Hi Mike

The Pressure in the Fuel Rail shouldn't drop back in the way you have described, so that does sound like this is the cause of your 'No Start Problem' rather than anything else, so now is the Chance to kill two Birds with one Stone

By Taking the 'A' Bank FPR right out of the Circuit altogether, which coincidentally is what I'm Planning to do myself (although for a very different reason)

There are Two ways of doing this, which is:

(1) Get a High Pressure Bridging Pipe made up using Top Quality Gates 25 BAR Fuel Hose (which is the method that I will be using)

(2) Again using Top Quality Gates Fuel Hose, Run a Pipe from the Fuel Outlet in the Engine Bay Straight into the Fuel Rail where the 'A' Bank FPR was connected, which was the method preferred by 'Greg'

It does sound like a problem with a Blockage in the 'A' Bank FPR which is holding back the Fuel Pressure from going into the Fuel Rail (props to DD) and so bypassing the 'A' Bank FPR with either Method (1) or (2) Would I'd be very Tempted to say have her running in no time

As for all those Vacuum Pipes 'Greg' can explain these far better than I ever could, so I will defer and hand you over to him

Although its 99.9% more likely that when the 'A' Bank FPR is taken right out of the Circuit She will Start (or of course you could get a New 'A' Bank FPR) although it really isn't needed anymore, as the later Cars don't have them fitted

I will also enclose a Link below, that much better describes these Two options as there are some Photos that you may find helpful

Bypassing the 'A' Bank FPR (Fuel Pressure Regulator) on 'A' Bank

 

Mike
The vac line to the ECU should be attached to a spigot in a small recessed hole on the side of the ECU. The bother end of this pipe goes to a spigot in the middle rear of the cross pipe that goes between the two manifolds across the rear top of the engine.
The vac pipes in your photos, I could not quite place or understand which pipes in the photo you were referring to. Are they under the dash, if so, they are probably aircon unit vac pipes, not engine ones. Either way could you clarify?
As to the fuel, I think you should pull an injector, one of the front two, as OB said, which come out easily. Leave it connected to the rail and stick the business end in a jamjar. Get someone to activate the starter while you see if you have a nice spray pattern. If not then bypass the A bank FPR and try again.
All your test so far are fine, but you MUST know if the injectors are spraying or not. I would do this next.

 

So here is the update, no good results just more GOOD information.

1. Taking the 'A' Bank FPR right out of the Circuit altogether; I ran a hose from the Fuel Outlet hose in the Engine Bay Straight into the Fuel Rail where the 'A' Bank FPR was connected.
   1. I attached my own 12 V power supply to the front right fuel injector, primed the system 3 time to build up pressure and trigger it. All I got was a small stream.
      
   2. The vac line to the ECU should be attached to a spigot in a small recessed hole on the side of the ECU. The bother end of this pipe goes to a spigot in the middle rear of the cross pipe that goes between the two manifolds across the rear top of the engine.
      1. To clarify the configuration,I believe the ECU in play to be the one at the "A" post. It has a small red tube attached and the red tube goes forward to the manifold and is attached according to the label on the front bonnet.

AS I mentioned at the very beginning this car had a "small fire" under the dash so I am beginning to the ECU to be the culprit. What say you? just to keep things confusing there appear to be three different ECUs.

1. Non Catalyst Car - DAC 5869
2. Single Catalyst - DAC 5870
3. Full Catalyst - DAC 5871

So how do I tell which is the correct one?

Regards,
Mike

 

Here is what the vac hose looks like and the chart.

 

Hi Mike

If you think its the ECU and it could be, contacting a supplier with your Chassis Number could be the best way to go then at least you will know what you are looking for in the event that you decide to get another one

Although there is another possible cause of your 'No Start' problem that is worth Checking out

There have been at least 'Two Instances' that I know of, where Guys have taken apart all the Fuel Hoses in the Boot/Trunk, cleaned out the Sump Tank and also replaced the Fuel Filter and the Fuel Pump

And then once having done so have inadvertently put the pipes back wrong, so Fuel is flowing the Wrong way round the System and 'Greg' will back me up on this as he was the one who helped to sort this out for those Guys at the time, which instantly fixed the problem and had their Cars running

So please could you take a Photo that would show what is connected where, with a 'Quick and Dirty' Diagram to go with it

