I have a 1986 Mercedes 560 SI V-8 5.6 liter. I want to know if there is another fuel pump that is compatible or must I use Mercedes parts only?

A cool car- well, you wanted the Merc now you have to pay the high price of being cool- I would fix it and get rid of it- there are faster cars that are cheaper to maintain- and those are all OLD now-

Let me be clearer- you are stuck buying Mercedes parts- $$$$$

Try a quick google search. You definitely do not have to pay big money. e.g. http://www.partsgeek.com/gbproducts/DC/6307- 05377244.html?utm_content=DN&utm_term=1986- 1991+Mercedes+560SEL+Fuel+Pump+Autobest+86- 91+Mercedes+Fuel+Pump+1990+1988&utm_source=google&ut m_medium=ff&utm_campaign=PartsGeek+Google+Base&gclid =CMirg7Sf68oCFQxahgodU7gPQQ

we have tons of quality used Mercedes parts for pre 1990;s car models www.donbenz.com