Jump to content

TDV8 starts but dies instantly


Escape
 Share

Recommended Posts

I've picked up the Range Rover Sport from a good mate's father. It's a 2007 TDV8 that seemed to lose power on the last drive, barely made it home and now refuses to start. To be exact, it fires up pretty quickly but dies before even settling at idle.  What I know so far:

- No fault codes (or none that the Lynx can see anyway)
- Fuel supply pump is running and there is fuel getting to the high pressure pump (haven't measured the flow yet)
- When cranking  there is fuel getting to the common rail (cracked lose an injector pipe and got a good squirt of diesel)
- Disconnecting the fuel pressure sensor doesn't seem to make a difference. Lynx doesn't seem able to read the sensor, Torque does give a value but that seems too high.
- RPM can be read, so CKP should be OK.

I know there are several members with a TDV8, hopefully someone can give me some pointers so we can pinpoint the fault.

Thanks,

Filip

Link to comment
Share on other sites

46 minutes ago, garrycol said:

Get the codes read with a proper code reader - if the engine will not start there will be fault codes in the system.

The Lynx isn't a proper code reader? :blink:

Link to comment
Share on other sites

Good call Paul, but not that easy to check. She on the bumps now and not easy to push from the trailer to the lift.

I did investigate a bit further this evening:

- Tried starting her again, same thing, fires up immediately but dies just as fast.
- Checked again for codes and did get a result: MAF circuit B frequency low.
- I checked for any blockage and then unplugged both MAFs and tried again. Same result, only now with additional faults for circuit A and IAT (as was expected). With all the starting I did get some smoke from the exhaust, greyish unburned diesel. So fuel is getting to the cilinders, just not being burned as it should. This also seems to rule out a blocked exhaust.
- Working my way along the air intake I had a look at the throttle valves. A bit oily but definitely not gunked up and both open.
- On a hunch I tried starting with the intercooler hoses disconnected from the manifold. She fired, tried to idle and then died. But it did last just a bit longer. With no correct reading from the MAFs that's not that much of a surprise. That seems to point to a blockage in the intake. It could be a failed turbo or blocked intercooler, but I find it strange it affects both banks. As far as I know they are completely separate from the air filter on. I did notice that with just one intake hose disconnected the improvement was less, so either both intakes have a problem or there is a commons cause. I ran out of time today, tomorrow I intend to blow through the intakes from the airfilter to the throttle housing. I've also thought about rigging 2 hoses from the MAFs to the throttle valves, to have a closed circuit but without the turbos and intercoolers.

Filip

 

 

 

Link to comment
Share on other sites

I am thinking fuel pressure even though the codes aren't suggesting it, bad fuel or blocked filter even. But while you have all the intake plumbing hauled out then a squirt of easy start? The fuel in the exhaust may just be from repeated starts. Does the fuel guage work? Is the ECU shutting down?

Link to comment
Share on other sites

Filip

One thing that springs to mind is the EGR side of things. Whilst not showing a fault I am very suspicious of anything that requires it's own exhaust in order to breathe. 

Otherwise you just need to work through it methodically. I have three TDV8's and I just keep plugging in, researching fault codes, changing parts and repeating the cycle until I make progress.

Link to comment
Share on other sites

Simon, yeah, I don't like EGRs either. Which is why I had a look at the throttle valves. I did not yet disconnect the EGRs, and yet there was an improvement. I could try jamming the throttle valves open, so the engine is sure to get clean air. I wouldn't mind researching the fault codes and working through it, but as said there aren't any (apart from the MAFs after disconnecting). What reader are you using?
I also don't have spare parts to just throw at it, would be easier if it was a P38...

Blanco, my first thought was fuel pressure as well. Now it seems to point more to the air intake side of things. Fuel guage is working, distance travelled and indicated range is plausible. The fuel can't be more than a few months old, the car was in regular use until a month or so ago, be it mostly short trips.
I'm getting sensor readings from the ECU while starting, so it seems to stay awake.

Filip

Link to comment
Share on other sites

 

17 hours ago, elbekko said:

The Lynx isn't a proper code reader? :blink:

2 hours ago, garrycol said:

No idea but if it is not reading the codes then it is clearly not suitable.

