Chevrolet 1977 light duty truck, Service Manual

Page: 678 / 861

R em ove check valve from pipe assem bly, being careful
not to b end o r twist the assem bly.
D iverter Valve and S ilencer Assembly
Inspection
1. C heck co n d itio n and ro u tin g o f all lines
especially the signal line. All lines m ust be secure w ithout
crim ps and n o t leaking. R eplace d e te rio ra ted lines.
2. D isconnect signal line at valve. A vacuum signal
must be available w ith engine ru nning.
3. C heck d iv erter valve attach in g screws for
tightness. Screws should be to rq u ed to 85 lb. in. (lO N m).
4. D efectiv e valves sh o u ld be rep laced (see
F unctional Test).
Replace
1. D isconnect vacuum signal line. D isconnect valve
outlet hose.
2. Rem ove d iv erter valve fro m pum p o r elbow.
Install
1. Install d iv erter valve to p u m p or elbow w ith new
gasket. T orque valve atta c h in g screws to 85 lb. in.
(9.5N-m).
2. Install outlet and vacuum signal hoses and check
system for leaks.
Air Injection Pump
Inspection
A ccelerate engine to approxim ately 1500 R PM and
observe air flow from hose(s). I f air flow increases as
en g in e is accelerated, p um p is o p era tin g satisfactorily. If
air flow does not increase or is not present, proceed as
follows:
1. C heck for p ro p e r drive belt tension.
2. Check for a leaky pressure relief valve. A ir m ay
be h eard leaking w ith the pum p running.
N O TE: The AIR System is not com pletely
noiseless. U n d er norm al conditions, noise rises in
pitch as engine speed increases. To d eterm in e if
excessive noise is the fau lt o f the A ir Injection
R eactor System , operate the engine w ith the pum p
drive belt rem oved. If excessive noise does n o t exist
w ith the belt rem oved proceed as follows:
3. Check fo r a seized A ir Injection Pum p.
4. Check hoses, tubes and all connections fo r leaks
and p ro p er routing.
CAUTION:
Do not oil A IR pump.
5. Check d iv erter valve.
6. Check A IR injection p um p fo r p ro p e r m ounting
and bolt torque.
7. R ep air irreg u larities in these com ponents as
necessary.
8. If no irreg u larities exist an d the A IR injection
p um p noise is still excessive, rem ove and replace pum p.
Replace
1. D isconnect the hoses at the pum p.
2. Rem ove p um p pulley as outlined.
3. R em ove p u m p m ounting bolts and rem ove
pum p.
Install
1. Install p um p w ith m ounting bolts loose.
2. Install p um p pulley as outlined.
3. Install and adjust belt as outlined.
4. C onnect the hoses at the pum p.
5. T ighten m o unting bolts to 20-35 lb. ft. (27 N-m -
48N-m).