2007 ISUZU KB P190 Workshop Repair Manual

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Page 2273 of 6020

ISUZU KB P190 2007 Workshop Repair Manual ENGINE DRIVEABILITY AND EMISSIONS 6E–103
FUEL SYSTEM ELECTRICAL TEST
Circuit Description
When the ignition switch is first turned ON, the engine
control module (ECM) energizes the fuel pump relay
w

Page 2274 of 6020

ISUZU KB P190 2007 Workshop Repair Manual 6E–104 ENGINE DRIVEABILITY AND EMISSIONS
Fuel Pressure Relief Procedure
1. Remove the fuel cap.
2. Remove the fuel pump relay from the underhood relay center.
3. Start the engine and alow it to sta

Page 2275 of 6020

ISUZU KB P190 2007 Workshop Repair Manual ENGINE DRIVEABILITY AND EMISSIONS 6E–105
6 Using the DVM and check the fuel pump relay powersupply circuit.
1. Ignition “On”, engine “Off”.
2. Remove the fuel pump relay from the relay bo

Page 2276 of 6020

ISUZU KB P190 2007 Workshop Repair Manual 6E–106 ENGINE DRIVEABILITY AND EMISSIONS
10 Repair the open circuit between the fuel pump relayand battery.
Is the action complete? — Verify repair —
11 Using the DVM and check the fuel pump p

Page 2277 of 6020

ISUZU KB P190 2007 Workshop Repair Manual ENGINE DRIVEABILITY AND EMISSIONS 6E–107
17 Replace the ECM. Is the action complete?
IMPORTANT: The replacement ECM must be
programmed. Refer to section of the Service
Programming System (SPS) in

Page 2278 of 6020

ISUZU KB P190 2007 Workshop Repair Manual 6E–108 ENGINE DRIVEABILITY AND EMISSIONS
FUEL SYSTEM DIAGNOSIS
Circuit Description
When the ignition switch is turned ON, the engine
control module (ECM) will turn ON the in-tank fuel
pump. The in-

Page 2279 of 6020

ISUZU KB P190 2007 Workshop Repair Manual ENGINE DRIVEABILITY AND EMISSIONS 6E–109
• The fuel injector(s).
4. Fuel pressure that drops off during acceleration, cruise, or hard cornering may case a lean condition.
A lean condition can cau

ENGINE DRIVEABILITY AND EMISSIONS 6E–109
• The fuel injector(s).
4. Fuel pressure that drops off during acceleration, cruise, or hard cornering may case a lean condition.
A lean condition can cause a loss of power, surging,
or misfire. A lean condition can be diagnosed using a
Tech 2 Scan Tool.
Following are applicable to the vehicle with
closed Loop System:
If an extremely lean condition occurs, the oxygen
sensor(s) will stop toggling. The oxygen sensor
output voltage(s) will drop below 500 mV. Also, the
fuel injector pulse width will increase.
Important: Make sure the fuel system is not
operating in the “Fuel Cut-Off Mode.”
When the engine is at idle, the manifold pressure is
low (high vacuum). This low pressure (high vacuum)
is applied to the fuel pressure regulator diaphragm.
The low pressure (high vacuum) will offset the
pressure being applied to the fuel pressure regulator
diaphragm by the spring inside the fuel pressure
regulator. When this happens, the result is lower fuel
pressure. The fuel pressure at idle will vary slightly
as the barometric pressure changes, but the fuel
pressure at idle should always be less than the fuel
pressure noted in step 2 with the engine OFF.
16.Check the spark plug associated with a particular
fuel injector for fouling or saturation in order to
determine if that particular fuel injector is leaking. If
checking the spark plug associated with a particular
fuel injector for fouling or saturation does not
determine that a particular fuel injector is leaking,
use the following procedure:
• Remove the fuel rail, but leave the fuel lines and injectors connected to the fuel rail. Refer to Fuel
Rail Assembly in On-Vehicle Service .
• Lift the fuel rail just enough to leave the fuel injector nozzles in the fuel injector ports.
Caution: In order to reduce the risk of fire and
personal injury that may result from fuel
spraying on the engine, verify that the fuel rail is
positioned over the fuel injector ports and verify
that the fuel injector retaining clips are intact.
• Pressurize the fuel system by connecting a 20 amp fused jumper between B+ and the fuel
pump relay connector.
• Visually and physically inspect the fuel injector nozzles for leaks.
17.A rich condition may result from the fuel pressure being above 376 kPa (55 psi). A rich condition may
cause a 45 to set. Driveability conditions associated with rich conditions can include hard starting
(followed by black smoke) and a strong sulfur smell
in the exhaust.
20.This test determines if the high fuel pressure is due to a restricted fuel return line or if the high fuel
pressure is due to a faulty fuel pressure regulator.
21.A lean condition may result from fuel pressure below 333 kPa (48 psi). A lean condition may cause a 44 to
set. Driveability conditions associated with lean
conditions can include hard starting (when the
engine is cold), hesitation, poor driveability, lack of
power, surging, and misfiring.
22.Restricting the fuel return line causes the fuel pressure to rise above the regulated fuel pressure.
Command the fuel pump ON with the scan tool. The
fuel pressure should rise above 376 kPa (55 psi) as
the fuel return line becomes partially closed.
NOTE: Do not allow the fuel pressure to exceed 414
kPa (60 psi). Fuel pressure in excess of 414 kPa (60
psi) may damage the fuel pressure regulator. Caution: To reduce the risk of fire and personal
injury:
• It is necessary to relieve fuel system pressure before connecting a fuel pressure gauge.
Refer to Fuel Pressure Relief Procedure,
below.
• A small amount of fuel may be released when disconnecting the fuel lines. Cover fuel line
fittings with a shop towel before
disconnecting, to catch any fuel that may leak
out. Place the towel in an approved container
when the disconnect is completed.
Fuel Pressure Relief Procedure
1. Remove the fuel cap.
2. Located on the intake manifold which is at the top right part of the engine.
3. Start the engine and allow it to stall.
4. Crank the engine for an additional 3 seconds.
Fuel Pressure Gauge Installation
1. Remove the fuel pressure fitting cap.
2. Install fuel pressure gauge 5-8840-0378-0 to the fuel feed line located on the upper right side of the
engine.
3. Reinstall the fuel pump relay.

