V12 HE

1984 Jaguar XJS


Five Star

March, 15, 2007 AT 11:34 PM

I recently aquired a 1984 Jaguar XJS V12 HE that had been sitting in a barn for about ten years. I can find no rodent damage to the wiring harness. It has lots of fuel pressure and very good spark but it doesn't have any pulse going to the injectors. The harness going to the fuel injection ECU in the trunk looks good (no rodent damage). I am trying to find out how the ECU gets the signal to activate the injectors. Does it get the signal in the form of a pulse from the ignition amplifier on top of the engine? (GM ignition module in the box).
There is constant 12 volts to the injectors but no pulse.
If I can make this car run I will restore it as the body is worth restoring.
The car has 140,000 km on the odometer.
Any kind of advice would be greatly appreciated.

2 Answers


Dave H

January, 6, 2010 AT 5:32 AM

The ECU utilizes an integrated circuit containing the digital fuel injection control chip and an analog-to-digital converter to translate information from the sensors. The fuel injection program is stored in a Read-Only-Memory (ROM) chip.
For any given manifold pressure and engine speed combination, the memory provides a fuel injection duration for optimum combustion. The ECU also monitors other sensors to modify the basic speed and pressure signals so that cold starting, mixture adjustment and other areas of engine operation can be controlled.



December, 28, 2011 AT 11:41 PM

Hello can anyone help me im a mazda mechanic I have a 89 xjs v12 it ran great it seemed then the regulators flooded the car I replaced both car didnt start for a day I figurrd was floided went out fired up ran fibe warmed up shut off restarted like 4 times drove 30 miles shut it off and wont start even days later got fuel psi got spark starts on starter fluid ( when keys on fuel pump never shut off always ran but car worked. I found loose ground wires by the radiator on both sides who knows how long I tightned still nothing seems as if injectors rnt opening everything else is a ok (ecu problems)? Is there a way to check it or do I just start replacing more stuff 7174199811 any hekp greatly appreciated

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