DIRECT FUEL INJECTION
Page 3B-20 90-855347R1 JANUARY 1999
Compressor Notes: To aid in starting when the air rail pressure is low and before the
compressor has time to build pressure, the direct injector is held open by the ECM. This
allows the compression from inside the cylinders to pressurize the air rail faster (1 or 2
strokes, or 60
0
of crankshaft rotation).
Idle Notes: Idle quality is controlled by fuel volume and fuel timing. The throttle shutters
will be open at idle speeds. The shift cut-out switch will interrupt the fuel to 3 of the cylin-
ders to assist in shifting.
The TPS signals the ECM to change the fuel and spark without movement of the throttle
shutters. The throttle cam is manufactured to allow the TPS sensor shaft to move before
opening the throttle shutters.
The crankshaft position sensor is different from the standard 3.0 liter sensor. The crank
position sensor serves two functions (flywheel speed and position).
Testing Electric Fuel Pump Pressure Output
Low Pressure Electric Fuel Pump
IMPORTANT: After completing fuel pressure tests, reconnect and secure fuel outlet
hose to fuel pump with full circle stainless clamps in Clamp Tool Kit 91-803146T.
1. Remove outlet fuel hose from low pressure pump. Install a short piece of hose (obtain
locally) onto pump outlet fitting. Install Schrader Valve t-fitting (22-849606) from
Schrader Valve Fuel Pressure Kit (849021A4) between outlet fuel hose (removed
from pump) and new fuel hose (installed on pump. Secure hose connections with sta-
straps. Connect Fuel/Air Pressure Gauge (91-16850A2) to Schrader Valve. Gauge
should indicate 6-9 psi (41.37 – 62.04 kPa).
57416
a
b
c
91-16850A2
d
a-Outlet Fuel Hose
b-Low Pressure Electric Fuel Pump
c-Fuel Hose (obtain locally)
d-Schrader Valve (22-849606)
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