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".

 

More ponderinds.

This may be an issue, may not be, but it needs ticking off.

1) Voltmeter on the coil pos post.
2) Take a reading..
3) Go to Start, and note the reading while its cranking.
4) Release the key, so it returns to Ign ON, and note that reading.

2 and 4 should be the same, or near as damn it.
This proved the Ign Switch electrical section is NOT reeking havoc

Most common failure of that switch is the loss of 12V going from the Ign ON TO Start position. I have had a few that failed the other way, lost the 12V on the return to Ign ON after Start position finishd with.
Engine started and ran as long as the key was held in the Start Position, NOT good for the starter motor, and when released, the engine stopped. 1st took a while to find, but a few have followed over the years.

Check the AB14 plug where the shielded wire is, the one facing the rear of the car, and make sure all is clean and OK.

4 or 5 months in storage should not have caused any real issues, unless the beast was outside, albiet covered.

 

In addition to Grant's latest tests, I think that out of my previous suggestions, the most important thing to test is:

Whether you can feel if the front injector you tried the jamjar test on is actually clicking when the car is cranking. I realise it is not spraying, but if you repeat the test can you feel it clicking?

If no clicking: turn off the ignition, get a helper to turn it on again while you BOTH snap the capstan with one hand and feel the injector for a click with the other. Let us know the results. If no capstan-triggered click let us know.

Once we know the results of these two tests, further tests can be suggested. In the meantime do Grant's suggestion about cleaning up the AB14 to ECU connector, and I suggest clean up the ECU pins and the large loom plug into the ECU. All of which may do it, and are in any case worth doing as maintenance.

 

Another update, still won't run but I've learned something.
Basically started over, rechecked all grounds (earths?) and recleaned all the connecters I could get at and rechecked the wire to pin 18. Some of the issues i was having in the last round could have been caused by not having the connector to the ECU fully seated, not sure.
I did pull the cover off the ECU, couldn't see any smoked components or traces.
Anyway with a fully charged battery, I started over.
With fuel pressure on the gauge and the key on, each time you rotate the capstan, the pressure drops a little. I repeated this 4 or 5 times to load the engine up with fuel before trying to start it and after that, it ran for a few seconds.
I'm sure the shielded wire is ok, is there a way to check the output of the amp to that wire? i did check the resister in the amp, it checked good.

 

Jim
Please check if the injectors are firing during cranking.

 

Gregs ask is important, so we wait.

In answer to your shielded wire ask.
YES.

I use a length of speaker wire, disconnest the shielded wire at the Amp and the ECU.
Connect the new wire at the amp, run it over the roof of the car, into the boot and connect it to Pin18. Go for start.

ANY wir e will do, I am a hoarder, its a Jag thing, and especially important to the V12 ownership. There is a fix somewhere in one of my sheds, trust me.

 

I'm sure they're not. With the fuel pump relay out the fuel pressure doesn't budge while cranking. They all appear to be firing rotating the capstan now that I have the ECM plug fully seated.

 

If that is the case (ie ALL injectors clicking on capstan snap, and NO injectors clicking on cranking), then I believe that the ECU is either

1. not receiving the signal from the amp along the white wire (could be amp, or wire, or signal TO the amp from the base of the dizzy); or
2. ECU bad somehow, always possible though unlikely

So in your position I would:

• Check the wires from the dizzy pickup to the amp, AND ensure the earth wire which is part of that bit of loom is earthed at the amp fixing bolt
• Do Grant's test on the white wire to the ECU as in post 16 above
• see if you can borrow a known good ECU and try it in place of your own

in that order.

 

Rechecked the wiring from the distributor. It does have a good strong spark while cranking.
I couldn't figure out how to easily get at pin 18 to do Grant's test but we did "load test" the wire, it will light an 1156 bulb with no issues.
I purchased a used ECM to try from a "running vehicle", same DAC4118 tag, waiting for it to arrive.

 

Unfortunately that is the only way to test them, by replacement when you have checked and verified what you have. 16CU are less failure prone than the 6CU, so the replacement 16CU probably will be ok.