Mazda 626 Station Wagon, Workshop Manual, Page: 129 / 577

TROUBLESHOOTING
STEP INSPECTION
RESULTS
ACTION
6 Visually inspect CKP sensor and teeth of
crankshaft pulley.
Are CKP sensor and teeth of crankshaft pulley
okay? Yes Go to next step.
No
Replace malfunctioning parts.
7 Measure gap between CKP sensor and teeth of
crankshaft pulley.
Specification
0.5— 1.5 mm {0.020—0.059 In}
Is gap within specification?
Yes
Go to next step.
No
Adjust CKP sensor.
8
Remove and inspect PCV valve.
Does PCV valve rattle?
Yes
Go to next step.
No Replace PCV valve.
9 Install fuel pressure gauge between fuel main
pipe and fuel distributor.
Connect a jumper wire between F/P terminal at
DLC in engine compartment and GND.
(See Section F)
Turn ignition switch on.
Is fuel line pressure correct?
Fuel line pressure
210—260 kPa {2.1—2.6 kgf/cm2, 30—36 psi}
Yes
Go to next step.
No
Zero or low:
Inspect fuel pump unit circuit.
Inspect for open fuel pump body relief valve.
Inspect for fuel leakage inside pressure regulator.
Inspect for clogged main fuel line.
Inspect PRC solenoid and related vacuum hose
and harnesses.
High:
Inspect pressure regulator for high pressure
cause.
Inspect for clogged fuel return line.
10 Is fuel line pressure held after ignition switch is
turned off?
Fuel line pressure
More than 150 kPa {1.5 kgf/cm2, 21 psi} for 5
min.
Yes Go to next step.
No
Inspect pressure regulator diaphragm condition.
If condition is okay, inspect fuel injector.
If condition is not okay, replace pressure regulator.
11
Disconnect vacuum hose from pressure
regulator and plug hose.
Start engine.
Does fuel line pressure remain within
±20 kPa
{0.21 kgf/cm2, 3 psi} while driving vehicle?
Yes Go to next step.
No Inspect for clogged fuel filter.
12
Connect vacuum hose to pressure regulator.
Install vacuum gauge to intake manifold.
Start engine.
Does fuel pressure gauge reading increase as
vacuum gauge reading decreases and/or fuel
pressure gauge reading decrease as vacuum
gauge reading increases?
Yes Go to next step.
No Connect vacuum pump to pressure regulator.
Start engine.
Verify fuel pressure gauge reading changes as
vacuum changes.
If changes, inspect vacuum line.
If does not change, replace pressure regulator.
13 Disconnect a vacuum hose from purge solenoid
valve and plug opening end of vacuum hose.
Attempt to start engine.
Is starting condition improved?
Yes Inspect if purge solenoid valve is stuck open.
No Go to next step.
14 Inspect MAF sensor for contamination.
Is there any contamination? Yes Replace MAF sensor.
No Go to next step.
15 Is there restriction in exhaust system? Yes Inspect exhaust system.
No Go to next step.
16 Inspect engine condition while tapping EGR
valve housing. Does engine condition improve?
Yes Replace EGR valve.
No
Go to next step.
17 Inspect starting system.
(See Section G)
Is starting system normal?
Yes Inspect for loose connectors or poor terminal
contact. If okay, remove EGR valve and visually
inspect for mechanically stuck EGR valve.
No Repair or replace components as required.
18 Verify test results. If okay, return to diagnostic index to service any additional symptoms.
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