Still working on my 1978 300d. Can the return lines be replaced with fuel resistant plastic line or does it have to be the cloth like OE line?
Refer: 300D Giving me Fits...

I heard that diesel injector return lines should be OE. As the non OE may transmit vibration and produce a lot of noise along you metal fuel lines. I just did mine and used OE line without any problem. When I first fired up the car after putting on the new injectors and lines it made a loud ticking noise for about 5 minutes of operation. It usually is a good idea just to put OE parts on it so that if anything does go wrong you know its not the parts. It reduces the stress of our common passion. Sound running old cars.

good luck

bob

I can tell you that my MBZ tech saw non-OE fuel return lines on my D and ripped them out immediately! Maybe this doesn't help with specific rationale, but going OE on the best engineered cars in the world can't be a bad thing.

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"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo

My manual (76 300d) refers to them as leak hoses. Dealer price $10 per M. 1M id enough to do my 5 cyl