my 1989 300e has, over the past 6 mos. or so, refused to start a few times, usually after i have turned it off for a brief period of time-- maybe 5 to 10 min. several weeks ago it would not start at all and my good friend who plays around with old mb diesels said he thought it was a fuel pump problem. the car cranks fine, it will start with ether, and he can hear the relay click when he turns it on. he doesn't know though whether it is the fuel pump or the relay that is broken. he thought he would just replace the relay to see if that was the problem. he stopped short on that fix when we found out the relay cost over $100.
if there anyway to determine if it is the relay or the fuel pump?
any help would surely be appreciated. thank you,
jude

is it possible for the fuel pump relay to sometimes 'work' and other times not? my gut feeling is that this condition is unlikely.

Jump pins 7 & 8 at the relay socket to emulate relay on state.

Whacking the pump(s) with a blunt object will often cause it to restart from a stuck position with a failing pump.

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1986 300E 5-Speed 240k mi.

jumping the pins. can i remove the relay. connect pins on the relay? and then put the relay back in its socket. suggest this as it is very difficult to make the connection at the socket.