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Dead Discovery Td5 ECU after wading?


plasticbadger
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I did a little too much wading in my Td5 last week. We had a lot of flooding locally and eventually I waded through 3.5 foot deep water. The truck stalled as we came out the flood, a quick check showed some water in the air box, but limited as it has a snorkel fitted (slight leak somewhere?). The truck then restarted fine, but stalled again a mile down the road. Again it restarted fine. I then went to work on Friday and did 70 miles trouble free, but then it died as I came into our village and won't restart.

The local garage has had a look and think the ECU has failed.

Is this likely with wading that deep? The ECU box was dry the next day when I checked, but signs of water around it. The ECU plugs are well packed with Vaseline following recent oil issues!

At the moment the truck just cranks and doesn't fire. The fuel pump runs and the engine management light is on.

How can I diagnose the ECU and get it replaced before work next week!!

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I doubt it will be the ECU if it has worked after the wading, especially for 70 miles as this is more than enough time for it to 'dry out' Inside the metal box the electricals are coated with some sort of varnish. All the ones I have seen that have died during wading have serious damage to the capacitors that fire the injectors.

I would suggest the most likely candidate is the crank position sensor or it's conector.

I'm not sure how to test one and they aren't cheap (though cheaper than an ECU). You need to find someone local to you who has a nanocom.

Have a look on the D2boysclub forum...

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its not exactly been perfect weather for things drying out recentlyif i were you i would unplug all ECU connections (providing it wont forget what it is) and spray WD40 on all contacts, both on the plug and the loom. and other connections about the engine bay that control engine parameters.

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its not exactly been perfect weather for things drying out recentlyif i were you i would unplug all ECU connections (providing it wont forget what it is) and spray WD40 on all contacts, both on the plug and the loom. and other connections about the engine bay that control engine parameters.

First thing I did the next day Mikey! Went through all connectors, sensors, earths, etc checking they were tight and dry, then liberally applying WD40. No sign of water in anything and made no difference.

Other than the one comment I've found regarding the fuel pump not running in event of crank position sensors failure, everything I read points to this. Can anyone confirm about the fuel pump not running if the CPS has failed?

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RAVE says:

In the event of a CKP sensor signal failure any of the following symptoms may be observed:

l Engine cranks but fails to start.

l MIL remains on at all times.

l Engine misfires (CKP sensor incorrectly fitted).

l Engine runs roughly or even stalls (CKP sensor incorrectly fitted).

CKP does not have any backup strategy and if it fails the engine will stop running and fail to start.

No mention of fuel pump although that doesn't mean anything. Is the MIL lit?

IME when someone says "the ECU has failed" that usually means "I have no idea what's wrong but let's try swapping parts at random".

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there is a small chance that when wading, (i assume you didnt have wading plugs in) that if this is the case, the pressure of the water, MAY, not definatley. but may have moved the CKP sensor out of position. assuming it is in the flywheel housing that is..

just a thought.

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IIRC the fuel pump still works without CKP, at the very least the initial priming as the ECU can't know if it works or not without the engine spinning. And even then it doesn't really know the engine is spinning without the CKP.

It may have failed due to the water, or moved, or something got inside the bellhousing while wading and damaged it... it's certainly a valid culprit.

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RAVE says:

In the event of a CKP sensor signal failure any of the following symptoms may be observed:

l Engine cranks but fails to start.

l MIL remains on at all times.

l Engine misfires (CKP sensor incorrectly fitted).

l Engine runs roughly or even stalls (CKP sensor incorrectly fitted).

CKP does not have any backup strategy and if it fails the engine will stop running and fail to start.

No mention of fuel pump although that doesn't mean anything. Is the MIL lit?

IME when someone says "the ECU has failed" that usually means "I have no idea what's wrong but let's try swapping parts at random".

I definitely have "engine cranks but fails to start", but when you first turn the key to crank there's no MIL, then within 1 second it illuminates.

The garage were quite honest, I dropped it off to them on Christmas Eve and they had a look for 20 minutes, gave me a call and said "we're not sure what's broken yet, could be the ECU"

there is a small chance that when wading, (i assume you didnt have wading plugs in) that if this is the case, the pressure of the water, MAY, not definatley. but may have moved the CKP sensor out of position. assuming it is in the flywheel housing that is..

just a thought.

As per most Td5s, my wading plug has never been out, I tried it once, but it wasn't shifting easily. In the depth of water there's every chance both sides of the CKP got very wet.

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Most LR garages worth using would have a spare Td5 ECU that they would use to verify the existence - or not - of an ECU problem. It only takes 5 min to reprogram one into a vehicle to see if it fixes the problem and it's something I would have done with a non starter at a very early stage, to rule it out.

CKP sensor doesn't show a fault in the ECU if it's u/s.

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The symptoms you are describing happen occasionally on my TD5 for no apparent reason. I have presumed the problem was a intermittent fault on the immobiliser I get out of the car turn on the alarm/ lock it using the key fob and then reopen it and usually it starts first time. However sometimes it fires and runs with the S & M lights flashing. If i repeat the procedure they then go out

Might be worth a try

Hugh

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  • 1 month later...

