Tracking down a gremlin in the electrical system or rebuilding the main relief valves on your mini-excavator requires the exact factory data found inside the 255-page JCB 802.7, 803, 804 service manual PDF (OEM #9803/3110). Inside, you get complete hydraulic schematics detailing the pump operation and rotary coupling, along with full wiring diagrams for the alternator and starter circuits. Expect detailed teardowns for the track gearbox, slew gearbox, and engine, backed by exploded views showing every ram pivot and boom linkage. Verify the starter motor commutator diameter is exactly 32 mm before reinstalling, and always tighten the track motor retaining bolts to a solid 113 Nm. A broken machine burns daylight and costs you money. Download this bookmarked file straight to your tablet, jump to the correct troubleshooting chart, and get those tracks moving again.
What's Inside This JCB 802.7, 803, 804 Manual
| System | Pages | Key Topics |
|---|---|---|
| Hydraulics | 2-14 | Hydraulic Circuit (Schematic), Servo Circuit |
| General Information | 15-22 | - |
| Service Schedules | 23-25 | - |
| Greasing | 26-47 | - |
| Hydraulic Pump - Operation | 48-57 | - |
| Hydraulic Pump | 58-92 | - |
| Main Relief Valves | 93-98 | - |
| Rams | 99-108 | - |
| Rotary Coupling | 109-112 | - |
| Pressure Testing | 113-127 | - |
| Options | 128-137 | Iso to 3CX Conversion Option |
| Body & Framework | 138-151 | Boom, Bucket, Ram Pivot and Linkage, Dipper, Kingpost |
| Engine | 152-197 | Technical Data, Fuel Lift Pump, Fuel Injectors and Fuel Pipe Assembly, Water Pump / Thermostat Housing Assemblies, Cylinder Head, Piston and Connecting Rods, Crankshaft |
| Gearboxes | 198-215 | Track Gearbox, Slew Gearbox |
| Track & Running Gear | 216-229 | Tracks, Track Rollers, Idler and Recoil Unit |
| Electrics | 230-250 | Alternator, Starter Motor, Circuit Diagram |
| Service Tools | 251 | - |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Track motor to undercarriage Retaining bolts torque | 113 Nm | p. 18 |
| Battery Voltage | 12V | p. 230 |
| Battery Capacity | 70 ampere/hour | p. 230 |
| Starter Motor Torque (on-load) | 15.69 Nm (1.6kgf/m, 11.57lbf/ft) | p. 230 |
| Starter Motor Commutator Diameter | 32 mm (1.26in) | p. 242 |
| Hydraulic Fitting Adapter Torque (SAE Tube Size 4) | 20-28 Nm | p. 20 |
| Hydraulic Fitting Adapter Torque (SAE Tube Size 6) | 46 - 54 Nm | p. 20 |
| Track Hydraulic Motor O-ring/oil seal replacement | Renew the O-ring 3, spring pin 5 and oil seal 22 | p. 68 |
| Track Motor oil leakage O-rings/gasket replacement | replace O-rings and and gasket | p. 69 |
| Fuel Tank Capacity | 50 L | p. 16 |
| Engine Oil Capacity (after first 100 hours) | 4.5 L | p. 16 |
| Track Gearbox Oil Capacity (each) | 1.2 L | p. 16 |
JCB 802.7, 803, 804 Common Problems This Manual Covers
JCB 802.7, 803, or 804 engine will not start or cranks very slowly during cold morning operations p. 231
Test the battery with a high rate discharge test using the procedures on page 231. Verify the voltage remains above 9 volts for 10 seconds. Inspect the starter motor commutator and ensure the diameter has not worn below 32 mm (1.26in) as shown on page 242.
Manual Section: ElectricsMachine hydraulics move slowly, dig weakly, or operate inconsistently after the fluid warms up to normal operating temperature p. 30
Check the main relief valve pressure. Connect your test gauge and verify the pressure reaches exactly 172 bar on an 803 model as outlined on page 30. If pressure is low, inspect the control valve spools and lubricate new O-rings and seals with hydraulic fluid before assembly on page 92.
Manual Section: General InformationLeft or right track drive motor fails to rotate, slips under heavy load, or leaks oil heavily p. 68
Drain the track gearbox and check for metal shavings. Refill the unit with exactly 1.2 L of oil as specified on page 16. Inspect the track hydraulic motor for external leaks and renew the O-ring 3, spring pin 5 and oil seal 22 according to the instructions on page 68.
Manual Section: Track Motor Fault FindingEngine runs hot under heavy hydraulic load with the temperature gauge rising quickly into the red zone p. 152
Inspect the radiator fins for dirt buildup and clean thoroughly with compressed air. Drain the cooling system and refill with exactly 2.65 litres of fresh coolant as detailed on page 152. Check the valve clearance cold and adjust to 0.2 mm to ensure proper engine breathing and timing.
Manual Section: EngineFrequently Asked Questions
What are the torque specs for JCB 802.7/803/804 track motor bolts?
The torque specification for the track motor to undercarriage retaining bolts on JCB 802.7, 803, and 804 machines is 113 Nm (11.5 kgf m, 83 lbf ft). This applies when attaching the motor/gearbox/sprocket assembly to the machine, as detailed on page 207.
What are the replacement specifications for battery?
The replacement specifications for the battery (Type N70) are 12V voltage and 70 ampere/hour capacity. When fully charged, the specific gravity should be 1.260 at 20°C.
What are the replacement specifications for starter-related components?
Replacement specifications for the starter motor (Type MOO2T54085) include a rated time of 30 seconds, off-load speed of 4000 rev/min, and off-load current of 130A max. For components, the commutator diameter is 32 mm (allowable limit 31 mm), and brush length is 18 mm (allowable limit 11 mm).
How do you fix JCB 802.7, 803, or 804 engine will not start or cranks very slowly during cold morning operations?
Test the battery with a high rate discharge test using the procedures on page 231. Verify the voltage remains above 9 volts for 10 seconds. Inspect the starter motor commutator and ensure the diameter has not worn below 32 mm (1.26in) as shown on page 242.
What format is this JCB 802.7, 803, 804 manual in?
Immediate download of the complete 255-page searchable Service Manual. Access it on any device, from a laptop at your desk to a phone in the field.
Can I print specific sections of this JCB 802.7, 803, 804 Service Manual?
Yes, print as many copies as you want, and there are no restrictions. Many mechanics print the section they need and bring it to the shop floor.
Are there wiring harness diagrams in this JCB 802.7, 803, 804 manual?
Yes, this JCB 802.7, 803, 804 Service Manual includes complete electrical wiring diagrams, wire routing, and connector pinouts.
Document Quality
This document is a scanned PDF, and you can search and copy text from all pages thanks to an underlying OCR layer. The text throughout is generally crisp and easy to read, with minimal blurriness or fading. Diagrams and illustrations are raster images, but their labels are consistently readable. Pages are clean with no notable stains or marks, though some exhibit a slight skew from the scanning process. There are a few blank pages interspersed, which appear to be intentional filler pages.
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