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D3 - Engine Bay Everything under the bonnet

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  #31  
Old 19th August 2017, 11:15 AM
erubus erubus is offline
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Another thought. I could measure the amount of fuel spilling from the injectors by physically measuring the fuel return to the tank at idle. If it is know what the fuel return volume [i]should[i] be at idle then it would be simple enough to see whether it is spilling too much. Is this a piece of information that anyone has published though?
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  #32  
Old 19th August 2017, 03:19 PM
Mechcanico Lee Mechcanico Lee is offline
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The item circled in the pic is a DRV ...it's part of the high pressure rail assembly, the IMV is on the high pressure pump .

To do a proving test on the pump ideally you need to either take control of imv duty or 'dead head ' the pump , cap off all injectors , disable drv , this is so you are taking away all the routes that the pressure can escape from , we use a pressure block here with an extra rail pressure sensor in it so we can confirm the cars own rail pressure sensor is reading correctly and also the block had a safety blow off valve that lets the pressure off when it gets to 2000 bar !!

Taking the submerged pump out of the tank sounds a big faff , plus the a8 has a saddle tank so it will have a suction jet assembly for tank level equalisation....to much to be messing with at this point .

You could do spills without any fancy gear , just check one injector at a time , a good one does not really spill so much and bad one squirts everywhere, you tube injector spills ...loads of vids showing you what it's about .

I think from what we know up to now with slow cranking over and lack of gear to rule out the other items I think chasing down the slow cranking is the best pathway for now , could you post up a vid of it cranking over so I can hear it cranking over .
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  #33  
Old 22nd August 2017, 08:34 PM
erubus erubus is offline
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I now have a new theory having had a couple of days without being able to get on the forum. My theory is that there are a combination of factors at play here. 1: I reckon the starter is weak 2: I think there may be one or more injectors spilling excessively - I have not yet tested this though and 3: despite all my previous protestations to the contrary, the battery aint great.

After opening the doors and boot but not switching anything on, connected up, the battery is reading around 12.2v on average, droping to about 10.4v when cranking. This is after having driven for 45 minutes coming home from work.

The old battery, which lives in the boot as a booster that will usually start it if the temp is below 65 degrees, sits at 12.66v but is only 800CCA and 850Ah. It still doesn't start the car.

I have found it surprisingly difficult to find an amps clamp that can do DC and is rated up to 1000A. I am going to try the electrical engineering technicians at work tomorrow and see if they have anything. Can get plenty of AC ones no problem!

When i attach the jump leads to the car, if I leave them for a minute with the DMM connected and wait for the voltage to rise to 12.88v or above, it starts every time. Anything below 12.88v and it just turns over regardless of which battery is connected.

Hopefully there should be a couple of vids attached to this post showing a cold start, hot running, switch off and restart attempt and a hot start attached o the jump leads.

Vids not uploading for some reason, just sticking on "sending request" will keep at it
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  #34  
Old 23rd August 2017, 07:21 PM
erubus erubus is offline
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Still don't appear to be able to get an amps clamp that does DC. I suppose i could test the resistance of the windings, and then check the volt drop when its starting and calculate the current drawn that way. I dont overly fancy being underneath the car while its on axle stands and getting started though. Even on the highest setting of my axle stands, I can only really squeeze in under the car. It would give me an idea of how big the job of changin the starter will be though.

Still cant upload vids soI have put them on youtube instead:

https://youtu.be/D4WgLlfe9oQ

https://youtu.be/y5YA4YxCN4g

https://youtu.be/EgPNA40_VBg
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  #35  
Old 23rd August 2017, 07:40 PM
ainarssems ainarssems is offline
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Quote:
I suppose i could test the resistance of the windings, and then check the volt drop when its starting and calculate the current drawn that way.
It does not work like that, you will find that measuring winding resistance it will be pretty much zero. It's the inductive and to some degree capacitative resistance that make up total resistance when turning. And any way it will be very low if you consider that to get 400A with 12v you need total resistance of 0.03ohm. Yo cannot directly and precisely measure resistance this low with off the shelf multimeter.
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  #36  
Old 23rd August 2017, 07:53 PM
erubus erubus is offline
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Ah well, thats that idea out the window haha.I'll need ot do a search for autosparks in the area and see if any of them are able to test it for me.
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  #37  
Old 8th October 2017, 07:37 PM
erubus erubus is offline
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Right well, I havent had much chance to get anything further done with this problem recently. Been busy with other cars, been in hospital after surgery complications blah blah.

