When your fuel injection equipment starts running rough, this 65-page Yanmar YPES-ML Series Service Manual PDF (OEM #M9961-03E080) gives you the exact teardown and adjustment procedures to fix it. Inside, you get step-by-step disassembly guides for the governor and feed pump, along with complete injection volume control adjustments. Open to the troubleshooting section to quickly diagnose pressure drops, or use the detailed exploded views to ensure every nozzle reassembly goes together perfectly. Verify your feed pump pushes a discharge volume of 230 cc/min at 1500 cam rpm, and torque the delivery holder to exactly 29.4-34.3 N-m before testing. Stop throwing expensive parts at hard-starting engines. Download this perfectly bookmarked file right to your tablet, jump straight to the exact injection spec you need, and get back to work.
What's Inside This Yanmar YPES-ML Manual
| System | Pages | Key Topics |
|---|---|---|
| Introduction | 2 | Features, Disassembly, Reassembly, Adjustment Procedure, Fuel Injection Unit, Fuel Injection Pumps |
| 1. for Safe Servicing | 6-8 | Warning Symbols, Safety Precautions |
| Fuel Supply System | 9-21 | Fuel Injection Pump Construction, Fuel Injection Pump Specifications, Function of Fuel Injection Pump, Injection Volume Control, Governor Construction |
| Disassembly, Reassembly and Inspection of Governor and Pump | 22-36 | Governor Disassembly, Inspection of Governor, Disassembly of Fuel Injection Pump, Inspection of Fuel Injection Pump, Assembling Governor |
| Adjustment of Fuel Injection Pump and Governor | 37-49 | Preparations, Top Clearance, Of Injection Timing, Plunger Pressure Test, Delivery Valve Pressure Test, Injection Volume (Measuring Injection Volume) |
| Fuel Feed Pump | 50-52 | Construction of Fuel Feed Pump, Fuel Feed Pump Specifications, Disassembly and Reassembly of Fuel Feed Pump, Fuel Feed Pump Inspection |
| Fuel Injection Nozzle | 53-59 | Functioning of Fuel Injection Nozzle, Type/Construction of Fuel Injection Nozzle, Fuel Injection Nozzle Disassembly, Fuel Injection Nozzle Inspection (Washing) |
| Troubleshooting | 60-62 | Troubleshooting of Fuel Injection Pump, Major Faults and Troubleshooting |
| Tools | 63-64 | Pump Mounting Scale, Measuring Device, Plunger Insert, Tappet Holder, Rack Indicator, Plunger Gauge |
| History of Revision | 65 | - |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Governor weight nut tightening torque | 68.6 - 73.5 N-m (7.0 - 7.5 kg-m) | p. 32 |
| Delivery holder tightening torque | 29.4-34.3 N-m (3.0-3.5 kgf-m) | p. 40 |
| Fuel filter element replacement | Disassemble and clean, or replace element | p. 60 |
| Fuel feed pump discharge volume | 230 cc/min at 1500 cam rpm, discharge pressure of 0.2 kg/cm² | p. 50 |
| Fuel feed pump closed off pressure | 0.3 kg/cm2 or more (at 400 cam rpm) | p. 50 |
| Stop solenoid replacement | Replace | p. 60 |
| Plunger diameter | 6 mm | p. 11 |
| Injection starting pressure (NP-DNOPD nozzle type) | 11.8 – 12.8 Mpa (120.3 – 130.5 kg/cm²) | p. 37 |
| Nozzle opening pressure (NP-DNOPD nozzle type) | 12.3MPa (125.4 kgf/cm2) | p. 54 |
| Injection pipe inner/outer diameter × length | Φ1.8/Φ6.0 × 500 mm | p. 37 |
| Injection pipe minimum bending radius | 25 mm | p. 37 |
| Plunger diameter | 6 mm | p. 11 |
Yanmar YPES-ML Common Problems This Manual Covers
Yanmar YPES-ML engine cranks but will not start because the injection pump delivers no fuel to the cylinders p. 60
Disassemble and clean or replace the fuel filter element as shown on page 60. Verify the fuel feed pump discharge volume reaches 230 cc/min at 1500 cam rpm. Inspect the stop solenoid and replace the unit if the plunger sticks during operation.
