Attention: TDR Forum Junkies 
I just completed replacing all of the brake and fuel lines on my '91 W250 since one of the lines failed from rust and I wanted to share some of the things I learned in the process.
-I bought a set of brake lines from a vendor of reproduction steel lines. The vendor did not have a listing for a '91 so I purchased the set for a '90 that was listed in the catalog. The '90 set is an eight piece set for a truck without ABS, but since I was planning to bypass the ABS, I figured it would be close enough. All of the lines fit except for two, the left rear, which was too long and had to be bent to fit, and the right front. The right front was too short so I bought a straight piece of tubing and fabricated the right front to match the one I took off. I believe the differences were probably due to the fact that the pattern that was used for the new lines was a truck that was not equipped with 4500# axles, as mine is.
-New rubber brake hoses are available from NAPA (the front outers and the rear)and Advance Auto (front center).
-The rear bleeder screws were rounded off and it took a pair of straight jaw Vise Grips to remove them. New replacement screws are available from NAPA.
-I removed the fuel tank in order to access one of the brake lines and discovered that the both of the fuel lines were rusted. Both the supply and return lines are 5/16" steel. I bought a 25' roll of tubing from NAPA and bent the new lines to match the old ones.
-I replaced all of the rubber hoses with SAE30R9 that I bought from NAPA. WARNING, this hose cost $7. 00 per foot. It is probably better, but my recommendation is to stay with 30R7 since my originals lasted for 18 years.
-The hoses at the sending unit on top of the fuel tank were in pretty bad shape but the ones at the engine looked o. k.
-The supply line from the tank to the engine is 5/16" from the tank to the engine compartment where it transitions to a 5/16" hose up to the lift pump. However, the return line is 5/16" steel up to the engine compartment but the connection on the engine is 1/4". To reduce from the 5/16" steel line to the 1/4" hose, Chrysler reduced the steel line by swaging it down to 1/4" at the engine end. I used a short piece of 5/16" hose and brass barbed hose fittings and a union to make the reduction to 1/4" hose.
-Since the fuel tank was removed, I decide to replace the fuel filter on the fuel pick-up. I was told by the Mopar parts guy that the original part number was superseded so I ordered the new one. The original filter looked like a nylon type screen material mounted in a plastic frame. The new filter had a paper looking element mounted in a metal frame. The new filter fit o. k. but I did not like the paper element. I checked the Cummins Filtration website and the catalog showed the new filter application to be for gas engines and was noted "Mexico Only". I decided to clean and re-use the old filter since it was not cloogged and otherwise looked o. k.
-Last but not least. The last time I towed with the truck it seemed to have lost performance compared to years earlier. I checked the obvious things, throttle travel, fuel filter, transmission kick-down etc. , but all seemed normal. When I removed the fuel pick-up fassembly from the tank, I noticed that the vent was full of dirt so I cleaned the vent and blew air through it. When I re-installed everything and took the truck for test drive, the performance difference was incredible. I believe that the blocked vent was restricting fuel flow for quite some time.
Sorry for the length of the post but I wanted to share the information that I learned and I hope it may helpful to other members. Please feel free to contact me me if you have any specific questions or need additional information, such as part numbers.
Jim
-I bought a set of brake lines from a vendor of reproduction steel lines. The vendor did not have a listing for a '91 so I purchased the set for a '90 that was listed in the catalog. The '90 set is an eight piece set for a truck without ABS, but since I was planning to bypass the ABS, I figured it would be close enough. All of the lines fit except for two, the left rear, which was too long and had to be bent to fit, and the right front. The right front was too short so I bought a straight piece of tubing and fabricated the right front to match the one I took off. I believe the differences were probably due to the fact that the pattern that was used for the new lines was a truck that was not equipped with 4500# axles, as mine is.
-New rubber brake hoses are available from NAPA (the front outers and the rear)and Advance Auto (front center).
-The rear bleeder screws were rounded off and it took a pair of straight jaw Vise Grips to remove them. New replacement screws are available from NAPA.
-I removed the fuel tank in order to access one of the brake lines and discovered that the both of the fuel lines were rusted. Both the supply and return lines are 5/16" steel. I bought a 25' roll of tubing from NAPA and bent the new lines to match the old ones.
-I replaced all of the rubber hoses with SAE30R9 that I bought from NAPA. WARNING, this hose cost $7. 00 per foot. It is probably better, but my recommendation is to stay with 30R7 since my originals lasted for 18 years.
-The hoses at the sending unit on top of the fuel tank were in pretty bad shape but the ones at the engine looked o. k.
-The supply line from the tank to the engine is 5/16" from the tank to the engine compartment where it transitions to a 5/16" hose up to the lift pump. However, the return line is 5/16" steel up to the engine compartment but the connection on the engine is 1/4". To reduce from the 5/16" steel line to the 1/4" hose, Chrysler reduced the steel line by swaging it down to 1/4" at the engine end. I used a short piece of 5/16" hose and brass barbed hose fittings and a union to make the reduction to 1/4" hose.
-Since the fuel tank was removed, I decide to replace the fuel filter on the fuel pick-up. I was told by the Mopar parts guy that the original part number was superseded so I ordered the new one. The original filter looked like a nylon type screen material mounted in a plastic frame. The new filter had a paper looking element mounted in a metal frame. The new filter fit o. k. but I did not like the paper element. I checked the Cummins Filtration website and the catalog showed the new filter application to be for gas engines and was noted "Mexico Only". I decided to clean and re-use the old filter since it was not cloogged and otherwise looked o. k.
-Last but not least. The last time I towed with the truck it seemed to have lost performance compared to years earlier. I checked the obvious things, throttle travel, fuel filter, transmission kick-down etc. , but all seemed normal. When I removed the fuel pick-up fassembly from the tank, I noticed that the vent was full of dirt so I cleaned the vent and blew air through it. When I re-installed everything and took the truck for test drive, the performance difference was incredible. I believe that the blocked vent was restricting fuel flow for quite some time.
Sorry for the length of the post but I wanted to share the information that I learned and I hope it may helpful to other members. Please feel free to contact me me if you have any specific questions or need additional information, such as part numbers.
Jim
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Good quality post. All things I need to tackle sooner rather than later.
