tools required:

an arm's length of rubber hose (garden or fuel variety, used preferably)

procedure:

Get a helper and have them turn the ignition key and crank the engine.

In either case, whether your engine starts but misses or engine cranks but does not start, the procedure is the same.

Hold one end of your rubber hose to your ear and with the other hand, move the other end of the hose to each f.i., listening for an audible click.

A f.i. that fails to "click" here is either

1. faulty or
2. there is an electrical wiring or signaling problem. Another test is required.

tools required:

a Bosch-Lucas NOID tester

e.g. 7188 bosch pfi noid test light

procedure:

Simply disconnect the harness connector of the suspected troublesome f.i. and insert the NOID tester. Get a helper and have them turn the ignition key and crank the engine. Watch for the tester to blink.

1. If it does not blink

a. and your engine runs but misses, there is something wrong with the harness. Turn off the engine and check for continuity from the connector back to the ECU.

b. and your engine does not run, test the other f.i.'s with the NOID tester to ensure at least a signal is coming from the ECU.

• If you get a signal on the other lines, inspect the troublesome harness for continuity from the connector all the way back to the ECU.

• If you do NOT get a signal on the other lines and if the wiring is OK, suspect the crankshaft sensor (c.s.) first. A faulty c.s. will cause a NO SPARK condition at the plugs, too.

2. If the NOID tester does blink, it may be that the driver circuit from the ECU is weak. This is unlikely. What is more likely is this f.i. is faulty due to fact that it has now failed two tests.

further tests to come...

tools required:

multimeter (using it as an ohm meter)

procedure:

"With the engine OFF and the fuel injector electrical connectors disconnected, measure the resistance of each injector. Each injector should measure about 2.0 to 3.0 ohms. If not, the injector is probably faulty. - Haynes, 4-12.

more to come ...

tools required:

1. two lengths of insulated auto electrical wire with small insulated alligator clips attached to each end. The alligator clips must be able to be attached to the fuel injector without grounding or shorting out against each other. It would be wise to use black and red insulation.
2. two spare battery terminals.
3. 12 V auto battery
4. optional 12 Ω (ohm), 1 watt or greater resistor. This may be found at an audio house or maybe even Radio Shack. Madisound Speaker Components, Inc. sells them $0.65 each for 1+ but you still have to pay S&H.

procedure:

Connect the spare battery terminals to the battery you are going to use. Connect one end of each of the wire leads you made to the terminals. Try not to touch the free ends together or you will short the battery.

You need to pay attention to polarity here. For the 1988 XJ40, the WN colored wire to the f.i. connector is +tive and the KB one is -tive.

See my thread, Jaɡ‧u‧ər Electrical Wiring Color Codes, for Jaguar color conventions.

Remove the faulty f.i. (or f.i.'s) and momentarily energize it by touching its electrical terminals with battery voltage. If you're going to energize it for longer than a moment, then I strongly suggest adding the optional 12 Ω (ohm), 1 watt resistor into one of the wire leads you made up.

conclusions:

If the f.i. now "clicks" then the ECU is not sending enough juice to the f.i. Check the ECU grounds and the wiring again between the ECU and the f.i. connectors. If everything "checks", you may (and I write may) have a bad ECU, but probably not.

If the f.i. still does not "click", then the f.i. may be stuck and is in need of cleaning

.... more to come.