Originally posted by pentoman
There's a chance on your W126 car, it's inside the cabin behind a panel in the front footwell's - anyone confirm?
Next time the car won't start, see if the fuel pump runs for a second or so when you switch the ignition on - it should buzz. If not, the relay most likely isn't switching on so replace it. (I actually repaired my, a bad solder joint).
Nope you missed this one. The fuel pump relay is located right of the brake booster on 126 bodied cars. It is identified by it's markings on top of it. It will have the word xZYL (x=number of cylinders the car has) along with an RPM limit which varies depending on which engine it has. Also your test is not a valid test since there are 2 sets of relay contacts inside the relay box. One for when the key is on and the car is running and one for when the car is cranking. The reason for this is the crank sensor does not make enough voltage to close the relay during cranking so the relay gets a signal from the starter circuit to turn the relays second contacts on.
Now sir I have a beef with your comments here! I didn't see you offering this gentleman any help before he had his problem fixed only snide remarks about us Americans being hang an hope mechanics. What are your professional credentials? After talking with my professional mechanic friends from the UK I know one thing and that is there are plenty of hacks/gomers world wide. So as my mother would say, if you can't say something nice about someone keep your mouth shut!