Abstract: A measurement of the quantity of gas entering or within the coolant of an internal combustion engine cooling system, is made with the engine running, preferably at high idle speed, and a test is performed to ensure that the thermostat is open, whereby it is known that coolant is circulating through the entire cooling system, by providing a radiator cap connected to an orifice of a known size that will allow gas to escape from the cooling system and measuring substantially the pressure differential across the orifice, such as by measuring the pressure on the radiator side of the orifice with respect to atmospheric pressure.

Abstract: A single pressure transducer tapped into the fuel system of an engine, at a point to be responsive to the pressure of the fuel operating against the pressure regulating bypass valve of the fuel system, is used to measure fuel pressure at low idle speed and at high idle speed of the engine; the two pressures when compared against normal pressure can determine bypass valve condition since lower than normal pressure at low idle speed in combination with normal pressure at high idle speed is an indication of a bypass valve which is stuck in the open position, and higher than normal pressure at high idle speed is indication of a bypass valve which is stuck in the closed position. The test can also discern other faults since a lower than normal pressure at high idle speed in combination with a lower than normal pressure at low idle speed is indicative of a bad pump.

Abstract: As used herein, the term "power" means a factor indicative of or related to horsepower, computed from acceleration and speed, with or without an empirically-determined inertia constant. A measurement of the operation of the governor of an internal combustion engine, such as a diesel engine having a primary distributing pump for providing fuel in a time related fashion to the fuel injectors, and in which fuel pressure is not an indication of governor operation, is the speed at which a line defined by two points measured on the power/speed characteristic of the engine intersects with an empirically-determined line emanating from the measured high idle speed point on the zero power speed abscissa of the power/speed characteristic. Two power measurements, each including time and speed, are made at different speeds as the engine accelerates with only its own drag, inertia and accessories as loads thereon.

Abstract: Electronic processing means are utilized in a composite measurement of performance of an engine cooling system thermostat, with diagnostic procedures to ensure viable measurement. The speed of the engine is initially tested to ensure the engine is at high idle speed, so that temperature in the cooling system will increase to that at which the thermostat will normally operate; and during the testing, the speed is continuously monitored to be sure it remains close to the initial test speed (near high idle) to minimize coolant pump pressure variations due to engine speed. Three temperature diagnostics are performed to ensure a viable test: first, if the temperature ever exceeds 15.degree. over the rated thermostat temperature, the test is terminated in a fault since the thermostat is presumed to be stuck in the closed position; second, if the temperature fails to increase by at least 2.degree.

Abstract: A parameter, such as oil pressure, is repetitively sampled along with indications of speed, such as clock counts from a flywheel tooth counter, the parameter value and speed indications being stored and retained through at least several samplings, the parameter samplings being analyzed to find one of interest, the related speed indication thereupon being converted into speed dimensions for use. Specifically, oil pressure and engine speed indications are simultaneously sampled and stored, being retained for several sampling intervals, successive pressure readings are compared to find the knee in the curve of oil pressure as the pressure regulator begins to cut in, the pressure ultimately determined to be at the knee and the related speed indication being brought out for use, with conversion of the speed indication to rpm dimensions.

Abstract: A single pressure transducer tapped into the cooling system of an engine, downstream of the pump, is used to measure coolant pressure at high idle and coolant pressure at low idle while the water temperature is such as to assure the thermostat is closed; the pressure readings are equivalent to the pressure across an orifice or restriction formed by the coolant bypass when the thermostat is closed; the combination of high idle pressure and difference between high idle pressure and low idle pressure permit diagnosing whether the pump is faulty or whether there is unduly large restriction in the engine, which otherwise could not be known with a single pressure reading.

Abstract: Diagnosing an internal combustion engine includes full throttle, specific speed tests such as measuring fuel pressure at two checkpoint speeds and at rated speed, and determining the pressure and speed where the governor reduces fuel pressure, an aneroid checkpoint of fuel pressure as a function of engine speed, and a fuel inlet restriction test, all without a dynomometer. The tests are performed with the throttle wide open, so that pressure can be measured downstream of the throttle at accessible taps, and/or to provide maximum fuel-flow test conditions. The speed comparisons are made during an acceleration with the throttle fully open, the instantaneous speed of which is accurately determined by flywheel tooth sensing.

Abstract: The first one of horsepower measurements utilizing an emperically-determined horsepower constant, made with electronic diagnostic equipment employing engine transducers, during three successive acceleration bursts from a low engine speed to a high engine speed is compared against the second and third ones thereof, the percentage difference therebetween being an indication of air accumulated at the fuel intake of the internal combustion engine.

Abstract: The turbocharger of an internal combustion engine is diagnosed by virtue of a single pressure measurement made during an acceleration of the engine using only its accessory loading, drag and inertia as a load, instead of making a profile of pressure ratio across the turbocharger under full load conditions on a dynomometer, as in the prior art. As the engine accelerates, pressure is continuously monitored, the ratio of the rate of change of the pressure with respect to time is made, and the maximum change in pressure per unit of time recorded; the minimum pressure sensed may also be recorded as an indication of the restrictive effect of the turbocharger when not being driven to its capacity.