Fuel System Diagnosis - Daewoo MATIZ Service Manual

1F – 34 ENGINE CONTROLS
Circuit Description
The fuel pump is an in-tank type mounted to a fuel send-
er assembly. The fuel pump will remain on as long as the
engine is cranking or running and the Engine Control
Module (ECM) is receiving reference pulses from the
crankshaft position (CKP) sensor. If there are no refer-
ence pulses, the ECM will turn off the fuel pump two sec-
onds after the ignition switch is turned ON or two
seconds after the engine stops running. The fuel pump
delivers fuel to the fuel rail and the fuel injectors, where
the fuel system pressure is controlled from 380 kPa (55
psi) by the fuel pressure regulator. The excess fuel is re-
turned to the fuel tank.
Caution: The fuel system is under pressure. To
avoid fuel spillage and the risk of personal injury or
Step
1. Relieve the fuel system pressure.
2. Install a fuel pressure gauge.
1
3. Turn the ignition ON.
Is the fuel pressure around the values specified and
holding steady?
1. Relieve the fuel system pressure.
2. Install a fuel pressure gauge.
2
3. Turn the ignition ON.
Is the fuel pressure around the values specified but
not holding steady?
Inspect the fuel lines for a leak.
3
Is the problem found?
1. Replace the fuel line(s) as needed.
2. Install a fuel pressure gauge.
4
3. Turn the ignition ON.
Is the fuel pressure around the values specified and
holding steady?
1. Remove the fuel pump assembly.
2. With the fuel pump under pressure, inspect the
5
fuel pump coupling hoses for leaking.
Is the problem found?
1. Tighten or replace the fuel pump coupling hoses
as needed.
2. Install a fuel pressure gauge.
6
3. Turn the ignition ON.
Is the fuel pressure around the values specified and
holding steady?
With the fuel system under pressure, inspect the fuel
return outlet for leaking.
7
Is the problem found?

FUEL SYSTEM DIAGNOSIS

Fuel System Pressure Test
Action
fire, it is necessary to relieve the fuel system pres-
sure before disconnecting the fuel lines.
Caution: Do not pinch or restrict nylon fuel lines.
Damage to the lines could cause a fuel leak, result-
ing in possible fire or personal injury.
Fuel Pressure Relief Procedure
1. Remove the fuel cap.
2. Remove the fuel pump fuse EF23 from the engine
fuse block.
3. Start the engine and allow the engine to stall.
4. Crank the engine for an additional 10 seconds.
Value(s)
380 kPa
System OK
(55 psi)
380 kPa
Go to Step 13
(55 psi)
– Go to Step 4
380 kPa
System OK
(55 psi)
–
Go to Step 6
380 kPa
System OK
(55 psi)
–
Go to Step 8
Yes No
Go to Step 2
Go to Step 3
Go to Step 5
–
Go to Step 7
Go to Step 8
Go to Step 9
DAEWOO M-150 BL2