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Call or Text (352) 722-5295Fuel lines on the 1994-1998 Dodge Ram 5.9L Cummins
The 12-valve Cummins has no fuel rail. The Bosch P7100 feeds six individual high-pressure steel injection lines, one to each mechanical injector. On the low-pressure side, short rubber hoses connect the cam-driven lift pump, and excess fuel returns to the tank through the overflow valve and a rubber return hose that runs under the intake manifold near the filter boss.
What fails and why
Heat does the damage. The rubber return hose under the intake manifold hardens from engine heat and starts to leak, letting air into the system. The short hoses and spring clamps at the lift pump distort and do the same thing. Symptoms are a fuel smell or drip, hard starting and air in the fuel. On any truck still wearing its original rubber, plan on replacing these hoses rather than waiting for them to fail.
Stock replacement vs. upgrade
For the rubber sections, use diesel-rated, heat-resistant hose and screw-band clamps instead of the factory spring clamps. For the steel injection lines, a genuine Cummins line is the straight replacement when one is damaged. Builders running high-fuel pumps upgrade the injection lines, and FASS lift pump kits replace the supply and return plumbing with Push-Lok hose.
What we carry
Genuine Cummins injection lines for every cylinder: 3925805 (#1), 3925806 (#2), 3925807 (#3), 3925808 (#4), 3925809 (#5) and 3925810 (#6), plus the 3926103 fuel injector return line. Dynomite Diesel universal high-pressure oversized injection lines in multiple lengths. Exergy fittings, including an M14x1.5 three-way tee, an M14x1.5 plug and nut, and M12x1.5 to -6AN and -8AN high-flow CP3 supply fittings.
Fitment notes
Each cylinder has its own injection line and its own Cummins part number, so order by cylinder. The Dynomite lines are universal and sold in multiple lengths; pick the length for your build. The Exergy rail cap and CP3 supply fittings are common-rail hardware. The 12-valve has no fuel rail, so check the product page before you order one for a 1994-1998 truck. A 1998 can be a 12-valve or a 24-valve: look for the P7100 inline pump with a shutoff solenoid on top. Verify by VIN.
Frequently asked questions
Why do I smell diesel under the hood of my 12-valve?
Start with the rubber return hose under the intake manifold by the filter boss. Engine heat hardens it until it leaks, and the short hoses at the lift pump do the same. Replace them with heat-resistant, diesel-rated hose and screw-band clamps.
Are the injection lines the same for every cylinder?
No. Each cylinder has its own line and its own genuine Cummins part number, #1 through #6. Order the one that matches the line you're replacing.
Do I need oversized injection lines?
Only when the fuel system has been built well past stock. Builders running high-fuel pumps upgrade the lines. For a stock truck, the genuine Cummins replacement line is the match.
Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.