New member with 300E problems

[G-Benz]

Love my Benzes!!! As a child, I grew up with my Dad owning at least one (and he still has his '71 280SE).

My 93 300E has over 104K miles on it. I am plagued with three problems:

1. Small problem: light bulb indicator lights up when brake is depressed...this does not occur if the headlight switch is switched on the 'parking light' or 'headlight' mode (including fog on or off settings). All bulbs are working and I even replaced the headlight switch, but to no avail. Also when headlight switch is off and I depress the brake after first starting the car, the switches below the shifter on the console flicker rapidly (I can only see this in the garage since the backlighting is dim when it occurs).

2. Sometimes the car will not start. Only happens with a warm engine. Turns over fine, but requires several tries. After reading a few similar posts, the fault seems to point to the overvoltage relay, but I am not sure.

3. Biggest problem: When cold starting, the idle pulsates in half-second cycles between 500 and 1200 rpms. This will persist until I rev the engine after a short warm up. I can also reinitiate this scenario by braking hard at low speeds or by putting the car in reverse. I disconnected the air mass flow sensor and the problem went away. I installed a new air mass flow sensor but the problem is still there. (At least I can return the $245 unit for a full refund).

Are these familiar problems or do I have a ghost in the machine?

I would like to begin fixing this car myself (other two Benzes still have warranties). I have a relatively modest tool supply, and can tear down and rebuild my aircooled VW motor with confidence, so I am a bit mechanically inclined. But the aristocratic nature of the Benzes has me a little intimidated, and I find myself reluctantly letting the dealership (at $100/hr) do the dirty work.

Am I asking too much for my first post?


I like what I've read so far!!!

[Pbalias]

G-Benz...

So far, I can't help you, but don't worry! This board is loaded with some kick-but techs that will help you get through EVERYTHING! It may take a little patience. By the way, don't be intimidated by MBs. After getting the hang of them, they are some of the easiest (and most fun) cars to tear down and put back together, it just takes PATIENCE and confidence! Hang in there, you'll get it sorted out.

Peter

[David C Klasse]

Giuilo,
Good job on the research. I am 95% sure you need a new overvolt relay for you warm starting problem. It cured the problem on my car. There is also a small chance it could be the fuel pump relay aswell, but I'd start off with the OVP.
And be sure and buy it from partsshop here on this site! They are the cheapest, have the best prices and the quickest service. And they need support to keep the site running! Good luck and I can assure you will love the forum.

[G-Benz]

Thanks for the tip...I will start with the OVR and see what is cured before pursuing further...nice car, by the way...and those rims!!!

[chowpit]

Recheck your brake light bulbs to ensure they are the same wattage. The bulbs should be 12v 21w. Incorrect bulb wattage can cause the failure light to come on.

There is a service campaign for the engine wiring harness which could be the cause of your engine running troubles (ask me how I know). Keep this in mind before you throw too much money at this problem.

[jeffsr]

This may sound silly, but check the third brake light (the one inside the rear window). Many folks miss this one when the bulb out sensor comes on.

[David C Klasse]

I suppose this won't help since it is telling you that one of your brake light is out, but did you check the license plate bulbs?

[G-Benz]

OK Scott, what about the engine wiring harness problem? I would like to know about this!

Jeffsr: Actually, I did have the third brake light fail at one time, and the indicator stayed on when I braked (regardless of whether the light switch was ON or OFF). Replaced that bulb and the indicator light was back to doing its usual weird stuff.

David: I didn't think to check the license plate light, but I will check that too.

Chowpit: Thanks for the tip about the bulb wattage. Might spend a few dollars and go through all of the bulbs, since one of the bulbs goes out intermittently.

[G-Benz]

Checked license plate lights...both okay.

Discovered one bulb in right rear taillight that is 27 watts instead of 21. Will replace when I can get to an auto parts store this evening.

[G-Benz]

Thanks everyone who posted for all of your help!!

Main problem seemed to be that several of the bulbs (although working properly) were not seated correctly. I am going to replace a couple of suspect bulbs including the 27W bulb.

Light no longer comes on for the first time in eight months!!

Strange that back when the problem first surfaced, the MB techs at the dealership couldn't solve the problem. They did charge me the usual $175 diagnostic fee to do this, and $100 for labor for replacing some of the bulbs!

Now, to tackle the other problems...

[nellotare]

Hello All,

I'm visiting friends in another town and on another computer so I can only check for messages occassionaly.. but here's my request. I have a friend in this town with a '95 - 300E that has had the problem of not starting when hot. He's taken it to the dealer in Raleigh and they couldn't figure out the problem. I told him about the OVR, vapor lock etc. .. Yesterday I physically was going to show him where/what to look for if it happend again etc. My problem is that I couldn't find the Overvoltage Realy! Where is it located on his car? Where is the fuse etc.? I had pictures from another post and thought I would find it in the same place.. but no such luck. I'll be leaving Sunday to go back home and hoped I could help him out before then. Any assistance will be greatly appreciated.

Thanks

[JCE]

On my '87 300E the OV relay (red top, 1 fuse) is between the battery and the glove box firewall - there is a removable plastic shield between the relays and the battery. looking at the firewall behind the battery after the shield is removed, there is a box with fins and cables (computer?). behind that finned box there are 3 relays arranged in this pattern as you look towards the center of the car - :' - where the lower dot (closer to the battery) is a relay, the upper dot (closer to the firewall)is a relay with 'Klima' printed on it , and the ' symbol (closest to the windshield wiper) is the OV relay. Your friends car is newer, and may have 2 fuses on the top, but this is the area where I would start looking. Good Luck.

[Jim Anderson]

My father-in-law was having real weird lighting problems that he had me look at. I couldn't really figure exactly what was causing it so I was just looking around. It was one of those double filament bulbs. The two soft solder contacts that always have spring pressure on them over time and vibration had deformed and shorted against each other. I don't think I would have ever have guessed that would happen. It was in an older simpler car and it scares me what a newer car would do. Just something else to check when you're out of things to check.

[Edited by Jim Anderson on 04-27-2001 at 11:33 AM]

[nellotare]

Thanks JCE, for the info.. I've printed it out.. so if I can't find it, then he'll have a piece of paper in the glove box to show an MB mechanic. I was looking in that area but never saw the red top.. will try again before heading home. Thanks again!

[G-Benz]

I thought I would go ahead and dig up my first thread I posted just to see how long it took to finally solve all of my issues!

My indie found the bad vacuum hose today that was causing my surging problems...so I've lived with this for nearly four years!

The OVP issue was soved within a week of posting, and after about a year later, traced the bulb-out indicator to those metal strips in the taillight housings!

Obviously, new problems crop up as time goes on (getting motor mounts, timing cover seal and neutral safety switch replaced), but my goal is to get the old W124 cosmetically and mechanically 100% by this summer!

Over 4000 posts later, I bid a hearty thanks to all of you who've contributed to solving my MB problems, as well as others here on this forum. I hope that I have been able to add my two cents worth with some of the things I've experienced and helped others to their ultimate goal...more of driving their MB, and less of tinkering!

Happy motoring!