Jaguar Repair: 82 Jag XJ6 wont start, deep cycle battery, licensed mechanic


Question
 I recently inherited an '82 jag XJ6 and am having troubles getting it to start.  I have replaced all wires, plugs, the rotor and cap, and while I know it is getting fuel, she won't seem to want to start when I want to (we had removed all but 2 plugs and it fired up but would not stay on) I have also purchased a new deep-cycle battery and all it seems to be doing is draining down while we try to diagnose the problem. I am aware that the fuel pump itself is working, I'm not so sure the injectors are working but,  we manually put fuel in the cylinders and it still refused to fire up. The starter works and to my knowledge, so does everything else except the front seat motor which is minor compared to the motor. I myself am a good amateur mechanic, but also have a licensed mechanic friend helping and my brother who is a military motorcade mechanic, and we're all stumped....... Have any suggestions?

Answer
Hi Joe,
It is important to keep the battery charged while testing as a battery that will spin the engine over fast, will not start the car when just slightly low even though it still spins the engine fast.

If an engine will not start with fuel sent into the intake, you have either lost ignition or compression. So first do a "Wet" then a "Dry" compression test of all cylinders. Do a conventional dry test first making sure you have the throttle open and get at least 4 or 5 revolutions. You should see 130 PSI to 160 PSI with little variation between cylinders.
squirt several shots of engine oil in each cylinder for the "Wet" test and you should get no more than a 10 to 15% increase in pressure.
Check the ignition timing to confirm that you have the correct timing. The specs sticker under the hood over rides what the manuals say. If the sticker is gone set it at 10 to 12 deg BTDC and it should start ok. Don't forget to confirm the firing order in the cap. (153624)
To check the injection system confirm there is power on one of the two wires going to the injectors while the key is on. spin the engine over while feeling the injectors to see if they are "clicking". To check fuel pressure you need to put a "T" in the fuel line going to the fuel rail and a pressure gauge. Be sure to use clamps as you have 35 to 45 PSI pressure in the line.
Let me know the results of each of these tests.
Howard