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Ask Mike Kelly Your Own Question
Mike Kelly
Mike Kelly, Auto Service Technician
Category: Car
Satisfied Customers: 5470
Experience:  17 years experience as an auto mechanic, foreign and domestic. 5 years running my own repair business.
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My Mercedes M class 2.7 Diesel 52reg runs fine when started

Customer Question

My Mercedes M class 2.7 Diesel 52reg runs fine when started but will not start when cold. I have had the fuel filter changed and all glow plugs renewed but engine still will not start when cold. as stated when it runs it runs fine.
Submitted: 3 years ago.
Category: Car
Expert:  Mike Kelly replied 3 years ago.
Hi,my name is mike and I will assist you with your question.
Are there any warning lights coming on?
Customer: replied 3 years ago.

No

Expert:  Mike Kelly replied 3 years ago.
From what you are describing this issue that you are having is consistent with a failing crankshaft position sensor which is very common on this vehicle to fail and results in the problem that you are having. The crank sensor would need to be ohm tested and likely replaced.
Customer: replied 3 years ago.

As the car does eventually run well it appears the Crank Sensor is not the problem.

Expert:  Mike Kelly replied 3 years ago.
The crank sensor when failing still allows the vehicle to run,the problem the crank sensor has is with the starting of the vehicle especially when cold. The crank sensor needs to be ohm tested and likely replaced.