My 1986 Jaguar XJS V12 won't start. I am not the original owner and got the car complete without knowing the history. The previous owner replaced the cam valve cover seals but messed up the distributor position and since then the car was not running and always kept in the garage. I did a bit restore since I had it, basically removed everything, cleaned them and put them back to the best order I could go. I set the #1TDC and then put back the distributor and made sure the rotor pointed to #1A plug, checked sparks on all plugs, all good. I also replaced fuel pump, fuel filter and fuel regulators so I assume it gets good fuel supply. But when I try to start the car, it cranks like it's temping to start, but only runs with bad missed fires and shaking when I keep stepping on the gas paddle back and forth quickly. Once I stopping pumping the gas paddle, it stops and all the lights on the dashboard go back to red.


I tried every possible ways I could think of but seemed no hope. Can someone help me out of this and show me the steps I need to do to get this car running?


Many thanks!

 

First: Does your car have the Lucas or the Marelli ignition. IF Lucas, there will be a cigarette-box sized black unit on top of the cabin end of the US Driver's side inlet manifold. Your symptoms sound like mis-timed spark to me
Assuming Lucas (ignore the following if not), then you should find a tiny "1" cast into the dizzy cap, at about the 11 o clock position, where the centre of the radiator is 12 o clock. This is the place for the HT lead to cylinder A1 (The frontmost cylinder on the US PASENGER side of the V). Thereafter the leads go round the dizzy cap ANTI clockwise in the firing order. Post again if you do not know the order, but it should be on a label on the inside of the bonnet (hood).
You need to check that the engine is at TDC on A1 cylinder and on the compression stroke (not the exhaust stroke) when the dizzy rotor is nearest to/at the "1" position on the cap. If it is not and is miles away, then you must loosen or remove the dizzy (three allen headed bolts inside) and replace it so it is.
See then if the car starts. If it does, fine-tuning the timing can be done as a separate operation.
Greg

 

Sounds like the firing order in the cap is out of whack.

Here is something I wrote a while back due to lots of cases the same as this.

Refitting the V12 distributor.doc

Simple fix really, just take your time.

 

Hi Greg, Thanks for the quick reply.


Yes, it is a Lucas ignition. I did do the timing setup but didn't help (unless I did the incorrect way). What I did was to remove the A1 plug and attached to a balloon to the hole to get the compression stroke TDC, and then installed the plug and attached the wire to "1" on the dizzy cap, then attached the rest of the wires according to the orders.


What could be the other causes in my case? Could it be the oxygen sensors or ECU cause this kind of symptom?


Thanks,

 

Hi Grant Francis,


Thanks too! I will follow your article to reset the wires and distributor position again and see how it goes.


At the meantime, can you think of other causes to this type symptom?

 

The problem on my car is that I don't see the timing mark anywhere on the pulley. How does it look like? or if I looked at the wrong place? since I am not familiar with this type of car at all.

 

British engineering, or sense of humour, at its very best.

The timing plate is under the front of the engine. Attached to the front edge of the upper sump by 2 bolts. The timing "mark" as such is on the rear most pulley of the crankshaft pully pack, and by that I mean the pulley that is closest to the engine, and the alternator belt is attached to.

NOT the easiest to see at any time.

You will need to raise the car, support it well, and actually get under the front a good distance to get a visual.

I gave up on that many years ago, and a wire coat hanger straightened out down the 1A plug hole works for me.

As I said in the write up, the engine must be on the Compression stroke, but I reckon you know that anyway.

Other causes:

EFI loom is toast, COMMON.
Spark plugs gapped wrong, COMMON.
HT leads are waaaay past their use by date, getting common.
TPS is out of adjustment, and the fueling maps in the ECU are confused, COMMON.
Throttle bodies are clogged with "V12 black goo", COMMON. Quick clean with a petrol soaked rag will sort those suckers.
Injectors are "dirty". I use Injector cleaner in the fuel with very good results.

The list is LONG, but that is the basics, and a NO runner is always a LONG check and recheck of ALL the related items. Then add the age factor, and the fun begins.

 

Hi Grant, I followed your list and reworked on my car today. I reset everything. Carefully checked all the connection, the #1A TDC at 10degree Before, aligned the distributor triggering unit and rotor pointer positions. doubled checked fuel pressure and two regulators, measured the coolant temp sensor, everything seemed fine, but still didn't start, same symptom. So I did the last try by unplugging the connector to the coolant temperature sensor and then cranked the engine. This time, the car started! but quickly shoot to 3000+ rpm and died in about one minute. I assumed that's the high idle protection switch kicked in. So most likely it is the coolant temp sensor now. But still it didn't explain why, as if it is the coolant temp sensor, it shouldn't be running. But I will get a new coolant temp sensor tomorrow and put it on to see if it works. will keep you all posted the updates.

