bluerhino

I have an 1989 190e 2.6. the car starts and run fine after it sits for a while. if i shut the car off (like to get gas) i will go to restart the car and it will crank but won't start (as a result of no power to the fuel pump) if it sits for a while, i can restart it and run it all day if i want. as lond as i do not shut it off. i am thinking overvoltage protection relay but am not sure if maybe power would get cut off somewhere else and cause the car not to start after being run for a while. anybody dealt with anything like this or heard anything about it?