Dielectric grease for distributor or not? - Mercedes-Benz Forum

 
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post #1 of 8 (permalink) Old 02-02-2011, 11:47 AM Thread Starter
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Dielectric grease for distributor or not?

Just a question for those out there doing their own work. Do you all use dielectric grease in your distributors to prevent arcing or do you not?

I've grown up using it, but none of my Benz manuals discuss it.

Have a '72 280SEL 4.5 that was dry when I got it, but was going to use it when I put it back together. I was wondering what everyone else does.
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post #2 of 8 (permalink) Old 02-02-2011, 01:35 PM
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There is no need for dialectric grease in that application. You will want to lubricate the ign point cam lobe lightly and you will want to remove the trigger point pack to clean and lubricate as well. The advance plate needs lubrication where it rotates aroung the base plate and the centrifugal advance needs a drop as well.
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post #3 of 8 (permalink) Old 02-02-2011, 02:04 PM Thread Starter
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I'm running Pertronix, so no points to contend with. Was just wondering because there seemed to be some evidence of arcing between rotor and cap which I would think dielectric grease would help elimiminate (as it does in the GM distributors).
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post #4 of 8 (permalink) Old 02-02-2011, 06:33 PM
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There is always some minor arcing at the air gap for the cap and rotor, it see'e from 8 -40000 v so it will always have some slight arc trails. I ran a dyno for years during that era and never really had a running issue caused from that specific condition. If the car still has the original efi system it still has trigger points in the lower section of the distributor.
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post #5 of 8 (permalink) Old 02-02-2011, 07:18 PM Thread Starter
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She does still have the original EFI. Pulled the distributor this weekend to check the trigger points and clean it all up. Thought I might be getting a bit of oil into the trigger points because the car does not like to start when hot. Turned out the trigger points were pretty clean...no oil in the bottom of the distributor. I think I have a leaking injector. When hot, the car holds pressure at 30 pounds in the rails for about 30 minutes, then drops like a rock to 5 pounds. I think she is vaporizing the fuel in the rails as the fuel leaks out. Once it is all vaporized, the pressure drops fast. Doesn't seem to hold pressure at all when cold. Not the cold start valve. Pulled it and it stays dry. Takes a few minutes to flush all that vapor out of the lines when you try to start her hot.

Thanks for the input on the dielectric grease in the rotor. I'll refrain from that.
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post #6 of 8 (permalink) Old 02-02-2011, 08:00 PM
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That fuel injection had a problem with winter fuel as it seems to vaporize quickly, hence the hard hot start. If the regulator had a leak it would make starting easier as the fuel rail would purge the vapor or bubbles much easier. We actually drilled a small hole in the regulator allowing a small leak that would facilitate purging much more quickly. The last 2 years the factory installed the hot start relay that would open the injectors momentarily during hot start to help with the issue. Set the fuel pressure at the lowest...... 28.5 and it facilitates a quicker purge.
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post #7 of 8 (permalink) Old 02-03-2011, 08:17 AM
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I've had hot start issues as well and solved them by replacing the injector seals. I bought the parts at Napa and was able to replace everything in about an hour. Pretty easy job actually.
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post #8 of 8 (permalink) Old 02-03-2011, 09:26 AM Thread Starter
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She actually has all new seals as of last summer. I think I actually have an injector leaking or perhaps the check valve in the fuel pump.
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