Chevrolet 10 Series 1970 Service Manual page 379

INLET
F i g . I p — F u e l
too low, too high, o r v a r ie s m a te ria lly at d ifferen t
speeds, the pump should be replaced.
V A C U U M SECTION INSPECTION A N D TEST
NOTE:
These p roced u res can be used only on
the combination pump.
T e s t the vacuum section of the pump by fully opening
the windshield w ip er v a lv e and ob serve w ip er blade speed
w hile altern a tely idling
W ip er blade speed should be fa ir ly constant re g a rd les s of
engine speed o r throttle opening.
NOTE:
A d ry windshield
speed. If windshield
p ro p e rly , make the follow in g inspection and test.
1. Make certain that hoses a re p ro p e rly connected at
pump, w ip er m otor and con trol at instrum ent panel
and double check v a lv e , and that connections are a ir
tight. Replace cracked o r d eteriora ted hose.
2. If windshield w iper does not operate p ro p e rly after
a ll points of leakage have been corre c te d , detach both
pipes at vacuum pump and join them with a p iece of
tubing. Slow ly operate
1000 rpm ; the w ip er should run at full speed op era t­
ing on engine vacuum only. If it does not, it can be
assumed that the w ip er m otor o r tubing is d efective.
The pump vacuum section is in operative if the wind­
shield w ip er operated p ro p e rly on engine vacuum, but
not on pump vacuum.
3. A fu rth er test of vacuum pump may be made by at­
taching a vacuum gauge to the in let p ort (p ort con­
nected to w iper m otor) with outlet pipe disconnected.
CA U TIO N :
A lw ays make this test o f vacuum
pump with outlet open.
4. With engine operating at 750 rpm the gauge should
show 10 to 12 inches o f vacuum. L e s s than 10 inches
o f vacuum indicates an inoperative vacuum pump.
OUTLET
P u m p ( N o n s e r v i c e a b l e )
and accelera tin g the engine.
w ill slow w iper
w ip er does not operate
engine fro m idle to about
F i g . 2 P — S t e p - V a n
1. O u t l e t V a l v e
2 . F u e l C o v e r
3 . F u e l D i a p h r a g m
4 . F u e l D i a p h r a g m S p r in g
5 . V a c u u m L in k
6 . F u e l L in k
7 . V a c u u m O u t l e t V a l v e
A s s e m b lie s
8 . D i a p h r a g m S p r in g
9 . P u ls a to r C o v e r
Removal
1. Disconnect fuel inlet and outlet pipes at fuel pump.
On " P " M odels, disconnect vacuum lines at pump.
2. Rem ove fuel pump mounting bolts and rem ove pump
and gasket.
3. On V -8 engines: if push rod is to be rem oved, r e ­
m ove fuel pump adapter and gasket then rem ove push
rod (307 and 350 engines).
4. If a new fuel pump is to be installed, tra n sfer fittings.
NOTE:
A fte r rem ova l of pump fro m engine and
before d isassem bly is started, plug a ll openings
and thoroughly wash
cleaning solvent to rem ove all d irt and grea se.
Installation
1. On V -8 engines: i f rem oved, install fuel pump push
rod and fuel pump adapter.
gasket or pipe fitting.
2. In stall fuel pump using a new gasket and tighten s e ­
cu rely. Use s e a le r
threads.
NOTE:
On V -8 engines, a p a ir of mechanical
fin gers o r heavy grea se may be used to hold fuel
ENGINE FUEL 6M -15
F u e l a n d V a c u u m Pum p
P u ls a to r D i a p h r a g m 1 0 .
F u e l I n l e t V a l v e 1 1 . A s s e m b ly
Pum p B o dy
1 2 .
R o c k e r A r m 1 3 . R e tu r n S p r in g
S e a l 1 4 .
R o c k e r A r m 1 5 .
B u sh in g
1 6 .
V a c u u m 1 7 . D i a p h r a g m
V a c u u m I n l e t V a l v e A s s e m b lie s 1 8 .
V a c u u m 1 9 . C o v e r
e x te rio r of pump with
Use gasket s e a le r on
on fuel pump mounting bolt
CHEVROLET TRUCK SERVICE MANUAL