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This instruction show you guide on how to repair ISUZU construction machine 4JJ1 engine DTC P0087 fuel rail pressure limiter open.
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P0087 DTC Information
DTC description
A typical common rail (fuel rail) system is composed of the following 2 fuel pressure sections: A suction side between the fuel tank and the fuel supply pump, and a high pressure side between the fuel supply pump and the injectors. The fuel is drawn from the fuel tank and then supplied to the common rail (fuel rail) by plungers that are located inside the fuel supply pump. The common rail (fuel rail) pressure is controlled by the ECM, which controls the FRP regulator based on signals from the FRP sensor. If the common rail (fuel rail) pressure becomes excessive, the common rail (fuel rail) pressure limiter opens to release the excessive pressure and returns the fuel to the fuel tank. If the ECM detects that the pressure limiter has operated and pressure has sharply decreased after the common rail (fuel rail) pressure had increased to an excessively high level, the DTC is set.
Condition for setting the DTC
Preconditions
・The ignition switch is ON. ・The engine is running. ・DTCs P0192 and P0193 are not set.
Setting conditions
・The ECM detects that the pressure limiter is activated with an excessive pressure in the common rail (fuel rail).
Action taken when DTC sets
・The ECM limits the fuel injection quantity. ・The ECM stops multi-injection.
P0087 Diagnostics
Note: If the machine runs out of fuel, air may be entered the fuel system. When there is air in the fuel piping, the smooth flow of fuel into the fuel supply pump is interrupted and this DTC may be set. Bleed air from the fuel piping after refilling the fuel.
OBD system check
Current DTC check
Connect a trouble diagnosis scan tool.
Turn OFF the ignition switch for 30 seconds or more.
Turn ON the ignition switch.
Observe the DTC information with a trouble diagnosis scan tool. Is DTC P0087 set?
Yes
⇒Go to Prioritized DTC check.
No
Go to Intermittent conditions of engine.
Prioritized DTC check
Observe the DTC information with a trouble diagnosis scan tool. Is P0089, P0091, P0092, P0192, P0193, P0201, P0202, P0203, P0204, P2146, or P2149 set?
Yes
Go to the applicable DTC diagnosis.
No
⇒Go to DTC check when revving engine.
DTC check when revving engine
Turn OFF the ignition switch.
Start the engine.
Operate to increase the engine speed from idling speed to maximum speed while observing the DTC information on a trouble diagnosis scan tool. Is DTC P0087 set?
Yes
⇒Go to FRP sensor signal voltage check.
No
An intermittent problem due to foreign material in the fuel is suspected.
Replace the fuel filter element.
⇒Go to Repair verification.
FRP sensor signal voltage check
Turn OFF the ignition switch.
Wait for 2 minutes to reduce the fuel pressure of the common rail (fuel rail).
Turn ON the ignition switch.
Observe “Fuel rail pressure sensor” display on the trouble diagnosis scan tool. Is “Fuel rail pressure sensor” display within the specified value?
values： 0.4 to 0.5 V
Yes
⇒Go to Injector inspection.
No
⇒Go to FRP sensor circuit inspection.
Injector inspection
Start the engine.
Perform “Injector stop” with the trouble diagnosis scan tool.
Check whether the engine speed changes as each injector is turned OFF. Are there any injectors that do not change the engine speed?
Yes
Replace the injectors that do not change.
Note: If an injector has been replaced, be sure to set the Injector ID Code on the ECM.
⇒Go to Repair verification.
No
⇒Go to Fuel filter return pipe inspection.
Fuel filter return pipe inspection
Inspect for breakage or twisting in the fuel system between the fuel filter and the fuel tank. Is the result normal?
Inspect the fuel tank vent hose for clogging. Is the result normal?
If possible, inspect for foreign material in the fuel tank or for foreign material that may cause clogging of the fuel. Is the result normal?
Are all of the results normal?
Yes
⇒Go to FRP regulator circuit inspection.
No
Repair or replace as necessary.
⇒Go to Repair verification.
FRP regulator circuit inspection
Inspect for poor connections at the FRP regulator harness connector. Is the connection status normal?
Inspect for poor connections at the ECM harness connector. Is the connection status normal?
Inspect the circuit between the ECM and the FRP regulator for high resistance. Is the result normal?
Are all of the results normal?
Yes
Replace the fuel supply pump.
Note: The fuel supply pump must be timed with the engine, and the ECM requires learning.
⇒Go to Repair verification.
No
Repair the circuit or connection as necessary.
⇒Go to Repair verification.
FRP sensor circuit inspection
Inspect for poor connections at the FRP sensor harness connector. Is the connection status normal?
Inspect for poor connections at the ECM harness connector. Is the connection status normal?
Inspect the circuit between the ECM and the FRP sensor for high resistance. Is the result normal?
Are all of the results normal?
Yes
Replace the FRP sensor.
⇒Go to Repair verification.
No
Repair the circuit or connection as necessary.
⇒Go to Repair verification.
Repair verification
Clear the DTC with a trouble diagnosis scan tool.
Turn OFF the ignition switch for 30 seconds or more.
Start the engine.
Perform a test-run under the conditions for running the DTC.
Observe the DTC information with a trouble diagnosis scan tool. A DTC should not be set.
More repair cases for ISUZU engine,please refer to:ISUZU Engine Trouble Repair
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