Porsche 928 Workshop Manual page 598

928 s4
928 GT Fuel System, Electronic Injection
24
Test point 13: Ground connections I
Plug connections
Ground connections
l
Engine ground, between engine and right
side of body
under engine.
l
Ground for ignition output stages above
the right ignition coil.
l
Ground for control unfts under the fuel
pressure regulator and the fuel pressure va-
porizer.
Are the ground connections tight and free from
corrosion?
Loosen the ground points, clean them and
tighten.them again as specified.
Note:
Never start the engine when the body-en-
gine ground lead is not connected.
This will destroy the control unit immedi-
ately.
Plug connections
Are all plug connections correctly wired up
and not loose or corroded? Separate the plug
connections. Neither the pins nor the sleeves
of the plug connections must be bent or cor-
roded.
l
At the central electrics. the relays for the
fuel pump, EZK and LH and
plug w.
l
At the EZK and LH control units, the 35-pin
plug in each case.
l
Plug connection for activating the ignition
output stages (green/white lead). Above
the central electrics
.
.
.
.
.
.
.
.
.
.
At the air mass sensor, a g-pin plug (only 5
contacts are occupied in the plug housing).
At temperature sensor, II a Z-pin plug.
At the engine speed reference mark sen-
sor, a 3-pin plug (behind the air mass sen-
sor).
At each of the 6 injector valves a 2.pin
plug (first remove the ring pipe cover).
Knock sensor plug connections. Front sen-
sor: plug connection at the front left, below
the fuel ring pipe.
Rear sensor: plug connection above the
right fuel ring pipe at the rear.
Hall sensor plug connection. Behind the
housing for the camshaft drive gear, cyl-
inder bank 1-4.
Plug connection for solenoid valve to
operate resonance flap (at toothed belt
cover for cylinder bank 5-E).
Plug connection, fuel tank venting solenoid
(at toothed belt cover for cylinder bank l-
4, below the water hose).
Plug connections for the output stages (on
the cover, left cross-wall).
Test point 14: Fuel pump voltage (V)
Fuel pump relay XX (XXVI) is activated by the
LH control unit against ground. To check fuel
pump activation, connect terminals 200 and 17
at the LH control unit plug with the test leads
and switch on the ignition. The relay will be
energized and the pump will run.
LH-Diagnosis/Troubleshooting
PrInted In Germany - XXV, 1990
D24-21