Mazda MX-5 1990 Workshop Manual page 179

TROUBLESHOOTING GUIDE
F
STEP
5
6
INSPECTION
Check if ECU terminal voltages are OK
(20, 20 and 20)
c::::r
page F-128
Check for correct ignition timing at idle
CT
page F-75
Ignition timing: 10 0
±
1
0
BTOC
G.
~l
lJJ
I
QJ
~. \ . ~ . . . . '--/
CONNECT TERMINALS \ \
~
I
ACTION
Yes Go to next step
No Check for cause (Refer to "Check Point
for Each Terminal")
CT
page F-132
Yes Check for correct idle speed
c::::r page F-76
Idle speed: 850 ± 50 rpm
¢
If OK, go to next step
c::;>
If not OK, adjust idle speed
CT
page F-76
No Adjust c::::r
page F-75
7 Check for correct fuel line pressure at idle Yes Go to next step
L7
page F-103
Fuel line pressure:
265-314 kPa (2.7-3.2 kg/cm
2
,
38-46 psi)
(Vacuum hose to pressure regulator
disconnected)
INSTALL CLAMPS
8
Check if strong blue spark is visible at each dis-
connected high-tension lead while cranking
engine
9 Check for correct engine compressicm
CT
page 8-10
Engine compression: 1,324-932 kPa
(13.5-9.5 kg/cm\ 192-135) - 300 rpm
10 Check if spark plugs are OK
WEAR AND CARBON BUILDUP
PLUG GAP
1.0-1.1mm
(0.039-0.043 in)
DAMAGE AND
DETERIORATION
DAMAGE
11 Try known good ECU and check if condition
improves
CT
page F-127
No Low
pressu re
Check fuel line pressure while pinching
fuel return hose
¢
If fuel line pressure quickly in-
creases, check pressure regulator
CT
page F-111
¢
If fuel line pressure gradually in-
creases, check for clogging be-
tween fuel pump and pressure
regulator
If not clogged, check fuel pump
maximum pressure c::::r
page F-108
Yes Go to next step
No Check ignition system (Refer to
Troubleshooting "Misfire")
Yes Go to next step
L7
page G-18
No Check engine condition
L7
page B-10
• Worn piston, piston rings or cylinder
wall
• Defective cylinder head gasket
• Distorted cylinder head
• Improper valve seating
• Valve sticking in guide
Yes Go to next step
No Repair, clear, or replace
c::::r
page G-20
05UOFX·027
F-35