I am working through a problem with a 240GL. It would start, definately firing and then immediately stop. After having worked through all the usual checks, both pumps worked, the relay was good, all wiring checked out, but the fuel relay was not received ground return from the ECU pin 20. Bypassing the relay would result in a startup but the running was very rough ( this seemed to be the main difference to the information I had observed in some of the other threads I had read in the forum). It caused me to suspect that the ECU was at fault because ignition, sensors and earth connections etc all passed and the AMM gave correct readings. I had been inspired to look at these factors after reading some informative comments from Bruce Young & Art Benstein, thinking that the ECU was getting a false "no spark" indication from the ignition.
Now here comes the rub, if I disconnect the AMM it starts fine and runs very smoothly, relays/pumps ECU all work as they should. I had heard of people limping to their destination by disconnecting a failed AMM and therefore would have expected it to run roughly. It is an LH 2.4 and the resistance between terminals 2 and 3 is right in the middle of spec at 3.2ohms. I can't check the burn off function because with the AMM connected it will not run.
So before purchasing a new AMM to see if that fixes it thought someone may have had this same problem and can help, while I go and clean up all contacts and have a closer look at my AMM.
Wayne aka Aquarius115