Chevrolet DB90 Series, Руководство по обслуживанию

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S ec. 6C-72
53 AND 71 SERIES DIESEL ENGINES
Figure 16—Fuel Flo w Test ITyp ical)
DISTILLATION RANGE, CETANE NUMBER,
AND SULFUR CONTENT are three of the m ost
im portant p ro p er ties in the se le c tio n of d ie se l
fu e ls for optimum com bustion and minimum w ear.
Engine speed, load, and atm ospheric tem perature
influence the se le c tio n of the fu els with resp e ct to
d istilla tio n range and cetane number. THE SUL­
FUR CONTENT OF THE FUEL MUST BE AS LOW
AS POSSIBLE, to avoid e x c e s s iv e deposit form ­
ation and prem ature w ear.
ENGINE OUT OF FUEL
The problem in restartin g the engine a fter it
i s run out of fuel ste m s from the fact that after the
fuel is exhausted from the fuel tank, fuel is then
pumped from the prim ary fu el stra in er and so m e­
tim e s p a rtia lly rem oved from the secondary fuel
filte r b efore the fuel supply b eco m es insufficient
to su stain engine firin g. Consequently, th ese com ­
ponents must be r e fille d with fuel and the fuel
lin e s purged of air in order for the sy ste m to p ro­
vide adequate fuel for the in jecto rs.
When an engine is run out of fuel inadvertent­
ly , th ere is a definite procedure to follow fo r r e ­
startin g the engine. The procedure is outlined below:
1. F ill the fuel tank with the recom m ended
grade of fuel o il. If only partial fillin g of the tank is
p o s s ib le , add a minimum of ten gallon s of fu el.
2. R em ove the prim ary fuel stra in er sh e ll and
elem en t from the stra in er cover and fill the sh ell
w ith fu el o il. In stall the sh e ll and elem ent.
3. R em ove and f ill the secondary fuel filte r
sh e ll and elem ent with fuel o il as in Step 2.
4. Start the engine. Check the filte r and stra in ­
er for le a k s.
NOTE: In som e in sta n ce s, it may be n e c e ssa r y
to rem ove a valve rock er cover and lo o se n a fuel
pipe nut in ord er to b leed trapped a ir from the fuel
s y ste m . Be su re the fu el pipe is retightened s e ­
cu rely b efore replacing the rocker cover.
P r im e r (J-5956) may be used to p rim e the
entire fuel sy ste m . Rem ove the filte r plug in the
fuel filte r cover and in sta ll the p rim er . P rim e the
sy ste m . R em ove the p rim er and in sta ll filte r plug.
FUEL FLOW TEST
(R efer to F igu re 16)
NOTE: T his te st should be run in conjunction
with Fuel P r e s s u r e T est.
1. D isconnect the fuel return lin e and hold the
open end in a suitable container.
2. Start and run the engine at approxim ately
1200 rpm and m easu re the fuel flow from the r e ­
turn lin e for one m inute.
NOTE: At le a s t .6 gallons of fuel on 53 S e r ie s
and .9 gallons on 71 S e r ie s e n g in e ,should flow
from the return lin e per/m inute. *
3. B e su re a ll lin e connections betw een the
fu el supply and the pump a re tight so no a ir w ill be
drawn into the fuel system ; then, im m e r se the end
o f the fuel return line into the fuel in the container.
A ir bubbles risin g to the su rface of the fuel
w ill indicate a leak on the suction sid e of the pump,
o r faulty check valve in the injector.
If the quantity of fuel i s l e s s than sp ec ifie d ,
th is w ill cau se a lo s s in pow er, rough running and
in d icates air in the sy ste m , or a r e strictio n in the
fuel sy ste m .
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT