weird 3.9 idling

Hi,
Do you think the ECU is learning to adapt to the changes that have been made, I had similar with the new MAF installed on my V8, my ECU mate was logging it as a fault but engine was running fine, after a few restarts I cleared the fault and logged fault has not reappeared.
Just a thought
Ian

Hi all,
resurrecting this thread, but unfortunately no good news…
Since my last post a lot of things had to be done in the attempt to cure the problem, and I can tell few things remained pretty unchanged.

1) all the trivial renewable (rotor arm, cap, leads and the like) + new vacuum unit on distributor fitted as a very initial step

2) new amplifier fitted (no improvement)

3) MAF, TPS and thermistors (coolant+fuel) checked with digital multimeter to standard values

4) new fuel pump fitted as old one blew

5) fuel pressure buildup and FPR performance after switching off pump checked to be ok

6) new stepper motor fitted made no difference as well


Present situation:

good start when cold, difficult, sometimes impossible, to start when hot.

When hot, it will start immediately but rev up to 3K if coolant sensor unplugged + come down very slowly after plugging it back

spark plugs all equally dark-ish, no sign od cylinder - specific troubles

idle oscillating between 450-1500, though now it will keep idling if drive engaged (auto-box - it used to stall at the beginning of the troubles)

trying to set base idle will result in idling to never increase above 450 RPM, no matter if all unscrewed, until screw will come off + engine will die immediately for too much air (RPM checked wit rovergauge software - idling mode/target rpm will never light up/indicate while trying)

base idle also oscillating but to a much lower extent and very rarely. If throttle is blipped engine will tend to die, progressive opening will revv up fine

while idling with drive engaged, it will tend to die if throttle opened, but if allowed to move on at idle RPM it will suddenly accelerate and respond properly to throttle operation

the above only initially and to some extent though, as accelerating further will results in engine cutting badly and hesitating, like a hiccup. Keeping foot still with same throttle will progressively decrease hiccup to normal running, but any further throttle opening will cause hiccup again. Pushing down to floor will make it jump and respond finely.

Sometimes releasing gas will almost cut engine: RPM drop suddenly as if ignition was put off for a fraction of a second and then put on again. This happens with both cold and warm engine.

When engine cuts shortly, or during hiccups, or when revving at 800 RPM with drive engaged, exhaust smells rich

To me it looks a mix of electrical and fuel injection problems, but after all these attempts, checking everything wit V-meter ohm-meter, anything-meter, never finding abnormal values and yet driving horrible really puts me off…

Any suggestions from the gurus?

I think at this stage I would want to look at compression testing. You might also want to make a careful check of all vacuum lines/hoses as there could be a small split that causes an intermittent air leak.

I might also be tempted to pop the plenum and ram housing off then remove the inlet manifold and the rocker covers and have a quick butchers at the valve train, cam followers and as far as possible maybe the camshaft to see if there are any indications of a worn cam, you can also check the followers. Assuming, cam,pushrods and followers are all good, clean up everything you took off, get a new inlet manifold gasket and put it all back together then see what happens.

What ignition timing are you running? Have you checked to see if the timing remains consistent - could your problem be a stretched timing chain?

Hi Kev, tanks for your suggestions.
I though I mentioned but only very early in this thread and only once, that the engine has been recently totally rebuilt. By saying totally I mean from changing cylinder liners on to everything that needed change. In fact I eventually kept only pistons + connecting rods. Pistons (not rings, just the pistons ) were from an identical but younger engine and well within specs. Liners, all bearings, camshaft, valves, valve guides + seals, pushers, rockers, timing chain and sprocket wheels etc....everything changed. Crankshaft was machined and bearings sized accordingly + checked with plastigauge.
Distributor is still the same but renewable parts I already mentioned have been renewed (not the plate though), MAF and TPS are original but well behaving at least electrically, injectors were kept after being cleaned and tested. Fuel pressure regulator is original, but pressure and leakiness have been checked carefully. ECU and speed sensor and inertial switch were not changed. Fuel pump, temp sensors, stepper motor, all pipes (vac, coolant, etc) were all changed as well. My car is no cat, so no fuzz about lambda sensors and the like. The resistor for fuel map is the correct green version and I get map #2 on rovergauge.
Ignition timing is 8-10 deg before. It oscillates with oscillating idle, but I cannot tell what comes first, I reckon it might as well be a consequence and not the cause.
Throttle valve position at idle is within specs as per workshop manual.
Everything looks fine, engine has power, temp is perfect, only idling is horrible and hiccup is almost embarrassing......

