Lost Power While Driving
 

My car is a 1988, SEL, 420, ( about 140,000 miles). I had driven about 100 miles when suddenly, the car lost power, the gas gauge dropped to zero and then jumped to full. I had just driven through road construction at a crawl in temperatures over 100. However, the car had no symptoms of overheating. After sitting about one-half hour I was able to restart it but was afraid to head on down the road, so I laid over and the next morning the car started right up so I headed out on my trip. About 10 miles down the road, the car lost power again so I had it towed to a mechanic. I'm assuming that the problem is in the fuel pump or some other component in the fuel delivery system. Is there a common problem with the fuel system in this car? How should the mechanic go about diagnosing the problem? He's not a Mercedes specialist but has serviced my car for years. I thought that perhaps I could give the mechanic a head-start on fixing the problem. Sorry for my wordiness.

Did it stumble, then quit or just shut off immediately??
Did you get any other strange indications on the dash - battery, ABS, or other light?
What condition is the battery? New? Alternator working? What's the battery voltage at an idle - around 13.8vdc? What's the battery voltage with the car off?

A fuel pump problem won't affect the gas gauge. This sounds electrical - low battery due to bad battery or alternator.

The power just stopped. No stumble. The battery is quite old (3-5years). I don't recall any other strange things or lights on the dash. I'll suggest to the mechanic that he check the battery and alternator. Thanks for your help.

OVP? Fuel pump relay?