87 XJS, won't start. Here's what has been done so far and what I've tried. Over the winter, new plugs, wires, cap, rotor, fuel injector hoses, vacuum advance unit. Car started right up and ran good afterwards. Put plates on as I don't drive it over the winter, first drive, no issues. Second trip out, started up and ran, stopped for fuel, would not start afterwards.
When you first try to start it, it fires a couple of times but won't start and it will repeat this after you let it sit for awhile. Installed a fuel pressure gauge before the "out" regulator, 36 psi and it holds. With the ignition on, opening the throttle causes the injectors to click and the needle on the pressure gauge to drop slightly each time you do this.( pump not running).
If i remove the fuel pump relay, the fuel pressure gauge doesn't drop while cranking the engine, injectors not firing? Check the spark, has a good strong spark. Checked voltage at coils, 12.3 volts. Checked the resister for the feed to the ECM, checks out, 6.7 K ohms. Checked the shielded wire for continuity, 1.2 ohms front to back. Checked the wire to ground, checks good. Unplugged the harness from the computer and checked the coolant temperature sensor resistance, about 2.5 K ohms from that end. Cleaned the connector to the resistor pack and checked the resistors, all seems good. C

omputer? New to this Jaguar thing, looking for fresh ideas.

 

My thoughts.

Lucas cars have a few common issues.

That shielded wire is suspect, I KNOW you tested it, and the numbers a low, I prefer closer to zero. Soooo, the fiddle factor, thanks to Doug, kicks in, reach down the back of the engine, that loom is there near the heater tap, CAREFULLY, move it around, dont be stupid with that fiddle. Try again. If that works, chances are the shielded wire is the issue. If no change at all, read on.

There is a wire FROM the starter relay TO the ECU, that "kick starts" the Injection PULSE circuit during cranking, coz the pulse in that shielded wire aint there yet, and that sounds like its missing. Pin 26 of te chart attached. I know that chart is NOT for your market, emissions crap we no got, BUT, the basics are identical.

ECU failures, never had one. The 6CU had its issues, but generally did well. The 16CU, unless Danny Dropkick did something real stupid way back, I seriously doubt it.

Earths, BORING, but they reek havoc now in old age.

I can no longer read wiring diagrams, so someone else will need to chime in if needed.

 

Further to Grant's vital points:

1. Are you sure that there is a strong spark while cranking ? Test for this by, (a) disabling the fuel pump and (b) removing a plug and having someone look at it (while earthed against the engine) as you crank.
2. If it is sparking while cranking, is there fuel actually spraying into the intake? The best way to check is (a) remove the king lead from coil to dizzy and then (b) undo the retaining collar on the front A bank injector and pull the injector out, still attached to its flexible and point it into a jamjar; then ask someone to crank the engine while you look to see if the injector is spraying.

The fault has to be caused by one or the other of these two systems not working. Report back with your findings and further diagnosis starts there.

 

Update,
Spark appears to be fine while cranking, voltage at coil drops a bit while cranking but I don't know what's excessive
Pulled 1A injector, no fuel while cranking or when rotating capstan with the ignition on.
I do hear injectors click when rotating the capstan, not sure how many
Rechecked the shielded wire, nothin obviuos wrong
Checked the start signal wire pin 26, it's good
On the initial try to start it, it will fire on a couple of cylinders, then nothing

 

Maybe try a noid light on each injector; if you hear them click when the capstan turns, at least some are being controlled by the ECU. They are fired in batches of 3 by the ECU; a ECU fault will affect at least 3 injectors. You said no fuel from 1A- could you feel/hear it click when the capstan was rotated? Is it possible that a bunch are clogged with rust debris?

 

OK, to assist the Fossil a tad, WHEN did this thing run properly, last week, last year, never really.

 

Question: did you hear or feel the injector that you tested was clicking when you tested it and found no fuel coming out?

If the injectors are clicking while cranking (and as mentioned above, a noid light should show this) and there is no fuel, it is a fuel delivery problem, not an ECU problem. To go steadily and thoroughly through the fuel system is the best way forward.

1. Check if the fuel pump is running, if not renew it
2. if so, remove the filter and run the pump feed input tube to the filter into a container and check (with the help of a friend to give the ignition a turn on, if when the fuel pump is running fuel is coming out. The ECU should allow the pump to run for about 2 to 3 seconds.
3. If fuel does indeed shoot out, renew the filter and blow out with compressed air the line to the A bank FPR rail input (if you have not already done away with it, which I suggest you do).
4. Reconnect the new filter and run the pump to ensure fuel is getting in a BIG stream to the A bank input point.
5. If no fuel delivered to the filter, remove and block off the tank feed to the sump tank (and at the same time check there is good gravity feed to the sump tank) and clean out the sump tank and renew its sock filter.

This will prove the fuel is getting to the rail and the injectors should fire if they are clicking and the fuel is there.

 

It ran good when i parked it last fall, ran good this spring until it out of the blue it wouldn't start 5 minutes after I shut it off.

 

Here's what I do know about the fuel system
Runs for 3 seconds on initial key on
Pump runs while cranking the engine
Good flow checked at the outlet of the filter
35~ psi at the rail, holds for hours with pump off
With key on, pressure drops a little each time when rotating the capstan so at least some injectors are firing
Cranking the engine with the pump relay out does not cause the pressure to drop so injectors are not firing
This happened suddenly, ran good, shut it off, 5 minutes later wouldn't restart.

 

Ok, so as I understand it we know that:
Fuel pressure is present at the rail, spark is OK and injectors are not clicking during cranking and no fuel is spraying out of them.

I therefore suggest:
Ignition on, snap open the capstan with your hand. Do you hear any injectors click? If no, then the signal from the amp to the ECU is suspect, or the amp/ignition system. I may be wrong but I do not think that the injectors can click if the white wire circuit is not working.

In any event, whether click heard or not, I suggest re-cleaning the resistor pack connector both sides, AND separate and clean both sides of the injector loom to car loom connector, pic here of the car loom (female) side of the injector:

The plug female holes in this photo are orientated the same way as the diagram on page 2 of the attached pdf shows.

On the pdf diagram the RED spots should all have 12v continuous ignition on. Check if they do. If they do, reconnect the loom and try the jamjar test again. If nothing, then one of thre things are wrong:

1. The ignition circuit is not telling the ECU the car is cranking,
2. the ECU is not earthing the injectors for some reason so they are not firing, this could be caused by loom faults including the connectors, an or ECU fault, which is always possible but the least likely. The injectors' circuits are always live, their activation comes from their being switched to earth by the ECU, so if you prove the circuits are live the fault zone is narrowed.
3. the injectors are stuck closed, unlikely as they were working before.

Report back, because an injector (disconnected from its plug) can be easily tested; and after that the continuity of the injector looms can be tested from the injectors to the ECU plug.

 

Further to the above and re-reading your last post, apologies for not taking it all in (age etc). If all, repeat all the injectors are clicking when the capstan is snapped open, then the injector circuit and the ECU circuits must be functioning. Obviously firing once on a signal from the TPS under the capstan is one thing, firing the injectors while cranking (ie the ECU is being told the engine is running) is another.

But what it does prove, IF all injectors fire on snapping the capstan, is that the injectors circuits are functioning. So much of my last post becomes redundant.

This would lead towards Grant's point about the signal to the ECU from the starter relay, from post 2 above: "There is a wire FROM the starter relay TO the ECU, that "kick starts" the Injection PULSE circuit during cranking, coz the pulse in that shielded wire aint there yet, and that sounds like its missing. Pin 26 of the chart attached".