Carefully checked gap twice. Plugs that came out were platinum4's

Might want to check the fuse on the OVP (do a search on OVP) should be behind the battery (behind the black plastic cover?) a relay with a clear plastic cover on top with a 10 amp fuse underneath the lid... might want to take it out and shake it to see if it rattles at all ( the most basic and primitive of all OVP tests)
Did the hill power problem correspond at all to the platinums?
Even if not you might want to get those out of there and replace them with Bosh coppers ( about$1.00 each) Mercs don't seem to like those high quality plugs as much as the cheepos. Check with your dealer for the right plug # but they should probably Bosh D7 D8 D9 DC7 DC8 or DC9.
Good luck.

Edit I see this thread is the active one You might want to delete the dublicate.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Hey, Thanks all.

I just put in the new platinum’s, cap, rotor, etc. Once it became a road hazard for my wife to be driving I have had to pour attention into this.

You know the drill. Wife complains about squeak, spray some oil at anything. Becomes dangerous for her, spray oil on everything. Until this week I took a peak for the squeak, but was not real serious.

That relay, one by that description is in the fuse box. Has a 10 Amp new style U.S. fuse flat on the top. Or is it behind the battery? There is a vacuum valve with an electric wire in the latter and some other devices down in there!

Scott

Try putting some Bosch coppers in place of the platinums. Not too expensive.

trants4md, my parts source shows that a 1985 500SEL should use Bosch W8DC sparkplugs. I'd verify this with the Owner's Manual and remove the Bosch Platinum sparkplugs ASAP. Older MB engines don't run well with the Bosch Platinum plugs ... stick with the sparkplugs specified for your engine. Call a MB dealer's Parts Department if you don't have an Owner's Manual. Your problem could be caused by a variety of things ... faulty oxygen sensor, bad OVP relay, etc. Rather than throw parts at the problem, after you install the correct sparkplugs I'd have either a dealer or an independent MB-versed tech diagnose the problem. An experienced tech should be able to sort out the cause quickly and inexpensively.

__________________
Fred Hoelzle

Hello,

When looking for the OVP relay, I was unable to find a relay behind the battery, but one matching that description was in the fuse box. According to the owners manual that is an empty space as I show in the picture below.

When I first shook it, it rattled a fair amount but with subsequent shakes it quieted down. I would expect some rattle when FD&H (Fat Dumb & Happy) as it is referred to in electronics. This is when no influence is applied. Also I would expect pieces of a blown relay to find a resting place inside when shook and then it would quiet down.

I metered the legs, the coil has continuity. The other pins are open. I do not know what it should be when FD&H. I measure no resistance in cross leg checks, I would have thought there might be some as the diagram on the relay cover shows some resistors on cross legs unless I am reading it wrong.

Any more information on this relay?

Attached Thumbnails

       

The OVP would affect the cold start issue but not necessarily warm power loss.
Though it may I just don't know that.
If it goes bad the expensive systems it protects like fuel injection computer, ABS systems...I'm not really familiar with your engine (m117 right) ... will stop functioning. There are a number of things that could be affecting cold start problems OVP is one of them and is difficult to test. Having a good spare OVP never killed any Benz owner that I know of though.
Other components are easier to test like the water temp sensor but the warm power loss makes it a lot harder to pin the issue on one of these.
Possibly a bad EHA?
The comment about throwing parts at it is something you could easily fall into with these diverse symptoms. And
Maybe you have some more specific symptoms...
- Does the exhaust seem overly rich?
- What is cold idle vs. warm idle?
- Is the power loss on hills all the time or intermittent when warmed above 80°C?
- Any other symptoms (aside from cruse control) like an ABS light on?
Testing that Cat seems like a good idea as well short of more specific symptoms.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Thanks for the good help and directions of where to start, To answer your questions.

Motor = 5.0L Fuel Injected V8 Vin:117.963
It really has no cold start problem, Instant start, First Time, Every Time. No power after start, Boggs with accelerator being depressed.

I do not smell fuel or gas smells. I don't have a variance between cold and hot idle. About 750 RPM. It is surprising it hasn't a higher idle speed when first started. But I cannot remember it ever having an increased idle when cold. This may be a clue as you have a fast idle position on most cars when first started. Our ambient temps here are pretty reasonable we range from overnight lows in the 40's at night to no higher than mid 70's during the day on average.

The power loss is on hills all the time, now this just started about a week ago. Prior to that I only had the cold power loss. Once warmed up to over 80C it ran fine until then.

I have no engine or other warning lights or gage irregularities. With the possible exception that the economy gage drops all the way into the red totally when I try to accelerate.

I am going to give it the TLC it needs tomorrow. I will check every hose again, burnish and coat every terminal with oxguard and check the flow out of the tail pipe. I really should look under at the Catalytic converter when it is warmed up as well. Just need to do the methodical step by step of good maintenance.

I found a good tread about using a vacuum gage to check the cat. If I can find that ol vac gage I will run that test as well. I have to go down to our building in town an get my other test equipment. Now that I own another MB I guess I will need it close again. Not to say there are more problems, MB owners are just more attentive to the little things, Ah, I remember those days well. De’ja’vu all over again.

I also ordered some CD manuals today! I hope they are the good ones!

Thanks again!!

Good luck tomorow...

One note about that... if the gage goes red under slight acceleration... say 1500 rpm's thats a pretty good indication of a vac leak... as that gage is measuring manifold vaccume pressure. Look for slits in the rubber... and try spraying ether or propane around suspect areas while listening for an increase in engine revs from the extra fuel drawn in there.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html