QuestionQUESTION: Next step is to confirm all powers "IN".
There are 4 relays lined up on the firewall under the hood.
The larger metal relay is the starter relay and the next is
a black plastic relay which is the "Main" relay, next is the
"Fuel Pump" relay also black plastic and the last is what
looks like a red plastic relay but it is the "Diodes".
Unplug the main relay from it's socket and take a test light
and check for power in the socket at pin number 30 (brown
wire) Look at the bottom of the relay for the pin numbers
next to each pin so you know which socket to probe. That
socket must be hot all the time. Then probe the socket where
pin 86 was, (white wire) and that should be hot in the "IGN"
position. Now connect your test light clip to a power source
and probe the socket where pin number 85 was and that should
be a good ground. If all that is correct make up a short
jumper wire with male flat spade terminals on each end and
plug one end into socket number 30 and the other end into
socket number 87. Now test any injector wire for power on
one of the terminals.
If you will follow along in your wiring diagram you will see
the procedure for testing that circuit.
Howard
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We're making progress! Following your pin test, I did locate
a loose ground wire to the main relay. Now that that is
fixed, I have power to the resistor pack, and to the
injectors. Still no flash when I plug in the noid light. Bad
resistor pack at this point?
ANSWER: Peter, how can you have a bad resistor pack when you have power to the injectors? Look at the diagram. It is a road map of the electrics of the whole injection system. The ECU grounds the injectors to make them operate.
If you have no pulse but do have power at the injectors then you need to start testing ALL inputs to the ECU and ALL grounds. First check to see if you have ignition, then confirm the ignition signal at the ECU plug and all power wires and all grounds at the ECU plug. You have the diagram use it. The injector wires at the ECU plug are only grounded by the ECU so they will not show as grounds when testing the ECU plug.
Follow each pin in the list on the ECU plug to see which you need to test for power and which you need to test for a ground.
Howard
---------- FOLLOW-UP ----------
QUESTION: Howard, checked the ECU plug, I have power in, all grounds
(except Injector grounds, as you mentioned) check out, still
no pulse to the injectors. I'm baffled. Could this be one of
those rare failed ECU cases? Any way to test the actual ECU
w/o replacing?
AnswerJaguar dealers use to have a tester but I don't know if they would keep one as they look at the series III as obsolete. The Jag dealer here would take them in on trade but would not put them on their used car lot. I bought most of them wholesale and resold them.
You didn't say that you had an ignition pulse signal at the ECU? (the most important input to the ECU)
Don't you have a British car specialist in your area? They would be reluctant to let you try an ECU off of a running series III but may try your ECU on their car. (little to no chance of a bad ECU doing any damage to a good car) That would tell you for sure if it is the ECU. Good chance they would have a good used ECU too.
Do you have a good "Deep Charge" battery in your car? (Deep Charge is a diesel or marine battery) If not do this, charge your battery and then charge up a second good battery and connect the second like a jumper battery used to jump start a dead battery car. This was an odd idiosyncrasy of the series III cars. The battery would spin the engine over very fast but would not start. The two batteries in parallel was a test for this.
Howard
