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Q: Will not always start

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Will not always start. Just had a new starter put in. Battery good Does it in cold condition or after it has been running awhile. The sits sits in a garage all week. Only used on weekends

My car has 169000 miles.
My car has an automatic transmission.

With an old diesel like yours, everything has to be right to start it up cold. First of all, all the glow plugs need to be working. I usually test the glow plugs by measuring the current draw with an inductive ammeter. A functioning glow plug will draw about 12-15 amps. If all your glow plugs are working, but you are still not starting, you need to check the compression. Compression on a diesel needs to be around 350 PSI or the engine will be very hard to start. If the compression is good and the glow plugs are good, you need to check the fuel delivery. That will be easy to see since you have the injectors out for the compression test, but it gets messy. Fuel delivery is not a problem as often as is fuel contamination. You may want to take a sample of fuel from the car and check it for water. All of this is pretty messy business, as is any work involving old diesels. If you decide to get some help with this, you can contact Your Mechanic to have a technician come to your home or office to ’check out your stubborn Mercedes and let you know what needs to be done.

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