QuestionQUESTION: My Jag won't start, it took two days to fully die.
I have spark to plugs, fuel rail is under pressure. Cold start sprays fuel from injector. All 6 regular injectors do not fire. I assume the Injection Main relay according to parts places but the manual states only a "block diode relay" and a "inhibitor relay". Where is the injector main relay located and does this sound like my problem ?
ANSWER: Hi Robert,
You can't assume that is your problem. You must do some simple tests. First you say the cold start valve (injector) operates. If that is true the engine should start up and only run a second or two and die. But you didn't say that.
Do this first, charge the battery up and take a second known good battery and connect it up to the freshly charged battery in the car as though you are "Jump starting" a car with a low battery. If the car starts and runs buy a new "Deep Charge" battery (diesel battery) for the car and use the old battery in any other kind of car.
(this was an odd thing the series III cars had about them)
If that don't make the car start, then check for power on one side of the injectors and if you have power get a wiring diagram of the injection system and start tracing important circuits like the signal from the ignition system to the ECU and power and grounds for the ECU.
Oddly enough, the most high tech component on the car is the ECU and it is the least likely failed part on the car. I worked on Series III Jags for many years and only seen one failed ECU.
There are too many expensive relays to guess at them failing without testing.
If you don't have a diagram of the injection system let me know and I will put one up on my web site that you can copy.
Howard
---------- FOLLOW-UP ----------
QUESTION: Howard, Thank you for the information. Last night I did hook a brand new battery from another car. It did not start still. I would love to have a wiring diagram of the injection system and the order of circuits. Another of your customer responses gave me partial info on how the circuits flow. Maybe test the start relay for power to main relay ?...and does the fuel pump activate after the main relay or before ? Another concern is the coil ballast. I think it got oil on it and I saw some smoke comming off it one day recently. Does it have anything to do with this circuit?
AnswerHi Robert,
There is a single bullet connector between the intake coolant rail and the cam cover about 6 to 8 inches from the rear of the head that must be connected for the injection system to operate. If you have had any of the wiring apart in that area it should be checked.
The Ballast resistor does get hot enough to smoke oil if it got on it. The only thing the ignition system has to do with injection is a signal is sent to the ECU to trigger the injection system two times per cylinder firing but is not timed to valve opening.
The fuel pump is activated by the flap in the air flow meter which triggers the fuel pump relay. Easy test, just remove the air filter turn the key on and reach in and push the door open on the air flow meter.
It sounds to me that you are trying to diagnose by logic. good luck, it never worked for me. I always needed to follow the yellow brick road (wiring diagram and test as I went)
Go to my web site and copy the diagrams #1 and #2.
http://mg-tri-jag.net/XJ-6InJect1.jpg
Http://mg-tri-jag.net/XJ-6InJect2.jpg
Let me know how you make out.
Howard
