Distributor cap/rotor keeps wearing out

[szegedin7]

Greetings all -- I recently had a problem with what seemed to be a misfire, which I resolved when I figured out that the distributor rotor had broken off a chunk.

Replaced the cap and rotor and after less than 1000 miles the problem returned. Took a look and there are deep grooves in the contacts of the cap on one side. It's as if it was mounted wrong, but the mounting seems more or less tight. So it runs rough, smoothing out a bit when it warms up.

Has anyone run into this? Is it that the shaft of the distributor is bent, causing that rotor to oscillate? Replacing the distributor should be a piece of piss?

This is a 1990 waterboxer.
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1990 Vanagon 2.1

[Igeo]

Is there lateral play in the shaft? Easy to replace these units.
Never re-bushed one personally; they are probabaly simply swapped out as a unit. Easy job.
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1987 Westfalia 2.1 WBX Manual

[szegedin7]

[Igeo]

If you do swap-out, have a timing light to set the timng.
https://www.youtube.com/watch?v=t7eficskDyk
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1987 Westfalia 2.1 WBX Manual

[MsTaboo]

Yep, sounds like worn shaft bearings in the distributer.

When replacing a distributer it's very important to watch your timing marks.
Have you ever done this type of work before? Do you have a Bentley manual?

It's always best practice to put the engine at Top Dead Center and marking where the rotor is pointing (should be #1 cylinder firing position) before pulling the distributer. This will make it easier to set the timing close to finish. Remember the helical gear on the end of the distributer shaft will want to twist as you insert the shaft, so it may take a couple tries to get the rotor pointing back at your marks.
A timing light is required to set the timing just right.
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Currently:
'90 Syncro Westy 3 knob w/Zetec

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[szegedin7]

[Igeo]

Yes, mark the rotor position, then as you withdraw the dist. observe how the rotor turns as the gear unwinds, and at what point the unit comes free. It will help you know where to start when you re-install.
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1987 Westfalia 2.1 WBX Manual

[djkeev]

[Steve Arndt]

The quality of replacement parts are not very good anymore. I would try some new parts of a different brand before swapping distributors. The 2.1 distributors don't really mechanically wear out. The older style with moving mechanical and centrifugal advance mechanisms do wear out.
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Steve
Steve's 87 Syncro project

[Igeo]

Thanks to Dave for the correction.
I would pull the dist. out and inspect for wear. If no lateral play, then put a new rotor and cap on the dist. and turn the shaft by hand. Make sure it feels smooth and that you can detect no uneven "contact". Does the cap fit squarely? Is the rotor snug? Things like that.
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1987 Westfalia 2.1 WBX Manual

[szegedin7]

Just out of curiosity-- does a distributor work by actually making contact between the rotor and the cap's contacts, or does it "arc" like a spark plug?

It seems that mine keep getting trashed by physical contact because of a furshlugginer distributor shaft, but are those contacts actually supposed to touch or not?
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1990 Vanagon 2.1

[Igeo]

No contact between the end of the rotor and plug tower terminals. The coil tower terminal does contact the top of the rotor. Can you pst a picture?
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1987 Westfalia 2.1 WBX Manual

[szegedin7]

[Wildthings]

You have to be carefully to get the cap on correctly or you will get contact between the rotor and the terminals in the cap. It is more difficult to get the cap on if you still have a dust shield under the rotor than if you do not. If you still have the metal shield over the outside, that too makes installing the cap a bit harder.

[szegedin7]

[andk5591]

May not be related at all, BUT if using a Pertronix or similar points module, you MAY need to grind down the bottom of the rotor since it sits too high and can chew up the cap. I have to do this on at least half of the conversions that I do.

Its nothing magical - see how low it sits before installing the magnetic pick up and then with the pick up in place. Remove enough material so the height is about the same. No prob if you take too much off, I usually have a slight gap.
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[tasb]

The distributor cap has a light duty spring under the carbon brush. When you place the cap on the distributor you should feel very light resistance from the brush making contact with the rotor button. If there's no tension or too much and you have to push the cap down there is something wrong. The finger of the rotor and the four metal cap contacts to not actually contact.
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Roads Scholar &
1957 Kombi low mileage 36 hp governor equipped M 178 Slow Drag Winner 2014, 2015, 2018

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[szegedin7]

[tasb]

A poorly fitting cap and rotor can certainly cause ignition miss.
_________________
Roads Scholar &
1957 Kombi low mileage 36 hp governor equipped M 178 Slow Drag Winner 2014, 2015, 2018

1965 hardtop Deluxe Microbus owned since 1990 M 620 factory 12 v 1500cc

1961 (October)Single Cab- Road Trip Workhorse

[Wildthings]