1998.5-2002 Dodge 5.9L Cummins Fuel Lines

Fuel lines on the 1998.5-2002 RAM 5.9L Cummins

There are two circuits. The low-pressure side runs from the tank through the block-mounted electric lift pump and the filter to the VP44, with banjo fittings at the lift pump and the filter. The high-pressure side is six individual lines, one per cylinder, from the VP44 to the injectors. Each line is its own part, which is why Cummins genuine lines are sold by cylinder number. Common-rail plumbing didn't arrive on the 5.9L until 2003.

What fails and why

The documented weak spot in the plumbing is pressure drop on the low-pressure side. A Turbo Diesel Register editor's gauge on a stock 1999 read 13-14 psi at idle, 12 psi at 2,000 rpm, 10 psi at 3,500 rpm with no load and 8 psi at 20 psi of boost, and a hot-rodded truck fell to 3 psi at 30 psi of boost. The stock pump meets spec, but it's marginal once power is added, and the VP44 needs at least 5-6 psi to stay cool and lubricated. Low supply starves the VP44, and a starved pump overheats.

Stock replacement vs. upgrade

For the high-pressure side, Cummins genuine lines are the stock-spec replacement for each cylinder. On the low-pressure side, the Turbo Diesel Register documents three traditional cures for the pressure drop: drilled-out banjo bolts, bigger fuel lines and a relocated lift pump. A banjo bolt upgrade is the smallest of those changes. Oversized high-pressure lines, like the Dynomite Diesel universal lines here, are for builds past stock fueling. Larger injectors raise fuel demand, so get the lift pump sorted before you size up anything downstream.

What we carry

Cummins genuine fuel injection lines for cylinders #1 through #6: 3943765, 3943767, 3943769, 3943771, 3943773 and 3943775. Dynomite Diesel universal high-pressure oversized injection lines in multiple lengths. A BD Diesel banjo bolt upgrade listed for the 1999 Cummins. Exergy Performance metric fittings, including an M14x1.5 three-way T, an M14x1.5 plug and nut, and M12x1.5 high-flow supply fittings that step to -6AN or -8AN line.

Fitment notes

Injection lines are cylinder-specific, so order by number. The BD banjo bolt upgrade is listed for 1999, and the filter housing and its test port changed for 2000, so check the product's fitment against your model year. The Exergy fittings carry common-rail and CP3 names; this engine has neither a rail nor a CP3, so confirm thread size and the job you're doing with us before you order. When injectors come out, the connector tubes and feed-tube o-rings should be replaced with them. Verify by VIN. More for this engine at the Cummins hub.

Frequently asked questions

Are the injection lines the same for every cylinder?

No. Each of the six lines runs from the VP44 to its own injector and is its own part, which is why the Cummins genuine lines are sold as #1 through #6. Replace a damaged line with the one for that cylinder.

Why upgrade a banjo bolt?

The stock low-pressure system loses pressure under boost, and a hot-rodded truck tested at just 3 psi at 30 psi of boost. Drilled banjo bolts and bigger lines are the traditional fixes for that drop, along with relocating the lift pump.

Does this engine have a fuel rail?

No. The 1998.5-2002 5.9L feeds each injector through its own line from the VP44. Common-rail injection started on the 5.9L in 2003, so check any rail- or CP3-named fitting against your job before ordering.

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.