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I have a 1988 190e Mercedes 2.6 litre petrol. It has the problem that starts OK but when it has run for a few mins and got warm will not start, leave it for half an hour and it will start. I have had a new relay put in and petrol pumps checked, went alright for a while after relay, but now back to the same. I have been to various garages. Do you have any ideas?

Peter

From the "Ask Jack" archives - 14 December 2009

Our records suggest the connection to the over voltage relay was the biggest problem with this model. It controls the fuel pump, but also several other electric components. This may be a contributing factor to the issues you describe, but obviously I'd recommend someone familiar with the product confirm this with some physical diagnosis.

The relay is located under the flexible plastic cover that sits behind the battery, it is about 2.5cm square and about 5cm tall. The outer housing is an aluminium casing and it may have one or two fuses located in the top of the casing. If you can locate this relay, try running the vehicle and wiggling the relay, if the vehicle faults you may find the relay or the contacts that it plugs into require attention.

Failing that it's a tough question to answer with any confidence. If this is not the issue, I suspect you may have a problem with the fuel injection system, this may be a complicated K-Jettronic system (semi-mechanical, semi electrical fuel injection system).

My recommendation is finding someone who has good experience in repairing such systems, otherwise it may end up costing you heavily in mis-diagnosis.

Let me know your location and we can ask around our licensed repair network for such a garage.