I have a 1948 D4 7U that needs to have the diesel fuel supply line replaced. The line goes from the bottom of the seat tank fuel shutoff to the injection pump. Here are my questions: What type of hose material do you recommend and what diameter? I also need to know what size fittings are on each end of the line. My machine is an hour away from me so I am unable to check it out. I would like to fab something up at home, then install it when I see the machine again. Thanks

Ang: I think it is 1/2” copper. The ends would have to be brazed, I don’t know if you can find the nut that goes on the pump side. Odd sized?
Maybe lower your standards and just cut off the bad section and use Hose/clamps. Economical and easier than making several trips to Vista. JM

Thanks Juiceman, several trips up there can be a pain, especially when you forget something!

yes. 1/2 inch copper. you can cut and add a flare or compression fitting or hose and clamps. just plain old fuel hose will work as long as it can be slipped over a 1/2 copper line. i guess you could flare a fitting and add a hose barb if you want.   could also cut out the bad section and sweat in a new piece of copper.

the original is half inch copper. when i replaced ours i used half inch fuel hose. hose it better as it will handle any vibration just need to sleeve it with more hose anywhere it rubs against a edge. i just removed the bad section fitted a hose barb to the fuel filter housing, slid the hose over the copper pipe(de-burred it first) and double clamped each end of the hose
its only gravity pressure so no leaks

if you use copper I suggest you put a anti vibration loop in it helps stop the vibrating and stress cracking. (injector lines have a loop for the same reason)
also you must use copper or brass olives or better yet use flare fittings. as the plastic ones as used with cold water will dissolve. and use a tube cutter not a saw to cut the tube.

also the threads are NPTand NPS (national pipe taper and straight) fittings made to the API fuel fittings standards they are tighter fit than normal NPT fittings

You can also buy the line from Cat in bulk length, 5P1201, you can sweat the new sleeves on 4F2739, the nuts are 2A1506. I would recommend putting an inline filter in, Cat 8H4681 Filter Group, and two of 3B8997 fittings, this will save the transfer pump from grit and rust particles and it also separates water somewhat. I mounted my filter by the injection pump and bolted it to the side panel.

Thanks to all for the great information, Angelo

d4angelo; I put a leak in the line on my D6 when a makeshift starter cable touched the line. Cut it with tubing cutter, put in new section and compression fittings, wrapped it with rubber to ease vibrations effects. No pressure, no leaks. Quick and easy in the fiel repair! Good luck.

Gary,  Do you have any pictures of your filter mounting?

Filter on my 5U D2. another photo on next page.