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  #1  
Old 07-19-2016, 01:32 PM
chazola's Avatar
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Join Date: Nov 2003
Location: London, United Kingdom
Posts: 1,241
W124 M104 won't start

Hello everyone, having issues with '92 W124 M104.092 not starting.

I have the infamous wiring harness problem it seems- I changed the plugs a couple of weeks ago and the car ran ok, but a couple of times was slightly hard to start. Then yesterday it took two tries to start, and the car felt slow (like my old 136hp diesel). Got it home and took a look at the wiring to the coils from the ECU, crumbling to bits. I'm handy enough with the soldering iron so I make a new harness up to just past the engine cover where the old wires aren't too bad- now I have no start.

Fuel pump is ok, plugs were wet after repeated tries to start. Changed to brand new, clean plugs. Starter is fine and engine turns over ok. Changed coils over for good spares I had, and back again. All electrical connections are ok and in correct order. I have 12v at the coil feed wires.

Any clues?!

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1993 320TE M104
---------------------------------------------------
past:

1983 230E W123 M102
1994 E300D S124 OM606 (x2)
1967 250SE W108 M129
1972 280se 3.5 W108 M116
1980 280SE W116 M110
1980 350SE W116 M116
1992 300E W124 M103
1994 E280 W124 M104
----------------------------------------------
"music and women I cannot but give way to, whatever my business" -Pepys

Last edited by chazola; 07-19-2016 at 04:21 PM.
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  #2  
Old 07-19-2016, 05:27 PM
I told you so!
 
Join Date: Jun 2002
Location: Motor City, MI
Posts: 2,855
I'd replace the entire wiring harness. Some mechanics won't bother diagnosing drivability problems unless the entire engine wiring harness is replaced.

It's strange that the problem is on your 1992. I thought the problem was chiefly limited to 93 to 95 models.
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  #3  
Old 07-20-2016, 08:18 AM
chazola's Avatar
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Join Date: Nov 2003
Location: London, United Kingdom
Posts: 1,241
My 'bad'... it's a '93, keyboard slip up. Anyway, got her started again, but wiring harness replacement is on the list.
__________________
1993 320TE M104
---------------------------------------------------
past:

1983 230E W123 M102
1994 E300D S124 OM606 (x2)
1967 250SE W108 M129
1972 280se 3.5 W108 M116
1980 280SE W116 M110
1980 350SE W116 M116
1992 300E W124 M103
1994 E280 W124 M104
----------------------------------------------
"music and women I cannot but give way to, whatever my business" -Pepys
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  #4  
Old 07-20-2016, 12:09 PM
lsmalley's Avatar
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Join Date: Oct 2006
Location: California
Posts: 2,156
Quote:
Originally Posted by chazola View Post
My 'bad'... it's a '93, keyboard slip up. Anyway, got her started again, but wiring harness replacement is on the list.
Yes, I was going to say your sig states 93. Anyways, what did you do to get it working again or did it just start up on it's own?
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1990 190E 3.0L
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  #5  
Old 07-20-2016, 02:40 PM
Stretch's Avatar
...like a shield of steel
 
Join Date: Sep 2009
Location: Somewhere in the Netherlands
Posts: 14,461
I'd check the wiring again. A simple continuity check from sensors / actuators to the ECU plug would be a good start.

Have you made attempts at getting some fault codes?
__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #6  
Old 07-21-2016, 04:12 AM
chazola's Avatar
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Join Date: Nov 2003
Location: London, United Kingdom
Posts: 1,241
It was a simple case of the wiring for the coil packs being the wrong way 'round- the wiring from where it enters the top of the engine to the coil plugs was so bad I couldn't see the colours on the feed wires, so found someone online who had listed the wiring colours and coil order, which turned out to be completely wrong for my car!
I tore into the old coil harness a bit more (it's encased in moulded rubber) and managed to find some bits of colour in the wires to check the correct order.

Haven't checked for codes but seems to be running fine now.

__________________
1993 320TE M104
---------------------------------------------------
past:

1983 230E W123 M102
1994 E300D S124 OM606 (x2)
1967 250SE W108 M129
1972 280se 3.5 W108 M116
1980 280SE W116 M110
1980 350SE W116 M116
1992 300E W124 M103
1994 E280 W124 M104
----------------------------------------------
"music and women I cannot but give way to, whatever my business" -Pepys
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