I think there are two basic questions whose answers will provide a step forward to solving it altogether:
1) how can it be that setting base idle cannot rise RPM above 450 no matter how much I unscrew it? Has anybody experience on the possibility of getting too high a base idle (i.e. >550+/-25) and having to screw it back down to the right RPM?
2) how can idle oscillate also while setting base idle, though to a lesser extent, given that the stepper motor is disconnected?

Thanks again to all contributions

Ciao

Adri

Still suspect timing / distributor

Hi cooltide, what would you be inspecting in the timing/distributor system? I could only think of checking tha gap, and that was ok. Another possibility I thought of but wouldn't know how to check is the silicon wires inside the distributor. They move and bend every time the vac unit will act so might as well be intermittently faulty, but a continuity check is not possible as far as I know. However while they might explain a sudden cut they wouldn't cause idling to surge and fall again in cycles. May be there are two problems going on in parallel though. Anybody who knows how to check the functionality of the ignition plate (if this is its name...)?

Thanks
Ciao

Adri

Let's stop for a moment.

Your problem is an iffy idle. Ignition system is a possibility and certainly Cooltide suspects this also, the distributor can be quite easily taken apart and reassembled but make sure you don't loose any parts.You might also want to check you have the correct distributor as there are a number of different part numbers for the V8 with different advance curves depending on model/country etc. I don't understadn what you mean by the silicon wires in the distributor, if you mean the leads on the pickup, then you can do a check when you measure the pick up resistance. If you wiggle the wires with the dvm in place you'll soon see if there is a break in contact when the meter reading drops out but it doesn't sound like that's your problem because the engine would die same as turning the ignition off.
The base plate shouldn't move when setting base idle, that's why the vac advance should be taken off and blanked for base idle setting so that there is no chance of accidentally getting even a little vac advance.
The ignition parts you say you have replaced - are they genuine Lucas parts?
You have said you have a new coil, is it a "high performance coil"? if it is bin it and put a standard one on it.
The main EFI inputs that tell the ecu to make the engine speed 700rpm+/- a bit are as far as you can tell correct.
Your ignition timing is at 8 -10 degrees BTDC, this is a bit advanced but should be alright.
You say you have been turning the idle adjustment on the MAF - are you sure you haven't been turning the CO trim? I'm sure you haven't but thought I should double check.
It appears you have a good basic understanding of what does what and how to set the base idle, double check there are no vacuum leaks and also that when setting the base idle, the vac advance is disconnected and blocked off, same on the air bypass hose.

What I also understand here is that you are saying you can set a base idle speed but the engine won't rev above 450rpm, this makes no sense to me because even if you disconnect the MAF and yank the throttle open it should rev. Or are you saying you can only set to a max of 450rpm using the adjustment screw in which case, you might need to tweek the actual throttle shaft, there is a small adjuster screw on the throttle linkage so you should be able to raise the idle speed.

So it seems the options are limited, some of the symptoms you describe sound familiar to me. I have an ecu that will allow the engine to start and run (sort of) sometimes it will be fine no issues at all but mostly it misbehaves, running rich, misfiring and stalling. The issue with it is an internal ecu fault but when the ecu is tested, no faults are found and the efi warning light doesn't come on but the ecu is shot. (it can't read the MAF). Swap it out, engine is perfect.

AFAIK, on a non-cat tune, the 14CUX ECU doesn't learn and doesn't store long term fuel trim data so that's not an issue.

Your best bet now is to probably try and get a local garage to put it on a gas analyser that way you can see a more accurate rpm figure but also watch the emissions, this should tell you what is happening in real time and you can then play around with it and see what makes any changes. Make sure that you have plenty of fuel and a strong battery for an analyser session, also, cooling needs to be 110%. you might also try an ecu substitution to see if that sorts it.

adri1957 said:

Hi cooltide, what would you be inspecting in the timing/distributor system?

