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  #1  
Old 06-14-2001, 10:54 PM
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Location: Maryland. USA
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Vehicle is a 1980 U.S. 450SEL.

Symptom is rough idle, stumble when accel from a stop until engine warm.

Clean dist cap and rotor. Problem temporarily resolved. I have found over the years that the distributor cap and rotor need to be replaced about every 45,000 miles. Burned conductors on the cap (all 8).

Is that normal?

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S, J.R. Brown
2000 G500 LWB Obsedian Black
2005 Toyota Tacoma Access Cab Off Road Sport
1993 Volvo 240 Sedan Anthracite
1980 450SEL Champange (owned it for 15 years. Great car)
1986 280GE LWB Anthracite (Sold it and kinda wish I hadn't)
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  #2  
Old 06-14-2001, 11:20 PM
dlswnfrd
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All Things Wear

Brother of The Benz, JRB
All mechanical machinery wear evidentually.
In a distributor; the shaft bushing or in a direct drive from the camshaft the support bushing.
Vacuum retard/advance units.
Electronic Components, i.e. solid state devices or points and condensers. Distributor caps and rotors conducting up to 40,000 volts through worn spark plug wires.
There is no set rule of thumb for replacing any one of these items.
My 1987 W124030 with 176K miles still has the original cap and rotor.
BUT, I just last week I was bragging about my original A/C compressor and this week it failed.
Visually inspect these items and replace them where needed, but it isn't neccesary to replace something just for the fun of it for a cap asnd rotor don't come cheap.
Happy Trails Beep Beep from The Spiderman in Houston!!!
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  #3  
Old 06-14-2001, 11:33 PM
JimF's Avatar
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a picture is worth a. . .

Check out these pics of distributor and rotor.

http://www.peachparts.com/Wikka/M119DistCapRotor

Nuff' said!
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  #4  
Old 06-15-2001, 07:37 AM
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Original cap and rotor on my car were replaced at 15 years and 185,000 miles. Probably could have gone another 15,000 miles as it actually wasn't too bad, but in the course of trying to fix my rough idle many things were replaced that probably didn't need to be.
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1999 E430
1995 E420 - retired
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  #5  
Old 06-15-2001, 09:06 AM
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Jim F.

Thanks for pointing me to the pictures. That is exactly what the contacts look like (less the corrosion).

Carbon was everywhere. Oh well.

Time to order some parts from FastLane. Don't know about you guys, but I've had some great servce (and turnaround times) from FastLane.

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S, J.R. Brown
2000 G500 LWB Obsedian Black
2005 Toyota Tacoma Access Cab Off Road Sport
1993 Volvo 240 Sedan Anthracite
1980 450SEL Champange (owned it for 15 years. Great car)
1986 280GE LWB Anthracite (Sold it and kinda wish I hadn't)
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  #6  
Old 06-15-2001, 12:00 PM
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I still find myself looking for root cause of the burning of the conductors on the cap. When compared to what I get out of my other vehicle with Bosch ignition systems.

Any thoughts out there?

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S, J.R. Brown
2000 G500 LWB Obsedian Black
2005 Toyota Tacoma Access Cab Off Road Sport
1993 Volvo 240 Sedan Anthracite
1980 450SEL Champange (owned it for 15 years. Great car)
1986 280GE LWB Anthracite (Sold it and kinda wish I hadn't)
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  #7  
Old 06-15-2001, 09:00 PM
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I had good luck with putting conductive grease on the conductors and rotor to help prevent the corrosion and burning.

Do the conductors have even wear? If one side of the conductors has more wear than the other side this could mean replacing more parts than just the cap and rotor.

I had a cap & rotor last 70,000 miles on one vehicle (replaced due to corrosion) and onother last 145,000 miles (worn out).

