Jaguar Repair/1986 XJ6 ECU not grounding injectors
The ECU is not grounding the injectors. There is power at the injectors and power from the injectors to the ECU. It will run for a few seconds because the cold injector is operating. Is there anything else that could cause this before faulting the ECU. The car has been sitting for a few years.
The ECU grounds the injectors for just a few milliseconds in groups of injectors and two times per cylinder firing and not in a specific time.
When the ECU quits grounding the injectors, you need to look at several things like powers to the ECU and grounds on The ECU. Then look to see that the ECU is receiving the ignition pulse signal to start grounding. That wire runs along the top of the coolant rail that is on top of the intake manifold. It is a single wire out of a harness and had a bullet connector half way back. This is the major signal to tell the ECU to do something. Another major info comes from the Air flow meter. The temp sensor is also a major influence. Air temp in the airflow meter and O-2 sensor are minor trimmers to adjust pulse width.
The reason the cold start injector operated is because it is not controlled by the ECU at all.
You need a diagram of the ECU wiring to check each important power and ground. If you don't have a good diagram let me know and I will post one on my web site for you to copy.