Help with over-fuelling TDV8

[Krikkit]

Problem with my L322 - parked it up one night fine, next day the right bank of the engine is spewing fuel smoke (it's white, persistent and stinks of diesel). Coolant level is unchanged and fine, oil level fine so I've ruled out a head gasket failure. Left bank of the engine is completely fine and smoke-free, so ruled out bad fuel or other global catastrophes.

I spotted a very slight crack in the cam cover/inlet on the smoking side, replaced it and no change (I wasn't really expecting it to be fixed but needed doing). Turbo replaced with a recon and no different. 4x replacement injectors fitted and no difference. I have swapped the MAF, MAP and throttles between sides with no difference.

There are now no visible leaks of any kind anywhere in the top end. The inlet isn't full of oil or anything to indicate a bad oil seal.

Reading the various sensor data with my laptop, I have:

• MAF reading on the smoky side is very high, roughly 10x higher than the good side (6kg/hr vs 60kg/hr), and the airflow from the airbox feels correct (the smoky side is drawing a lot more air)
• EGR values the same to both sides (both commanded and actual), EGRs were new in October
• Throttles are moving and the same values both sides
• Turbo actuator is free and operating correctly
• MAP sensor reading about the same for both sides
• Intercooler outlet temperature for the smoky side is much higher
• Checked the wiring loom back to the ECU from the injectors, no funny cross-overs or anything
• No stored trouble codes

Any ideas? My current thinking is the ECU has somehow failed, as all the mechanical causes seem to be resolved.

Edit: finally sorted a video

https://youtu.be/UL-Uw-VvpPE

Edited by Krikkit on Tuesday 25th July 21:44

[Krikkit]

Said smoky side, it's actually more pronounced than it looks here.

[Krikkit]

Bigmanmike. said:

My car did that when egr valve was blocked. Egr replaced and fixed bro. Could be glow plugs too happened with me. u prob don't have egr because its so old? Mine didn't have any codes either untill 8k miles later for egr

EGR working as it should and not blocked, glow plugs not relevant as it doesn't change if warmed up for a few minutes (and it's way, way more fuel than normal)

[Krikkit]

Peanut Gallery said:

Could an injector have failed open? - How hard to test the residual pressure in a fuel rail on either side, does the pressure drop faster on the smokey side when engine is turned off - or is there one cylinder that the exhaust is cooler than the other 3, meaning that cylinder has not woken up?

The symptoms are as if they're all wide open - unplug one injector and it marginally improves, but nothing significant. Can't get to the exhaust manifold while it's running as it's buried too deep.

I've swapped all 4 for used replacements, taken from a running lump that I've no reason to think was broken.

Peanut Gallery said:

The fact the air flow meter thinks 10 times more air is going in, the ECU could be trying to dump 10 times more fuel into that side - if you swopped the leads to the air flow sensors over (or swopped the MAFs over), does the ECU then over-fuel the other bank?

I've both swapped the MAFs (no change) and tried to trick the ECU by plugging in the smoking side to the one on the OK side, no change. Unfortunately I initially couldn't decide whether it was chicken or egg, whether it was the turbo stuck in maximum boost pulling extra air (and therefore more fuel to correct it) or the opposite way.

[Krikkit]

Megaflow said:

This is an out there idea... but I wonder if there is an air leak and all the excess air being pulled through the MAF is going to atmosphere not to the engine. The engine thinks it is putting in enough fuel to deal with all the air, but the air isn't there, so it can't burn the fuel, hence why it comes out the back unburnt.

Just a thought.

Thanks it's a good thought indeed - the inlet on the smoking side is full of smoke too (EGR recycle presumably), so it's effectively its own smoke tester. Unless the intercooler has popped between the two sets of cylinders, and it's then going into the "good" half and being combusted, there's no leaks.

[Krikkit]

Megaflow said:

Just for the sake of clarity, when you swap the MAF’s between banks, it is still the same bank with a massive mass flow reading, correct?

Correct, the faulty side always shows the high reading.

From the highly scientific holding your hand next to the airbox outlet, the MAF reading is correct - the smoking bank is drawing a massive doubt more air than the ok side.

[Krikkit]

coetzeeh said:

when last were the turbo inlet pipes replaced?

I noticed excessive smoking on one side of my TDV8 recently and local Indie found a split one side - did not show any error codes.

I've no idea, but I've checked them and they're not leaking (either the large plastic inlet pipe, the aluminium outlet pipe to the intercooler, or the intercooler to inlet manifold pipe)

[Krikkit]

Peanut Gallery said:

That air must be going somewhere, I am guessing!!

Do you have access to a small air generating device, or even better a smoke machine? - blow air into that inlet, and look for where it is coming out? - My money is more and more on that MAF telling the ECU there is a ton of air coming in, dump more fuel now!

There's no leaks - the high fuel content means that the air inside the inlet is effectively a smoke machine of its own, remove an inlet pipe 10 minutes after the engine is off and it's still full of smoke.

[Krikkit]

Megaflow said:

The ECU is going to inject fuel based on that number, and judging by the grey smoke and unburnt diesel coming out of the back, that air is not making it to the cylinder to burn with the fuel. Very curious.

Indeed, and is why I originally went down the route of the turbo being stuck in maximum boost configuration originally. But then if that all seems normal, could it be the opposite way?

