Chevrolet 1977 light duty truck, Руководство по обслуживанию

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sh arp increase in m an ifo ld vacuum , shuts off the injected
air to the exhaust port areas and prevents backfiring
d u rin g this richer period.
O n engine overru n the total air supply is dum ped
through the muffler on the d iv erter valve. At high engine
speeds the excess air is d um ped through the pressure
relie f valve w hich is in co rp o rated in the diverter valve.
T he check valve (Fig. 6E-37 and 38) prevents
exhaust gases from e n te rin g and d am ag in g the air
in jection pum p, as back flow can occur even under
norm al o p e ra tin g conditions.
O N -VEH IC LE SER VICE
Drive B elt
Inspection
1. Inspect drive belt fo r w ear, cracks or d e te rio ra ­
tion and replace if required.
2. Inspect belt tension and adjust if below 70 lbs.
using a tension gauge.
Adjustment
Loosen p u m p m o u n tin g bolt and p um p adjustm ent
bracket bolt. M ove p um p until belt is p roperly tensioned
then tighten ad ju stm en t bracket bolt and m o u n tin g bolt.
Use a belt tension gauge to check adjustm ent.
CAUTION: Do not p ry on the pum p housing.
Distortion o f the housing will result in
extensive dam age to the A ir Injection Pump.
Replace
1. Loosen p um p m o unting bolt and pum p ad ju st­
m ent bracket bolt, then swing p um p until drive belt m ay
be rem oved.
2. Install a new d rive belt and adjust as outlined
above.
Pump Pulley
Replace
1. Hold p um p pulley from tu rn in g by com pressing
drive belt then loosen p um p pulley bolts.
2. Rem ove drive belt as outlined above then
rem ove p um p pulley.
Install
1. Install p um p pulley w ith retain in g bolts h and
tight. Install and adjust drive belt as outlined above.
2. Hold p um p pulley from tu rn in g by com pressing
drive belt then torque p um p pulley bolts to 24 lb. ft.
(32N -m ).
3. R echeck drive belt tension and adjust if
req u ired .
Pump Filter
Replace
1. R em ove d rive belt a n d p u m p pulley as
previously outlined.
2. Insert needle nose and pull fan from hub (Fig.
6F-41).
NO TE: C are should be taken to prev en t fragm ents
from en terin g the air intake hole. D o not in sert a
screw driver betw een pum p and filter. It is seldom
possible to rem ove the filter w ithout destroying it.
Do not attem p t to rem ove the m etal hub.
Install
1. Install the new filter by draw ing it on w ith the
pulley and pulley bolts (Fig. 6E-42). Do not attem p t to
install a filter by h am m erin g it on o r pressing it on.
2. D raw the filter down evenly by alternately
to rq u in g the bolts. M ake certain th a t the o u ter edge o f
the filter slips into the housing. T he slight am o u n t o f
in terferen ce w ith the housing bore is norm al.
NO TE: The new filter m ay squeal upon initial
o p eratio n until i t ’s O.D. sealing lip has w orn in.
Air Hoses and Tubes
Inspection
1. Inspect all hoses for d eterio ratio n or holes.
2. Inspect all tubes for cracks or holes.
3. Check all hose and tube connections.
4. M ake rep airs or replace p a rts as needed.
5. Check all tube and hose routing. Interference
m ay cause wear.
6. If leak is suspected on the pressure side o f the
system or any tubes a n d /o r hoses have been discon­
nected on the pressure side, the connections should be
checked for leaks w ith soapy w ater solution.
7. W ith the p um p running, bubbles will form if a
leak exists.
Replace
To replace any hose a n d /o r tube, note routing th en ,
rem ove hose(s) a n d /o r tube(s) as required.
Install
1. Install new hose(s) a n d /o r tube(s), routing them
as w hen rem oved.
2. T ighten all connections.
Check Valve
Inspection
1. The check valve should be inspected w henever
the hose is disconnected from the check valve or
w henever check valve failure is suspected. (A p um p that
had becom e inoperative and h ad shown indications o f
having exhaust gases in the p um p would indicate check
valve failure.)
2. Blow through the check valve (tow ard the
cylinder head) then attem p t to suck back thro u g h check
valve. Flow should only be in one direction (tow ard the
exhaust m anifold).
Replace valve w hich does not
function this way.
Replace
D isconnect p u m p outlet hose at check valve.