hello,
I bought a 1981 xj 12 which did not run for 2 years now a slept outside. That was not very good for the car.
The problem now is that the six injectors on the ridersside do not inject. I have fuelpressure on all injectors. I got 2 injectors on both side out of the manifold (the front ones) . If i switch the ignition only the one on the passengerside pulses short. The left one does nothing. If i put a led on de wires tot the injectors i get a pulse. I think that the plus is to weak to get the injector pulse.
Who can help me

thanks in advance
Robbert Peter
netherlands

 

Robert, welcome to the forum's.

The '81 V12 has what is known as the Bosch D Jetronic EFI system. It is the Grandaddy of what we have today.

Inside the distributor, just under the rotor arm, is a "trigger board", and there are 2 versions of that board. (1) a 3 wire board with reed switches imbedded in the mastic, (2) a 4 wire board with Hall Effect sensors imbedded in the mastic.

Version 1 is unrelaible.

Version 2 is super reliable.

The fact you got NO pulse as such on one bank reeks of trigger board issues, and more than likely a version 1 board.

If it is a 3 wire board, the following is a simple test.

Remove the cap, CAREFULLY, and get a magnet on a stick. Make sure the area you are in is QUIET, and wave that magnet over one end on the board, and LISTEN CAREFULLY, and you will hear the reed switches "click".

Now do the same on the other end, and you should hear the same "click".

That "cicking" MUST be the same, as in the volume and intensity to the ear. A half hearted "clicking" will NOT fire the amp, which will not fire the injectors.

The injectors are in 4 groups of 3.

1a, 3a, 5a
2a, 4a, 6a
1b, 3b, 5b
2b, 4b, 6b

One group out is NOT trigger baord issues.

If yours has a 4 wire trigger board let me know, as somewhere in the library is the test procedure for that unit, coz Hall Effect sensors are SILENT.

The rotor arm has a magnet imbedded in the heel, and that is what triggers the switches. The 3 wire rotor has a different shaped magnet to the 4 wire, DUH, and the reasons behind that have never really been sorted. It has been discussed more than the other question, "Which oil is best for my car". I think????? the round magnet is for the 3 wire, and the square magnet is for the 4 wire. These magnets were NEVER very strong, but check that there is magnetism in the heel of the rotor. I reckon there is coz you got half a system working.

NEXT. Wiring loom has fried itself. More common than Aussies and Beer. Age is attacking that loom for sure, and a simple rebuild (DIY simple enough) will save a lot of heartache and language down the track.