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Discussion Starter #1
I just recently purchased a 1992 300se, it is the first mercedes i have owned. I would like to staye up front i am very mechanically inclined but i don't know a damn thing about mercedes. The xar has 152k on odometer but it quit working along with speedometer 3days after i got the car. Check engine light is on and abs light, i have not been able to run the codes yet.
The problems started when driving the car just dropped out dead, and wouldnt refire, next day it started and died. All symptoms pointed to crank shaft position sensor which i purched, and installed.
This is where my major issue started, i needed to jump start the car after i put in the cps. The car fired right up, and idled great but if i applied gas it bogged down and died. I found a short in the pigtail fuel injector 6. Upon checking further the entire harness was degraded to the point where i couldnt believe it was running. I then purchased a used harness (i do not have much money) this one is much better. I installed it. Car starts no problem but again if i push the gas pedal the engine bogs out and dies, but if i gently push the pedal it will do just fine. Once it bogs it will rough idle and fall flat . Shut it off restart it idles fine if i pit it in gear push gas it shudders boggs down and dies. Ive checked vacume lines there good.
I dont know what to look into next, so i would greatly appreciate any help.
Someone i know told me to look into some voltage protector relay which i havent had time to study up on yet.
Thank you for any help
A.Stoner
2616883
 

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'99 S420 116K
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These cars are not that much more complicated than ANY other car, but they have some quirky electronics and wiring issues that can make you bonkers. And it seems you have a lot going on here. Thanks for warning us about your mechanical abilities. Pics of the car, details about work you know has been done, etc, are always helpful, too.

Lucky for you, there are few things about your vehicle that have not been addressed by this forum, and I suggest you spend a few HOURS, DAYS, WEEKS of research to bring you up to speed on the most common bugaboos. Remember, it'a all about Air, Fuel, and Spark, just like all other cars, except MB engineering does it better, not necessarily cheaper.

Be prepared for fluid, filter, fuse replacements, thermostat, belt, tensioner, timing chain guides, fuel pump/filter/regulator, brake pads/rotors, possible trans needs, A/C condenser, fans, and a possible head gasket. Overwhelmed yet? I better not mention monowiper, windows and sunroof yet.

MB's are extremely sensitive to battery issues, low battery will cause all sorts of odd behaviors, and your idea of checking codes is spot on. Do that and get back to us.(y)

I'd look at throttle body wiring for deterioration, voltage regulator(brushes) in the alternator, and the OVP (Over Voltage Protection) device if this model has one, located between the battery and the firewall behind a large cover. You may have blown a fuse mounted to that device when you jump started the car.

I'm not sure if you have an electronic ignition device that is prone to quirkiness, I'll let a more knowledgeable member address that, but if you do, it can be a serious matter.

DO NOT START THROWING PARTS AT THIS VEHICLE!. The most expensive car you can own is a old, used, CHEAP Mercedes. It may be too late now, but many buyers pay a few bucks to have a MB indie shop go thru potential purchases to insure there are no surprises.

Don't get discouraged, you found the right forum to keep you on the road, but expect to invest a few bucks to get the vehicle to the point of just doing routine maintenance.:cool:
 

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1995 Mercedes S420, 1995 SL320, 2000 Land Rover Discovery II, 1985 Lotus Turbo Esprit
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All good advice above. Throttle body needs to be looked at for sure. The wiring goes bad just like the main harness, and it will definitely cause the symptoms you described. So if your harness was shot, chances are your throttle body will need to be dealt with also.

These cars generally do not like to be jump started, so yes you may have blown a fuse as well, which could be contributing to the issues, if not the main culprit. Check all the fuses in the main box under the hood, not just the one in the trunk.

And if the battery isn't up to par, you'll need one of those too. These cars are very sensitive to voltage issues caused by worn or incorrect batteries. Check the battery to ensure it's the proper size and test it as well. If it's too small get a new one -- the car needs a Group 49 with at least 850CCA. Avoid jump starts in the future (giving and receiving), as you can potentially damage the computers too.

Alternator voltage regulator could be bad also, but you'd likely be getting a warning light for that one. Still doesn't hurt to replace it as a precaution anyway, as your mileage is definitely around the time they go bad. They're cheap and easy to do.

Don't be scared of the car, if you're mechanically inclined you can handle a lot of the work yourself. I'm most definitely NOT mechanically inclined and even I manage to get a lot done myself.
 

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Discussion Starter #4
Again i would like to thank you for your information and advice. I will say i am discouraged but i will keep plugging away at it
If someone could help me with more concise location of the OVP the battery is located in the trunk, alomg with small fuse panel but nothing else is in the battery box area.
I appreciate the help.
A.Stoner
 

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If someone could help me with more concise location of the OVP
Someone more knowledgeable than me will correct me, but I do not think there is OVP on any of the w140s.

EDIT: StarTek confirms that the Base Module (N16/1) is the power distributor:

StarTek also has lots of good info on diagnostic steps:
 

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1995 Mercedes S420, 1995 SL320, 2000 Land Rover Discovery II, 1985 Lotus Turbo Esprit
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Yeah, no OVP on these cars. Check the main fuse box under the hood, on the driver side. I forget which fuse controls the ABS system, but just check all of them to be sure. You're not going to find much else in the trunk.
 
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