Kubota Common Rail Assembly 1J801-50603 | Genuine OEM Fuel Rail for V2403-CR Engines

The 1J801-50603 is the genuine Kubota common rail assembly (Kubota catalog listing “RAIL,ASSY”) for the V2403-CR Tier 4 Final common rail diesel engine used across Kubota’s L, M, and MX series tractors from roughly 2014 through 2021. The rail is the high-pressure accumulator at the heart of the common rail system. It receives fuel from the supply pump, holds it at injection pressure, and feeds all four injectors while giving the engine ECU a stable pressure reference to control against. This is a Bosch-built component supplied through Kubota, and 1J801-50603 is the current part number, superseding the earlier 1J801-50600 and 1J801-50602 rails.

If your V2403-CR is setting rail pressure fault codes, hard starting, or derating after a fuel system failure, the rail is often replaced along with the injectors or supply pump during a common rail system repair, especially after fuel contamination has pushed debris through the entire high-pressure circuit. Valley Fuel Injection is an authorized Kubota dealer and a diesel injection specialty shop, so we can help you diagnose before you buy.

Application & Fitment

This rail fits the Kubota V2403-CR (including V2403-CR-EF03) Tier 4 Final common rail diesel engine. Confirmed equipment applications include:

• Kubota L4060 (DT, GST, HST, HSTC, Limited)
• Kubota L4701 (DT, F, H)
• Kubota L4760 (GST, HST, HSTC)
• Kubota L4802 (DT, DTM, F, H)
• Kubota L47 TLB and M62 TLB tractor loader backhoes
• Kubota L5060GST, L5460 (HST, HSTC), L6060 (HST, HSTC)
• Kubota M5660SUH and M5660SUHD
• Kubota MX4800 (DT, F, H), MX5200 (DT, F, H), MX5400 (DT, DTC, F, H, HSTC)
• Kubota MX5800H and MX6000 (H, HSTC)

Some CAT mini excavators built on Kubota power (306, 307.5, 304E2, 304E2 CR, 305.5E2 CR) are reported to use this rail under CAT part number 477-7728. We treat those applications as probable rather than confirmed, so please verify with us before ordering for a CAT machine.

Important: this is not the same rail as 1J804-50603, which serves the L3301, L3560, L3901, and KX040-4 family. The two numbers look nearly identical and are easy to mix up. If you are not certain which rail your engine takes, send us your engine model and serial number and we will confirm the correct part before anything ships.

Cross-Reference Part Numbers

• Kubota 1J801-50600 and 1J801-50602 (earlier versions, superseded by 1J801-50603)
• Bosch 0445224084 (commonly cited Bosch reference for this rail)
• CAT 477-7728 Engine Fuel Rail (reported cross for CAT-badged Kubota-based engines)

Frequently Asked Questions

My parts book calls for 1J801-50600 or 1J801-50602. Is this the right part?

Yes. Kubota superseded 1J801-50600 to 1J801-50602 and then to 1J801-50603, which is the current production number. All three interchange, and this rail is the correct replacement for either earlier number on a V2403-CR engine.

What is the difference between 1J801-50603 and 1J804-50603?

They are different rails for different branches of the Kubota common rail engine family. 1J801-50603 is the V2403-CR rail for the L4060 through L6060, M5660SU, M62, L47, and MX series tractors, while 1J804-50603 serves machines like the L3301, L3560, L3901, and KX040-4 excavator. Ordering by engine serial number is the only sure way to get the right one, and we are happy to verify that for you.

How do I know a bad rail is actually my problem?

Persistent low rail pressure codes, a pressure limiter that vents repeatedly, damaged high-pressure fittings, or metal contamination after a pump failure are the usual reasons a rail gets replaced. The rail is rarely the first suspect in a no-start, so before you spend the money we recommend proper diagnosis. Our diesel fuel injection services team tests and repairs Kubota common rail systems in house and can help pinpoint the failure before you order parts.

Why Buy From Valley Fuel Injection

Valley Fuel Injection & Turbo in Woodland, California has specialized in diesel injection since 1993. We are an authorized Kubota dealer for Kubota engine sales, parts, and service, which means the rail you get from us is genuine Kubota, not a gray-market or lookalike part. Common rail buyers tell us the same two worries every week: counterfeit hardware and wrong-number fitment. We eliminate both. Every order is checked against your engine serial number, and because we diagnose and repair these systems in our own shop, you get real technical support from people who work on the V2403-CR, not just a parts counter.

Pricing & Availability

Call 530-668-0818 for current pricing and availability on the Kubota 1J801-50603 common rail assembly, or reach us through our contact page. Please have your engine model and engine serial number ready so we can confirm fitment before you buy.