Kubota 1J508-50503 Fuel Supply Pump Assembly | Genuine Denso HP5 Common Rail Pump

The Kubota 1J508-50503 is the genuine fuel supply pump assembly for the Kubota V3800 common-rail Tier 4 diesel engine family. Built by Denso as an HP5-type high-pressure pump, it is the component that generates rail pressure for the entire injection system. When a supply pump wears out, the symptoms are hard starting, long cranking, power loss under load, and low rail-pressure fault codes. This part number is the current Kubota supersession of 1J508-50500 and 1J508-50501, so if your parts diagram shows either earlier number, 1J508-50503 is the pump you order today.

Application & Fitment

Confirmed engine applications:

• Kubota V3800-TIEF4 (V3800 Tier 4 Final)
• Kubota V3800-TIE4B
• Kubota V3800-TIE5B
• Kubota V3800-CR-TI-EV13

Confirmed equipment applications:

• Kubota SVL95-2, SVL95-2S and SVL95-2SC compact track loaders
• Kubota SVL97-2 and SVL97-2C compact track loaders
• Kubota M5 series tractors: M5-091 (HD, HDC, HF, HFC), M5-111 (HD, HDC, HF, HFC, 12V and 24V) and M5L-111
• Kubota M5N series tractors: M5N-091, M5N-092, M5N-111 and M5N-112
• Kubota M6 series tractors, including M6-101DTC and M6-111

Always confirm fitment with your engine model and serial number before ordering. We verify every order against current Kubota parts data.

Cross-Reference Part Numbers

• Kubota 1J508-50500 (superseded by 1J508-50503)
• Kubota 1J508-50501 (earlier interchange for the same pump)
• Denso HP5S-0020 (Denso HP5 series common-rail supply pump reference)

Doing a complete fuel-system repair on a V3800? We also supply the matching genuine injector kit (1J508-53076) and common rail assembly (1J508-50602) for this engine.

Frequently Asked Questions

Will this pump fit my SVL95-2 or SVL97-2 track loader?

Yes. The SVL95-2 series and SVL97-2 series loaders run the V3800 common-rail Tier 4 engine, and 1J508-50503 is the genuine supply pump for that engine. It is the same pump Kubota lists for the M5, M5N and M6 series tractors above. Have your machine or engine serial number handy and we will confirm the exact part before we quote.

Is this a genuine Kubota pump or an aftermarket copy?

This listing is for the genuine Kubota assembly, manufactured by Denso as an HP5-type common-rail supply pump. These pumps run at very high pressures with extremely tight internal tolerances, which is where cut-price copies fail. As an authorized Kubota dealer we supply the current factory part with the correct supersession and full Kubota parts warranty.

How do I order, and what information do you need?

Call 530-668-0818 with your engine model and serial number, or send them through our contact page. We confirm the correct part number for your engine, then quote current pricing, availability and lead time. The assembly ships at roughly 9 lb.

Why do I see this pump cheaper online?
Short answer: it is usually not the same part — and a pump failure does not stay in the pump. Read why ↓

Search any OE number and eBay, Amazon and a dozen storefronts will show it well under dealer cost, sold by outfits with no name, no address and no phone number. We lose business to those listings every week — and we see a lot of them come back through our shop. Here is what is actually different.

• The part number proves nothing on its own. Counterfeit injectors and pumps are stamped with the same OE numbers as the real thing, in housings cast to look identical. The number in the listing title tells you what the seller claims it is, not what came off an OE line.
• “Remanufactured” is not a regulated word. A genuine reman unit is stripped to bare components, has its wear parts replaced — nozzle, plunger and barrel, solenoid, seals — and is then run on a calibration bench until it meets the original flow and response spec. A cheap one is very often cleaned, resealed, painted and shipped. Both get called remanufactured.
• No full teardown, so no idea what is worn. A proper rebuild means the unit comes apart completely and every part gets inspected and measured against spec — not just the ones that are obviously bad. Skip the teardown and you are reusing worn internals inside a freshly painted housing. It will run on the truck. It will not last.
• No factory-spec bench load testing. A unit is not finished until it has been run under load on a test bench and made its numbers across the range, not just at one easy point. That bench time is most of what you are paying for. Sellers working on price cut it first, because nobody can see it in a photo.
• The warranty has to be honored by someone. Everything we remanufacture in house carries a one-year warranty, with 30 days on electrical components. Parts we supply as an authorized dealer carry the manufacturer’s own warranty. Either way you call us, a real shop in California, and we sort it out. A marketplace warranty usually means shipping the part overseas at your own cost and hoping for a reply.
• No core program. We credit your rebuildable core back in full. Discount sellers generally will not take one, so the gap narrows the moment you account for the core you are now stuck holding.
• A pump failure does not stay in the pump. When a high-pressure pump comes apart it sends metal downstream through the rails, the lines and every injector. That is the whole reason fuel contamination kits exist. A pump that was never tested to spec is the cheapest possible way to buy that repair.

We are an authorized dealer and a working fuel-injection shop — we have been rebuilding and testing this hardware in Woodland since 1993, and the people who answer the phone are the people who run the benches. Not sure this is the right part for your engine? Call us with your serial number before you order and we will confirm it. Send your rebuildable core back and the core charge is refunded. And if a price somewhere else looks too good, call 530-668-0818 and we will tell you straight whether it is a deal or a problem.

Why buy from Valley Fuel Injection & Turbo

We are an authorized Kubota dealer and diesel fuel-injection specialists in Woodland, California. Diesel injection is all we have done since 1993, and we rebuild and test the same common-rail systems these pumps serve. When you buy a supply pump from us, you are buying from a shop that can also tell you whether the pump is actually your problem and what else to inspect while the fuel system is open.

Pricing & availability: this genuine Kubota fuel supply pump assembly is supplied to order. Call 530-668-0818 or request a quote for current pricing, availability and lead time. Have your engine model and serial number ready so we can confirm the exact fitment for your machine.