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M119 Distributor caps refurbishment

4K views 9 replies 4 participants last post by  robm.UK 
#1 ·
Some years ago the Bosch caps on my '93 SL500 were arcing so badly that I bought replacement BERU caps that in my opinion are better than the original Bosch caps.

Recently though even the better BERU caps have been tracking and arcing. I had to stop and do the well practiced caps removal and moisture wipe. I was wiping them with a rag and the Allen key and managed to scratch them!!

Today I removed both caps and polished them using a Dremel drill and a brush and pad with 3M 'fastCut'.
When they were burnished and all traces of tracking removed I coated them with a two part epoxy resin.
They now look almost new apart from the scratches that I made with the Allen key.

Before:



After:



Hopefully now good for a few thousand more kilometres ;)
 
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#2 ·
I put silicone grease on the metal parts of the cap and rotor but my issue was mostly too much current going thru them so it helped reduce burning the metal. The issue is the same as yours, mine was just harsher. So I was thinking you could coat the plastic with silicone grease and it should stop or greatly reduce tracking. I used silicone spray, grease is way better but also a much bigger mess to clean. For mine I'd just spray the cap with brake cleaner, then spray with silicone and done. Tracking starts small and builds up but I can't see how it could start at all on silicone grease. You may not have too much power, but your rotor alignment may be off which causes a similar problem. So imo you need to be sure your rotor is lined up with the cyl when it fires. If not then it has to jump further and you have more wear and tracking as a result. In my Chevota, which used a Chevy eng, I had to adjust the timing plate to ensure the cap and rotor were as close as possible. You may have both mechanical and vacuum adv which can add up to be a lot, so it may look aligned when static but might be way off when advanced. I cut a big window in an old cap so I could see the alignment, and I could actuate vac adv while watching it. I could do this with the eng off, then fire it up and watch it with and without a timing light to be sure it was in the ideal spot. Pita but I was determined to get it right, and I certainly didn't want any spark energy jumping to the wrong cyl.
I also used metal plug wires because carbon wires only make things worse. Not sure but I think most or all have metal now? Another option that I had to do to one car was lengthen the rotor contact because when lined up the spark still had quite a gap to jump. If you get too close it'll hit at higher rpms, which I assume is the cap and rotor moving around a bit, but I didn't notice until very high rpms, like over 7, but of course it depends how close you make it! So soldering or gluing an extension on may extend life too, and optionally you can use a wider rotor tip so when it's not aligned it's still reaching out to minimize that gap.
Ideally you want good connections on the wires to the plugs and cap, and no leakage, so use silicone grease on the metal and rubber boots.
To solve a moisture issue I had on one eng I ran a vac line to it to keep air moving through it and suck up the steam, which worked! ******* Racing ;)
 
#3 ·
I put silicone grease on the metal parts of the cap and rotor but my issue was mostly too much current going thru them so it helped reduce burning the metal. The issue is the same as yours, mine was just harsher. So I was thinking you could coat the plastic with silicone grease and it should stop or greatly reduce tracking. I used silicone spray, grease is way better but also a much bigger mess to clean. For mine I'd just spray the cap with brake cleaner, then spray with silicone and done. Tracking starts small and builds up but I can't see how it could start at all on silicone grease. You may not have too much power, but your rotor alignment may be off which causes a similar problem. So imo you need to be sure your rotor is lined up with the cyl when it fires. If not then it has to jump further and you have more wear and tracking as a result. In my Chevota, which used a Chevy eng, I had to adjust the timing plate to ensure the cap and rotor were as close as possible. You may have both mechanical and vacuum adv which can add up to be a lot, so it may look aligned when static but might be way off when advanced. I cut a big window in an old cap so I could see the alignment, and I could actuate vac adv while watching it. I could do this with the eng off, then fire it up and watch it with and without a timing light to be sure it was in the ideal spot. Pita but I was determined to get it right, and I certainly didn't want any spark energy jumping to the wrong cyl.
I also used metal plug wires because carbon wires only make things worse. Not sure but I think most or all have metal now? Another option that I had to do to one car was lengthen the rotor contact because when lined up the spark still had quite a gap to jump. If you get too close it'll hit at higher rpms, which I assume is the cap and rotor moving around a bit, but I didn't notice until very high rpms, like over 7, but of course it depends how close you make it! So soldering or gluing an extension on may extend life too, and optionally you can use a wider rotor tip so when it's not aligned it's still reaching out to minimize that gap.
Ideally you want good connections on the wires to the plugs and cap, and no leakage, so use silicone grease on the metal and rubber boots.
To solve a moisture issue I had on one eng I ran a vac line to it to keep air moving through it and suck up the steam, which worked! ******* Racing ;)
Thanks for your useful and informative advice.
I too am a great believer in silicone grease and use for many purposes knowing that it is a very good electrical insulator.
Donkey's years ago my uncle who worked for a UK power line company gave me a tub of silicone grease that he used on 30Kv. transformers that I'm still using to this day.
When I kept the car in the UK I did squirt some WD40 into the caps but the next time I had to wipe out moisture the WD had turned to a yellow sludge!
Using the silicone grease in the caps is a much better idea, but silicone sprays should be used with great caution in the engine bay because silicone can destroy the sensitive element in MAF sensor.
 
