Yanmar YPD-MP2, YPD-MP4 Service Manual – Factory Specs for Fuel Injection Pumps

I’ve seen too many guys chase fuel delivery problems with aftermarket PDFs that skip the critical steps. You get halfway through a pump rebuild and realize the torque values are generic, the timing marks don’t line up, and now you’re eating warranty time. That’s why this Yanmar YPD-MP2, YPD-MP4 Service Manual sits on my bench. It’s 66 pages of Yanmar’s own documentation – not some third-party reprint. Every plunger stroke, every governor spring, every delivery valve spec came from the same engineer who designed the MP pump.

Page 2 tells you straight: keep the workbench clean. Rust kills these high-precision pumps.

Chapter 2 lays out the pump construction: Fuel Injection Part, Governor Part, Delivery Part. You need to understand how the timer mechanism interacts with the cam shaft before you touch a wrench. The manual covers the F.O. Feed Pump and the Cold Start Advancer – two spots where I see rookies cross-thread fittings because they skipped the section on function.

Disassembly and Reassembly: The Hydraulic Head Procedure

Section 3 walks you through separating the pump body from the governor body, then pulling the hydraulic head CMP. It gives you the exact sequence for disassembling the cam shaft – don’t do it backwards or you’ll wreck the bearings. The reassembly instructions include bottom clearance adjustment for fuel injection timing (Section 4.2). That value changes depending on cam classification, which is listed in the specs table on page 5. You need a dial indicator for that step.

Fuel Injection Nozzle Adjustments – Why Opening Pressure Matters

If the nozzle opening pressure is off by even 50 psi, the engine will smoke and lose power. Chapter 5 covers washing, inspection, and reassembly of the nozzle. It tells you how to adjust opening pressure and run the injection test. This is the same procedure Yanmar factory techs use.

What the Specifications Table Tells You About Plunger Diameter

Section 2.2 lists pump specifications for the YPD-MP2 and YPD-MP4. You’ll find plunger diameter, delivery valve opening pressure, and governor speed ranges. I’ve had guys ask me if they can swap a YPD-MP2 delivery valve into an MP4. The manual shows the differences – don’t guess.

8 Chapters That Cover the MP Pump from Start to Finish

From safety symbols (Chapter 1) to the tool list (Chapter 8), this manual doesn’t waste space. Chapter 6 gives you a troubleshooting table for major faults: no start, rough idle, black smoke. It cross-references symptoms to specific sections. Chapter 7 lists tightening torques for pump part and mechanical governor part bolts – in Nm and ft-lbs. I still check those values every time.

Cold Start Device: What the Manual Explains

The C.S.D. section (2.7) details the cold starting advancer. If your Yanmar cranks but won’t fire when temps drop below 40°F, that advancer might be stuck. The manual shows the structure and how to test it without pulling the pump.

You can pair this manual with other shop resources like the Ammann Yanmar ViO15-2A, ViO20, ViO25, ViO30, ViO35 2006 Service Manual OEM for the full machine. If you’re working on a ViO75, check the Ammann Yanmar Vi075-A, B7-Σ-A, SV100 2007 Service Manual | OEM Factory Specs. The Ammann Yanmar B55W Service Manual – 191 Pages of Factory Specs also shares the engine platform. For driveline work, you’ll need the Manual Transmission service manual.

Every pump has its own personality, but the factory procedure is the only one that keeps the fuel system reliable. Download the Factory Manual and get the step-by-step that matches your YPD-MP2 or YPD-MP4.

Does this manual cover the TNV engine series?

Yes – the introduction specifically states the MP pump is for Yanmar TNV models.

Are torque specs listed in ft-lbs or Nm?

Both. Chapter 7 gives values in Nm with ft-lb equivalents.

Can I use this manual for the YPD-MP6?

No. The YPD-MP6 has a different hydraulic head design and governor calibration. Using this manual on an MP6 will give you incorrect bottom clearance values. You need the specific MP6 service manual from Yanmar. I’ve seen a shop destroy a pump trying to make MP2 specs work – the cam classification table doesn’t match. The adjustment procedures for torque-rise point and reverse angleich are unique to the MP2/MP4 series. Stick with the right manual.

How many pages cover troubleshooting?

Chapter 6 runs about 5 pages, including the fault table and the fuel injection pump troubleshooting flow.