Espace 3 v6 non starter after engine change

[BrianM]

After running the car for two years without the rad cap on, it was time to admit it. Either scrap it or fix it. Well the car has the leather, three sunroofs, I tinted the windows, fitted sat nav, dvd head rests, 240v inverter, rear air bags & otherwise up to date. Also last yr did the gearbox which was an epic of a job if you remember. So as we are due to drive from the UK to Germany I decided to swap out the engine from the spare car. I really now wish I swapped my gearbox into the spare as now I have created my new nightmare!   Both cars were running before I started this repair, now all I get is three pops of backfire & then nothing other than a smell of petrol if I keep cranking. I have double checked all wiring connectors & earths. I changed the crank sensor & swopped out the ecus as I thought they may have changed the reluctor. Sounds like it wants to fire on the wrong cylinders then nothing. I have a clip, no faults found in engine or controler. Has oil pressure fuel & spark. I can see all sensors, Injectors timing, coil timing in clip. I can actuate bank a,b,c injectors etc, I thought I was a good mechanic but this has me beat! All thoughts welcome.
Oh, we go on holiday In a days time so I just added a dci to the fleet! I would still rather take the lx7 if you know where I have gone wrong.
Is it poss that the ecu has a memory where the engine stopped last time. I see the ignition timing change as it cranks but maybe the cylinders are too wet by then to start.

[renaultsan]

 I did not see any replies to this problem, has it been sorted?

Terry

[BrianM]

No not yet, but I need to get it running before the end of the month. I have tried to turn the engine by hand until the next cylinder compression, in the hope to change the timing but with no joy. I assume this is waking up the ecu & it is reading the change in position of the crank, i'm going to try this with the tdc sensor disconnected. Do you have a similar problem, or a cure maybe? I should be so lucky, lucky, lucky, lucky......

[roy4matra]

No not yet, but I need to get it running before the end of the month. I have tried to turn the engine by hand until the next cylinder compression, in the hope to change the timing but with no joy. I assume this is waking up the ecu & it is reading the change in position of the crank, i'm going to try this with the tdc sensor disconnected...

This won't make any difference Brian if I understand what you're implying.  The TDC sensor picks up from a set of registers where there is one missing to denote TDC so it always knows where TDC is by this, whilst it reads the rpm from the rate of all the others passing it.  If it uses the flywheel teeth as the registers for rpm then there is a single register for the TDC position, plus there is often a cam sensor too, so this is used not only as a cross check, but allows for quicker response since the ECU knows which of the cycles the engine is on.

Since you have changed engines over, did you check that both flywheels were the same and fitted in the same place so the timing marks would be correct?  (I can't remember this engine and whether the flywheel only fits in one position).  It does sound from your description as if the timing is out, which is why I wonder about the flywheel registers...

Also you mention swapping ECUs so I assume you have a way to get around the immobiliser coding or did you swap all three items so they match?

Roy

[BrianM]

Hi Roy, thanks for your input. I did indeed swop out the ecu, body controller & immo chip from the donor car. & it did the same turn - pop- die as with my original ecu set. Looking at the figures in clip I can see the timing change when cranking. I just thought it would remember where the crank stopped rather than wait for the tdc marker. This engine does not have the cam sensor. All a bit strange. I didnt think to check the flyweel position as I didnt take it off.  Looking at the wiring loom, it is quite short & is direct from the ecu to the coil pack without any loom connectors. Unlike the injector loom which breaks at the back of the engine.

[BrianM]

I checked the wiring from the ecu to the coil pack plug today, both cars are the same. I had swapped out the coil packs incase one was faulty, I can't imagine both are duff. Both engines were runners before I started this swap, I am befuddled!

[roy4matra]

I checked the wiring from the ecu to the coil pack plug today, both cars are the same. I had swapped out the coil packs incase one was faulty, I can't imagine both are duff. Both engines were runners before I started this swap, I am befuddled!

To recap Brian, you say they turn over fine, and there is fuel and spark so it suggests the timing is incorrect.

If the engine is getting fuel but is not starting, then after a short period of turning the engine over without success, the spark plugs should be wet with fuel.  Have you removed the plugs and confirmed this?  If you have, and you definitely have a spark at each plug, and it won't start then leaving aside compression (which we'll assume is O.K.) then it has to be timing.