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ISUZU KB P190 2007

Page 2280 of 6020

ISUZU KB P190 2007 Workshop Repair Manual 6E–110 ENGINE DRIVEABILITY AND EMISSIONS
Fuel System Diagnosis
StepAction Value(s) Yes No
1 Was the “On-Board Diagnostic (OBD) System Check” performed? — Go to Step 2Go to
OBD
System Check
2

6E–110 ENGINE DRIVEABILITY AND EMISSIONS
Fuel System Diagnosis
StepAction Value(s) Yes No
1 Was the “On-Board Diagnostic (OBD) System Check” performed? — Go to Step 2Go to
OBD
System Check
2 1. Turn the ignition OFF. 2. Turn the air conditioning system OFF.
3. Relieve fuel system pressure and install the fuel pressure gauge.
4. Turn the ignition ON.
NOTE: The fuel pump will run for approximately 2
seconds. Use the Scan Tool to command the fuel
pump ON.
5. Observe the fuel pressure indicated by the fuel pressure gauge with the fuel pump running.
Is the fuel pressure within the specified limits? 283-376 kPa
(41-55 psi) Go to Step 3Go to Step 17
3 Does the fuel pressure indicated by the fuel pressure gauge remain constant?
NOTE: The fuel pressure will drop when the fuel
pump stops running, then it should stabilize and
remain constant. — Go to Step 4Go to Step 12
4 1. When the vehicle is at normal operating temperature, turn the ignition ON to build fuel
pressure and observe the measurement on the
gauge.
2. Start the engine and observe the fuel pressure gauge.
Did the reading drop by the amount specified after the
engine was started? 21-105 kPa
(3-15 psi) Go to Step 5Go to Step 9
5 Is fuel pressure dropping off during acceleration, cruise, or hard cornering? — Go to Step 6Check for
improper fuel
6 Visually and physically inspect the following items for a restriction:
• The in-line fuel filter.
• The fuel feed line.
Was a restriction found? — Verify repair Go to Step 7
7 Remove the fuel tank and visually and physically inspect the following items:
• The fuel pump strainer for a restriction.
• The fuel line for a leak.
• Verify that the correct fuel pump is in the vehicle.
Was a problem found in any of these areas? — Verify repair Go to Step 8
8 Replace the fuel pump. Is the action complete? — Verify repair —
9 1. Disconnect the vacuum hose from the fuel pressure regulator.
2. With the engine idling, apply 12-14 inches of vacuum to the fuel pressure regulator.
Does the fuel pressure indicated by the fuel pressure
gauge drop by the amount specified? 21-105 kPa
(3-15 psi) Go to Step 10Go to Step 11

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ISUZU KB P190 2007

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