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XJ40 ( XJ81 ) 1986 - 1994

XJR sport Cranks but won't start

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Old 10-07-2017, 03:09 PM
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Unhappy XJR sport Cranks but won't start

Hello, i just registered on this forum cause i hope to soon get into the exciting world of owning an XJ40 or one of it-s cousins but because there aren't many Jags in my country i have found it to be a bit dificuilt, however i managed to find a pretty good XJR sport but i need a veteran's help! here is some info if i can read my vins correctly its a late 1990. model it's VIN's serial starts at 60, so me and my friend who owns a Daimler went to check it out today and because it's fuel pump had been broken, we replaced it, but it still didn't want to start, it cranks and it brings the fuel up to the injectors but it seems that the injectors are not working, registering at 0,25 Volts so any thoughts on what it might be, the rest of the Jaguar is fine and besides this the engine looks to be in great condition, but we can't be sure until it starts and neither we or the owner have any more ideas so any help would be nice cause right now she does look a lot like my first jag so i'd love to see how she runs and hopefully confirm this....

if any other info is needed i will gladly supply it, thanks in advance,

Stefan S.
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Old 10-07-2017, 04:23 PM
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You need to download Jaguar publication S91_AJ6 4.0 Engine Management.pdf
Lots of info in the publication.It is a large file (about 14mb) so I cannot attach it here.
I did upload it to the large file section somewhere on the forum and it is on jagrepair.com website.

bob
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Old 10-07-2017, 04:26 PM
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Thanks very much Bob, i will be sure to do so right away, cheers!
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Old 10-07-2017, 04:29 PM
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done, i will have a look at it now, any other publications you could point me in the direction of would be awesome! p.s. i can't open Jag repairs XJ40 page....
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Old 10-08-2017, 01:18 PM
 
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Hi Stefan,

Welcome to the Jaguar Forums! It's great to have you with us, and I hope you become the new owner of the 1990 XJR Sport.

Probably the three most common causes of a crank-but-no-start condition are low battery voltage, a failed crankshaft position sensor (CPS), or a problem with the fuel pump or its circuit. So given that you have fuel pressure at the fuel rail, I would check the battery and CPS.

If the battery voltage falls below about 10.5 volts while cranking, the Engine Control Module (ECM) will not trigger the ignition to fire, so you'll have no spark and potentially no fuel injector operation. Many digital multimeters cannot react quickly enough to measure true voltage sag while cranking, so use an analog voltmeter with a traditional needle meter if available, or better yet, use a good quality battery/charging system analyzer (in the U.S., Midtronics is probably the best-known brand).

The CPS provides the primary timing signal to the ECM, so if the CPS has failed, or its electrical connector is contaminated with oil or its wiring harness is damaged, the ECM will not know when to fire the spark plugs. Diagnosing an intermittently failing CPS can be difficult. A simple test is to watch the tachometer while cranking the engine: it should read about 200 rpm; if it reads 0 rpm, there is a problem with the CPS or its wiring.

Try this URL for Jag-Repair.com:

JagRepair.com - Jaguar Repair Information Resource

Cheers,

Don

Last edited by Don B; 10-08-2017 at 01:21 PM.
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Old 10-19-2017, 06:26 PM
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Don, thanks for the thorough reply i did not see it for some reason, we've not looked at the cps, we have so far changed the injectors, the lucas fuel pressure regulator and the fuel filter, same problem, the spark is there we have checked a few plugs, the injectors fire but it seems like no fuel comes out when the rail with the injectors is slightly out of the engine it wants to start but doesn't. just coughs a little.

Do you think it could be the CPS?

Do you think it could be the reacent fuel pump change, maybe it does not generate enough pressure even though when cranked while the injectors are out it sprays fuel...

any other ideas, besides the CPS we will check that next, but i read somewhere that if it is the cps there would be no spark and if started using starter spray it should carry on working, and our car does not.

The car starts fine using starter spray but dies if taken off said spray.
The car has no fuel getting to the spark plugs.
and the battery is new. the inertia sensor is not triggered and if i am not mistaking there would be no fuel getting to the injectors if it was....