As when it comes to reconnecting everything that has been taken apart, it is all to easy to Connect the Fuel Supply up wrong, where in the event that this may have happened, then we can hopefully help you sort it out

 

The main fuelling ECU has been moved, if that is what is in your photo. The factory location, in in the RHS buttress in the boot. MAybe that is the ECU that drives the Marelli ignition? I think you have proved you have a spark, so I would not worry about any Marelli bits as they do the spark only.
Now i know nothing about the Marelli system, but I think apart from a wire from the engine ignition amplifier to the fuel ECU in the boot, which tells the ECU what the engine is doing, the systems are completely separate.
If you are just getting a dribble when a pressurised injector is clicked, that is the problem. Start there. I would take the inlet basket filter out of the injector and see if it is clogged, and then concentrate on getting that injector working properly on the bench with a rigged up pressure supply, or take it to an injector specialist and get that one fixed. I would also blow out the fuel rail to ensure that it is not clogged.
Then back in the car and see if it sprays when connected up to the system (but not in the manifold) and take it from there).
Fuel ECUs can go wrong, but it is vanishingly unlikely in a case like this.

 

Hi Mike

I think that Greg is right about the Injectors, is there a way that you can get some Injector Cleaner/Wynns Carb Cleaner into the Fuel Rail to see if you are able to get that Injector to Spray better than it does at the moment and also help to un-glue the others as well

And if it does then you need look no further

 

Gentlemen, here is what I found today I will start shopping for a ECU while we continue the chase.

1. Fuel is flowing the Wrong way round the System, Photo with a 'Quick and Dirty' Diagram attached.
2. The main fueling ECU is that what is in your photo? No, it's the Marelli Digital Ignition as you said.
3. The factory location, in in the RHS buttress is the Electronic Fuel Injection ECU as you said.
4. Apart from a wire from the engine ignition amplifier to the fuel ECU in the boot the systems are completely separate. I agree the Digital Ignition diagram shows a white wirer going to the EFI ECU but I don't see it as an input to the EFI ECU so I will do a bit of checking.
5. A dribble when a pressurized injector is clicked. I have bench tested that specifc injector and it work on the bench.
6. Blow out the fuel rail. Done, it is not clogged.
7. I hooked up the injector to the fuel injection harness. The connector had 12 V on each terminal. I fed WD 40 from a spray can into the injector and energized it via the ignition and nothing came out. All the injectors were rebuilt and tested. I'll admit that I only pulled one off the car to do my bench test which was good.
8. I also pulled the trunk ECU. The hose was attached to it and to the cross over pipe. Proper air flow a.k.a. vacuum.

I guess you can double click on the image to see a smaller version.

Thanks again for the help.
Mike

PS. I bought a new battery, just in case.



Fuel System Sketch



Fuel System Plumbing



Sump PLumbing

EFI ECU with hose leading to crossover pipe

Pressure at end of fuel rail. Pressure drop gradually to 10 psi

In situ testing of injector with WD 40 aerosol can as the fuel source.

 

Hi Mike

If the Injector is just dribbling when connected to the Fuel Rail with the Fuel Pump Running but Sprays OK when out of the Car
then it could still be the FPR on 'B' Bank

I know you said it was replaced not too long ago but was it replaced with a Brand New One, as if the diaphragm inside is porous, then it may not hold back enough pressure for the injector to spray

Or it could be the Signal (or lack of) from the ECU where one of the easiest and the least expensive ways of Testing this, is to get yourself a 'Noid Light' ebay $25 then you can Test the Signal to each and every Injector one at a time

It may also be worth Checking on the Fuel Pump, as depending on where the Fuel Pump was manufactured it is not uncommon for the Plus and Minus Terminals to be the wrong way round, as was the Case when I fitted a New Fuel Pump to my own Car

The Fix was very simple and just involved swapping the Wires to the Fuel Pump around

So maybe not surprising that She wouldn't Start!

 

Michael
That fuel system sketch is correct. Do you mean that it was NOT like that and you have changed it to be correct, or are you mistaken as to what it should be?
I am still MOST unclear about what testing you are actually doing. A few questions:

1. Have you actually pulled an injector, but still attached to the rail, and turned the starter using the ignition key, and seen if it sprays or not; Yes or no (forget the WD 40 stuff, it is no test)?
2. The leak back of fuel pressure: Once the pump is not running, fuel pressure will drop. If your gauge pic is the pressure measuring the pressure in the rail, after the A bank rail inlet and before the B bank FPR, fuel pump running, then the rail pressure is fine.