A bit of a late update, but I thought I'd close this one down for future reference.

The main non-start issue seemed to be 'open circuit injector harness', so once the harness was dried out and WD40ed the truck ran. Obviously my first attempt at drying everything out wasn't sufficient. Following this and drying out all other connections we were left with a fault code for the air mass flow meter. The truck ran, but had no power and drank fuel, plus I was getting an occasional cough. I removed the ECU and took it apart. It seems to be 99% sealed with a hole in the front bottom corner that had allowed water in, causing some signs of shorting out along the base of the circuit board. Again dried out and applied WD40. I also fitted a new OEM AMF. At this point the truck ran fine, but lacked some power, but no smoke or other outward signs.

I read somewhere on here that you can get this power loss with a slight air leak in the fuel filter, which I had undone to check for water. I dully replaced the filter with a Landrover one and it seems now all issues are resolved. Oh, and I found the snorkel was still drawing some air through the air box drain, so I sorted that out.

I think I've learned my lesson and will be keeping my wading down to a sensible depth!

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  • 11 months later...

A long time since I started this thread, but I wanted some help / advice.

So after the above post it seemed that all was not well, the truck was well down on power, just better than with the MAF gone. I've run the truck for 20,000 miles since then, as I took it to Croatia and its now back as my daily driver. It runs fine, but struggles to start from cold and ticks over a little rough and is very rough at high revs. Running it along side other td5s on the motorway I would estimate its 25-30% down on power. Since the above post I've done:

Checked all air inlet pipe work for leaks

Changed the air filter

Cleaned the crud out the inlet manifold and the MAP sensor

Changed the injector seals

So I think that now leaves me with

Pull the injectors again and measure the piston heights to check for a bent conrod

Turbo fault?

Fuel pump fault, you can hear it running, but it does sound different to some others I've heard

Fuel pressure regulator fault

Any other ideas?

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[1] Do a compression-test.

[2] get the fault-codes read.

(1) will tell you if you've got any bent conrods; (2) will guide you if there's anything like imbalances between cylinders.

Did the garage you first took it to show you the diagnostic log from the ECU before telling you they thought it was the problem? If not then I['d go back to them and ask for a refund: You shouldn't even _think_ of swapping hard parts before looking at the logs and seeing what the actual fault is.

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Thanks

[1] Do a compression-test.

[2] get the fault-codes read.

(1) will tell you if you've got any bent conrods; (2) will guide you if there's anything like imbalances between cylinders.

Did the garage you first took it to show you the diagnostic log from the ECU before telling you they thought it was the problem? If not then I['d go back to them and ask for a refund: You shouldn't even _think_ of swapping hard parts before looking at the logs and seeing what the actual fault is.

Thank you,

1) how do you compression test a td5? I have two glow plug seized into the head, but even then there's only 4! There's no way of putting the compression tester in the injector holes.

2) it's not showing any engine related faults. I got the log from the garage, loads of 'no circuit' and 'low current' to start with, once the MAF was replace it went back on the code reader and came up with nothing. The management light isn't on.

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A "Compression test" these days is done electronically - it's more appropriately described as a "cylinder balance" test.

Part one is where the test system disables the injectors then cranks the emgine. A current/voltage probe hooked to the starter motor measures the current taken on the compression stroke of each cylinder [it of course knows which cylinder is currently on the compression-stroke by reading the crankshaft- and camshaft-position-sensor data].

A few 15-second cranking sessions are needed to get consistent results.

Part two - the engine is started, and the test system snaps the throttle open letting the engine run to the rev-limiter just as during the standard MoT emissions-test, then brings it back to idle. It repeats this until the on/off throttle behaviour is consistent. This establishes the baseline response-curve. Then the test-system disables one injector and repeats the full-throttle-acceleration test. It does this for each injector in turn.

Final test is a ~scatter~ test where the engine's held at a series of set RPMs through the range then individual injectors are "missed" for a single injection in a controlled random pattern.

The result is a series of tables and graphs which show to what extent each cylinder is 'pulling its weight' - it can spot a cylinder that's only a percent or two 'down' on power compared to its buddies, and suggest the likely cause too.

Best thing is, it's all automated: I had it done on a Mercedes a while back and the guy just hooked it up to the test box, hit "start" then we went back to the office for a coffee while the computers did all the hard work. They got the right result too ['soft' hydraulic valve-lifter on one cylinder].

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One of the reasons I did away with the MFU (Multi Function Unit) on my Disco was the annoying feature that the rear wipers wont work with it fitted unless all the doors are closed - just what LR's rationale for this feature is/was I'm at a loss to explain. I despise all car electronics, they are unpredictable and a constant cause for concern -- the only one remaining in the beast is the electric window unit now relocated behind the window switch unit in the centre console instead of in its original inaccessable location up under the glove box.

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