294183-5040 Pump Plate For Denso Hp3 / Hp4 Supply Pump

As the drive gear rotates, mechanical torque passes through the pump plate boundary between the trochoid feed section and the high-pressure plunger chamber. This partition simultaneously seals the low-pressure gallery from the plunger cavity while defining the clearance that determines internal leakage path length. When the plate's flatness drifts beyond 0.02mm, pressurised fuel short-circuits back to the inlet, reducing suction control valve response and starving the plungers under load. This physical relationship makes the 294183-5040 pump plate a mandatory replacement at each overhaul-for wholesale buyers, this translates into predictable, recurring demand across the commercial vehicle aftermarket.

The sealing face is finished to 0.015mm TIR flatness across the entire surface, with parallel relationship held to 0.01mm over plate thickness. The seal groove bottom diameter is machined to ±0.02mm tolerance with Ra 0.8μm surface roughness, ensuring uniform O-ring compression without extrusion into clearance gaps. Nitrided case-hardening achieves HRC 45–50 without distorting bore concentricity (0.015mm relative to pilot bore). Each batch includes a dimensional inspection report recording flatness, groove geometry, and hole positions for every plate-traceability that verifies compliance before assembly.

This plate fits Denso HP4 supply pumps with body numbers 294050-0320, 294050-0360, 294050-0490, 294050-0500, 294050-0620, 294050-0630, 294050-0850, 294050-0950, 294050-1010, and 294050-3900. It supersedes earlier variants 294183-0030, 294183-0050, and 294183-0160 across HP3 pump bodies-consult the cross-reference tables for 294000-series applications where the 294183-5040 is listed as the current service part. An online VIN-to-pump-body lookup tool is referenced in Denso service documentation to confirm correct revision before ordering.

Before withdrawing the old plate, mark the gear pair relationship with a permanent pen to ensure the pump drive gear is reinstated in the same rotational position. Sweep a dial gauge across the housing face-runout exceeding 0.03mm indicates housing distortion that a new plate cannot correct. Clean the O-ring groove with a non-metallic probe to avoid scoring the sealing surface. Installation reverses disassembly: seat the new 294183-5040 over the dowels, reinstall the rotor set (stamped side outward), and torque the three cover bolts in a staggered sequence to 12–14 N·m.

Replacing the feed pump plate at a planned overhaul typically costs 12–15% of a complete pump exchange, yet it directly governs the trochoid rotor operating clearance. Allowing this clearance to grow by 0.04mm due to plate distortion reduces volumetric efficiency by an estimated 7–9%, forcing the SCV to run higher duty cycles and accelerating plunger and gear wear. For a Class 8 truck running 120,000 miles annually, deferring replacement adds approximately $180–$240 per year in fuel penalty and downstream repair costs. Installing the 294183-5040 at scheduled overhaul-every 400,000–500,000 miles-restores the leakage path to factory specification and protects the gear train from torque ripple, delivering maintenance cost avoidance that substantially exceeds the plate unit price across the fleet.

Q1: How do I determine whether the pump plate and the feed pump cover should be replaced as a matched set?
Inspect the cover's thrust face where the rotor set runs-if visible scoring or galling is present, the cover has worn beyond the point where a new plate alone can restore the correct rotor end-float. Replace the cover if its bore exceeds the wear limit specified in the pump's service bulletin; otherwise, the plate can be installed independently.

Q2: What is the packaging standard for export sea shipment, and are plates protected against corrosion during transit?
Each plate is vacuum-sealed in anti-rust vapour-phase paper and packed in heavy-duty cartons with foam dividers. Master cartons are palletised and stretch-wrapped with desiccant packs; corrosion protection remains effective for 18 months from the pack date under normal container conditions.

Q3: For mixed-batch orders combining the 294183-5040 with other part numbers, how are batch lots managed?
Each part number is assigned a unique lot code laser-etched on the plate; the packing slip groups items by lot and includes a separate dimensional certificate for each lot. Full traceability back to heat treatment records is maintained for every batch.

Q4: Does the 294183-5040 require any additional surface preparation before installation?
The plate is supplied with a light machining oil film-degreasing is not recommended, as the film aids initial seating. Ensure the mating face on the pump body is cleaned to ISO 4406 level 17/15/12 before fitting; no additional coating or lapping is required.

Q5: Under what circumstances does the warranty cover a returned plate?
Warranty applies to manufacturing defects confirmed by dimensional inspection. Coverage is voided if the plate shows impact damage, incorrect torque application, or installation on a housing that failed the pre-installation runout check-these are installer errors and are excluded from claims.

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