 

So just now I got the new coolant temp sensor and gave it a try. With the new sensor, the engine cranks and temp to start but not able to, same symptom as before. If I disconnect the coolant temp sensor, the engine will start after two times cranking and then the idle will shoot directly to around 2800 rpm. The Engine will run at that idle for about half minute to one minute and then die. I can rule out the coolant temp sensor now as their resistances measured the same. But what other causes can contribute to this problem? I really need some help here. Thanks!

 

Ok
Am I right in thinking that when it runs it seems that ALL cylinders are firing, not just a few banging here and there?

If so, when it stops, test for a spark still being present. If it is, this eliminates ignition timing, so it is on to fuel and air supply.

When it stops immediately test for fuel being present at the fuel rail (a CAREFUL crack of the B bank fuel rail to FPR joint will show if there is rail pressure). If there is pressure, and spark, and the car will not start, it is an injector problem. This could be caused by injectors beinge blocked, or the loom misbehaving, or the resistor pack plug and socket needs cleaning, or something more complex. Before getting into the remedy if it IS fuel, I suggest reposting after you have done these tests.


Also how much of Grant's list have you fixed/checked:
EFI loom is toast, COMMON.
Spark plugs gapped wrong, COMMON.
HT leads are waaaay past their use by date, getting common.
TPS is out of adjustment, and the fueling maps in the ECU are confused, COMMON.
Throttle bodies are clogged with "V12 black goo", COMMON. Quick clean with a petrol soaked rag will sort those suckers.
Injectors are "dirty". I use Injector cleaner in the fuel with very good results.



Running at 2800 RPM on a closed throttle MUST mean you have a massive air leak, or throttle butterflies are wildly mis-set, or AAV wide open. The ECU will shut off the fuel at 1400 RPM, let alone 2800 RPM if the throttle position sensor is set properly and working properly. It could be that this function is misleading you too.
Greg

 

Hi all, here's the updates. I spent the last two days redid everything and got the car started. It's now in good running condition. It ended up a faulty auxiliary air valve, #1A fuel injector and possible the fuel regulator on the return side. Here's what I found and why I thought this way.


First, I decided to start from the ground zero and removed everything from the top so it gave me a clean startup and easy to work on everything. with everything removed, I first reset the position of the distributor. So #1A Compression 10 degree BTDC, rotor pointer to 1A, etc. and Double checked the triggering unit position and adjusted screw to max retard position. While I was on this, double checked and tested the vacuum advance module. Then I tested the auxiliary air valve, and found the first problem. The valve was wide open at any temperature. So I rebuilt it with a new bulb and tested it. Then I replaced all fuel injector hoses so this is a good time to test all fuel injectors. I used compressed air and found the #1A injector was not working. Luckily, I have an old Bosch injector that fits to this application so had it replaced and put the fuel rail on. I wasn't able to check the fuel regulators, but as the plugs are all wet I assumed there were two much fuel and the return regulator could be jammed so I replaced it as it looked pretty toasted anyway. I put the rest of the things back, double checked the connection and decided to give it a try. After several cranking, the engine started and shoot to about 1400 rpm right away, two to three minutes after, the idle speed started to drop down to about 1000rpm, given the air conditioner belt was off, I accepted this idle and decided to do a road test. I drove about 10km and came back on parking, the idle became now around 700rpm, looked good. Looking back, I think the most likely cause should be the air valve and the fuel injector so the fuel supply was too abundant.


Any comments or thoughts?

 

Well done.

Snaps of the blood letting, yours, is mandatoy.

Glossary of language learnt, keep that CLEAN of course.

All jokes aside, WELL BLOODY DONE. Systematic point to point, ALWAYS works. No system = anger and no results that make any sense.

10km is deemed a GOOD run, and after all the starting attempts there will be HEAPS of rubbish to burn out of the engine and exhaust, so as the confidence rises go for a BLAST, that should sort it out some more.

 

From a complete stranger to this engine, congratulations.
Persistance pays.


Do you have a Jaguar notes system. I did at one time.
On a slick Dell AXIM 5 pocket computer. Far more
advanced than I at the time. I used the "notes".
Should have used the MS Works part. It sync with an old XP machine.
It crashed. I got it back up sans the notes!!! Had I used Works,
it would have been saved!!!


Live and learn???


Carl

 

Same none starting issue for me. Mine is an '87. It was running until I took the distributor cap off to check to see if the rotor is still "springy." I serviced it about 10 years ago and thought it would be a good thing to refresh. it was fine.

Put the cap back and tried to start it. No go. it cranks fine. I double checked the wire connections and order (twice). All is correct.

next I tried some starting fluid in the intakes. The car starts for a second so it is firing. I then noticed that I wasn't hearing the fuel pump pressure come up when I first turn on the key so I thought my fuel pump went bad. Ordered a new one. Installed it this afternoon. No joy!!

What next?