P.S. when i go to Jagrepair.com and go into the xj40 section it refuses to let me click on the links and all of the highlighted links appear to be plain text like "engine" which i tried to click on multiple times...
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Old 10-19-2017, 06:49 PM
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[QUOTE=Stefi88;1778774
Do you think it could be the CPS?
any other ideas, besides the CPS we will check that next, but i read somewhere that if it is the cps there would be no spark and if started using starter spray it should carry on working, and our car does not.[/QUOTE]

Quote:
Originally Posted by DonB
The CPS provides the primary timing signal to the ECM, so if the CPS has failed, or its electrical connector is contaminated with oil or its wiring harness is damaged, the ECM will not know when to fire the spark plugs. Diagnosing an intermittently failing CPS can be difficult. A simple test is to watch the tachometer while cranking the engine: it should read about 200 rpm; if it reads 0 rpm, there is a problem with the CPS or its wiring.
HTH

Larry
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Old 10-19-2017, 06:56 PM
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Thanks for the fast reply Lawrence, i have read that, but since i am unable to test that right now, i just asked about other ways to possibly know if it's the CPS and told as much info as i know to hopefully rule it out or see if there are other ideas cause i have been reading many posts in the last hour or so, we will watch the tachometer needle closely, for now we know it does spike , but i haven't been looking at it while i crank to remember if it reads 200 rpm, i know it does spike a bit but not sure where it stays, but since the car is not yet mine i just want to see if i can get as many ideas in before each visit so i can test as many things as i can...
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Old 10-19-2017, 10:16 PM
 
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Quote:
Originally Posted by Stefi88 View Post
The car starts fine using starter spray but dies if taken off said spray. The car has no fuel getting to the spark plugs.
and the battery is new. the inertia sensor is not triggered and if i am not mistaking there would be no fuel getting to the injectors if it was....

P.S. when i go to Jagrepair.com and go into the xj40 section it refuses to let me click on the links and all of the highlighted links appear to be plain text like "engine" which i tried to click on multiple times...
Hi Stefan,

Since the engine will start using starter fluid, you have spark, and therefore the CPS is working, at least intermittently. It would be worth watching the tachometer while cranking the engine to see if you get a reading of about 200 rpm. If the reading is 0 rpm or if the tach needle jumps around, you might suspect the CPS is failing.

Your account begins with replacing the fuel pump in an attempt to cure a no-start condition. At that time, did you rule out other possible causes of fuel pump malfunction, such as a failing fuel pump relay, corrosion on the ground or grounds used by the fuel pump circuit, etc.?

One thing that would be worth doing is to check the Vehicle Condition Monitor for any stored Diagnostic Trouble Codes (DTCs)? To do so, turn the key to position II (Ignition ON) but do not start the engine. Press and release the VCM button on the trip computer to the right of the steering wheel. Watch the small display window below the speedometer where the odometer/mileage display normally appears. DTCs are displayed in the format of "Fuel Fault" or "FF" followed by a number, such as "Fuel Fault 12" or "FF19." Write down anything that appears and report it here so we can try to help.

Regarding jagrepair.com, note that many of the XJ40 documents are misfiled in the XJ6 & XJ12 section, the X300 section, and perhaps in other sections.

Cheers,

Don
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Old 10-20-2017, 02:27 AM
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Hello Don, again thanks for such a thorough reply, we have checked the fuel pump circuit, cleaned it and the pump works. however my possible thought is that for some reason the pressure is lost somewhere between the boot and the injectors, im not sure because the injectors do spray when out of their sockets and again we did not have the manometer to measure the pressure of the pump at the injectors so my hope is that a second fuel pump change would possibly solve it. The car coughs every once in a while as if it gets a drop of fuel and wants to start but then quickly goes back to dry cranking. Having said that, keep in mind i am doing this with a friend who knows a lot about cars and a mechanic and so my thought is the least relevant one cause i know very little about the inner workings of what makes a Jag tick.