Finally got round to checking the injector spills today. The car has been sitting all weekend, which means that the engine was cranking over extra slowly (there appears to be something draining the battery slowly - yet another problem)

I got 50ml centrifuge sample bottles from one of the labs at work and attached one to each injector. I then tried to start the engine. It took three attempts, none of which actually started the engine. I would guess by ear, that the engine was cranking in the region of 90-100 rpm.

Numbering the cylinders 1 - 4 from the front of the engine, left hand side and 5 - 8 from the front right hand side I got: 1 - 0ml, 2 - 10ml, 3 - 0ml, 4 - 0ml, 5 - 20ml, 6 - 13ml, and 7 and 8 were both 0ml.

So I'm assuming that this means that injectors for number 2, 5 and 6 are knackered and are the cause of my staring issue, combined with the slow cranking as well probably.

Can the injectors be repaired to reduce the spills?

Do the injectors require special tools/procedures that would make it very difficult to do the job?

I know the 2.0 TDi is supposed to need special tools but there are plenty of articles of people doing them without. at least there seems to be a light, albeit very distant, at the end of the tunnel!
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  #38  
Old 9th October 2017, 10:36 AM
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Dezzy Dezzy is offline
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Quote:
Originally Posted by erubus View Post
Right well, I havent had much chance to get anything further done with this problem recently. Been busy with other cars, been in hospital after surgery complications blah blah.

Finally got round to checking the injector spills today. The car has been sitting all weekend, which means that the engine was cranking over extra slowly (there appears to be something draining the battery slowly - yet another problem)

I got 50ml centrifuge sample bottles from one of the labs at work and attached one to each injector. I then tried to start the engine. It took three attempts, none of which actually started the engine. I would guess by ear, that the engine was cranking in the region of 90-100 rpm.

Numbering the cylinders 1 - 4 from the front of the engine, left hand side and 5 - 8 from the front right hand side I got: 1 - 0ml, 2 - 10ml, 3 - 0ml, 4 - 0ml, 5 - 20ml, 6 - 13ml, and 7 and 8 were both 0ml.

So I'm assuming that this means that injectors for number 2, 5 and 6 are knackered and are the cause of my staring issue, combined with the slow cranking as well probably.

Can the injectors be repaired to reduce the spills?

Do the injectors require special tools/procedures that would make it very difficult to do the job?

I know the 2.0 TDi is supposed to need special tools but there are plenty of articles of people doing them without. at least there seems to be a light, albeit very distant, at the end of the tunnel!
After a leak off test, if you feel that a couple of the injectors are excessive and could be sticking then they can be sent away and tested by specialist and exchanged for recons if faulty.
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  #39  
Old 19th October 2017, 07:08 PM
erubus erubus is offline
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FIXED

I had the three injectors that had high leak off volumes changed for second hand units from our sponsors (I think it's our sponsor anyway, prestige motor services, but they also seem to use the name A8parts) Got the injectors for £45 each in the end after asking for a discount and had them fitted for £140 at APDC Autos in Kirriemuir. I've used them before and highly recommend them. Both the guys are Audi trained master techs that have started out on their own.

The car starts on the button every time now. Just a couple of turns and it fires into life. It seems smoother as well although I'm not sure but it seems to be using slightly more fuel, early days for that though. The MPG had gone down considerably while it was at the garage, it had been sitting idling for a while to get it hot and was taken or a pretty spirited test drive from what I gather haha, so it might just be taking a while to get the average back up.

I have to say a HUGE thankyou to mechanicoLee for holding my hand and guiding me through the proper diagnostic techniques to get to the bottom of this problem. Without your help I would have given up and scrapped the car by now probably, I certainly would have sold it on at a considerable loss.

I can finally enjoy my A8 for more than a commuting bus!

gill
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  #40  
Old 19th October 2017, 08:04 PM
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Congratulations.
Well done for persevering, now you can enjoy her.
You are correct, our sponsors do use both names. Glad that they were able to help you. Nice folk.
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