Fiat-hitachi Excavator 1999 Technical Manual – OEM Control System Specs

Description

If you are working on a Fiat-hitachi Excavator 1999 Technical Manual job and the hydraulic pump is acting up, you do not have time to guess. I have seen guys replace pump regulators three times because they skipped the control logic. This 19-page document is not a service manual—it is the patent-level description of how the prime mover and hydraulic pump talk to each other. You need this if you want to understand why the pump delivery pressure drops when the engine lugs. Specs matter. Do not trust a third-party rewrite.

Control System for Prime Mover and Hydraulic Pump

Page 1 of this manual opens with the United States Patent 5,911,506. Nakamura et al. lay out a reference pump-delivery rate calculating portion that uses a stored table based on control pilot pressure. You follow this logic to trace why the pump is not delivering enough flow at low RPM. The diagram shows the target engine revolution speed signal feeding the fuel injection control unit (governor). If you have a hunting idle or black smoke, start here.

Target Engine Revolution Speed – What the Manual Shows

This section (page 1 and 2) details how the target delivery rate is calculated by dividing the reference delivery rate by a ratio to the maximum engine speed. Real-world use: when the operator commands a faster cycle, the system adjusts the pump swashplate angle through a solenoid output current. The manual includes the actual formula and the constant used for target tilting. Do not try to reverse-engineer this from a generic hydraulic textbook—use the factory data.

Solenoid Output Current: Getting the Drive Right

A solenoid output current calculating portion converts the target tilting into a drive current sent to a hydraulic control valve. If your machine has a slow swing or weak dig, check the current at the solenoid connector. The manual provides the block diagram but not specific amp values—those are in the full shop manual. Still, understanding the control loop prevents you from replacing a good valve body. For more on this concept, compare it to a Manual Transmission where the shift logic determines the engagement.

Fuel Injection and Governor Integration

The governor gets a target engine revolution speed signal from the same controller. The manual shows the dual pump delivery pressures (PD1 and PD2) feeding back to adjust fueling. That means a worn pump can trick the governor into over-fueling. I have seen this melt pistons. Page 1 references foreign patent documents from Japan (62-94625, 4-167205, 7-119596) that support the control method. If you are chasing an intermittent high idle, you need this technical manual on your bench.

Why OEM Documentation Beats Aftermarket for This Excavator

Aftermarket manuals for the 1999 Excavator often skip the pump control patent because they focus on mechanical repairs. This 19-page OEM document is the original Hitachi Construction Machinery Co. submission. It contains the exact drawings, claim language, and response diagrams. You cannot get that from a reprint house. The Fiat-hitachi engineers designed the system around this logic. If you want to troubleshoot the pump regulator without replacing it, buy the factory manual.

Who Needs This 19-Page Manual

DIY mechanics and home garage enthusiasts who own a Fiat-hitachi Excavator and are comfortable with electrical schematics will get the most out of this. If you are a shop owner, hand this to your technician before they crack open the pump housing. It saves time. A quick read of the abstract (page 1) clarifies the target engine revolution speed calculation. One shop foreman told me it cut his diagnostic time by two hours on a similar Hitachi control system. That is the value of factory data.

Does this manual cover engine overhaul?

No. This is a 19-page technical manual focused on the pump control system.

What torque specs are included?

The manual does not list torque specs directly. It covers the electronic control logic for the hydraulic pump and prime mover. For torque values, you would need the full service manual.

Can I use this to fix a fuel injection issue?

The manual includes a fuel injection control unit (governor) section. It shows how the target engine revolution speed interacts with the governor to control fuel delivery. If your problem is related to the governor’s response to pump load, this manual will help. If it is a mechanical injector problem, you need a different document.

Is this the same as the service manual?

No. This is a technical manual describing the patented control system. It complements the service manual but does not replace it.

Access the Factory Manual and keep a copy on your tablet or laptop. When the pump starts acting up, open page 1 and trace the signal flow. That is how you get a fix that stays fixed.

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For a broader understanding of hydraulic control principles, see Manual Transmission (different domain, but the concept of control inputs applies).