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1989 300E
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Discussion Starter #1 (Edited)
Can anyone tell me if there is a connection here? My 89 300E was running fine. I removed the barely working Becker Grand Prix stereo, replaced with an after market stereo and now the car won't start. Turns over and over and over. I checked all the fuses and cleaned the connections on the OVP and pump relay. Starts with starting fluid and the pumps don't make any noise.
Am I missing something? Is there anything about the 4 pin plug on the back of the Becker that would do this? Thanks all...
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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17,407 Posts
Did you disconnect the battery prior to removal??? If not, then most likely the alarm system tripped the ignition immobilizer.
 

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1989 300E
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14 Posts
Discussion Starter #3
No, I didn't disconnect the battery. Just removed the connectors and pulled the radio. How do I fix this??
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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17,407 Posts
Try disconnecting the negative terminal for 15-20 minutes, followed by the positive terminal for another 15-20 minutes.

Then reconnect battery, starting with positive terminal and negative terminal last.
 

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1989 300E
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Discussion Starter #5
I had the battery out for about 20 minutes while I was checking and cleaning the pump relay and OVP. Are there any reset procedures or work arounds for this? I didn't know the car had theft protection.
 

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1989 300E
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14 Posts
Discussion Starter #7
It would be nice to just reset it and have the car running as it was but I guess if all else fails that will get it back on the road. I was wondering why there was a horn next to the brake booster, must be for the alarm. Didn't know the car had one.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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There should NOT be a horn next to the brake booster. You very likely have a aftermarket alarm that is monkeying up your car by interfering with the factory alarm system.

Yank it, chuck it and chances are your car will be all right.
 

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1989 300E
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Discussion Starter #9
I just looked again, it's definitively factory. Same horn as the ones in front and it's wired to the factory harness, the one going into the fuse box. Maybe some years are different then others.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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Since you did not fill out your profiile, I am assuming you have a US spec vehicle.


Please do everyone the favor of telling us exactly what you have and where you are located.
 

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1989 300E
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14 Posts
Discussion Starter #12
OK, I removed the passenger floor cover. I don't have a large aluminum box, just the small black one. It has the 14 pin and 8 pin connectors but they have already been unplugged. I can't find any relays behind the cluster.
I have the two fuse OVP, the fuses are good and read 10 volts across the pins. I opened the fuel pump relay box, looked it over and see no bad joints. When I turn on the ignition the relay connects for a second, pumps run, then stops.
Since the alarm box was already disconnected I must assume that removing the Becker radio wouldn't have anything to do with the car not starting. But it ran fine the day before I changed out the radio. I don't know what to look for now..
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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I would replace ALL fuses with the updated copper core type.. Many electrical issues have been resolved by upgrading to the non-corroding fuses.

A whole vehicle fuse kit can be bought for about $5 from joetlc.com
 

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1989 300E
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Discussion Starter #14
Got it figured out. The 14 pin plug was ALMOST pulled off the alarm box. Seems the top few pins were still touching ( 1, 2, 3, 4 ), pushed in at an angle. These must have been right on the edge of touching and not touching. I pushed them in just a bit and the car started right up, running smooth as it was. I'm sure a previous owner disconnected the alarm for one reason or another and got the car to run by pushing in only the top pins. This doesn't look like a good solid fix idea. I'll have to figure out a hard wire connection.
I guess it was a coincidence that the plug moved while I was changing out the radio, I never touched the passenger side. Thanks for the help, it sent me in the right direction.
 
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