Honda CB900F Service Manual page 380

IGNITION SYSTEM
TROUBLESHOOTING
Inspect the following before diagnosing th e system .
- Faulty spa rk plug
- Loose spa rk pl ug cap or spa rk plug wire connection
- Water in the direct ig nition coil (leaking ig nition co il secondary vo ltage)
If there is no spark at either cyl inder, temporarily exchange the ig nit ion coil with a known- good one and perform th e spa rk
te st.
If the re is spark, the excha nged ig niti on coi l is f aul ty.
" Ini t ial volta ge" of the ig nition primary co il is the battery voltage w it h the ig nit io n switch ON and engine stop switch at RUN
(The engine is not cranked by the starter motor).
Unusual condition
Probable cau se (Check in numerical order)
Ig nit ion coil No initial voltage w ith ignit io n and l.
Fa ulty engine stop switch.
primary
engine stop switches
ON. (Other elec t rl-
2.
A n open circuit in Black/Whit e wire between the ignition
voltage cal co m ponent s are normal)
coil and engine stop switc h.
3. l oose or poor con nect of th e ignit io n coil primary wi re
terminal, or an open circuit in primary coil (Check at th e
ECM co nnector) .
4. Faulty ECM (when th e in it ial vo ltage is norm al whil e d is-
connecting ECM connector)
In itial vo ltage is no rm al, but it drops l. Incor rect peak vol tage adaptor co nnections.
down to 2 - 4 V w hile cranki ng the
2.
Undercharged batt ery.
engi ne.
3. No vol tage between t he Black/w hite
(+)
an d Bod y
ground (-) at th e ECM m ult i-connector or loose ECM
connect io n.
4. An ope n circuit o r loose co nnection in Gr een w ire.
5.
A n open ci rcuit or loose co nnect io n in Blu e/black and
Yell ow/blue wires between the ignitio n co ils and ECM .
6. Sh ort circuit in ignition prim ary co il.
7. Faul t y side stan d switch or neutral sw itc h.
8. An open cir cu it or loose co nnect io n in No.7 re late d cir-
cult w ires .
.
Side stand swit ch line: Gr een/w hit e wi re
.
Neut ral switc h line:
lig ht g reen w ire
9.
Faulty ignit ion pulse generator (measu re th e pea k vo lt-
age) .
10. Faulty ECM (in case wh en above No . 1 - 9 are norm al).
l. Faulty peak voltag e ad aptor co nnectio ns .
Init ial voltage is norm al, but no peak
2.
Faul t y peak volta ge adaptor.
voltage while cranki ng t he eng ine .
3. Fault y ECM (in case w hen abo ve No.1, 2 ar e no rmal) .
l. Th e m ulti m et er impeda nce is too low; below 10
Init ial voltage is normal, but peak volt- MQlDCV.
age is lo we r than standard v al ue.
2.
Cranking speed is too low (battery under-cha rged) .
3. The sampling timi ng of the teste r and measured pu lse
w ere not synchronised (sy st em is normal if measu red
I
v olt age is over the st andard v olt age at least once).
4. Faulty ECM (in case when above No .1 - 3 are normal).
l. Faulty spark plug or leakin g ignition co il secondary cur-
Initial an d peak voltage are normal, but rent ampere .
does not spark.
2.
Faulty ig nit ion coil (s).
l. The multimeter impedance is t oo lo w ; be low 10
Ignit io n pulse Peak voltage is lower tha n standa rd M Ql DCV.
generator val ue.
2.
Cra nking speed is too lo w (battery under charged).
3. The sampling t im ing of th e t est er and me asured pulse
we re not sy nch ro nis ed (system is no rma l if m easured
voltage is over the standa rd vo ltage at least o nce).
4.
Faul ty ECM (when above No.1 - 3 are norm al ).
l. Faulty peak vol ta ge ad aptor.
No peak vo ltage.
2.
Faul t y ignitio n pulse gen erat or.
17-3