Chevrolet DB90 Series, Service Manual

Page: 79 / 242

S ec. 6C-73
53 AND 71 SERIES DIESEL ENGINES
Figure 17—Fuel and Crankcase Pressure Check (Typical for 6-711
If the quantity of fu el returned is e x c e ssiv e ,
the r e str ic ted fitting is too la rg e or not co rrect
s iz e and m ust be rep laced with co rrect restr ic ted
fitting in order to hold p r e ssu r e to in jectors for
fu ll pow er.
FUEL PRESSURE TEST
The fuel p r e ssu r e gauge can be u sed in check­
ing fu el p r e ssu r e at the intake m anifold with the
engine in operation (fig. 17). R em ove the plug from
the fuel intake m anifold and in sta ll the fuel gauge.
Start engine and run at sp e cified speed and read
p r e ssu r e gauge. R efer to "Fuel P r e s s u r e ” chart
opposite:
Uneven running, e x c e s s iv e vibration, stallin g
when idling, and a lo s s of pow er may be caused by
an in su fficien t fu el supply to in jecto rs due to one
o f the follow ing conditions:
1. Clogged prim ary o r secondary fuel filte r
elem ent.
2. A ir in the sy ste m due to lo o s e fuel lin e
connections or filte r gask et lea k s.
3. C logged injector fuel filte r s .
4. Fuel lin e r e str ic ted or leaking.
5. D efective fuel pump.
FUEL PRESSURE
Engine
SPEED (RPM)
1200
1800 2100 2200 2600
6V-53
6-71
V -71
30-65
45-70
45-70
45-70
45-70
45-70
45-70 45-70
CRANKCASE PRESSURE TEST
(R efer to Figure 17)
The crankcase p r e ssu r e indicates the amount
of a ir that has p a ssed between the o il control rin gs
and the lin er into the cran k case, m ost of which is
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT