here is some info
1992 Oldsmobile Custom Cruiser RWD V8-305 5.0L
Vehicle Level Powertrain Management Fuel Delivery and Air Induction Description and Operation
Description and Operation
Notes
Fuel Delivery System
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The fuel metering system consists of the following components:
Fuel pump electrical circuit.
Fuel supply components, including:
Fuel lines and pipes.
Fuel pump.
Fuel tank.
Throttle Body Injection Assembly, including:
Fuel injectors
Fuel pressure regulator
Idle air control valve
Throttle position sensor
BASIC SYSTEM OPERATION:
The fuel supply system begins with gasoline in the fuel tank. An electric fuel pump, located in the fuel tank with the fuel level gauge sending unit, pumps fuel to the throttle body through an in-line filter. The pump is designed to supply fuel at a pressure above the pressure needed by the injectors. A pressure regulator located in the throttle body assembly keeps the fuel available to the injectors at a constant pressure. The unused fuel is returned to the fuel tank by a separate line.
MODES OF OPERATION:
The ECM uses voltage inputs from several sensors to determine how much fuel to give the engine. The fuel is delivered under several conditions, called "Modes." All modes are controlled by the ECM, and are described below.
STARTING MODE:
When the ignition is first turned ON, the Electronic Control Module (ECM) turns ON the fuel pump relay for two seconds, allowing the fuel pump to build up system pressure. If the engine is immediately started, the fuel pump will continue to operate. If the key is left in the ON position, but the engine is not started, the ECM will turn the pump OFF. The fuel pump will remain OFF until the ECM detects the crank signal, or in the case of a faulty fuel pump relay, the oil pressure switch detects approximately 4 psi of oil pressure which will then bypass the fuel pump relay.
Fuel delivery from the injectors (which deliver fuel in all operating modes) is controlled by changing the amount of time the injectors are turned on or "pulsed" by the ECM. The ECM checks the coolant temperature sensor, throttle position sensor, and the crank signal, and determines the proper air/fuel ratio for starting. This ranges from 1.5:1 at -36°C (-33°F) to 14.7:1 at 94°C (201°F).
CLEAR FLOOD MODE:
If the engine floods, it may be cleared by pushing the accelerator pedal down all the way. The ECM then pulses the injector at a 20:1 air fuel ratio. The ECM holds this injector rate as long as the throttle stays wide open, and the engine speed is below approximately 600 rpm. If the throttle position becomes less than approximately 80%, the ECM returns to the starting mode.
RUN MODE:
The run mode has three conditions, called Open Loop, Closed Loop and Highway Mode.
OPEN LOOP:
When the engine is first started, and engine speed is above 400 rpm, the system goes into Open Loop operation. In Open Loop, the ECM ignores the signal from the Oxygen sensor, and calculates the air/fuel ratio based on inputs from the coolant temperature and Manifold Absolute Pressure (MAP) sensors.
The system will stay in Open Loop until the following conditions are met:
The Oxygen sensor has a varying voltage output, showing that it is hot enough to operate properly. (This depends on temperature).
The Coolant temperature is above a specified temperature.
A specified amount of time has elapsed after starting the engine.
CLOSED LOOP:
The specified operating conditions vary with different engines, and are stored in the programmable read only memory (PROM). When these conditions are met, the system goes into Closed Loop operation. In Closed Loop, the ECM calculates the air/fuel ratio (injector on-time) based on the signal from the Oxygen sensor. This allows the air/fuel ratio to stay very close to 14.7:1.
HIGHWAY MODE (SEMI-CLOSED LOOP):
When highway driving meets certain conditions, fuel control may enter Highway Mode (or "Semi-Closed Loop") for better fuel economy. These conditions are met when the ECM sees the correct values for and operation of; engine temperature, spark timing, vehicle speed, and canister purge control. A vehicle under Highway Mode will lean out to as much as 16 to 1 air/fuel ratio. Indications of this mode are seen by monitoring block learn and oxygen sensor values with a scan tool. Block learn and Integrator values will vary only slightly. Oxygen sensor voltage, while normally varying between 100 and 1000 millivolts (0.1 to 1.0 volts), will tend to remain fixed in the 100 millivolt range (0.1 volt). During Highway Mode operation, the ECM will periodically go into Closed Loop operation in order to perform a systems check. If systems operation passes, the ECM will allow Highway Mode to continue.