Click to expand...

I wouldn't to be fair. I'd replace it with the good spare one I've got. Same as most efi parts. If I couldn't get to work, it would cost me more than a distributor is worth.
I think Kev suspects the ecu and he knows his stuff. If I couldn't achieve base idle rpm, I think I'd check top dead centre marks are correct initially, but to be honest, I have not re read the whole thread

O.K. lets have another go.

Yes, you are right, the base idle screw is on the plenum, my mistake but you understood what I meant which is the important thing.
I don't have the pick up resistance figures to hand, IIRC I have posted them somewhere in here, do a search hopefully they will appear! if not I'll have to dig for them.

You say the ignition parts are not genuine. I wouldn't rely on them. From experience, pattern ignition parts just don't seem to work.
You say on the base idle thing, you can get to 450rpm but beyond that the engine dies because there is too much unmetered air so your mixture is too lean, this would point me to the MAF, what is your CO Trim set to? Perhaps the other thing to try is to unplug the MAF so the ecu defaults to limp home which is really rich (like 6mpg, yes I've been there! but it works great if you drive it like you stole it) then see if you can get it to idle. Remember to re-set the ecu though if you deliberately make it fault. If not the MAF then you have an inlet leak making it too lean.

A gas analyser is useful for diagnostics but the range of niggles you describe are more likely to be related to the EFI but the problem is that certain perceived issues can be either or indeed a combination of both. I would respectfully suggest that at this time you have an engine that runs this tells us that fundamentally everything you need is there, fuel, air, spark BANG!

Go back to basic principles. Don't be put off or scared by the V8 and EFI this is a really basic engine and not particularly sophisticated. The ECU does not influence the ignition in any way but the ignition can upset the EFI because the injection pulse trigger comes from the ignition system, more specifically, from the coil. Check your electrical system as well. Make sure your earth connections are clean and strong, bad earth can be a really big headache (been there too!).

As Cooltide wisely advises, you might want to double check the timing marks, they don't necessarily line up correctly and you could have the wrong ignition timing. I assume you have done a suck test on the dizzy to be happy the vac advance actually works (I know this won't affect base idle but will affect throttle response)

What happens if you play around with ignition timing? Does it run/idle better with more advance? have you tried retarding the ignition back to the recommended standard of 4 degrees BTDC.

Hi all,
I did the search and found a post by Kev indicating the resistance value to be between 2K and 5K ohms, so I will check that asap

ignition parts
I read very often about the need to keep with original ignition parts. I tried to buy good quality, and still have old cap + arm. Old leads were crap and did need a change, cap + arm have been renewed as a general renewal policy. I will put them back and try them out. New leads should be ok, or they fail all at once as plugs all look the same indicating a non-cylinder specific problem. I know this is only deductive evidence, but keeping on buying new parts just to try them out can become very expensive.

idle setting
As for the 450RPM max this is what happens: start with the screw completely in, engine will not start; unscrew progressively, it will start but die immediately; unscrew further, it will idle at 300 RPM +/- a few; unscrew further, it raises up to 450. At this point the screw it approx half way in (another 13 turns to come off completely if my memory is correct). Unscrew further, no increase above 450; unscrew totally, the screw comes off, it sucks external air and dies immediately.
I don't know if this relates to MAF setting. MAF volts for the CO setting are 1,55. I must say that I tried running the car from 0.99 up to 1.75 with 0.1 step increases and couldn't tell much difference apart from hot starts more difficult on the lower end of the scale.

connections and electricals
I agree checking all connections once more is a wise suggestion, as is checking the timing marks. Do you happen to know where the 6800 resistance in between coil and ECU on the RPM pickup point is located? I could never find that part, so I ignore if it is working at all (if any is present).

