance, repaired dizzy refitted, Car stopped dead about 1klm from home at 6 at night... tried old dizzy cap, fitted old set of points, tried another dizzy no go... push the car to a friends 1klm away... Next night, confirmed 12v at coil, confirmed points arching, no HT getting to the plugs... Can only be the new rotor button, fit an old crusty shitty one. Bang off she goes... get the car home, remove points re-fit Pertronix Ign Module, double confirm that yes the 50klm old new rotor button causes no HT to the plugs. How strange.. Purchase another new Bosch Rotor Button.

Fith instance (today), New rotor button fitted, original Pertronix module fitted, new dizzy cap fitted. Car got about 3klm down the road and died at the lights, pushed off the road, check over everything, try to start, bang off we go another few hundred metres down the rd, pop fart bang dead.... Sit for 5mins, start off we go again... pop fart bang dead... sit for 5mins, off we go again.. and repeat another 6 times... The final time the car died just at the top of a large hill on the home straight to my place. Managed to roll down a few streets before I go home to the bottom of my driveway.

Confirmed no spark, 12v ok. Fitted another new Pertronix Ign Module, dead, Fitted Bosch GT 40 Coil, dead... Jump in the reliable daily and buy a new rotor button, this time its a Fuel Miser brand like the one I originally had before all this started... Bang off she goes again...

So............ why have I had TWO brand new Bosch Rotor buttons fail... They seem to be made from bakerlite compared to the Fuelmiser one being more plastic... The must be shorting the HT to GND.... WHY.....

This is as far as it would roll....

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Edited by hanra, 19 February 2012 - 03:37 PM.

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#2 wot179

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Posted 19 February 2012 - 03:52 PM

Tis Lucas,Prince of Darkness,that is to blame.

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#3 hanra

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Posted 19 February 2012 - 04:00 PM

Well thats who I would of blamed. But the rotor buttons are Bosch items...

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#4 wot179

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Posted 19 February 2012 - 04:04 PM

Yeah,sorry.I had nothing else.

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#5 _WantOneNow!_

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Posted 19 February 2012 - 04:05 PM

Its wierd how sometimes things just f***kup for who knows what reason? Maybe consider that its a sign from above?
Cheers Mick.

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#6 _torbirdie_

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Posted 19 February 2012 - 05:14 PM

There appears to be no physical damage to the rotor button?

Was there continuity between the end of the rotor and the centre contact? What is the tension like on the contact inside the dizzy cap? Does it sit at exactly the same height on the shaft as the one you replaced it with.

Is the dizzy and rotor button an older points dizzy? Not that it may be your problem, but none of the clearances of the older style wasnt set up to carry the higher voltages of those big super coils , and is why with the later model bosch electronic setups there are significant differences in the design of the rotor and cap.

You know its definitely shorting to ground, rather than the spark not going anywhere? can you hear arcing, sparking inside the cap when cranking it with the defective rotor? can you actually see any telltale traces of a short inside the cap or

Edited by torbirdie, 19 February 2012 - 05:17 PM.

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#7 _oldjohnno_

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Posted 19 February 2012 - 07:21 PM

The first thing I'd be checking would be the plugs and plug wires. Are the wires in good condition and without excessive resistance? Or are you trying to run old-style solid cores with a modern high-energy setup? Is the engine a habitual plug-fouler perhaps?
Any of these things could cause repeated failures of the cap and/or rotor by allowing excessively high voltages to be developed that will soon create tracks to ground. This can happen pretty quickly with high-output systems. If there is any doubt about the wires I'd put a good set of spiral cores on before running it again and possibly damaging the new rotor.
Another thing to try is to cut the side out of an old cap so you can fit the rotor and cap and physically see if there are any excessive gaps that again would cause tracks to ground to develop.
One thing about the old Mini motors (I used to play with Minis and still love em) is that the offset drive dog makes it trivially easy to change dissies. So until you were sure the problem was resolved you could carry a complete spare in the boot. Though I spose there are a lot harder cars to push than a Mini...

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#8 hanra

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Posted 19 February 2012 - 07:40 PM

The dizzy is a points 29D. The Pertronix module consists of the pick up and also a magnet which fits around the shaft. It's designed for this dizzy.

The leads are not sold core leads, they are 9years old. Dizzy cap is brand new Bosch.

This ignition system has basically been ok for the past 8 years. I have been using a Pertronix module for quite a few years now. I recently changed to the Flame Thrower Pertronix coil which has a 3 ohm primary winding (same as the old bosch it replaced). The leads I will have to measure. It's never been a plug fouler. This car has never ever left me stranded until a year or so ago when I fitted an MSD coil with .6 ohm primary.... Which obviously destroyed the Pertronix as it can only handle a 3 ohm primary. That's when all these problems started.

Both Bosch rotors that have failed have looked perfect. Continuity ok. But as I mentioned the Bosch rotor buttons appear to be Bakerlite, where as the rotor button I have been using for the past 8 years was more of a plastic. Like this new Fuelmiser one I've just bought.

I checked the previous faulty one with a mega up to 1000v and it was ok.

Oh...... After pushing 650kg for a kilometer... It becomes heavy... But yeah hate to do that with a kingo or falcon...

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Edited by hanra, 19 February 2012 - 07:44 PM.

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#9 _oldjohnno_

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Posted 19 February 2012 - 07:59 PM

Something is making those rotors fail, I'd be checking those 9 yr old leads as well as the rotor to cap clearances.

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#10 _oldjohnno_

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Posted 19 February 2012 - 09:49 PM

The wear pattern in the middle looks unusually big for something that only should only be touching the tip of a carbon brush maybe 5mm in diameter... Normally it's just a small shiny dot.

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#11 Peter UC

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Posted 19 February 2012 - 09:57 PM

Considering it's a points dissy, is supposed to get 12V? I know in the Holden points dissy the coil only gets 9V.

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#12 rodomo

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Posted 19 February 2012 - 10:45 PM

Camira/Nissan Pulsar Delco? rotors fail frequently tracking to the dissy shaft.
I have been to a 40's Willy Jeep one ANZAC day that had no continuity through the brass arm as pictured above.
Fitted dodgey second hand rotor from the bloke's tool box and away it went.

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#13 _torbirdie_

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Posted 19 February 2012 - 11:21 PM

Considering it's a points dissy, is supposed to get 12V? I know in the Holden points dissy the coil only gets 9V.

Pete, the voltage across the points in the dizzy go from supply voltage 14V engine running (open) to 0V closed, regardless of whether there is a resistance wire in series with the coil or what voltage is seen across the coil when the points are closed.

Not sure that the system in question is even running points(perhaps as a sensor to trigger module), if the points were used conventionally the only consideration would be the primary resistance of the coil and whether that creates a current that will burn out the points quickly.

Edited by torbirdie, 19 February 2012 - 11:28 PM.

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#14 hanra

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Posted 20 February 2012 - 06:37 AM

My system has been running a Pertronix ign module for about 6yrs without fail. I've wired the ign so there is 12v during cranking and operation. No ballast resistor.

Edited by hanra, 20 February 2012 - 06:38 AM.