I am trying to get my 1991 300E (6-cylinder gas) started after a long hibernation. The engine turns over for a short time if I spray carburator cleaner into the air inlet while cranking. I disconnected the fuel line at the carburator and cranked the starter. No gas was coming out. I thought if I could see if electricity was getting to the fuel pumps' leads I could rule out faulty fuel pumps. No electricity at the fuel pump lead while cranking. I am assuming there is a relay of some sort between the battery and the fuel pump, but im not sure where it is or how to test it. I would really appreciate any insight.

On USA versions the fuel pump relay is part of the MAS system relay.

Removing the relay & bridging pins 1 & 2 will run the pumps

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I removed the MAS module and put a wire between the #1 and #2 sprockets with the ignition off expecting to hear some whining or something from the area of the fuel pumps but heard nothing. There was a bit of sparking. Should I be expecting a different result?

I bridged the female part of the socket from the 1 port to the 2 port with a bit of wire. This resulted in fuel pressure at the injector. I assumed that meant that the MAS module is faulty so I replaced it. Now I am back to having zero fuel at the injector while cranking. If there are no other components involved I am beginning to wonder if it is likely that the fuel line is clogged, perhaps at the filter? Does anyone have any ideas?

A fresh fuel filter will give you a good check from the fuel source . The adjoining fuel accumulator will be very easy to replace at the same time.
mak

I replaced the MAS relay and have fuel pressure at the injector. Now when I try to crank, it appears that I have no spark, so I am going backward. I had been using jumper cables while test starting and I read that the OVP relay could be adversely affected by jump starting. I have replaced the battery, and checked the fuse on the OVP. The fuse is not blown. I checked the Distributor cap and rotor, and it looked okay. If anyone has any ideas on what to try, I would really appreciate some guidance.

Possibly in the OVP relay a solder track near the big zener diode may have been damaged due to the jump. re solder if so.worked for me .
mak
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