The first thing we did was check the VCM, it reports a FUSE 2 problem and a PAD (i thought it was PRO but found out on the forum i was wrong) which has all to do with the car not moving for a while.
We have tackled the FUSE 2 issue i have checked every fuse in all 3 fuse boxes twice all of them are fine,i even replaced many for good measure, so could that be the culprit or a symptom of something?

I will take another look at Jagrepair and it's sections, thanks for the tip again and i will check the CPS when i got there next, but i am really hoping for some more ideas, the car is around 50km away so it takes some time for me to go, and get back so it would be great to have as much info as possible before i go so i can maybe test a few things...

Thanks again,

Stefan S.

Last edited by Stefi88; 10-20-2017 at 02:36 AM.
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Old 10-20-2017, 06:17 AM
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Fuse boxes are known to have dry joints behind the fuses so that might be one reason. fuse 2 indicates which fuse box the problem resides in I always get confused but number three fuse box is in the armrest so that narrows it down a bit
The fact that you are getting both spark and fuel means that you should get the engine running. Two other things to check, is the air filter clogged or wet? Are the spark plugs wet?
If the filter is wet remove it, if the plugs are wet take them out and heat them up with a small gas flame and crank the engine over with your foot hard on the accelerator, this will shut off the injectors and help to dry out any possible flooding.
Replace the plugs and try again, do not apply any accelerator at this point.
All the best.

Last edited by Robman25; 10-20-2017 at 06:18 AM. Reason: Typo
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Old 10-20-2017, 01:51 PM
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Hi Rob, well the plugs are bone dry even after a long crank and the air filter, we didn't check but we used starter fluid and the car started right away so that is why we ruled it out and we even used LPG to run the car to see how the engine runs ( sorry if it is not called lpg its the Gas and the car ran fine and we checked the engine for problems this way). The annoying thing is everything is where it should be, spark is there fuel is there but no, the car ran fine, then the fuel pump died it sat for six months now it does not run it is so frustrating....
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Old 10-20-2017, 02:24 PM
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I take it the battery is fully charged, as has been mentioned? How old is the petrol in the tank? Can you rig up a fuel pressure test rig to see that there is sufficient pressure, should be around 42psi.
Dry plugs seem strange I would expect to seem some dampness if the injectors were firing petrol into the cylinders. I think that you might need to remove the injectors and try to rig up an injector clean, you tube has a few clips on doing this at home.
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Old 10-21-2017, 05:05 AM
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The battery is fully charged, there was very little petrol in the tank, we didnt bother to spill it when we changed the pump and instead poured around 15l of petrol on top of it, we will test the pressure, that is on our agenda for sure and also, two plugs as i recall seemed a bit damp three were bone dry and one we weren't really sure did we touch it and make it damp or was it damp before, but still we were cranking for quite a few times, they should have been wet by then, we put up a second set of incetors so im pretty sure that all 12 injectors can't be bad, if it were the injectors it had to have shown some signs of life other than a short cough....
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Old 10-21-2017, 05:11 AM
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Pull the king lead from the coil, withdraw the injectors and crank the engine, you might want to place a piece of cardboard underneath the injectors. They should all fire a nice spray of fuel at the ame time. If that doesn’t work i’m not sure where you go from here as you seem to have covered all the bases.
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Old 10-30-2017, 07:52 AM
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Ok, update, the Injectors are spitting some fuel into the engine, but its either not enough or at the wrong time, so any remedy to this or an idea what could be causing it?

The VCM shows PAD could the start issue have anything to do with the brakes?

My friend who owns a Daimler says that the transmission lock seems not to work, could that be confusing the engine and making it inject less fuel than it should?

When cranked, the needle goes to 200 rpm as it should, could it still somehow be the CPS?

We also changed the ECU with the one from my friend's Daimler, still the same.

any ideas what could be causing this problem?

a list of what has been done to the car:
1. Changed Battery with new one
2. Changed fuel filter
3. Changed air filter
4.Changed fuel pump
5. Checked fuel pump pressure
6. Changed Injectors (albeit with second hand ones, all 6 spray on cardboard)
7.Changed fuel in the tank with fresh one
8.used Contact spray on all of the ignition relays and any electronics we could get our hands on in the engine bay

Additional info:

Car starts right away using Started fluid
Car has been sitting for a long time
Car has been sitting unstarted for around 6 months prior after the fuel pump died on it.