ACCELERATION MODE:
The ECM responds to rapid changes in throttle position and manifold pressure or air flow, and provides extra fuel.
DECELERATI0N MODE:
The ECM responds to changes in throttle position and manifold pressure and reduces the amount of fuel. When deceleration is very fast, the ECM can cut off fuel completely for short periods.
BATTERY CORRECTION MODE:
When battery voltage is low, the ECM can compensate for the weak spark by:
Increasing the amount of fuel delivered.
Increasing the idle speed.
FUEL CUT-OFF MODE:
No fuel is delivered by the injector when the ignition is OFF. This prevents dieseling. Also, fuel is not delivered if no reference pulses are seen from the distributor, which means the engine is not running. This prevents flooding. Fuel cut-off also occurs at high engine rpm, to protect internal engine components from damage
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1992 Oldsmobile Custom Cruiser RWD V8-305 5.0L
Vehicle Level Powertrain Management Fuel Delivery and Air Induction Testing and Inspection Testing and Inspection Procedures Diagnosis By Symptom Cranks But Will Not Run
Cranks But Will Not Run
Notes
Definition: Engine cranks OK, but does not start. May fire a few times.
POSSIBLE CAUSE ACTION
No fuel in tank.
Put fuel in fuel tank.
Water contaminated fuel.
Drain fuel tank and add clean fuel.
Low fuel pressure.
Check fuel pressure.
Pinched or collapsed fuel hose/line.
Repair/replace as required.
Inoperative fuel pump.
Verify fuse/fuse link integrity.
Check fuel pump relay. ^
1992 Oldsmobile Custom Cruiser RWD V8-305 5.0L
Vehicle Level Powertrain Management Fuel Delivery and Air Induction Testing and Inspection Flow of Diagnosis
Flow of Diagnosis
Notes
Diagnostic Circuit Check
"Service Engine Soon" Light Wiring Diagram
Typical Scan Data Values
Circuit Description:
The diagnostic circuit check is an organized approach to identifying a problem created by an electronic engine control system malfunction. It must be the starting point for any driveability complaint diagnosis, because it directs the service technician to the next logical step in diagnosing the complaint. Understanding the chart and using it correctly will reduce diagnostic time and prevent the unnecessary replacement of good parts
Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
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This step is a check for the proper operation of the "Service Engine Soon" light. The "SES" light should be "ON" steady.
No "SES" light at this point indicates that there is a problem with the "SES" light circuit or the ECM control of that circuit.
This test checks the ability of the ECM to control the "SES" light. With the diagnostic terminal grounded, the "SES" light should flash a Code 12 three times, followed by any trouble code stored in memory.
Most of the procedures use a Scan Tool to aid diagnosis, therefore, serial data must be available. If a PROM error is present, the ECM may have been able to flash Code 12/51, but not enable serial data.
Although the ECM is powered up, a "Cranks But Will Not Run" symptom could exist because of an ECM or system problem.
This step will isolate if the customer complaint is a "SES" light or a driveability problem with no "SES" light. An invalid code may be the result of a faulty "Scan" tool, PROM or ECM.
Comparison of actual control system data with the typical values is a quick check to determine if any parameter is not within limits. Keep in mind that a base engine problem (i.e. advanced cam timing) may substantially alter sensor values.
Installation of a "Scan" tool will provide a good ground path for the ECM and may hide a driveability complaint due to poor ECM grounds.
If the actual data is not within the typical values established, the C-Charts will provide a functional check of the suspect component or system.
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Fuel Pressure, Engine Running 62-90 kPa (9-13 P.S.I.)
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Fuel Pump Circuit
When the key is first turned ON, without the engine running, the ECM will turn the fuel pump relay ON for two seconds. This builds up the fuel pressure to normal operating pressure. If the engine is not started within two seconds, the ECM will shut the fuel pump OFF and wait until ignition reference pulses are present. As soon as the engine is cranked, the ECM turns the relay ON, which powers the fuel pump. The ECM continues to power the fuel pump during engine operation. If the fuel pump relay fails, it is backed up by the oil pressure switch, which continues to operate the fuel pump as long as oil pressure remains above 28.0 kPa (4 psi).
A faulty fuel pump relay can result in long cranking times, particularly if the engine is cold.
An inoperative fuel pump would cause a no start condition. A fuel pump which does not provide enough pressure can result in poor performance.
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