It is reading the codes and sensors, just not showing any that would explain the engine dying. Lynx has served me fine over the years on other vehicles, though not as user friendly or complete as the Rovacom. The only thing I'm really missing is a reading of the fuel rail pressure on the TDV8, like it does on the TD6.

Link to comment
Share on other sites

I was responding to the other guys comments about Lynx but in your first post you did say "No fault codes (or none that the Lynx can see anyway)"  - you did not provide any qualifications but I now see that you are now getting some.

Link to comment
Share on other sites

@Simon_CSK today's tinkering seems to confirm your EGR theory.

First the good news, I got it to start and idle more or less. Too low on revs and lumpy, on the verge of stalling. Touch the accelerator and it dies. Now for the strange part, I didn't really change anything. I was looking at the intake system again, rigged up 2 hoses directly from the MAF to the intake but that made things worse again. The longest time the engine kept running was with the right bank all plumbed as standard and the left bank open at the throttle valve. What struck me was the amount of smoke coming out of the intake after each attempt. It looked very much like exhaust gasses. Only way those could get into the intake would be via the EGRs (don't even want to consider any worse scenarios!). But the smoke made it all the way back to the airfilter, which means it had to pass backwards through the turbo? 
If one or both EGRs are stuck open, that would explain the difficult starting and stalling. So I guess I'll have to go in. At least the EGRs are not buried under the cylinder banks as on the TDV6...

Filip

  • Like 1
Link to comment
Share on other sites

Just seen this and I would agree that EGR's are well worth a look. Scarily the head of the valve can detach from the stem which means the stem will move about freely and give you no EGR fault code (ECU thinks it is operating) whilst it is actually letting as much exhaust gas as possible through that bank.

From where you are getting the EGRs out is quite straightforward job - you can blank them on the 3.6 without the EML coming on or showing any codes

 

You are correct that on a 3.6 that the intake is totally separate for each bank after the air filter. On a 4.4 there are two filters so they are separate from the start

  • Thanks 1
Link to comment
Share on other sites

On 6/15/2021 at 9:31 AM, Escape said:

What reader are you using?

Filip

I am using an ICarsoft one for Land Rover and Jaguar. Fairly basic but does do the job I need it to do. Did want to buy the Lynx but when you have as many different models as I do then it becomes very expensive however now having practice with it and getting results I may invest in a Lynx for one model and add to it when the need arises.

15 hours ago, Escape said:

@Simon_CSK today's tinkering seems to confirm your EGR theory.

Filip

I am getting good at this diagnosing lark :rofl: Just wish I could do it for my own problems :o

Link to comment
Share on other sites

@L19MUD thanks a lot for the info and especially confirming you can blank the 3.6! I forgot to mention only one exhaust (RH) has black spots under it from the repeated starting, seems to confirm the RH isn't doing much, likely EGR stuck open. Will dive in and blank tomorrow.

@Simon_CSK the reason I got the Lynx is because it was a very reasonable price for the complete package. I don't want to be limited to one model, as I never know what will turn up next. I am disappointed there doesn't seem to be any more updates coming, now only for the Lynx Evo. I've heard good things about the ICarsoft, so will have a look.

Link to comment
Share on other sites

Can't really offer much insight other than what's already been provided. My only experience with diagnostics tools has been with the IID BT from Gap Diagnostics and I know for a fact that reads a hell of a lot more than most other more expensive tools.

My only problem similar to this was a dead lift pump in the tank but that failed to start, would just crank and crank.

I'm 99% sure that I could get all the fuel rail pressures using the IID Tool on my old 3.6 so the fact that you can't implies it's not as capable. I've now got a 4.4 and also an IID Tool but need to transfer it over to my ownership. Will try and find some time to look at it today to see if it dumps rail pressures.

You said it reports some codes - can you list those? I've usually found that the most innocuous code is actually the most relevant.

Link to comment
Share on other sites

9 hours ago, Escape said:

 

@Simon_CSK the reason I got the Lynx is because it was a very reasonable price for the complete package. I don't want to be limited to one model, as I never know what will turn up next. I am disappointed there doesn't seem to be any more updates coming, now only for the Lynx Evo. I've heard good things about the ICarsoft, so will have a look.

