Chevrolet 70 Series 1970, Service Manual

Page: 523 / 841

ENGINE FUEL SYSTEM 6M-30
F uel Output T est
When in je c to rs a r e rem oved fro m an engine
fo r output te stin g and, if sa tisfa c to ry , re in sta lle d
without d isassem b ly , extrem e c a re should b etak e n
to avoid re v e rsin g the fuel flow. When the flow is
re v e rs e d , d irt trap p e d by the filte rs located in the
in je c to rs is back-flushed into the in je c to r com ­
ponents.
The fuel m anifolds in cylinder heads d irec t
th e fuel into the in je c to r through the filte r cap lo­
cated above the fuel rack . To avoid re v e rs in g the
fuel flow when checking fuel output on the com ­
p a r a to r u se the ap p ro p riate ad a p te r. Do not c ro s s
the lin es when using ad ap ter (J-7041-130).
O p erate the in jecto r in the com p arato r (J-7041)
to check the fuel output a s follows:
1. P lace the in jecto r in the co m p arato r, as
shown in fig u re 20. Then, tu rn the wheel to clamp
the in je c to r and ad a p te r in position.
NOTE: Make s u re the counter on the co m par­
a to r is p r e - s e t to 1,000 stro k e s. If fo r any re aso n ,
th is setting has been a lte re d , r e s e t the counter to
1,000 stro k e s by pulling the s e le c to r wheel to be
changed to the rig h t and rotating it to its p ro p e r
position; then, re le a s e the wheel.
2. P u ll the in je c to r ra c k out to the NO FUEL
position.
3. S ta rt the co m p arato r by turning on the
sw itch shown in fig u re 20.
4. A fter the co m p arato r has s ta rte d , push the
Engines re q u irin g a m inimum and maximum
sp eed control, to g eth er with m anually controlled
in te rm e d ia te speeds, a r e equipped with a lim iting
speed m echanical governor.
The lim iting speed m echanical go v ern o rs p e r ­
fo rm the following functions:
1. C ontrols the engine idle speed.
2. L im its the m axim um operating speed of the
engine.
3. Gives the o p e ra to r com plete control through
out the in term ed iate range.
The governor assem bly num ber, type, an d id le
speed range a r e stam ped on the nam e p late attach ­
ed to the governor housing. G overnor sp rin g s and
up p er le v e rs fo r 6V-53 engines is illu s tra te d in
fig u re 21, also 6-71 is shown in fig u re 23, while
8V-71 is shown in fig u re 22.
The governo r is mounted between in such a
m anner that one end of the governor weight shaft
in je c to r ra c k into the FULL FUEL position and
allow the in jecto r to o p erate fo r approxim ately 30
seconds to purge the a ir that may be in the sy stem .
5. A fter 30 seconds p r e s s fuel flow s t a r t but­
ton. T his w ill s ta r t the flow of fuel into the vial.
The co m p arato r w ill au tom atically stop the flow
of fuel at a p re -d e te rm in e d num ber of s tro k e s .
6. A fter the fuel sto p s flowing into the vial,
pu ll the ra c k out to the NO FUEL p osition.
7. T urn the co m p arato r off and r e s e t counter.
8. O bserve the reading on the vial. R efe r to
"F u e l Output C hart" following:
FUEL OUTPUT CHART
Fuel Output
Injecto r
Min.
Max.
N45 11
17
N55 24 30
N60 30 36
N65 (Brown) 32 38
N65 (White) 38 44
9. The co m p arato r may be u sed to check and
s e le c t a s e t of in je c to rs which w ill inject the sam e
am ount of fuel in each cylinder at a given th ro ttle
settin g , thus resu ltin g in a sm ooth running engine.
10. An in je c to r which p a s s e s all of the above
te s ts may be put back into s e rv ic e . However, an
in je c to r which fa ils to p a s s one o r m o re of the
te s ts m ust be disassem b led and reb u ilt.
is splined to a d rive p late attached to the driven
blow er tim ing g ea r to provide a m eans of driving
the governor. The o th er end of the shaft is sup­
po rted by a bearin g in blow er drive support.
A cover and le v e r assem bly, control housing,
sp rin g housing, and governor weight and shaft a s ­
sem bly a r e the b asic p a r ts of the governor.
OPERATION
The governor holds the in je c to r ra c k s in the
FULL FUEL position fo r s ta rtin g when the speed
con trol le v e r is in the idle position. Im m ediately
a fte r sta rtin g , the governor m oves the in jecto r
ra c k s to the position re q u ire d fo r idling.
The centrifugal fo rce of the revolving gover­
nor low and high speed weights is converted into
lin e a r motion which is tra n s m itte d through the
r i s e r and operating shaft to the o perating shaft
le v e r. One end of th is le v e r o p erates against the
GOVERNOR
NOTE: FOR GOVERNOR ADJUSTMENTS ON ENGINE REFER
TO SECTION 6C UNDER "ENGINE TU N E-U P."
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL