Testing - Mercury 40 Service Manual

Testing

Install clear fuel hose(s) between fuel pump and car-
buretor(s). Run engine, and inspect hose(s) for air
bubbles. If air bubbles are found, see "Air Bubbles in
Fuel Line" . If air bubbles are not found, see "Lack of
Fuel Pump Pressure".
PROBLEM: AIR BUBBLES IN FUEL LINE
Possible Cause
Low fuel in tank.
Loose fuel line connec-
tion.
Fuel pump fitting loose. Tighten fitting.
A hole or cut in fuel line. Inspect condition of fuel
Fuel pump anchor
screws loose.
Fuel pump gaskets worn
out.
90-852572R1 JANUARY 1998
Corrective Action
Fill tank.
Inspect and tighten con-
nections.
lines and replace any
found bad.
Inspect and tighten all
screws.
Rebuild fuel pump.
PROBLEM: LACK OF FUEL PUMP PRESSURE
Possible Cause
Anti-siphon valve.
Air in fuel line.
Dirty or clogged fuel fil-
ter.
Dirty or clogged fuel
pickup in fuel tank.
Worn out fuel pump dia-
phragm.
Defective check valves
in fuel pump.
Broken check valve re-
tainer.
Pulse hole plugged.
Hole in pulse hose.
Loose pulse hose.
Boost diaphragm gasket
distorted or out of place.
Corrective Action
Refer to "Checking for
Restricted Fuel Flow
Caused by Anti-siphon
Valves" preceding.
"Air Bubbles in Fuel
Line," preceding.
Clean or replace filter.
Clean or replace pickup.
Rebuild pump.
Rebuild pump.
Rebuild pump.
Remove pump and
clean out hole.
Replace pulse hose.
Tighten connection.
Check seal between
mating surfaces where
"rib" divides pulse
chamber. Gasket must
align with rib. Align or re-
place gasket as neces-
sary.
FUEL SYSTEM - 3A-9