Playing around with timing
If I advance it it will idle better (slightly higher RPM), never tried to run it though. If I retard it idle will go down. In both cases it will oscillate as described previously

one more bit of info
something I realized today while driving is that when I stop at traffic lights with drive engaged idle goes down to 1200 for a few secs that drops to 800-900 and there it stays with no oscillations...in other words: idle is erratic only if allowed to be so while in neutral or park, if in drive or reverse it remains steady and low. When I release brakes and push on gas it will then tend to die unless I let it move a few meters at idle, then it will pick up fine.


Anyway, thanks for the encouragenent, I try very hard not to be put off, and I try to go back to basic principles, but every time I try it seems to go even more basic than me.... :-(

So, many thanks for all suggestion, at least it looks something will keep me busy.... Any more thoughts very welcome.

Ciao

Adri

O.K. I've had a quick read up on idle problems and I suspect your problem could be your CO trim is too high but this assumes there are no other potential problems such as a vacuum leak or timing scatter. You doubtless understand that timing scatter will cause the idle speed to vary.

As I understand it, if CO trim is too high, the engine will run O.K. on the throttle but when it returns to idle the mixture can change and variable amounts of unburnt fuel stay in the inlet system which can cause the idle conditions to change.

You said your CO trim value is 1.55v, this is at the top end for a non-cat tune, perhaps drop this down to 1.0v and also retard your ignition to 4 degrees BTDC +/- 1 degree and see what happens. If this set up allows you to get it set up then you will need a session on a gas analyser to tweek your CO trim and ignition timing for optimum values. Please make sure you make a note of relevant settings before making changes so you can go back to where you are if need be.

If you have changed the cam from standard then you wold need to alter both CO trim and ignition advance to get to a good tune with acceptable emissions. After I changed the cam in mine, I now run CO trim at just over 1.6v and ignition at 10 degrees BTDC.

If you still can't set base idle and experience unstable running at low rpm then there is clearly a mechanical fault rather than an efi problem. Vacuum and compression testing might be useful in assessing what issues might be there. Anyway, see how you get on and keep us posted on progress.

adri1957 said:

Playing around with timing
If I advance it it will idle better (slightly higher RPM), never tried to run it though. If I retard it idle will go down. In both cases it will oscillate as described previously

one more bit of info
something I realized today while driving is that when I stop at traffic lights with drive engaged idle goes down to 1200 for a few secs that drops to 800-900 and there it stays with no oscillations...in other words: idle is erratic only if allowed to be so while in neutral or park, if in drive or reverse it remains steady and low. When I release brakes and push on gas it will then tend to die unless I let it move a few meters at idle, then it will pick up fine.

Click to expand...

Fluctuating idle is most often due to sticky stepper or an inlet leak.
The situation you describe between in and out of gear says inlet leak. In gear, the ecu increases the engine speed to account for the extra load so the effect is the same as adding a small amount of throttle, the need to let it move on tickover before opening the throttle is very likely an inlet leak somewhere, what happens is an inlet leak means lean/weak mixture at low speed, the engine will want to stall due to fuel starvation but as engine speed increases and you can add throttle the mixture evens out and the engine can run better and so picks up. The other thing that can cause similar symptoms would be a defective vac or mechanical advance in the distributor so maybe do a suck test on the vac advance and then see if the rotor arm can be moved by rocking it gently by hand, you should be able to move it a couple of degrees and then let go and see it spring back to position, you can hear the mechanical advance when doing this but don't be heavy handed you'll break something.

I would be inclined to run some vacuum and compression tests and also have a good look at the ignition timing, if the timing is wandering as happens with a stretched timing chain it is going to get upset. When properly set up, the engine will have a smooth and stable idle with crisp throttle response.

HTH

Hello kev, many thanks for taking the time to go over this matter again.
While I will have to wait for trying the settings and adjustments you suggest (it' s pouring very hard these days, and alway at weekends or late afternoons when one has free time to spend...) I realize there is a gap in what I used to take for sure: when is it that you call it wandering timing? I thought timing would change according to RPM, which in turn will change according to timing....but apart from the catch22 situation how far a mark needs to be from the set/wanted value and how often, to call it "wandering"? In my case it is not absolutely fixed and it changes just a few deg (by eye a should reckon from 4 up to may be 12) but that varies with idle, so how can I tell if it is real wandering or just a consequence of erratic idle?
Distributor has been overhauled since this problem started and I can tell the mechanical advance mechanism is fine, as is the rotor arm spring effect while moving it by hand, and the timing chain+ sprocket are only 5K miles old. Camshaft was standard, so I don't expect to have to change settings accordingly.
If one had to look for leaks and all common places had already been proof-tested to be fine, where would he look for? Which kind of tests could be run to check for vacuum? As I understand it, If there was a leak wouldn't base idle tend to be unadjustable but higher than normal? Or did I get it wrong?