Filip

I bought the ICarsoft in January and was looking at the price of the kit needed. My brother is in the motor trade and has a comprehensive reader that I have access to so was looking for something specific to Land Rover's (Added bonus is that made my brother crazy) to allow me to resolve the problems with my cars at home. I didn't know if I could use the technology or if "I was too old to learn" :rofl: so rather than investing £1500.00 for the Lynx (That would give me all the cars I currently have) I took a safer option to learn first.

Link to comment
Share on other sites

A little update, not much good news unfortunately...

Last weekend I made and fitted blanking plates for both EGR valves. No discernable difference, in fact I couldn't get the lumpy idle to last for a bit (as happened last week). Rechecked fuel supply pressure while cranking and as there was a slight drop I pressure as the engine tried to fire, so decided to swap the filter for starters. That seems to have cured the slight drop, but hasn't improved the starting. But this does seem to rule out the fuel supply pump. 

While starting today I had the oil filler cap off for a change. A bit of smoke, maybe more than I'd expect but I guess some blowby is normal. I couldn't feel for pressure pulses and at the same time turn the key, so that will have to wait till later today for a pair of extra hands.

Starting to reach the end of my tether...

@Simon_CSK the Icarsoft certainly is cheap! If that had been available, I might have opted for it. Mind you, my Lynx Pro was 'only' about €1000, for full LR coverage up to D4/RRS.

Filip 

 

Link to comment
Share on other sites

Fairly lengthy post inbound... I've been genning up on the engine from the workshop manual and trying to remember what I learnt previously.

EGRs

On the subject of EGR valves I don't think you can do the old trick of simply blanking them off on a 3.6TDV8 - it complies with ECD4 for emissions which I think mandates that the engine needs to be able to detect when the EGR valves are inoperable. If you physically blank off the valves without mapping them out of the ECM then it's likely to get confused. In fact you don't actually need to do any physical mods to blank off the EGR valves (in fact I think it's generally advised not to bother) because you can map them out in software and tell them to simply shut off the whole time.

I don't think the "monitoring" on the 3.6TDV8 is particularly intelligent so when you physically blank off the EGR valves it just tries to compensate because it's not behaving as expected (perhaps reducing performance in order to meet emissions requirements). On the more moden engines such as the 4.4TDV8 where the DPFs became mandatory I think that they have to do more active EGR monitoring so are even more "challenging" to circumvent. My inclination would be, depending on how much you're willing to invest in getting this running, either get them mapped out properly (but the mappers usually want a good running engine first) or buy some new replacement EGRs and install them to get things back to standard. If I remember correctly it was £138 for a pair of them when I replaced mine so not a massive investment.

Fuel Pressure

Can you clarify where you are at the moment - you have the engine running indefinitely but a very lumpy idle? Previously you had it firing up (still lumpy?) but then dying after a couple of seconds?

Have you got a copy of the workshop manual? It's available from the fullfatrr.com wiki. Here is an interesting plot from the manual about what the rail pressures should be (presure in bar on the left, RPMx100 on the bottom, blue is high boost, red is low boost).

image.thumb.png.bb1b280324d7af27c5111743fadef109.png

Back to EGRs

Interestingly in the Emissions Control section of the workshop manual it lists if you have the following symptoms:

  • Difficult to start
  • Poor / Erratic idle
  • Lack of power when accelerating

Then the possible cause is EGR valve(s) stuck open - which is where we've reached a consensus so far. However based on the comments above at the start of the post I don't think you can simply blank off the EGR valves and expect everything to function normally because the ECM will still be trying to compensate for things not behaving as they should. Further testament to this theory is that there do appear to be some DTCs highlighting that the ECM can measure the flow through each EGR valve.

I don't know whether you can do it on your Lynx but there is a test to check if the EGR valves are operating correctly. Warm up the engine and turn the ignition off. Tell the EGR to go to 0% and then 100% PWM, if it's functioning the reported value should be between 5 and 95% (I remember being able to do this sort of live with the GAP Diagnostics Tool). The fix for this is new valves.

