Problem: Engine Turns Over But Will Not Start Or Starts Hard When Cold; Problem: Unable To Reduce Engine Rpm To Slow Idle - Mercury 40 Service Manual

Problem: Engine Turns Over But Will Not Start Or Starts Hard When Cold

Possible Cause
Improper starting procedure used.
Fuel tank empty or too low. Improperly mixed fuel.
Contaminants (water, dirt, etc.) in fuel.
Fuel tank air vent closed or restricted.
Pinched, cut, restricted fuel line or loose fuel line
connection.
Dirty or restricted fuel filter.
Choke solenoid or enrichment valve not operating.
Needle and seat in carburetor that is either stuck
open (flooding) or closed (no fuel).
Improper carburetor jet, restricted jet or idle mixture
screw out of adjustment.
Improper float level.
Low fuel pump pressure.
Defective anti-siphon valve.
Needle and seat in carburetor that is either stuck
open or closed.
Improper float level.
Carburetor loose on intake manifold.
Reed block loose or gasket defective.
Improperly routed or restricted bleed hose(s).
Damaged fuel pump diaphragm.
Carburetor mixing chamber cover leaking air.
Off idle holes plugged.
Main nozzle or idle nozzle air bleed holes plugged.
Damaged reeds.
Fuel pick-up outlet tube in fuel tank cracked.

Problem: Unable to Reduce Engine RPM to Slow Idle

Possible Cause
Chipped or broken reeds on reed block.
3B-14 - FUEL SYSTEM
Corrective Action
Review starting procedure as outlined in "Operation
and Maintenance Manual".
Check fuel in tank and replace or add whichever is
necessary.
Check air vent on fuel tank. Air vent must be open
all the way and free from any contaminants.
Inspect all fuel lines and replace as needed. Tighten
fuel line connections.
Inspect and replace or clean all fuel filters.
Inspect solenoid or valve and wiring. Replace as re-
quired.
Refer to carburetor disassembly in this section.
Refer to carburetor adjustments in this section.
Refer to carburetor adjustments in this section.
Refer to Section 3A "Fuel Pump".
Refer to Section 3A "Fuel Pump".
Refer to carburetor adjustments in this section.
Refer to carburetor adjustments in this section.
Check tightness of carburetor nuts.
Using a pressure oil can, apply 2-cycle oil around
reed block housing/crankcase housing matching
surfaces and carburetor base. If engine RPM
changes, tighten bolts/nuts or replace gaskets as
required.
Refer to bleed hose routing in Section 4A "Power-
head".
Refer to Section 3A "Fuel Pump".
Tighten screws or replace gasket.
Blow with compressed air.
Blow with compressed air.
Refer to Section 4A "Powerhead" for reed inspec-
tion.
Replace.
Corrective Action
Replace reeds.
90-852572R1 JANUARY 1998