Last edited by Stefi88; 10-30-2017 at 09:54 AM.
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Old 10-30-2017, 08:17 PM
 
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Quote:
Originally Posted by Stefi88 View Post
Ok, update, the Injectors are spitting some fuel into the engine, but its either not enough or at the wrong time, so any remedy to this or an idea what could be causing it?
You mentioned in your first post that the "...injectors are not working, registering at 0,25 Volts...." Do you mean that you measured the voltage supply at the injector electrical connectors and it was only 0,25 volts? Or, do you mean the injector coils measured 0,25 ohms? The EMS manual states the coils should measure approximately 2.5 ohms. The injectors are wired in parallel and all fire at the same time. If memory serves, the injectors have battery power (12+ volts) at all times, but the ECM completes the circuit to ground repeatedly to open the injectors in pulses as necessary for the desired fueling.

If you don't have battery power on one of the wires to each injector while cranking the engine, perhaps there is a problem with the electrical circuit between the ECM and injectors. Corrosion on ECM connector pins is one possible cause. Corrosion on the ground points referenced by the ECM is another possible cause. There are two on the intake manifold studs and one on the firewall/bulkhead behind the cylinder head.

Regarding your fuel supply, is it possible the new pump is not providing sufficient pressure, or its electrical circuit has a problem such as an intermittent connection? In all the things you've changed, did you also change the fuel pump relay?

Is it possible that while replacing the fuel pump the fuel pipes under the car were kinked or otherwise damaged? This can happen if the fuel lines are not disconnected from the underside of the fuel tank before it is pulled rearward for access to the pump.

Quote:
Originally Posted by Stefi88 View Post
The VCM shows PAD could the start issue have anything to do with the brakes?
No - the PAD warning lamp indicates that either a brake pad wear sensor has worn down to the point that its internal wire is touching the brake rotor and completing the circuit to ground, or its electrical connector is diconnected or contaminated, or there is another problem with the sensor's electrical circuit, such as a broken wire in the harness. This should have no connection with engine starting.

Quote:
Originally Posted by Stefi88 View Post
My friend who owns a Daimler says that the transmission lock seems not to work, could that be confusing the engine and making it inject less fuel than it should?
As far as I know, on the '90-'92 cars the start inhibit switch is part of the transmission rotary switch, and when open it prevents the starter from cranking. I don't know if it prevents the injectors from pulsing, but I don't think it is that complex in its operation.

Quote:
Originally Posted by Stefi88 View Post
When cranked, the needle goes to 200 rpm as it should, could it still somehow be the CPS?
Intermittent failure of the CPS is not uncommon, but the fact that your engine will start on starter fluid would suggest the CPS is not the cause of your no-start condition.

Cheers,

Don
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Old 10-31-2017, 04:41 AM
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Old 10-31-2017, 04:47 AM
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Thanks for the continuous replies Don you are a vault of information!

the 0,25 volts i measured was at the injector electrical connectors, but, since the injectors will now fire (as suggested we put a piece of cardboard and cranked, all 6 injectors sprayed) i don't think that is an issue, we used contact spray on the ECM connections, but will look for the ground points, anything else that you know ot that could be causing such a strange problem? The fuel is in the rail, the spark is there, why won't she start damn it!
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Old 10-31-2017, 07:11 AM
 
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Just a few thoughts before I head to work:

Was the spray pattern of the injectors a nice cone shape with the fuel atomized evenly, or were the injectors dribbling drops of fuel?

Could the spark be weak? Are the plugs the correct Champions and properly gapped? Have you checked the condition of the distributor cap and rotor, as well as the coil and ignition amplifier? Deterioration of the insulation on the wires at the amplifier and coil is a known issue. Plug wires, especially the king lead from the coil to the distributor cap?

Is the CPS mounted correctly in its bracket, and is the bracket mounted correctly on the timing cover?

Have you checked your battery voltage while cranking?

Check all the things on the diagnostic list frenchfairplaydriver posted.

Cheers,

Don
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