Porsche 928 Workshop Manual page 385

24
LH-Jetronic
928
TEST POINT 6
2 = Idle speed contact
18 = Ground
3 = Full load contact
Note:
If idle speed switch has a break, there will be
no coasting shutoff.
If idle speed switch has a short circuit, there
will be a single cutout at high idle speed.
If full load switch has a break, there will be
no full load enrichment.
If full load switch has a short circuit, enrich-
ment will be too early and consequently fuel
consumption too high.
1. Checking Fuel Injectors
If engine can be operated, pull off plugs
on injectors separately.
If fuel injectors are okay, engine speed
should drop each time.
If engine cannot be operated, measure
voltage on one plug of injectors against
ground.
One of both terminals should have
battery voltage.
Measure coil resistance of fuel injectors.
Specification: 15 - 17.5 ohms
(+ 15 .30 "C/+ 59 .86 "F).
2. Checking Injection
Timing
Adjust oscilloscope according to
instructions supplied with tester.
Connect adapter line (Bosch "L-Jetronic"
No. 1 684 463 093) between one fuel
injector and corresponding plug.
Caution!
Tester leads must not have contact with
ground.
a
24 - 116
Troubleshooting LH-Jetronic Printed in Germany