 

DRINKS, and heaps of them.

Reading very carefully.

Cap off, so lots of things disturbed.

Cap back on, no start, bugga.

Starts with Ether, so it has spark of sorts, which pretty much eliminates cap related items, MAYBE.

No pump priming is USUALLY the pump relay, the one in the BLACK socket in the boot. It is "powered up" by the Main relay, the one in the RED socket. The EARTH of the fuel pump relay is ECU driven via the Orange wire from that Black socket.

Things to check here:

The enertia switch has not tripped, they do that, so pull UP on the button, and then push it down again to reset it.

The terminals have not "pushed out" of either socket as the relay was pushed back into place.

The Main battery cable has a plastic cover about 6" down from the battery, and under that cover are 2 HEAVY Brown wires. These wires are the +ve supply to those relays and other things. The spade terminals can easily dislodge, simply by removing the battery cable, and that will stop all fuel related bits doing what they should. Remove them, aand then CAREFULLY replug them, ensuring the 2 mating bits actually mate. It is easy for the spades to slide down the side of the apposing blade.

Come back when that is checked, and I will step some more out for you.

 

Grant,

Did all the steps you mentioned.

Checked the cutoff switch in the driver compartment

Checked the relays; even swapped them out with the relays under the hood just above the fan.

Made sure the two heavy wire are properly seated on their spades on the connector attached to the battery cable

Double checked the wiring connections on the new fuel pump.

Thought I heard a slight hum when I turned the key one position but it was not as pronounced as I am used to hearing the fuel pressure come up.

There is a definite click from on top of the motor somewhere when I turn the key; llike a relay of some sort.

Car still catches with either sprayed into the intakes but does not catch otherwise.

 

OK,

Fresh coffee, so here goes.

Turn the key to the IGN position 3 times from OFF. Now turn it off. Take 2 spanners, and rags, and TAKE BLOODY CARE, and CRACK the fuel inlet double nut thingy where is attaches to the fuel rail. I place some rags under and around the area. Just CRACK that fitting. If you get a SPURT of fuel, GOOD, the pump is pressurising the system. If you get a dribble of zero, the pump aint pumping.

That click you hear on top of the engine when you turn ON the key is NOT good, it sounds like the injectors are clicking, and they should NOT. Not hearing it, it is a guess from experience only.

The new pumps do only hum, as compared to an old pump.

Next, based on NO spurt of fuel up the front.
Into the boot, expose the pump, and get to the wires. Unplug the wires from the pump. Connect a volt meter to the +ve wire, get someone to turn ON the ign, and watch the meter, you will only get a 2 second signal before the ECU switches OFF the earth path. If you see 12v, GOOD. Now look at the bottom of the pump. You will se a + and - for the respective terminals. Ensure the wire with the volts in it is attached to the + post, DONT LAUGH, the original pump and the new pump can have the terminals opposed. Some cars have the LARGE terminal as the NEG, some cras have it as the POWER. Many on here, including ME, have been caught out, and the pump will work, it is that clever, but in reverse and will NOT pump fuel for obvious reasons.
Once sorted and confirmed, the pump should pump fuel.
If you see no volts in that wire, check back.

If you got fuel up the front, the following is suggested:
Volt meter the injectors, Ign ON, any injector will do, and ensure you have 12v at the wire.
Look down on the panel behind the RH headlamp, inside the engine bay, and you will see a Silver metal box, about the size of a cigarette packet, with a multi pin plug hanging out the bottom, unplug it, FUN will be had, clean it, and then replug it. This is the resistor pack for the injectors, and that dirty plug reeks havoc.

Lets know what you find, then I will move on to the messy stuff.

 

OK.
I have to get the car moved to a new storage location today so have a tow truck coming later. Will be able to get into the detail once it gets to its new storage.
I did notice on the new pump that the posts seemed to be reversed. On the original the small spade terminal was the NEG (-) with the small black wire. The POS (+) was the large spade terminal and the larger reddish wire.

The new pump does not have spade terminals however the nut posts are reversed; the larger post is to the NEG terminal and the smaller one is the POS.

 

Talk with ya soon.

Good notice there, you will go far in the V12 world, trust me.

 

Grant,

It will be Friday or Saturday before I can get back to the car since it is now in a different storage location. The connections for the fuel injector control unit (cigarette sized silver box on right hand side) are all clean. Assuming the following what are my next steps?

Assumption 1: I have good fuel pressure at the fuel rail intake connection.

Assumption 2: I don't.

I should note that the gas has been sitting a while but it has a couple of cans of Sea Foam fuel stabilizer and a big bottle of Lucas Fuel injector cleaner in it. Tank is over 2/3rds full. As I mentioned previously it did run.

I did fail to mention that I have the cruise control connector disconnected. I wouldn't think that would make any difference.

P.S. I didn't understand what you meant by "good notice there"