So please give us an answer to Q.1. If the injector is not spraying, and not clicking, then I would do as follows;

• rig up a good 12 v source to a spare injector plug (all over ebay) and an earth.
• keep the injector out of the manifold but still attached to the rail.
• jump the pump so it is running
• just touch for a millisecond on and off the injector plug loom you have rigged up to the 12v source. If the injector sprays you KNOW the problem is the signal to the injectors through the injector loom.
• Now the causes are something else, could be loom, could be all sorts of things, but then they system can be tested and the fault found.

 

Hi Mike

This is the kind of Injector Test Rig 'Greg' is talking about



As Greg says: Only dab the power on for a millisecond, or you could burn out the Coil in the Injector, so I find it best to use a 9 volt Battery

This is ideally a 2 person Job, where one of you operates the Can while the other dabs the Power on and the Rubber 'Thing' on the end of the Spout was made from the Waterproof Cover of an old HT Lead

In this Photo I'm Testing and Cleaning the Injectors of a 4.0L XJS with AJ16 Engine (very crude but effective and certainly did the Job)

 

Your few questions:

1. Have you actually pulled an injector, - YES
2. but still attached to the rail, - YES
3. and turned the starter using the ignition key, - YES
4. and seen if it sprays or not; YES, but no spray

I did as follows;

• rig up a good 12 v source to a spare injector plug (all over ebay) and an earth. DONE
• keep the injector out of the manifold but still attached to the rail. DONE
• jump the pump so it is running DONE
• The injector sprayed so now we KNOW the problem is the signal to the injectors through the injector loom (see video attached)

Any suggestion where to start? Should I start at the ECU to see if there is an output signal? Which pins should I check?

Thanks
Mike

Pressure at end of rail

 

I assume you have a marelli car. I knw nothing about them, but plenty of people here do. There is a shielded wire that goes from the marelli system somewhere under the bonnet (I think from the ignitionamplifiers but I am not sure. On the Lucas cars it is from the amplfier) that goes to the ECU in the boot; NOT the one in the cabin you photo'd above. This wire tells the ECU that the engine is turning and the ignition is firing; the ECU therefore lays on the correct firing pulses, according to the signal data.
One possible cause is that your ECU is not getting this signal.

Ask a knowledgeable Marelli owner to tell you how to find this important wire.

The attached is a sticky from the top of the forum, it deals with Lucas cars, but the ECU signal prt is the same apart from the location of this special wire.
https://www.jaguarforums.com/forum/x...he-v12-178286/

 

Hi Mike

As someone with a 'Marelli' Car the same year as yours, I would suggest that you eliminate the most Expensive Suspect on the 'No Start' list which is the ECU which was one of the problems that I've struggled with myself on one of my other Cars which was a V12 Coupe

Where following a suggestion from someone who was on a different forum, I was able to borrow a 'Noid Light' from some friends of ours who build Kit Cars using V12 Engines, which was really a revelation when it came to Testing my Engine as a 'Noid Light' really is the 'only way to fly'

As it turned out the ECU was not getting a Signal and I had checked everything else that I could think off, including the white shielding wire and even put on a New Crank Position Sensor (CPS) which I mistakenly thought was 'Plug and Play' (and sometimes it is) I only replaced the Front as this is the one most likely to go wrong

The thing I didn't realise at least not at first, is that the Gap on the CPS can be Crucial, as the CPS should have a Maximum Gap of: 0.042 or the ECU won't Trigger!
For which I must Thank electrical Genius 'Warrjon' for saving the day!

At first glance there really doesn't seem to be any adjustment, up until I found a 'Shim' which had fallen on the floor when I took the old one off, where having put that back in place, including one or two gentle 'Taps with a Hammer' On the Bracket and NOT the CPS

Another Test with the 'Noid Light' showed that the ECU was now getting a Signal!

At which point we were then all 'Singing and Dancing' so to speak, as the Engine 'Fired Up Straight Away!'

And so the possible problem that you think you may have with the ECU could be down to Adjusting the Gap on the Front CPS 0.042 or the ECU won't Trigger!

While the Gap for the Flywheel Sensor should also be the Same, it is far more likely that you might only need to adjust the Gap on the Front CPS where doing this stuff without the aid of a 'Noid Light' could have you Climbing the Walls!