So if the plugs are getting wet, how have you proved the plugs are definitely sparking?  This engine has coils sitting over the plugs so it is not easy to test as when we had H.T.Leads and you could simply hold the end of one near earth and watch the spark as the engine was spun over.  So you need to make sure you really do have a spark, not just an electrical supply to the coils.

Now we come back to what I still think is the most likely.  These engines were running before you swapped them.  After the swap neither will run.  Since they get their timing from a combination of flywheel, TDC sensor, and injection computer, and wiring, something has to be wrong ON BOTH vehicles.  It would be very unlikely to have two damaged or faulty components  i.e. both TDC sensors having failed; or both ECUs etc. so the one area which I feel the most likely suspect for an error is with the flywheel/pick-up.  In doing the swap something has been changed or overlooked that has thrown the timing out.  You may have to pull them apart again to inspect and compare them carefully.

I have seen engines put in before, which won't then start, and it has been because there was something different with the flywheel...

Now if each flywheel stayed on the original engines, it could be that the position of the pick-up is different, or the sensor wiring reversed.  The TDC sensor wiring is polarity conscious.  We once changed a sensor only to find the engine wouldn't run afterwards, and the fault was that although the TDC sensor plug will only fit one way, the two connections inside it had been reversed, so wrong polarity, and no start.  As soon as we reversed the connections it started fine.

You may have checked the obvious things, and even checked them many times, but as someone once said, once you have exhausted all normal possibilities, you must then consider the other things no matter how much they may not seem right.  Please let me know what you find Brian.

Roy

[BrianM]

Hi Roy, it is nice to have you to bouce this problem off!!
I'm a mechanic of old school, I did my apprenticeship with a BL dealership. So there is nothing I dont know about old allegro, marinas, tr7, mgb etc, then MOTs eventually with the RAC. At this time we had mk3 escorts with the famous duff distributors & other cars where electronics were being brought in to engine mangement. Then I stepped out of the industry until a few years ago. I like to think my fault tracing is logical. I've read up on the system in the Espace & it's pretty basic with just the tdc sensor & a few others to keep it going. I have only swapped out one engine the faulty engine is sat under cover in the drive here. So just trying to get one car going. I was thinking that if the flywheel was fitted in a different position then the wiring would be different from ecu to the coilpack. The reason I brought the ecu over from the donor car was because I suspected this. Yes the plugs get wet, there certainly is a spark, I used easy start down the inlet holding the butterfly open with a screwdriver - the backfire almost blew my hand off!!   I'm going to put my old strobe light on it to see whats going on & i'll report back. Oh, the first thing I did was to bring over the tdc sensor from the donor.
I just tried again & pop, pop, pop, this is before there is a full revolution of the flywheel. That is what makes me think that there is a memory of where the crank stopped the last time it ran.

[mhi]

This is an ignorant amateur's thought process -- offered with caution, to be used with even more caution. When this fool rushes in, he may trample all over the angels...

If you're getting backfiring, at least one cylinder must be sparking while its inlet valve is open. I can think of (only) three categories for a possible cause: 1. control electronics/software faulty, 2. input from sensors to electronics incorrect, or 3. output of electronic controls mis-wired. It seems that 2. has been ruled out by swapping ECU etc., and 1. is well covered by investigations so far.

That leaves incorrect connection of the ECU output. Is there a way to confirm that the spark plugs are connected correctly, so that the cylinders fire in the intended sequence? If cylinder number 1 sparks when the ECU intends to spark number 3, for example, you might get popping noises as described? Connecting the injectors in the wrong sequence would prevent the engine starting but couldn't cause a spark while the inlet valve was open.

Is there any other output from the ECU to the engine apart from spark plugs and injectors? Does it also control valve timing or throttle opening? Presumably it's not possible to connect the spark plugs to the connections intended for injectors.

(My Espace's engine's more primitive, with one coil and a mechanical distributor, so mis-wiring the spark plugs would be easy, but obvious. The family's much newer other car has a coil over each plug, but still with a lead to each, so could be connected in the wrong order.)

If my thoughts are completely wrong, I suppose they may at least give the experts a bit of a laugh.

  - Mark.