Every 45K miles seems a little premature for the cap to wear out.
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  #8  
Old 06-16-2001, 12:58 AM
dlswnfrd
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Tolerances

Brother of The Benz, JRBrown
As you can see when looking in the cap at the machining marks of the conductors, they are machined differently.
This resulted from the loose tolerance in molding the cap and conductors.
The base diameter of rotation of the rotor plus clearance is the machined diameter you see in the cap.
Assume you have a clearance of 0.060 or 1/16 inch between the tip of the rotor to the conductor in the cap, this is the "spark gap" between the two.
If the resistance of the spark plugs and thier wires is at minimum, then the arcing in the cap is minimumal.
The conductive grease helps contain the arcing.
But a dry air gap is the designed method to conduct the coils energy.
Concerned preventative maintainance extends the life of any component; especially spark plugs and wires.
Happy Trails Beep Beep from The Spiderman in Houston!!!
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  #9  
Old 06-16-2001, 09:57 AM
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All 8 contacts are identical regarding the burn/witness marks. Plug wire resistance is within spec. Plugs were 30k old. Standard Bosch WR9DC. No platinum or other odd ball stuff. Am I using the wrong sparkplug? Bosch website calls for a 7511 in Super which is a W9DC.

Is that (R)esistor difference causing a problem? WR9DC vs W9DC

What is a good source for conductive grease? It's worth a try.
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S, J.R. Brown
2000 G500 LWB Obsedian Black
2005 Toyota Tacoma Access Cab Off Road Sport
1993 Volvo 240 Sedan Anthracite
1980 450SEL Champange (owned it for 15 years. Great car)
1986 280GE LWB Anthracite (Sold it and kinda wish I hadn't)
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  #10  
Old 06-16-2001, 11:03 AM
dlswnfrd
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So Much Hot Air

Brother of The benz, JRBrown
Do you mean to tell me that after all of that hot air I directed at your problem I was way out in left field?
If all things are within spec and the plugs are relatively new(30K miles ?), maybe the cap just wore out.
I can't read between the lines to determine why it did what it did.
Your spark plugs at the 9 heat range is normal for a 103983 engine.
I use the cheap kind, copper core Champion RS9YC and they are resistor type gapped at 0.052 inches with a Jacob's Omni-Magnum Electronic Ignition.
I am going to revert to OEM ignition to-day, removing the Jacob's unit.
I've made other mods to the engine and I want to see what the Jacob's unit really provides me as it was the first change I made many years ago. Jacob's was new on the block then and I'm sure thier products have improved over the years.
Replace the ignition components completely and you will be as new again and at piece of mind.
Happy Trails Beep Beep from The Spiderman in Houston!!!
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  #11  
Old 07-30-2001, 11:36 AM
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I came across some literature, http://durranceeng.com/ that said that I should not have been running WR9DC plugs but should be running W9DC plugs. Lose the R(esistor). http://durranceeng.com/even_more.htm

The MB plug wires already have the necessary "setup" to fight radio noise.

So we'll see over the next few years what happens.

Thanks everyone.
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S, J.R. Brown
2000 G500 LWB Obsedian Black
2005 Toyota Tacoma Access Cab Off Road Sport
1993 Volvo 240 Sedan Anthracite
1980 450SEL Champange (owned it for 15 years. Great car)
1986 280GE LWB Anthracite (Sold it and kinda wish I hadn't)
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  #12  
Old 07-30-2001, 11:41 AM
WDurrance
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Well you beat me to it...I was going to type the explanation for not using resistor plugs.
Regards,
Randy D.
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  #13  
Old 07-30-2001, 12:07 PM
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What is a good source for conductive grease? It's worth a try. [/B][/QUOTE]

I HIGHLY doubt you want to put conductive grease anywhere within the ignition system secondary - particularly not inside the distributor cap. INSULATING grease (i.e. high-voltage anti-corona grease) might be more appropriate, if anything at all.

Steve
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  #14  
Old 07-30-2001, 12:27 PM
WDurrance
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Dielectric Grease

There does seem to be a lot of confusion about "tune-up" grease. This right up there with "Soylent Green is People!"...but the truth is...Dielectric Grease is Non-conductive. It is intended to help keep the cheap rubber boots on 'merican cars from arcing down the spark plug insulator. I worked (briefly) with a guy that would not believe it even after I took an Ohmmeter and proved it was an insulator. Ah the memories... .
Regards,
Randy D.
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