So what I would suggest you do, is borrow or buy a 'Noid Light' $25 on ebay

(1) Check the ECU is getting a 'Signal' with the 'Noid Light'

(2) If No Signal, then try adjusting the Gap on the Front CPS 0.042 Maximum Gap (which may require some fettling!)

(3) Re Check with the 'Noid Light' if you get a Signal this time, then pour yourself a drink!

(4) Obviously Start the Engine and give thanks to 'The Jaguar Gods'

(5) If 'No Luck' then try and borrow an ECU or get one from a breakers yard and if that works and unless you want to go and buy a new one I would leave it as it is, as they are pretty robust and not known for going wrong

(6) At this point you should know with a fair degree of Certainty whether or not it was a Faulty ECU to blame, or whether it was the Gap on the CPS

(7) If She runs then you are 'Laughing Sandbags' or if not the next thing on the List would be to Check that all the Injectors are Spraying, which could involve the removal of the Fuel Rail, which can be done with all the Injectors attached and Tested using a very simple rig

Where as I may have mentioned Six of my Injectors were all Blocked where after Cleaning them I got her Started, for which I would like to Thank 'Greg' and 'Grant' for showing me how to do this

(8) Its not over till its over and I'm sure you can get her running, as for one thing you are methodically running through all the steps and not cutting cornersGood Luck

I'm sure you'll get there, its only a matter of time and that fire hasn't helped!

Alex

 

Here is where I am and the plan...

1. I decided to build a new harness since everything I've heard is bad about aging. All the wires were "crispy" and there were at least 6 solder repairs and a few broken connectors.

2. I also purchased a "Noid Light " and a test light to sort out the ECU as needed.

3. It's very interesting and it makes a lot of sense that the CPS should have a Maximum Gap of: 0.042. I'll check and shim.

4. Check the Gap for the Flywheel Sensor.

5.If 'No Luck' then I'll buy an ECU

 

Hi Mike

That certainly sounds like a very good plan to me

But didn't know about those joins in the Harness, which is also where the 'Noid Light' will be very useful in fault finding that

In the event that you can't get the Gap on the CPS, then you 'may' have to elongate the fixing holes a little bit with a small round file or even make up your own Shim, though hopefully it will only need a very small adjustment

Good Luck!

I think we're closing in on the 'No Start' problem

Alex

 

I went shopping for an ECU and let it sit for a few months until I got the courage to try it in case it wasn't the final fix. I finally got the courage to try and it fail to start.

At some point in the past the ABS booster pump failed and now it is burned out. If that device wawsn't sending the right message to the ECU would that keep it from starting?

 

dmichael,

There isn't anything in the ABS brake system that can preclude the car from starting.

So, at least that isn't the problem!

Good luck

Paul

 

Hi Paul, thanks for sticking with me...

I think I have checked everything twice but I guess I'll go through it again. The last thing I checked was the connector to the injector with a fuel injector test light (NOID) , no blinking. I then checked both sides of the fuel injector connector and I have 12 V to ground on each side. Is that right?!
The other item I checked, that I hadn't been checked before, is the power resistor. I opened it up and everything looks fine, nothing shorted/ burnt.

Should I have 12 V on both sides of the connector? Oh by the way, the ECU is brand new.

Any suggestions?

Best,
Mike

 

I'm sorry for a dumb and johnny come late question. Which ECU?

Yes, I believe you will find 12v on one side of each injector plug and the way that the system fires, in time and in batches, is to ground. That is, there is always a potential with 12v applied and the control (to fire injectors) the ECU will momentarily send ground signals to fire the injectors in time.

I've never had to run this test but I understand that if everything is hooked up, turning the throttle by hand with the key in the run position, you should hear a definite CLICK as all injectors fire at once. It's a good way to know that what needs to happen CAN happen, electrically.

I'm sorry I'm so late to this. I think that when most of you ALLS work was being done I was spending my first summer driving my recently revived 1990 XJS all up and down the east coast. I feel guilty sometimes because of allllll the help I have been so freely given.

- Did you ever rebuild your harness?
- Did you give the resistor pack, and it's plug, a good cleaning, out of the car and, using a whole can of electrical parts cleaner, spraying into the pack and letting dry?
- Continuity at that coaxial cable is very important. Engine bay, LH top of engine near the fuel rail, to the boot ECU.

I need to look at some electrical diagrams so I can (maybe) be more helpful.