[BrianM]

Hi Mark, you are quite right in your thinking. Very good for an amateur! I thought. Today I used a variable resistor on the temp sender & a hair dryer in the inlet hose to convince the ecu that it was a hot engine & thus not flood the plugs with fuel. So I cranked it over & got lots of popping back instead of just pop pop pop & then having to take the front plugs out to dry them. I then used some fly leads to cross the ecu to coil pack connector so I could get it to fire on different cylinders. Still the same, backfiring! didn't seem to make much difference which coil pack I connected to. So next is to scope the tdc sensor & mark up tdc no.1 on the crank pulley so I can use a strobe light to see where it is firing. Will update when I can, thanks for the conversation, all thoughts are welcome & keep my brain ticking

[mhi]

I looked at MR315Espace_JE_A_E_D_Engine.pdf from the vault -- is this right for your car? -- for  the layout. That makes it look as though this engine (Z7X) has 3 ignition coils, each producing sparks for two cylinders at the same time: 1 and 5, 2 and 6, 3 and 4. (Does this remind anyone else of the primitive 2-cylinder engine fitted to the Citroen 2CV?) The ECU controls which pair of plugs to spark based on a non-adjustable crankshaft position sensor.

The camshafts control the valve opening, entirely mechanically, so only one of each pair of cylinders should have any air-fuel mixture in it when the relevant pair of spark plugs fire. The other should be also close to TDC but between exhaust and inlet strokes.

All right, here's my next thing I would try to check: has the cam belt been disturbed during your engine transplant? If the camshaft timing is wrong for either row of cylinders, or both, then you could get backfiring. The electronics could be working perfectly.

As before, do laugh at my errors. I'm a software engineer, not a garage technician!

  - Mark.

[BrianM]

Yes thats the right engine, just a big 2cv!!   Looking at where the slot is in the flywheel that denotes crankshaft position, it is in the same place as my other engine. I didn't even remove the cam covers on this so no chance of the cams out of timing.
I'm back to thinkng that there is a memory of where the ecu saw the crank stop the last time it ran as it pops before it gets to the marker. Or the crank has to be in a certain position after the ecu has been disconnected for a period. It would be different if there were cam sensors that would give the ecu more information. I checked the crank sensor & it appears ok on my scope.

[mhi]

Still in the "ask innocent questions" mode: there's a note about connecting or installing the two pinking sensors the right way round in the manual in the vault. Around page 224 of the PDF, ...

"When the sensors are removed they must be repositioned correctly so that the computer may correct the advance setting if necessary for the cylinder or cylinders concerned.

"Pinking sensor no 1, with the green connector, must be fitted to the front cylinder bank (corresponding to cylinders 1, 2 and 3).

"Pinking sensor no 2 with the blue connector must be fitted to the rear cylinder bank (corresponding to cylinders 4, 5 and 6)."

Are these one of the clues which the ECU uses to work out which cylinder it is supposed to be injecting fuel into, and when to fire the spark? Can they be connected the wrong way round, and would that confuse it enough to cause misfiring? (I'm still puzzled how the ECU can work out which injector to operate, without a signal from the camshaft, in a 4-stroke engine. Perhaps it just sprays fuel out of all of them, and relies on 5/6 of the petrol waiting around until the relevant inlet valve opens.)

[GrahamT]

I'm not familiar with the Espace ECU and the way it works, but have worked on a few others. It won't remember where the crank is when it stopped. It will just sense the gap that Roy described to "sense" TDC. What if the engine was turned without the ignition on? It has to check from scratch.
Even if you think the cam belt hasn't been disturbed, it is worth checking. It may well have slipped a few teeth and is one of the few things easy to check.
It does sound like the TDC sensor isn't detecting TDC at the right time though. Flywheel or sensor positioning issue?
No camshaft sensor is unusual as well! Glad I have a primitive diesel!! :-)

Good luck,
Graham

[BrianM]

There is a marker in the flywheel that the sensor picks up to determine tdc but as you say this is a 4 stroke engine which means that the crank rotates @ a different speed to the camshaft. Also the marker does not appear to be tdc on cly no. 1. With so many modern engines ther are no timing markings other than to time the camshafts & this is done when all the pistons are equidistant from the cylinder head as to allow the valves to open when positioning the camshafts. To determine tdc on no.1 i have viewed the camshaft lobe through the oil filler in the cam cover.   The document you reference to is for the older engine, mine only has the one sensor, interestingly the newer vvc engine reverted to two!
If it does not remember where the crank is when stopped, then how come it fires before it does one revolution before it sees the tdc marker?  Flywheel has not been touched nor camshafts, just complete engine out of one to another. I can see the gap in the flywheel, it is in the same position as other engine, I scoped the senor & it sees the gap. Swapped out sensor, swapped out coil pack, checked wiring, no faults in ecu. Swapped ecu even. Will check ecu to coil pulses next.