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  #1  
Old 07-15-2006, 10:49 PM
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Location: Chicago
Posts: 39
1991 300e shuts off

I hope someone can help. The car is 91 300E with 95K miles. Replaced the battery and coolant today, drove to a gas station and filled up with gas. After driving about 15 min the car shuts off in middle of the road and all the dash board lights lit up. Tried to restart (it cranked and cranked) several times with no luck. After about 5 minutes it fired up and once I reached the house it died again. Thinking maybe it's a vapor lock I opened the gas cap and the gas bullbles out (it was 99 degrees outside). After waiting about 5 minutes restarted it again and pulled into garage. This is what I then did to troubleshoot:

1) Cleaned ICV
2) The distributor rotor looked fine
3) Checked OVP and it was fine. Just in case I replaced with a spare one I had.
4) Checked spark plugs and they looked fine.

Started the car and it fired up immediately. Drove around the neighborhood several times and it drove fine. I then let it idle and it shuts off after 5-8 minutes. Before it shut down the idle was steady 600 rpm and then it went down to almost zero and then immediately shot back up 800 and after a few minutes it shuts down.


This is what was done about a month ago:
Had fuel pumps and fuel filter replaced by the dealer.
Transmission filter and fulid changed by the dealer
Had all four tires replaced and tie tods replaced

This new problem stumps me and I am reaching a point where the car seems to be taking me to a bottomless money pit. Thanks.
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  #2  
Old 07-15-2006, 11:13 PM
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I have a '91 300-SEL that may have the same motor as yours. I may stand corrected, but mine is the 12 valve, single cam M103 engine.

I went through something very similar to your situation a few years ago and it turned out to be a faulty fuel pump relay. In my '91, that function is housed in a MAS controller that costs around $500.

The next time this happens, do the following if it won't restart immediately.

Find the MAS unit. It's generally silver and a bit larger than a pack of cigarettes and has a black knob on top of it. Located on drivers side near firewall. The black knob is rotated counter-clockwise, then the unit is pulled straight up to remove. Jumper pins 1 & 2. Those two pins are the closest to the left side(driver side). You may here the pumps run. If so, try to start the car. If it starts, you found your problem, but good luck with the $500.

This is just one more thing to consider.

Here's a pointer to online MB documentation.

http://mb.braingears.com

And here's what the MAS looks like:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1KU172UOY1UM1DWA7I&year=1991&make=MB&model=300-E-002&category=P&part=MAS+Control+Unit
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1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"


If you want to live in a country ruled by religion, move to Iran.

Last edited by Mike Murrell; 07-15-2006 at 11:18 PM.
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  #3  
Old 07-21-2006, 02:13 PM
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Location: Chicago
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Mike, sorry for the delayed response. Right after I read your post I ordered a MAS unit (car is 91 300E 95K miles) and upon further search on this great forum I learned the crank position sensor or reference sensor can also be a culprit. Before ordering one I decided to see if I can replace it on my own and realized that I will have heck of a time replacing one end of cable. One plug is on the EZL unit and the other one is under the oil filter assembly (almost impossible, at least for me) to remove the screw. I am waiting for the MAS unit to arrive after which I will take it to the dealer (Loeber motors in Chicago $260) and have him replace the sensor. Hopefully this will solve the problem.

I had believed only Mercedes had this sensor problem malfunction. But I read in my local paper yesterday that Nissan is recalling their Sentras and Altima due to failure of this same type of sensor (article below).

“Nissan North America is recalling about 200,000 2003 models of Altima and Sentra sedans that came with a 2.5-liter engine because a sensor could overheat in stop-and-go traffic and make the engine die.
The Nashville-based automaker doesn't know exactly how many cars might be affected, nor has it given an estimate on the cost. But the company notified the National Highway Traffic Safety Administration two weeks ago that it would recall 186,279 Altimas and 14,587 Sentras that came equipped with a 2.5-liter engine to fix the problem.
Nissan discovered the problem while doing follow-up work on an earlier recall involving about 630,000 Nissan and Infiniti cars. That recall, which wrapped up last year, was blamed on a bad connection in the electronic control module, a central computer unit that governs much of a vehicle's operation. The cars either wouldn't start, had reduced power or stalled while running.
The fix could involve replacing the sensor or reprogramming the electronic control module.
The problem is not extensive, Pearson said. "As long as there's adequate air flow in the engine compartment, things are OK," Pearson said. "But it mainly happens in hot weather, stop-and-go traffic, the engine compartment heats up to the point where the circuit is broken in that sensor." •