Manual Section: 7. TroubleshootingEngine starts but immediately runs away at high RPM and will not shut down normally p. 27
Inspect the governor components for excessive wear. Measure the governor shaft to bushing clearance limit, which must not exceed 0.5 mm according to page 27. Reassemble the assembly and torque the governor weight nut precisely to 68.6 - 73.5 N-m using a calibrated wrench.
Manual Section: 3. Disassembly, Reassembly and Inspection of Governor and PumpSputtering, hesitation, and uneven power under load accompanied by rough running and black smoke p. 54
Test the nozzle opening pressure on a pop tester. Verify the NP-DNOPD nozzle opens at exactly 12.3 MPa as specified on page 54. Inspect the nozzle contact surface for wear exceeding the 0.1 mm limit. Reinstall and torque the throttle type nozzle nut to 98 N-m.
Manual Section: 6. Fuel Injection NozzleHard cold starting condition that temporarily improves after bleeding air from the diesel fuel system p. 43
Perform a delivery valve pressure test. Pressurize the system and verify the pressure drop time from 100 to 90 kg/cm2 takes at least 5 seconds, detailed on page 43. Torque the delivery holder to 29.4 N-m and check the injection pipes for hidden cracks.
Manual Section: 4. Adjustment of Fuel Injection Pump and GovernorFrequently Asked Questions
How do I bleed fuel on a YANMAR YPES-ML?
To purge air from the fuel line, complete the fuel oil piping and operate the pump tester. For issues like 'Air sucking' causing the engine not to start, the remedy is to bleed air from the system. However, the manual does not provide a detailed procedure for bleeding fuel.
How do I troubleshoot a no-start on a YANMAR YPES-ML?
To troubleshoot a no-start condition, check for causes such as no fuel in the tank, a closed fuel tank cock, clogged fuel pipe system or filter element, air sucked into the fuel system, a damaged fuel feed pump, or fuel freeze. Remedies include resupplying fuel, opening the cock, cleaning or replacing elements, repairing connections, replacing the pump, or using fuel for cold weather.
What are the torque specifications for various components on the YANMAR YPES-ML fuel injection equipment?
The governor weight nut should be tightened to 68.6 - 73.5 N-m (7.0 - 7.5 kg-m). The lock nut for the angleich spring assembly requires a tightening torque of 2.5 ~ 3 kg-m. When reassembling the fuel feed pump, the tightening torque is 15 ~ 25 kg-m, and the fuel injection nozzle nut should be tightened to 98 +5/-0 N-m (10 +0.5/-0 kgf-m).
What are the key specifications for the YANMAR YPES-ML fuel injection pump?
The YPES-ML fuel injection pump is designed for 2 or 3 cylinders, featuring a plunger diameter of 6 mm and a cam lift of 7 mm. It has a maximum fuel injection volume of 40 mm³/st and a maximum fuel injection pressure of 13.5 MPa (137.7 kg/cm²). The maximum cam speed is 2000 rpm, with a right-hand direction of revolution when looking from the drive side.
What is the standard injection starting pressure for the YANMAR YPES-ML fuel injection nozzle?
The standard injection starting pressure for the YPES-ML fuel injection nozzle is 12.3 MPa (125.4 kgf/cm²). During adjustment, the target pressure is 12.3 ±0.5 MPa (125.4 ±5 kgf/cm²). This pressure is adjusted using shims on the nozzle tester.
How quickly can I access this manual after?
Instant PDF download. You get the full 65-page searchable Service Manual immediately after payment. Open it on your laptop, tablet, or phone right in the shop.
Am I able to print pages from this manual?
Yes. The PDF has no DRM restrictions, so print any page or section you need for your shop. Works with any standard printer.
Document Quality
This document is a scanned PDF with an OCR layer, allowing you to search and copy the full text. The text quality is generally crisp and easy to read throughout the manual. Diagrams and illustrations are primarily raster images and photos; while most labels are readable, some fine details may lose sharpness when zoomed in. The pages are clean with no noticeable scan artifacts, stains, or skewed content. There are no notable blank or filler pages present.
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