How do you know (visually)when to repair or replace a distributor cap and/or rotor? Can you clean/service either without replacing them? I realize they're relatively cheap, but I don't know how old the ones on my new-to-me used 1992 190E are and I don't want to spend $70 if I don't have to. The issue my car has is it seems down on power. Spark plugs and wires and compression check all show good.

pull it and see if it looks good.... contacts should be clean.

does your 190e have a 4 cylinder engine? they don't have much power...

should have more than enough if you have the 2.6

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1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride). Sold with 179k miles. Replaced with Hyundai Equus

1994 e320 Cabriolet 108k



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


[/SIGPIC]

If it looks like this
http://www.peachparts.com/shopforum/attachments/tech-help/10596d1060551590-thanks-steve-you-nailed-one-cap1.jpg
you need a new one.

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95 SL500 Smoke Silver, Parchment 64K
07 E350 4matic Station Wagon White 34K
02 E320 4Matic Silver/grey 80K
05 F150 Silver 44K

I have 2.6. It feels like a 4 cylinder.

Aside from cleanliness, also look to ensure that all the angles are still sharp and not irregularly shaped.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

The distributor cap in that photo is nasty! It looks like the rotor went bizzerk and sprayed electical charge everywhere.

If I ever have my cap off, I check for buildup on the contacts and scrape it off - just like we used to do with the old engines w/points. If there's ever any roughness on the end of the rotor, that can be smoothed down w/a points-file.

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Don't Chrome them; polish them

95 S420 119 V8 motor has two caps and rotors. I cleaned and with 000 steel wool and filed the rotars flat and clean, then sprayed the inside of the caps with circuit board "conformal coating" of the type like printed circuit board are coated with. That was several years ago at 60K. I am now at 120K and have never had them opened since. I did replace the spark plugs at about 90K but did not open the caps again. Seemed to lengthen the service interval some. If the caps have any cracks in the body of course they must be replaced, but cleaning and coating seemed to work for me. Original 12 year old caps still being used. DanielW

Does this look like normal wear and tear...

I would replace the rotor and cap in those photos, it does look normal, nothing bad about it, just time to replace.

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red

The HEI ignition system is so powerfull that the rotor can short to ground via the distributer shaft, causing all sorts of backfires through the intake and exhaust.

I just had that happen on my '84 Vette, a new Accel cap/rotor($26.00) and some Delco plugs(18.00) later and it runs great. What's not great is that itt blew out the right side collector gasket when it backfired, drat.

I can't let mine go that far. Wish I could....I have two, and they're not cheap.

(anybody have some cheese to go with my whine?)

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

Costanza, the distributor cap and rotor are in really poor condition ... long overdue for replacement in my opinion. I replace the distributor cap, rotor and spark plugs every 30,000 miles in our 124 cars. With the price of gas today it's best to have an engine running at peak efficiency.

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Fred Hoelzle

Thanks. I did replace with a new set I picked up on eBay for $50! I don't notice the car running any better, but I guess I feel better.

costanza, I recommend replacing the spark plugs also, and make sure they are gapped correctly. How did you conclude the ignition wires were fine? If they are original it would be a good idea to replace them too. Use Beru or Bosch ... whatever brand/style is in the car originally ... you may want to call your local MB dealer and check what style ignition wire set they sell for a 1992 190E.

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Fred Hoelzle