Injectors; Cold Start Valve; Fuel Pump; Tank Pump (Pre-Pump) - Volvo 240 1989 Service Manual

Design and function
Fuel system LH2.4 - 240
o
o
280 150 ...
..
Vi!llve
pump
Tank
pump
Injectors
The injector is fin ed with a solenoid, a magnetic
actuator and a fuel needte which opens or shuts a
nozzle.
The control un it feeds current to the injectors
in ca lculated time units. This ensures that all
the injectors spray a fine fuel mist simultane ·
ously .
While the starter motor is opem ting, there are two
injeclions per rotalion. This is redu ced to one for
normal
dri~ i ng.
Injection occurs in the intake manifold
near the intake
~alves.
Disa ssembled injectors should only be inspected
using specially designed equipment in order to mini ­
mize the risk of explosion from fhe fu el mist.
Cold start valve
(eenail! models)
At cold start, a lot 01 fuel condenses on the cold
surfaces in the lorm of droplels . Having a separate
cold start valve improves cold starting. It's placed
farther away from the engine block than the ordinary
injectors and delivers the fuel more as a gas Ihan as
drops. The cold slart valve is controlled directly by the
conlrol unit, ralher than by the thermal time swifCh . It
culS in when the temperature is aboul -15
c
C
(5°F)
and when Ihe engine rolation is below approx. 900
rpm. It culs out permanently if the rpm exceed the
permissible limit.
®
Fuel pump
The fuel pump is an eleclric roller pump , cooled by the
fuel which flows through it. It has a non-return valve
and an overflow valve which opens if the pressure
gels 100 high .
Both the primary pump and Ihe fuel pump operate
when either the starter motor or Ihe engine is running .
However, should the engine stop while Ihe ignition
remains on , the conlrol unll wi ll cut off the current to
the pumps in order 1 0 eliminate Ihe risk of fire in Ihe
even! of an accidenl.
@
Tank pump (pre-pump)
The electric Impeller pump in the fuel tank keeps
pressure in the fuel lTne prior to the (main) fuel pump
to prevenl vapor lock.
The pump has a coarse, slralner Iype filter and a non ­
return valve to maintain a certain amounl of pressure
in the system even if the main pump is not in
operation .
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