Mercedes Benz repair: Mercedez Benz 420SEL, mercedez benz, fuel pumps

Question
I have a 1991 420SEL with a 110,000 miles.  It is not starting; it cranks but then shuts off as soon as you stop cranking.  If you spray some carburater cleaner in it, it will start but then shuts off in a few second.  Someone told me it was a fuel pump issue.

I would greatly appreciate if you could advise what the possible issues could be and where to start.  Also, my understand is (not too mechanically inclined) it has two fuel pumps.  Is there a way I can do this myself?  If not, how much would a mechanic charge me to change the fuel pumps?  Where is the best to get these fuel pumps at a reasonable price?

Thanks for your help

Answer
Greetings!
You want to check your relay before you get into spending all that money on fuel pumps. They are probably around six hundred for both. The relay should be in the engine compartment just behind the front firewall and says kickdown on it. Some has a mas control relay which has a clock like dial on the top and is a silver box with a black dial on top.If it has a regular relay , then these can be repaired by taking apart and soldering the burned part on the inside of the relay making sure your solder does not run onto anything it not suppose to be on.It may take a few questions before hitting the right combination on this car. Thanks and i hope this helps you