Many thanks
Ciao

Adri

See comments in red.

adri1957 said:

Hello kev, many thanks for taking the time to go over this matter again.
While I will have to wait for trying the settings and adjustments you suggest (it' s pouring very hard these days, and alway at weekends or late afternoons when one has free time to spend...) I realize there is a gap in what I used to take for sure: when is it that you call it wandering timing? I thought timing would change according to RPM, which in turn will change according to timing....but apart from the catch22 situation how far a mark needs to be from the set/wanted value and how often, to call it "wandering"? In my case it is not absolutely fixed and it changes just a few deg (by eye a should reckon from 4 up to may be 12) but that varies with idle, so how can I tell if it is real wandering or just a consequence of erratic idle?

With vac advance disconnected and engine at idle the speed should not change enough to dial in mechanical advance so the timing shouldn't wander around. If you are suggesting there is a variation of up to 8 degrees then there is clearly a problem. Slack timing chain, play in dizzy shaft and drive gear. I am afraid that could be a timing case off job, a real PITA I know!

Distributor has been overhauled since this problem started and I can tell the mechanical advance mechanism is fine, as is the rotor arm spring effect while moving it by hand, and the timing chain+ sprocket are only 5K miles old. Camshaft was standard, so I don't expect to have to change settings accordingly.
If one had to look for leaks and all common places had already been proof-tested to be fine, where would he look for? Which kind of tests could be run to check for vacuum? As I understand it, If there was a leak wouldn't base idle tend to be unadjustable but higher than normal? Or did I get it wrong?

Base idle might be difficult to set if there is a vacuum leak although it would need to be small otherwise there would be much bigger running issues. Don't focus only on vacuum, do a full compression test (i.e. wet and dry). There are a couple of places you can measure vacuum off the plenum, for testing purposes, there is no harm in popping off the hose that puts vacuum on the accumulator to operate the heater vent system. With vacuum you are looking for a good stable reading, depending on what result you get, you can get a feel for whether the valve timing is late or early or if there is a vacuum leak, also, fuel mixture and ignition timing will have an effect. Vacuum tuning can be useful but it is not as good as using a 4 gas analyser. I am afraid that without getting hands on I don't think I can offer any more but keep us posted.

Many thanks
Ciao

Adri

Click to expand...

Hi folks,
while waiting to have those tests made as suggested by kev, I checked a few things over again and discovered something “interesting”.

First, the marks on the pulley are perfectly aligned to BTDC, so after reducing the CO trim down to 1 V as suggested I was ready to check timing, but when I started the engine it would rev up to a steady 2.5K.

I suspected something wrong with stepper motor and tried to operate it with rovergauge but to no avail. A spare stepper motor would not work either, so I suspected a faulty wire and in fact they are faulty at some point after the Y junction to the main harness (cannot tell which of the 4 though). If I wiggle them it will reestablish the connection and there is a position where it keeps. I wonder if some of the issues were due to a wire with intermittent fault. However it would stay now +/-steady at 1400-1600. If I operated the IACV with rovergauge it did eventually get down to 800, so it looked as if the ECU didn't want to bring it down. This attitude of the ECU could in turn be due to other conditions such as temp sensors or the like, so I also checked fault codes and…surprise… there was now a coolant sensor fault. The sensor itself gave correct ohm readings at various temps, but the connector to the sensor had a bad crimping and green wire came off, may be while I pulled the whole harness while wiggling the other wires to operate the stepper motor.

