93 Mercedes 190E 2.6 - Starting Issues

So I bought a 93 Mercedes 190E 2.6 (V6) for my son as a first car - safe and affordable. All seemed well when we first purchased the vehicle back in November 06. It drove fine for several weeks
straight, with driving at least some distance at least a few days per week.
Beginning in December 06, the car sat for a couple of weeks without being driven at all, in cold weather outside (some rain, but not too bad). Tried to start it up after about 2.5 weeks, and it would try to turn over but would not start. My wife got it to start later that same day, but as soon as it was put in gear, it died.
Next, the check engine light came on during one short drive. We decided to wait and see. We drove the car infrequently for a week or two and during one drive, with the check engine light still on, the cars head and taillights began blinking while we were driving. We got to our destination and it was running rough. Tried to restart and at first it started a couple of times but died when put in gear. Then, it wouldnt turn over. The lights blinked even when the key was out and the engine was off.
Had the car towed to a mechanic the next day, and of course, as soon as it was there it started right up. They said the alarm was disabled and could not explain the lights blinking. The main focus, though, was on the starting issue. They said the diagnostic machine said the check engine light was due to the need for an oxygen sensor, so we replaced that. The light has remained off since. They also could not get the car to not start. They drove it for a few days and no problems. They suggested a likely culprit was the electrical override relay, so we replaced this too.
After picking the car up, we have only driven it infrequently for about 3 weeks. One time, started it up fine and drove for a few minutes. No problem. Yesterday, about a week later, started the car fine, drove for about 5 minutes, idling began getting rough, and parked at the store. Wouldnt start after that. It tried, but couldnt quite do it. This was last night. This morning, it started fine. Drove for about 5 minutes home, then turned it off. Turned it on and idled the engine for a couple minutes, then turned it off again. Tried to start it again, and same issue. It wouldnt start.
I should note that weve had the same gas in the car since we filled it up back in late November - it was 89 octane from Chevron.
This seems to be an issue with the 190s according to what I read. Some say it may be the gas, others point to mechanical items. Several say replace the relay weve now already replaced.
Im looking for input and would appreciate any suggestions. Seems like when we dont drive much, this issue tends to happen. Help! Thanks.
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Well first things first Mercedes reccomends high octance in its rigs, if you switched it you may have loosened up debri in the fuel system and its causing some havok in there. Next thing is the wiring harness for the engine, from 1988-1995 MB was forced (by the US) to use a biodegradable insulation on the wiring, turns out engine heat speeds up the degredation about 50 years or so, have it checked but make sure youre willing to spend 1000 on a new one. Its as easy as plugging it in and going, but its expensive and can cause all those problems. Also all those pesky gremlins wiring wise can be dirty corroded fuses, I suggest spending 10-15 dollars and get all new copper one from any auto store, it will help I promise.
Jason

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I would check two things... fuel pump relay. It is located behind the black plastic cover behind the battery... says kickdown on it... Look for the date stamped on the side of it... if it is same year as the car, change it.
Another possibility is the distributor cap and rotor... they also have a date stamped on it... a circular shape... in the middle is year... one the side is arrow to month. If it is old. chang it.
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Thanks for the reply - Ill check those things this week. Im still getting used to this car. Where is the distributor cap/rotor? Sounds basic, I know, but once I see it, I can deal with it... Its less obvious than the old Fords I used to work on! Thanks again
"Tiger" wrote
> I would check two things... fuel pump relay. It is located > behind the black > plastic cover behind the battery... says kickdown on it... > Look for the date > stamped on the side of it... if it is same year as the car, > change it. > > Another possibility is the distributor cap and rotor... they > also have a > date stamped on it... a circular shape... in the middle is > year... one the > side is arrow to month. If it is old. chang it.
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