For those of you who own US-spec 928s from 1980 - 1984, I've provided the connector to the J-Jet controller pin description.

If you're having starting problems, this information could help.
This is how the system works. AFC [Air Fuel Control] relay XVI pin 30 always has 12 Volts regardless of ignition switch position. The AFC relay switches between pins 30 and 87, and the 12V at pin 87 then goes to the fuel injectors.

a. Measure voltage at pin 30?
-- If 12V present, next (for all test cases below, have the ignition turned on) is there 12V at pin 87? If yes go to (b)
-- If no, check the connection at the battery. A direct cable connects the battery to the AFC relay pin 30. Is there 12V at AFC relay pin 85? If there is no voltage, the ignition switch could be bad or the path between the ignition switch and AFC relay has an open or short circuit.

b) is there 12V at the fuel injectors (pick any one to check)?
-- If yes, this says that your problem could be with the fuel injection "ground" path. Go to (c)
-- if no, there is a wiring problem between the AFC relay and fuel injectors.

note: it may be confusing to see 12 V at both sides of the fuel injectors. The reason is when the engine isn't running, the circuit is open from the L-Jet module pins to ground. So with very little current flowing there is no voltage drop across the fuel injectors.

c) is there 12V at L-Jet connector pin 10 and 29?
-- if no, there is a wiring problem between AFC relay pin 87 and L-Jet connector pin 10 and 29.
-- If yes, check grounds for the L-jet controller. L-Jet connector pins 5, 16, 17 and 35 should have a very low resistance (via ohm check) to ground. For this check, set your VOM to Ohm mode and measure the resistance between the L-Jet connectors and a ground point on the car. If the Ohm reading is high to infinite, there is a wiring or connector problem with the ground points.

If all tests show OK, the L-Jet could be bad.

L-Jets are pretty reliable systems. As with any other system, the majority of problems in no-start or hard start situations are bad or non-existant signals from sensors or no voltage due to relays.

 

Rich,
This great info! Thanks for posting.

 

Very cool, thanks very much!

What type of output is 22 (Lambda test connection) and 11 (Fuel consumption)?

I don't think these are used pre-82, but could be metered with a -04 box?

 

Brillant! Great info.

 

Great, really, really helpfull!! BTW do you know what kind of impulses should the injector get from the ECU? And what kind of impulse comes to terminal1 on the ECU(I know it is engine speed, but what kind of impulse?) Thanks a lot,

Klim

 

Excellent thread - and a much needed pin-out. One question though - where does the other end of terminal nr.5 end? I am reading good ground on the rest, but nr. 5 seems to be missing. But where does it terminate? There is a common ground point for the L-jet harness just south of the airpump regulator, but this has no connection to terminal nr. 5.

Any idea?

Thanks

K.c.

 

this helped me out tons today. thanks rich!

 

Great info....

 

Here is some more
See pg 18 for test values