diesel fuel 'hard' lines- correct replacement - Mercedes-Benz Forum

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post #1 of 2 (permalink) Old 11-03-2007, 07:54 PM Thread Starter
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Date registered: Jul 2007
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diesel fuel 'hard' lines- correct replacement

Hi on my 1975 240d, in replacing the old style hand primer pump with the newer style- I disconnected the fitting/line that comes from the main fuel filter and goes to a fitting near the hand primer pump to gain access to switch the hand primer pumps. In doing so, the hard plastic fuel supply line going to the fitting snapped- not surprising as its 30 years old. There are several of these low pressure fuel lines that are a very hard, once probably clear, plastic like material that get pushed on 'barbed' fittings without hose clamps. My question is- do you have to replace these plastic like lines with exactly the same material, or can you just use rubber type fuel line that is diesel fuel compatible. Does anyone know what the internal diameter of this stuff is? I stopped in at my local MB dealer to ask about it- he said its 8mm inside diameter and said go to NAPA- NAPA says they don't carry any metric hose- but for sure its smaller than 8mm anyway.
Lastly, if alternate style rubber hose is ok, do you want to/should you add a hose clamp where the lines go onto the barbed fitting ends? Thanks!
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post #2 of 2 (permalink) Old 11-04-2007, 09:36 PM
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Vehicle: 1966 250SE Coupe
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I would simply order the correct premade lines from the dealer. They need to be clear so you can see if you have air in the fuel system.

If you choose to replace them with diesel rated fuel hose, then yes, you'll want to use hose clamps.

Remember, don't cut the plastic line off the barbed fitting with a knife. You could scratch the barbed fittings putting sort of a line across them. Then you'll forever possibly have a leak source.......not an external leak maybe, but enough of a syphoning type leak that it'll loose prime when parked for long periods. Instead, used the wire wheel on a bench grinder to eat through the old hard plastic fuel hose.

1966 250se Coupe
Blaugr√ľn/electric sunroof/4 on the floor
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