Porsche 928 Workshop Manual page 381

24
LH-Jetronic
928
TEST POINT 1
Checking Ground and Plug
Connections
See page 28 53.
1.2 If battery voltage is not displayed, pull
off relay XVI and bridge terminals 30
and 79.
Recheck voltage on LH multiple pin
plug between terminals 9 and 5.
TEST POINT 2 2. Fuel Pump
The fuel pump relay is activated
Power Supply for LH Control negatively by the LH control unit.
Unit and Fuel Pump
1. LH Control Unit
Switch off ignition and pull off multiple
pin plug on LH control unit.
1 .I Switch on ignition.
Measure voltage on multiple pin plug
between terminals 9 and 5.
Specification: battery voltage.
If value deviates from specification,
measure voltage on plug X connected
on central electric board between
terminal 8 and ground,
4
3
2
1
I I
I
;X'
I
I I
8
7
6
5
.l Connect terminal 17 on disconnected
LH control unit plug on ground with a
piece of wire.
2,
3.
Fuel pump relay should be activated and
fuel pump must run.
If pump does not run, check fuse no. 13
and relay XVII activation as well as fuel
pump relay.
Checking Control Signal
for Electronic Ignition
to LH Control Unit
Pull off multiple pin plug on LH control
unit; leave plug on electronic ignition
control unit.
3.1 Connect positive test lead of oscilloscope
on terminal 1 and negative test lead on
ground.
Specification: battery voltage
24-112
Troubleshooting LH-Jetronic
Printed in Germany