Having the engine shut off right in middle of traffic is the most horrifying experience one can get and the car, being a Mercedes, will not get any sympathy. I am lucky the shut down did not occur on a highway on a middle lane but occurred near my home. I will keep everyone informed if replacing the MAS unit and crank position sensor solved the problem.
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  #4  
Old 07-23-2006, 11:31 AM
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Location: Northern Calif. (Fairfield Area)
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I'm surprised your car has a MAS unit. By 91 the 300Es had pretty well gone to the single unit that controlled everything. I would look harder at other components before the crank sensor. If you had an early ML, I'd say yes, but MBs in general don't have much problem with the crank sensor. If you do have a MAS, the fuel pump relay is in it, so that's a good bet. It could also be the EZL.
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  #5  
Old 07-23-2006, 11:53 AM
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Mine did it too and it turned out to be the fuel pump relay. It is a black one located next to the OVP relay.
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  #6  
Old 07-23-2006, 12:01 PM
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Hi
Did the tach go to zero when the engine cut off? This would be diagnostic of the crank shaft position sensor. Removing the sensor from the crankcase has been one of my worst jobs soo far. It was kind of bonded in place.
In case the MAS has a problem, check the fuel pumps too. They might draw too much current on their way out and could damage a new MAS too.
I bet it is the crank shaft position sensor though.
I know what you mean by getting no sympathy when standing in the middle lane with a dead Mercedes...
Good luck, Bruno
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  #7  
Old 07-24-2006, 09:57 AM
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Quote:
Originally Posted by MB fan 2
Mine did it too and it turned out to be the fuel pump relay. It is a black one located next to the OVP relay.
A 91 doesn't have a fuel pump relay.
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  #8  
Old 07-24-2006, 09:59 AM
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Quote:
Originally Posted by Bruno_300TE
Hi
Did the tach go to zero when the engine cut off? This would be diagnostic of the crank shaft position sensor. Removing the sensor from the crankcase has been one of my worst jobs soo far. It was kind of bonded in place.
In case the MAS has a problem, check the fuel pumps too. They might draw too much current on their way out and could damage a new MAS too.
I bet it is the crank shaft position sensor though.
I know what you mean by getting no sympathy when standing in the middle lane with a dead Mercedes...
Good luck, Bruno
Hopefully the two new fuel pumps installed by the dealer a month ago are not drawing much current.
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  #9  
Old 07-27-2006, 10:28 AM
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Update

Just wanted to update as to what was done. As Mike suggested I replaced the MAS and had the dealer replace the crank shaft position sensor ($330). Drove the car for more than 20 minutes yesterday, hot day in Chicago, and no problems. Drove the car on the highway and it was a smooth ride. So it seems either the MAS or the crank shaft position sensor was the problem. Bruno, the tech did go to zero when the engine cut off.

Hopefully, I will have no problems for a while. Another $600 bucks out of pocket. I figured it's either $600 or a payment book if I replace this car so I chose to pay $600.
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  #10  
Old 07-27-2006, 10:40 AM
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I think you wasted money on the crank sensor. You never said why you replaced the pumps, but if they were old and tired, they were probably drawing excess currnt through the MAS unit which houses the fuel pump relay. Let's hope the problem is solved.
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  #11  
Old 07-27-2006, 11:16 AM
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Autozen, the pumps were old probably original. Around early March of this year they started to make a buzzing sound which is indicative of pumps going bad so I had the pumps and filter replaced. Everything was fine until last week when the car shut down on a hot day after about 15-20 minutes of driving and it would not start until it cooled down. After restarting it shut down again after about 5 minutes or so until it cooled down. After reading the archives I decided to also replace the crank sensor.

Since the MAS and the crank shaft sensor were original I just did not want to take a chance of the car shutting down so I decided to replace both.
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  #12  
Old 07-28-2006, 05:50 AM
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Quote:
Originally Posted by autozen
I think you wasted money on the crank sensor.
And I think he wasted money on the MAS unit.
But whatever, glad the problem is solved.
Bruno
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  #13  
Old 07-28-2006, 09:49 AM
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Quote:
Originally Posted by Bruno_300TE
And I think he wasted money on the MAS unit.
But whatever, glad the problem is solved.
Bruno
How so?
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  #14  
Old 07-28-2006, 10:06 AM
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Well, he reported that the tach signal immediately dropped to zero when the stalling happened. This can be explained by the crank sensor that fails to deliever the tach signal both to the ignition and the tachometer. I had this happen on my car: ignition stopped at 65 MPH and tach dropped to zero immediately. A failing MAS unit would not give such symptoms (at least not that I am aware of). Also there are several reports both on this forum (as well as on the German forum) that for some reasons it is a common pattern for the crank postion sensors to stop operating at high engine temperatures first.
Have a nice day, Bruno
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