Once the connector was put back to working order with some soldering, idle would still oscillate around 800, from 450 up to 1200, I decided to check the timing and while operating the strobo light I discovered another weird behavior.
The light was connected to lead #1 and it worked fine as long as idling was above 450. In these conditions I set the timing to 4-6 as suggested, but when idle dropped to 450 the strobo light stopped working. I tried other leads and discovered that 2 4 8 will work but 6 won’t, and 3 7 work but 1 and 5 won’t. If a little throttle is given to bring idle back to above 450 then all leads will trigger the strobo light. This is both reproducible and lead/plug unrelated, as swapping leads and/or plugs doesn’t change the pattern: at 450 RPM 2-4-8-3-7 will always trigger the strobo, 1-6-5- will always be down. However it cannot be a no-spark situations as 3 cylinders off would not allow engine to idle at a steady 450 (450 is the best idle experienced so far…)so it must be just weak spark or something like that.

I think this might point to faulty dizzy cap/arm or reluctor ring, so may be a little more centrifugal force will allow contact or field generation as if too a big gap was present at low RPM. However, it must be speed related AND position specific. Today’s tests stop here as it was the end of the day, but tomorrow I will check if there is something in common with position # 2 4 8 5 7 as opposed to 1 5 6 at cap contacts or ring spikes.

Does anybody know how much play is admitted between distributor shaft and distributor case?

Any suggestions?

Thanks

Ciao

Adri

Just an update + unfortunately very bad news…
I disassembled and completely overhauled the distributor, but didn’t find anything relevant that could point to pattern in the ability to trigger strobo response. No excessive play, wires are ok and pick-up resistance is within specifications. I re-checked air gap + cleaned and lubricated everything and put it back.
Then I made the typical mistake of putting it back 180° wrong so when I realized it, I just lifted it a little and rotated the arm by 180° + put it back. At that point no way to start the engine….. no spark, not even at the coil lead, so I spent the day running the tests as per the workshop manual but everything seemed ok up to test #6, with only exception of test 4 where it is stated that from battery +ve to coil -ve should read 0 with ignition off and still 0 with ignition on then rise while cranking. I found 12V in off, 0,1V in on and up to 0.5 while cranking. Don’t know if that is the expected result, however after everything else failed and the distributor came down and back another 2-3 times, I decided to swap contacts from amplifier to coil, as while putting them back following the diagram I remembered feeling they were originally in the opposite arrangement, but trusted the digram eventually. So, spark was back…! (and diagram is wrong!) coil lead + all 8 spark leads tested individually all giving reasonable sparks.
Yet the engine dind’t start.
Fuel pump is running, stepper motor is working, timing is correct (checked while cranking to make sure I didn’t do it wrong a second time), every cylinder has a spark, but the engine is still dead. Not even a single firing, nothing.
I tried to figure out some sort of apparently irrelevant manipulation that could be incidentally related to the removal + refitting of the distributor but nothing came up to my mind that could explain the situation. Might be a very unlucky independent break down occurring at the very same time, but even so I wouldn't know what to think of.

Anyone out there with an idea to what else could be checked?

Thanks

Ciao

Adri

Sleeping over it brought some suggestions to me.
As far as I understand it, although distributor and coil are in the list of objects to be tested in the section specific to fuel injection troubleshooting, the ignition circuit itself does not include them. Hence having sparks doesn't mean there is power to ignition. There are two places where something might have gone wrong: one is the wiring between coil and ECU, through which the ECU picks up the engine RPM and knows it is revolving. If that were faulty my logic would suggest there is no power to injectors. However I looked for this bit of info and couldn't find any clear statement. The second bit that might go wrong is the main relais that, by being called so is deceptively indicating that if key-ignition works (in the sense it does something, at least noisy....) then it would be OK, while in fact it might as well be dead and yet, I think, starter would operate and plugs would have sparks. So as soon as I will have some spare time will check these two points + post results.
Obviously all suggestions will be very welcome.

