Automotive Instrument Functions

All Jeep Vehicles

OEM Instrumentation

Tachometer The tachometer is the most important meter to install in any modified engine. The tachometer provides valuable information to the driver, such as, engine RPM, optimal shifting points, and maximum engine RPM (Red Line) to prevent serious engine damage from occurring.
Oil Pressure Oil is the lifeblood of any engine. As a human's blood pressure is essential to keeping us alive, oil pressure is essential to keeping an engine alive. If the oil pressure is too low, the engine can seize up or other internal parts can sustain serious damage. Higher-than-normal oil pressure may, however, indicate a plugged oil filter or an oil pressure valve stuck in the closed position.
Water Temperature The water temperature in an engine indicates the engine's operating temperature. With the ability to monitor water temperature, you can make sure that your cooling system is adequately protecting your engine from overheating. In addition, you can monitor the engine temperature in an effort to achieve maximum performance.
Fuel Level Fuel level meter is used to monitor the amount of fuel in the tank to prevent the driver from running the fuel tank dry. This is a necessity for the any vehicle driving long distances!
Voltmeter The voltmeter measures voltage across the battery when the engine is not running, and reads charging system voltage when the engine is running. Knowing the system voltage is essential for all modified performance vehicles and automotive audio enthusiasts. Excessive voltage can damage the battery and other electrical components, including the ECM (Electronic Control Module), the vehicle's computer. 

Optional Instrumentation

Ammeter Amperage is a measure of current, and an ammeter measures amperage, the electrical current charging or discharging the battery. This meter monitors the output from the alternator back to the battery to indicate any problems in the system. Excessive charging current can damage the battery and other electrical components. This meter would be recommended for the auto accessory enthusiast who is adding many amplifiers and audio / visual equipment, which will increase strain on the battery and alternator.
Fuel Pressure The fuel pressure meter displays the pressure that is built up in the fuel lines between the fuel pump and the carburetor (0-15psi) or in fuel injected engines (0-100psi) between the fuel pump and the fuel injectors. Insufficient fuel pressure in both fuel injected and carbureted systems would starve the engine of fuel, causing a no-start condition. If the engine is starved of fuel while running, it will run lean, which can cause excessive combustion temperatures and lead to engine damage or destruction. Excessive fuel pressure in a carbureted fuel system could flood the carburetor with fuel; and in a fuel injected system, it could damage the fuel injectors, causing them to leak. 
Boost A boost meter is used on turbo applications to enable the driver to monitor increased intake pressure (boost) provided by the turbocharger. Excessive boost pressure can cause detonation, which will damage or destroy an engine.
Vacuum A vacuum meter is used to monitor the amount of negative pressure (suction) in the intake manifold. A vacuum meter reading is used to diagnose a variety of engine problems, from a blown head gasket to worn valve guides. It also can be used to monitor fuel economy, with high vacuum readings indicating good fuel economy and low vacuum readings indicating poor fuel economy.
Oil Temperature Just like water temperature, oil temperature is essential to the life and performance of any modified engine. If the engine oil is too hot, viscosity breakdown and oil oxidation will occur and the engine oil will not be able to protect the engine.
Transmission Temperature Similar to oil temperature, transmission fluid temperature is important to the life and performance of any transmission. Keep an eye on your transmission temperature. If the transmission fluid is too hot, the transmission fluid will oxidize. This can cause gum and varnish to form, which will cause the transmission valves to stick. The oxidation can also cause the transmission bands and clutches to slip, which could lead to major transmission damage.

Courtesy of Splitfire Spark Plugs