#4 ·
Hi All,

Reference m119 distributer caps the most important improvement is actually venting the caps.

Please refer to the thread below for useful information. 500E board has lots of m119 related data and How-Tos also well worth a look

Thread 'Essential M119 Ignition "Tune Up" mods' FYI - Essential M119 Ignition "Tune Up" mods | M119 Engine

There was a certain guy who embarrassed himself on the thread ;)
 
#5 ·
Hi All,

Reference m119 distributer caps the most important improvement is actually venting the caps.

Please refer to the thread below for useful information. 500E board has lots of m119 related data and How-Tos also well worth a look

Thread 'Essential M119 Ignition "Tune Up" mods' FYI - Essential M119 Ignition "Tune Up" mods | M119 Engine

There was a certain guy who embarrassed himself on the thread ;)
Venting the caps has proved to be a very worthwhile modification.
There was nothing to be embarrassed about, RobM only pointed out the difference concerning the depth of the venting slots and air-flow direction.

Update on my refurb mod: This month I took my 1993 SL500 for its annual technical inspection (which it passed). Before going for the test I had a look inside the distributor caps and both were still looking good with no evidence of tracking.
 
#9 ·
It's all good, I don't think anyone except @robm.UK is concerned about dates of who said what and when..... that is the point that is lost.

My thread was created in good faith with to raise awareness nothing more or less than that. I do not feel I made errors and will not be changing the thread.

Everything that could have been said on the thread was said and it got locked so no biggie as said before time to move on and agree to disagree on this subject. No hard feelings form my end. Note that I have created dozens of How-Tos and will continue to do so. I will not respond further there is simply no point
 
#10 · (Edited)
It's all good, I don't think anyone except @robm.UK is concerned about dates of who said what and when..... that is the point that is lost.

My thread was created in good faith with to raise awareness nothing more or less than that. I do not feel I made errors and will not be changing the thread.

Everything that could have been said on the thread was said and it got locked so no biggie as said before time to move on and agree to disagree on this subject. No hard feelings form my end. Note that I have created dozens of How-Tos and will continue to do so. I will not respond further there is simply no point
You can use this type of rhetoric as much as you like, but you can’t hide from your posts. So when I questioned the veracity of your claims that you discovered the source of the problem with the vent design of the distributor caps 5 years prior in 2016 and that the solution to this problem was all your own work, it was your posts from 2019 that betrayed you.

Hey, don’t get me wrong, I’m not perfect. But I do listen to others perspectives and show consideration and respect.

Suffice also to say that my concerns were definitely not about exclusivity, enforcing copyright, or implying that anyone stole my work as was suggested. This was way off the mark.

To be honest, I was surprised that you came all the way over here to Benzforum to snipe, especially after you said over at 500eboard in Post in thread 'Essential M119 Ignition "Tune Up" mods'“Lets move on shall we please @robm.UK? Sorry to anyone reading this...”, which, as a consequence, was a bit insincere.

But on the positive side, raising awareness is good 👍, which is why I already thanked you for promoting my modification. But I am now beginning to understand why you won’t acknowledge your sources and address the technical inconsistencies in your thread. Although this is basic forum etiquette and duty of care for most folks, I presume your ego won’t let you. So I’ve been flogging a dead horse it seems.

Needless to say I worked very hard on the analysis and research to be sure that my vent solution worked before I published my findings in 2017. If you play around reducing the size and number of the vents it will compromise the outcome. No two ways about it.

So, I couldn’t leave your post over at 500eboard without saying something because anyone following your downgraded version of my solution might run into problems, and I really don’t want other folk to be inconvenienced or to have that kind of negative feedback associated with my recommendations.

I mean this when I say that it’s all good for me too. I certainly have no hard feelings, and nothing to regret. I am a little wiser regarding your character traits now, and I am pleased to have had this opportunity to make these points, which I was denied when the thread was locked over at 500eboard.

Sure would have saved us all a heck of a lot of time if you had only remembered what you wrote in 2019!

Regards
Rob
 
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