Thanks

Adri

adri1957 said:

Sleeping over it brought some suggestions to me.
As far as I understand it, although distributor and coil are in the list of objects to be tested in the section specific to fuel injection troubleshooting, the ignition circuit itself does not include them. Hence having sparks doesn't mean there is power to ignition. There are two places where something might have gone wrong: one is the wiring between coil and ECU, through which the ECU picks up the engine RPM and knows it is revolving. If that were faulty my logic would suggest there is no power to injectors. However I looked for this bit of info and couldn't find any clear statement. The second bit that might go wrong is the main relais that, by being called so is deceptively indicating that if key-ignition works (in the sense it does something, at least noisy....) then it would be OK, while in fact it might as well be dead and yet, I think, starter would operate and plugs would have sparks. So as soon as I will have some spare time will check these two points + post results.
Obviously all suggestions will be very welcome.

Thanks

Adri

Click to expand...

I'm not sure you're quite right there but I think I see what you are saying. There is only 1 wire from the coil to the ecu, IIRC it breaks out from the loom by the connector for the MAF.

Check carefully the loom between the ignition amplifier and the coil, under the protective sleeving there is join, corrosion build up on this can cause running problems. Equally, you should carefully remove, inspect and if necessary repair all of the connectors that attach to the coil - I have had the problem of corrosion and broken wires at this location. If the efi trigger signal is not getting through, you can have sparks but no injectors.

Currently you are saying you have sparks and as far as you know they happen at the right time. If that is so leave that bit alone for now. Try crankin ghte engine over, remove a couple of spark plugs - if the plugs are wet then you have fuel, if dry then you don't so you'll know if you need to look at the efi trigger and/or ecu.

You can listen for the right relays. Turn the ignition key to "ignition on" you should hear 3 relays click. One ids the main efi power relay, one is the fuel pump relay and the third (if fitted) is the abs pump relay. So 3 clicky relays says good (in theory) to go.

You need to remember the fuel injectors work on a switched ground, not switched live. The power is always supplied to the injectors via the ecu but if the main efi relay is not switching and this does happen, the ecu is dead and you won't get any fuel even if other parts of the system appear to do what they should.

If we assume you have both fuel and sparks bu tit doesn't want to go, mark the position of the distributor, slacken the clam then advance the ignition timing a bit then try it again.If it still won't fire, add more advance. This is a peculiarity of Range Rovers, I have had this a number of times over the years, everything as it should be but no fire! Advance it up a bit and it will start, once it has been run and warmed up a bit, re-set timing and all is well.

BTW, get genuine ignition parts, no really, I mean it. I know they are expensive but trust me, only genuine ignition parts will do. Good luck!

Hi all,
major update here….
I decided to take the long way and removed the right hand seat, removed the ECU, removed the plastic case from multiplug and carried out all fuel injection tests as per workshop manual. I was expecting to find faults either in coil-to-ecu or injectors or something related to fuel supply but everything was perfectly working and within specifications.
While removing the under dash panel to get access to ignition switch to check for continuity with coil I noticed 2x25A fuses in very bad shape. One was interrupted and the second has the plastic melted but still electrically ok. The whole thing didn’t look very healthy and I just removed the melted fuse leaving the socket empty. The two fuses are connected to a black relais with 4 contacts. The wires from fuses to relais are spliced together and are purple-green, away from fuses (to whatever they serve) wires are purple-grey, and the fuse has additional fat brown, thin black and thin purple yellow wires.
So, all tests are OK only problem these fuses and may be the relay.
There was spark, there is fuel, plenty of air, it ought ot start….I tried and it just started + run so smoothly i don’t remember since a long time.
Correct idle, no oscillations, no stall when blipping throttle, no stall when putting to drive. Just a normal RRC. I nearly forgot how it feels…
Now, while I am obviously happy for this outcome, I am ****ed off by not having been able to point out what was the real fault. I can hardly believe the unknown fuses can be the reason, and I suspect something has been moved and put back to place and working order. May be I’ll never know now :-((
I have taken pictures of the fuses but don't know if I can attach anything to this message. I would appreciate some suggestions as to how show the picts and then I would obviously be grateful to whom could recognize and indicate which fuses + relais are they.
However, a new harness was already on its way that I will be able to check for continuity on the bench and then replace the old one where I already know something is weird with stepper motor wiring.

Many thanks for all help and support up to here

Ciao

Adri