Genuine Bosch high-pressure connector tube for Cummins ISBe and QSB industrial and off-highway engines. Carries fuel from the rail through the head into the injector, sealing metal-to-metal at both ends. Six are required per engine.

Fitment

• Cummins ISBe 4-cylinder 3.9L and 6-cylinder 5.9L
• Cummins QSB4.5, QSB5.9 and QSB6.7
• DAF CF65, LF45 and LF55

Serves the CRIN1 injector family, including Bosch 0445120231 / 0986435597. This is a different part from the Ram truck connectors — if you are working on a Dodge or Ram pickup, you need F00RJ01572 (5.9L) or F00RC00647 (6.7L).

Replaces these part numbers

Cummins 3975703 · DAF 1876292

Why it has to be replaced

The sealing tip of a connector tube deforms slightly under torque and takes a permanent impression from the injector it was clamped against. Fit that tube to a new injector and the impression no longer matches, which leaves a leak path at the highest-pressure point in the fuel system. Bosch and Alliant Power both specify replacing all six every time injectors are serviced.

A tube can look perfect and still be finished. What is worn out is a shape you cannot see.

Symptoms of a failed connector tube

• Fuel in the valve cover — the most common sign
• Rising oil level and a diesel smell on the dipstick as fuel dilutes the oil
• Hard starting, particularly when hot
• A miss on one cylinder that follows the tube rather than the injector
• Raw diesel smell after a hard pull with no visible external leak

Warranty and shipping

Valley Fuel Injection has been a Bosch factory-authorized diesel service center since 1993. We ship nationwide from Woodland, California, typically within 1–2 business days. See our warranty terms and shipping policy.

Not sure which tube your engine takes? Call (530) 668-0818 with the year and application and we will confirm it.