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Discussion Starter #1
I recently changed the engine wiring harness and now the car won’t start. I would really appreciate your help!!

I have a 1995 E320 convertible (cabriolet) W124 with 112k miles. I changed the original engine harness as the the car started idling low/rough to the point where it felt like it was going to stall. Also, the harness had really degraded.

I replaced the original harness 1244402933 from 2004 with a Delphi harness 1244402933 from 2007 that I bought on eBay.

After installing the new harness the engine only cranks but does not start. I’ve rechecked all the connections from the new harness install and all connectors appear to be good.

I’m not sure what to do next and would really appreciate any input you have.

Thanks
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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16,854 Posts
Check the OVP relay, as a faulty OVP will cause a crank but no start condition. If it is more than 10 years old, just replace it with a new genuine MB or KAE(hler) unit.

Also check the resistance coming off the crank sensor, as it will also cause the same condition.

Of course, this is assuming you installed the new harness correctly. Also, what about the throttle body? It is also affected by the same eco junk wiring disease.
 

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In addition to Steve's suggestions ^^, you should determine which missing element of the process you are missing. At a very high level, the engine requires spark, fuel, and compression. Chances are very good you have compression but fuel and spark are very easily affected. There are so many possible causes of your issue, it makes good diagnostic and fiscal sense to eliminate what is working and only chase down what is not.
 

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Discussion Starter #4
Error on my part -

"I replaced the original harness 1244402933 from 1994 (not 2004) with a Delphi harness 1244402933 from 2007"
 

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1995 E320 2 Door Coupe 98,000km
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Error on my part -

"I replaced the original harness 1244402933 from 1994 (not 2004) with a Delphi harness 1244402933 from 2007"
What ever you do don't start throwing parts at the car. You absolutely must check the CKP(crank shaft position sensor) first before anything. CKP is the first thing the ECU checks while cranking. If it doesn't see a signal there will be no spark and no injector function period. Make sure that you connected the CKP after the harness swapout. Perhaps you dropped the connector down into that dark area and forgot about it(just sayin). Disconnect the CKP connector and check it with a meter looking back towards the ECU. You should see resistance of some sort across the center pin and outer ring(not open and not shorted). Inside that connector check the outer ring to ground. It should be a direct short to battery negative ground. At the CKP itself, take it out and check the resistance from the center pin to outer ring(not shorted and not open). It's tough to remove so you could do the following instead; take connector number 2 off the ECU and check for resistance across pin 29 and pin 30. Do the same procedure for the Camshaft sensor(much easier because it's at the top front of the engine).
 
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