EasyManuals Logo

Mariner Mercury 135 JET User Manual

Mariner Mercury 135 JET
797 pages
To Next Page IconTo Next Page
To Next Page IconTo Next Page
To Previous Page IconTo Previous Page
To Previous Page IconTo Previous Page
Page #154 background imageLoading...
Page #154 background image
3A-4 - FUEL SYSTEMS 90-824052R3 JUNE 2002
Fuel Pump
General Information
FUEL PUMP DESCRIPTION/OPERATION
The fuel pump is a crankcase-pressure-operated,
diaphragm-type pump. Crankcase pulsating
pressure (created by the up-and-down movement of
piston) is transferred to fuel pump by way of a
passage (hole) between crankcase and fuel pump.
When piston is in an upward motion, a vacuum is
created in the crankcase, thus pulling in a fuel/air
mixture (from carburetor) into crankcase. This
vacuum also pulls in on the fuel pump diaphragm,
thus the inlet check valve (in fuel pump) is opened
and fuel (from fuel tank) is drawn into fuel pump.
Downward motion of the piston forces the fuel/air
mixture out of the crankcase into the cylinder. This
motion also forces out on the fuel pump diaphragm,
which, in turn, closes the inlet check valve (to keep
fuel from returning to fuel tank) and opens the outlet
check valve, thus forcing fuel to the carburetors.
CHECKING FOR RESTRICTED FUEL FLOW
CAUSED BY ANTI-SIPHON VALVES
While anti-siphon valves may be helpful from a safety
stand-point, they clog with debris, they may be too
small, or they may have too heavy a spring.
Summarizing, the pressure drop across these valves
can, and often does, create operational problems
and/or power-head damage by restricting fuel to the
fuel pump and carburetor(s). Some symptoms of
restricted (lean) fuel flow, which could be caused by
use of an anti-siphon valve, are:
1 - Loss of fuel pump pressure
2 - Loss of power
3 - High speed surging
4 - Preignition/detonation (piston dome erosion)
5 - Outboard cuts out or hesitates upon acceleration
6 - Outboard runs rough
7 - Outboard quits and cannot be restarted
8 - Outboard will not start
9 - Vapor lock
Since any type of anti-siphon device must be located
between the outboard fuel inlet and fuel tank outlet,
a simple method of checking [if such a device (or bad
fuel) is a problem source] is to operate the outboard
with a separate fuel supply which is known to be
good, such as a remote fuel tank.
If, after using a separate fuel supply, it is found that
the anti-siphon valve is the cause of the problem,
there are 2 solutions to the problem; either 1) remove
the anti-siphon valve or 2) replace it with a solenoid-
operated fuel shut off valve.

Table of Contents

Questions and Answers:

Question and Answer IconNeed help?

Do you have a question about the Mariner Mercury 135 JET and is the answer not in the manual?

Mariner Mercury 135 JET Specifications

General IconGeneral
BrandMariner Mercury
Model135 JET
CategoryEngine
LanguageEnglish

Related product manuals