Electrics

Another possibility is that the ECM is getting dodgy signals from various sensors (possibly a chafed wire or even a dodgy sensor). Everything on this engine is monitored so given you've confirmed that air and fuel are getting through correctly it's making me lean towards an electrical issue. Basically the Land Rover ECUs will do pretty much everything they can to prevent someone destroying the engine (compared to stories I've heard of other brands which will carry on running but then detonate catastrophically).

Camshaft Position Sensor

Located on the rear of the left hand cylinder head. It's a hall effect sensor which has a 5V, ground and signal output. It's used by the ECM to determine TDC of #1 cylinder. If the ECM detects a fault (total failure or unexpected signals) then it should log a fault and will continue to run the engine but deactivate the boost pressure control. Having said that if the fault is logged then once you turn off the engine supposedly the engine will crank but won't start until you clear the fault.

Crankshaft Position Sensor

Located on the rear of the engine block on the left hand side. It produces a square wave signal proportional to engine speed. Again a hall effect sensor to pick up on a ring on the rear of the crankshaft. There are two missing teeth that represent 12° of rotation.

I'm pretty sure that the ECM uses this signal to drive the tacho on the dash so if that's reporting the engine RPM correctly then it's probably OK.

MAF Sensor

Again if this fails then similar symptoms to what you're seeing could be expected to be seen.

Conclusion

Still no closer I feel to diagnosing your issue - are there any faults (even transient) that you've seen with the diagnostics tool? Any faults might give an indication of what's going on - I'd be very surprised if nothing has been logged, if nothing is logged then it really makes me doubt the validity of the reports given by the Lynx.

  • Thanks 3
Link to comment
Share on other sites

2 minutes ago, L19MUD said:

EGR's on my 2010MY 3.6 blanked for the last 2 years/15k miles no bad effects and no fault codes

I don't think it's guaranteed that the ECM will detect a fault - ultimately if everything's operating as expected then why should it log a fault? As I said it's not the most intelligent system, but if something else on the engine is worn / misbehaving etc., then it might cause issues.

I've heard reports of both sides so to speak - those that mechanically blank and experience no issues and those that do have issues. It may be down to usage and driving style - ultimately if you can keep the emissions down and everything burning correctly then it may not be an issue. Someone else who just potters around town might then have problems.

Link to comment
Share on other sites

Thanks a lot for your effort Ed! 👍 I do have the manual and have been going through it looking for clues.

I'll try and answer all your questions:

- I can't get the engine to run anymore. That only worked last Tuesday, while I was looking at the intake and had one intake hose disconnected. Now it starts, tries to settle at idle, very lumpy and usually dies within a second or so. Just enough to get a couple of revolutions after the starter has disengaged, rpm rising to 600-700 once and immediately dropping, bouncing around 500 rpm a couple of times before stalling. It feels like it just needs a little bit more to catch and keep running, like last week. That was a very lumpy and rough idle, but last until I turned it off. Tacho signal confirmed by the dash and diagnostics, so I agree the CKS should be OK.

- EGRs have both been blanked, from what I read on other forums and confirmed by @L19MUD that shouldn't throw any codes on a 2007 3.6. Even if it does throw a code, I don't think that should prevent starting. Especially if a faulty EGR was the problem in the first place. As per above, I certainly can't get the engine running to play around with EGRs.

- Fuel pressure: I can't read the fuel rail pressure with Lynx (it has no problems on other engines like the TD6), Torque gives values and while those seem off you could see it rise when cranking and falling again when stalling. We did get an error code for FRP when we tried disconnecting it to see if that made a difference (it didn't). What we did was measure the supply pressure from the pump in the tank. I was told those have a habit of running but failing to maintain pressure. It's regulated to only 0.5bar so I'm not sure how important it is, on the other hand with such low pressure any drop would mean a big difference.

- I'll recheck the wiring/connectors were possible. At the moment we're leaning towards a mechanical problem, like skipped timing chain or something else causing loss of compression.

- The fault codes I saw were all for stuff we disconnected: fuel rail pressure, EGR and MAF. I'll see if any come back ater the next attempt when I've confirmed all connectors are properly seated.

Filip

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy