Mazda MX-6 1998, Workshop Manual, Page: 68 / 1282

TROUBLESHOOTING [ENGINE CONTROL FS]
STEP
INSPECTION
ACTION
23 CHECK FUEL PRESSURE LEAKDOWN
•
O bse rve all W arnings, C autions and Notes.
• Install fuel pressure tester.
• Connect NGS tester.
• Key on, engine off.
• Access Output Test Mode and active fuel
pump to obtain maximum fuel pressure.
• Exit Output Test Mode. Key off.
• Verify fuel pressure remains within 34 kPa
{35 kgf/cm2, 5 psi} of maximum pressure
for 1 minute after turning pump off.
• Does fuel pressure remain within 34 kPa
{0.35 kgf/cm2, 5 psi}?
Yes Go to step 25.
No Go to next step.
24
CHECK PRESSURE REGULATOR
DIAPHRAGM
• Key off.
• Install fuel pressure tester.
• Start and run engine for 10 seconds.
• Key off. Wait 10 seconds.
• Start and run engine for 10 seconds.
• Key off. Remove vacuum hose from fuel
pressure regulator.
• Inspect for fuel in vacuum hose or regulator
port.
• Is vacuum hose and regulator port free
of fuel?
Yes
Go to step 28.
No REPLACE fuel pressure regulator.
RESET PCM to completely clear DTCs.
cr After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
25 CHECK FUEL PRESSURE, ENGINE
RUNNING
• Key off.
• Install fuel pressure tester.
• Disconnect vacuum hose at fuel pressure
regulator and plug it.
• Drive vehicle with heavy accelerations
while observing fuel pressure gauge
reading.
• Does fuel pressure reading hold steady
within 21 kPa {0.21 kgf/cm2, 3 psi}
during test?
Yes
UNPLUG vacuum hose and RECONNECT to fuel
pressure regulator.
Go to next step.
No
Go to step 29.
26 CHECK FUEL PRESSURE REGULATOR
RESPONSE TO VACUUM
• Key off.
• Install fuel pressure tester.
• Install vacuum gauge to intake manifold.
• Start engine and observe both gauges.
• Accelerate and decelerate engine speed to
vary vacuum gauge reading.
• Does fuel pressure gauge reading
increase as vacuum gauge reading
decreases, or decrease as vacuum
gauge reading increases?
Yes
REMOVE vacuum gauge and fuel pressure tester.
Concern is elsewhere.
a- 01-01A ENGINE SYMPTOM TROUBLESHOOTING
[FS]
No Go to next step.
27 CHECK VACUUM SUPPLY
• Key off.
• Install fuel pressure tester.
• Disconnect vacuum hose at the fuel
pressure regulator and plug it.
• Install hand held vacuum pump to fuel
pressure regulator.
• Start engine and let run at idle.
• Observe fuel pressure while applying
vacuum.
• Does fuel pressure change as vacuum
changes?
Yes SERVICE vacuum system.
UNPLUG vacuum hose and RECONNECT to the
pressure regulator.
RECHECK fuel pressure.
No REPLACE fuel pressure regulator.
RECHECK fuel pressure.
01-01A-40