Hello One and All! My name’s Scott and I am a mechanoholic. I am trying to be in recovery but then I bought this MB.

As I Get Older I really can't afford to be pulling out any more hair, so when I started trying to diagnose this current problem I decided to turn to the Internet and google led me here.

I am certain we will be frequent visitors in the years to come. I have always been a pretty fair mechanic, but without shop manuals it has been a pig in a poke under the hood of this 500SEL.

This is my third MB. After spending thousands restoring my 280C and finally after a few years of enjoying her then seeing her go down the road without me, I thought I would never again be in this market. But this pristine and near-perfect 85 500SEL just waived its wipers at me and here we go again.

I used the excuse it was a Christmas Present for My Wife!

She has 192,000 well cared for miles, The MB, Not My wife. My brother and sister-in-law owned her from birth and were meticulous about her care. His wife drove her until we got her in 2003.

My wife now drives it and for several years now she drove it one block to the gallery and one block back each day. Now we are in our new home four miles away and she drives that all highway. About once a month we will take it to the valley about 50 miles away and I will work it out a little on our coastal roads. Blow out the carbon if you will. I also take it to the store on occasion if I am not in work clothes.

For the last few months, When she started it (Starts first time, every time!) it has required more and more time to warm up before she can put it into gear and head down the one block. It would not die, just, best description, "choke out?, Bog?" and return to an idle when she let off the gas.

Now I have been tracking this for months when I could give it some time. As of the past two weeks it also has a power loss warm, when at the low end of the RPM range and when pulling hills. Big time on hills. It reminds me of a nearly plugged catalytic converter, but I have not gotten into it that far as of yet. I believe I have read all the threads but nothing fits exactly as this is.

I have already done the following;

I think Unrelated?, Replaced the cruise control switch, it would set itself on bumps due to being broken inside. (Note: Shop replaced switch, now it will not work at all, Shop mechanic says he has no idea why and cannot fix it!) But it is better than taking off on its own when my wife is driving her. So I will look into it when I have a manual.

Replaced the rear fuel filter.
Replaced the Plugs with Bosh Platinum’s.
Replaced the Distributor Cap with Bosh Cap.
Replaced the Rotor with Bosh Rotor.
Ran a bottle of injector cleaner thru it.
Cleaned Air Filter.

Pulled the Electrical Plugs on Cold Start Valve, Temp Sensors and several other sensors and burnished the pins and then put oxguard on them to prevent corrosion. Here at the beach this is a good Idea anyway.

Checked all the vacuum hoses easily accessible for cracks, but I hear no vacuum hiss from anywhere.

Checked Plug Wires, Clean and good continuity.
Oil Level OK and Near Fresh.

Ran the motor and looked at and listened to everything carefully and seen nothing out of place or unusual. It is full factory. All but one air cleaner mount rubber is in place.

O.K. HELP!! I don't know what to do next. As I do not have manuals, I first need to secure them.

I have read some terrible reviews on the Chiltons, Haynes Paper manuals and the ALLTECH C.D. Rom Manuals. I have tried to see what kind they have in the Fast Lane reviews but those pages won't come up. Any recommendations. eBay has some offered for $10.00 but they have not responded to my inquiry about who wrote theirs before I buy. I guess anything will be better than nothing but what is good?

Thanks in advance for your assistance, I promise, as I tinker I will share also, as I guess I should now get the SL I have always wanted and make them a hobby. Unless you know of a good twelve step for MB Program.

Scott

Sounds familiar. I'd do a search on platinum plugs and see what that turns up.

__________________
1987 300e manual 250,000 km (sold)

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?

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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

trants4md, the lack of power under all engine temperature conditions smacks of a clogged catalytic converter IMO. The economy gauge going into the 'red' when accelerating seems normal as it's sensing vacuum. I take it that the needle is responding more dramatically than 'normal' under acceleration. I have to go right now, but later I'll search for a simple method to diagnose a plugged catalytic converter.

__________________
Fred Hoelzle

I concur re: spark plugs--
Platinums should be given the flotation test.
Throw them in the river-- if they float, you can re-use them.
Seen more than a few horrible running mid-80s V-8s fixed by going back to
proper plugs.

My dislike of platinum plugs does not extend to cars designed to run them.
NOT trying to start a platinum plug debate--
if they work for you--peachy.

If the injectors are steel-- give them the flotation test as well.
Updated injectors are brass. Replace seals as well.

No EHA on an 85.

Fuel distributor or warm-up regulator are likely culprits.
Fuel pressure test will show bad regulator.
For Distributor. we fabricated a test rack with eight clear graduated cylinders and a set of fuel lines made of Tecalan fuel line and fittings.
Allows inspection of injector spray pattern, as well as differential volume readings per cylinder(injector) Test can be re-run after swapping injectors cyl to cyl to identify either bad injector or distributor.
Contact area shops-- find someone with the proper test equipment. You don't want to guess on a fuel distributor.
Bosch sells a fancy version tester, ours does the same thing.

Fuel distributors have gotten ungodly expensive from Bosch($1400-1800)
the last I checked. We have had fairly good success with an outfit called
Python fuel injection for rebuilt units.
Do not take a fuel distributor apart--
you are asking for trouble. I know of no source for internal parts or selas/o-rings..

__________________
Todd Haven
Parts Manager
MPH Automotive
Houston,TX

The good news is I have found the main problem, sort of! All you who assisted and said vacuum leak were correct. But where the leak is caught me off guard.

In tracking every vac line I came to the large line connector to the left of the throttle body air intake that goes into the intake manifold. Upon pulling the line and plugging the tap into the manifold my idle immediately smoothed out. The motor purred again! By this time the engine was warmed up.

Tracing down hose from there looking for a vac leak I tested every hose and connector under vac pressure. Every hose OK. Not a bad hose in the entire system. Then I reconnected it one section at a time. When the C4020-13554 Warn up regulator was reconnected it went ruff again and I had major engine hesitation on acceleration.

It appears that I have a vacuum leak internal in the warm up regulator diaphragm.

Does anyone know if a rebuild kit is available, or will I have to build my own diaphragm parts?

I am certain I can do something as the regulator is not staked together, but it never hurts to get a kit if possible!

trants4md

Scott, glad to hear that you pinpointed the problem. I've got no idea if a rebuild kit is available.

__________________
Fred Hoelzle