Megaflow said:

Have you done a compression test?

No, but it ran perfectly the night before the issue started, I did about 80 miles in it with no noticeable issues. I don't have the kit for a diesel comp test.

Megaflow said:

Krikkit said:

There's no leaks - the high fuel content means that the air inside the inlet is effectively a smoke machine of its own, remove an inlet pipe 10 minutes after the engine is off and it's still full of smoke.

This comment is interesting. Are you saying the inlet manifold is still full of smoke are turning off? If so, there shouldn't be smoke in the inlet and it sounds like it is stuck in the inlet.

The EGR is position is running 5-10% from a cold start, so I'd expect the fuel-rich smoke to be cycled back through, it's thinner than the exhaust.

Megaflow said:

Have you got any error messages when you scan it?

Nothing logged.

[Krikkit]

Thanks all for continued suggestions, really appreciate it!

Megaflow said:

A thought just occurred to me, does it have inlet throttles?

It does, and both sides are working (and swapped between them). The data when running both sides were showing the same values.

Peanut Gallery said:

I am no diesel mech, no where near clever enough! - But.. In the old days diesels used to drink as much air as they could, and then they worked as hard as the amount of diesel that is squirted in.

With that in mind, if the air was being pushed into the engine, and the extra fuel was being pushed into the engine, why is the fuel not burning and taking the engine to max revs?

That was my thought as well, but it's running so rich it's not combusting properly, hence not producing enough power to raise the revs.

Peanut Gallery said:

Are there any cross-over pipes between the banks? - would a dump valve be sticking open, allowing the turbo to suck air in and just push it straight out the dump valve?

Nope, they're effectively completely independent in terms of gas flow and sensors etc - two of everything.

[Krikkit]

Thanks guys, I'm pretty sure that's not the issue as I can set the EGR to 0%, and you can hear it closing, but for the sake of an hour or so removing the inlet and loom I'll triple-check it

[Krikkit]

The EGR has a separate position sensing circuit, so the ECU can read its requested and actual positions, if they don't match it can adjust the opening within certain bounds, when it's outside the adjust limit it'll throw a code.

Currently they're <1% different between requested and sensed position, but there is a chance that's the issue and both are incorrect. That wouldn't really explain the high airflow at the inlet, but definitely worth checking.

[Krikkit]

Megaflow said:

I have done some googling on this, and I think it is worth removing the EGR valves for a closer inspection.

This thread has very similar issues and the fault was the head of the EGR valve breaking off, there was no associated fault codes because the valve was still moving so the ECM didn't know there was anything wrong.

https://www.fullfatrr.com/forum/topic33905-15.html

Thanks, as I said I don't think this will be the issue as the amount of fuel/smoke is much more pronounced than your usual bad EGR, and they were new not long ago, BUT I'll fetch it out this weekend to test.

Megaflow said:

Also might be worth checking the combi IMAP/IMAT sensor as it seems they get gunked up which won't help.

Checked/swapped both MAP and MAF/IAT (which are combined). The MAP I keep removing and cleaning every few minutes of running as it's getting coated in fuel/oil stuff.

[Krikkit]

Had a pair of OEM EGRs in October, so shouldn't be a quality issue, but like I say I'll check it anyway

[Krikkit]

Piersman2 said:

Have you considered that the EGRs may not be working properly?

On my old 3.6TDV8 it was running ste and I put it into my local specialist. They checked it all out, no error codes so suspected turbos were on way out. Swapped both, made no difference although old ones were starting to go.

Much head scratching, no obvious reason what the problem could be. Eventually they started a strip down to try and find something wrong and had their eureka moment when they took of the EGR valves... one of them was missing the end of the valve stem. The car thought the valve was operating as expected, the garage had been able to hear it operating as normal, but it just wasn't sealing (or opening) as it should have done, effecively it was just wide open all the time.

My paperwork for the car showed that the EGRs had been replaced by the previous owner several tens of thousands of miles previously, but he hadn't used JLR EGRs, he'd got some cheapies from China, and the valve head had just snapped off.

Made the car run like a bh, chugging and smoking all over the place.

Well I owe you a pint (or several) for this one - this was exactly the issue, I think it's a design change as the OEM originals I took off in October have circlipped-on heads to valve stems, this one is screwed and snapped off around the middle of the thread.

Found it exactly as in the pic when I removed it from the cooler.




This was the smoke level while it was broken, hopefully someone else will find this thread and avoid expense and head scratching!

Edited by Krikkit on Tuesday 25th July 21:44

[Krikkit]

Megaflow said:

Boom, there it is!

It is easy to forget with modern ECU's that they will only throw a fault code for what they can 'see'. In the case of this failure, as far as the ECU is concerned, the valve moves, so it is fine.What is can't see is the valve has failed mechanically.

Indeed, it would've been much higher on my list for failure if it wasn't right in its supposed minimal chance of failure... The annoying thing is I'll need to re-do the other side as well, wouldn't surprise me if that falls to bits as well.

[Krikkit]

Piersman2 said:

Only because I'd trail blazed a very similar experience to the OP with my garage as they scratched their heads over it for 3 weeks, and he'd clearly already done most of what my garage had done to try and solve it.

Genuinely pleased the OP found it and has got it sussed, nice to be able to pay back a little to the karma scales sometimes!

I'll try and pay it forward.