1.2TDi enormous fuel consumption

WallK

WallK

Member
Hello!
My little 3L started eating diesel like crazy.
It was 4.3-4.6 l/100km (60-65 imperial mpg), never going above 5l/100 (56mpg)
After the fight with braking lights on dashboard (was a faulty brake light switch, changed it twice because first one I installed was giving me flashing glow plug light) car started chugging 9 l/100km (30mpg)!

While the glow plug light was flashing car wasn't driving properly, I wasn't been able to drive faster than 104 km/h (it just didn't allow me to rev higher and switched to 4th gear for a couple seconds. Then it's gone back to 3rd). It's all gone with a new brake light switch.

I thought at first that number on DIS were wrong, but couple of fuelups later -- fuelly told me I'm doing 11.1 l /100km (25mpg)! Check last couple fuelups here on Fuelly.

This is really unacceptable now ):
And the car doesn't even drive for all the money it spends, it it not powerful city vehicle.

Two different Lauches, Delphi and VCDS (I'm not sure if it was a legitimate one) didn't find any faults related to engine whatsoever. Only couple AC related ones (I'll try to fix my flaps, I promise!). As far as I can tell "desired injection amount" number is very close to "injection amount" one (while you press on the gas pedal).

Mechanics in my city region haven't seen A2 before and told me they don't know what to do. I've spent uncomfortable sums on this "diagnostics" and I'm pretty frustrated now.

Where should I look, what should I check?

Thank you!
 
Dont just blindly check for fault codes. You have to look at live values while driving - MAF, MAP, temperatures, injector readings etc - check if all values make sense and are within the specs.

And no matter if it's an A2 or whatever A6, PD engine is PD engine.
 
3dB said:
Dont just blindly check for fault codes. You have to look at live values while driving - MAF, MAP, temperatures, injector readings etc - check if all values make sense and are within the specs.

And no matter if it's an A2 or whatever A6, PD engine is PD engine.
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I'm on my own in this, it seems. I'm waiting for my own VCDS to get here so I'll diagnose the problem myself. Where can I find normal range of values for my car? Haven't found it in elsawin, maybe I'm looking in the wrong place?

I think mechanics I visited were just lazy. Before owning a car I thought you just place your car in a loving hands of people in repair shop and in a couple hours/days drive off with a perfectly running car. Oh how wrong was I...

audifan said:
You have checked for fuel leaks? Any bad smell of diesel while driving?
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Haven't found any smell. And no discolored snow under car overnight as far as I can tell.
 
Your Webasto will be on a lot but there again it probably was before. just trying to find reasons to increase fuel useage. Nobody is helping themselves to your fuel? Get under the car and really check for leaks from the tank all the way forward checking the fuel filter area very well, when was the filter last changed? In the engine bay check all fuel pipes and tandem pump. do all the checks first with the engine off then again with it running and get someone to rev up the engine not just at idle. At the same time use you scanner checking the injectors. Also look for leaks from Webasto. To double the fuel burn to me sounds more likely a leak. Remember the fuel is at high pressure after the tandem pump so a small leak from there will have a larger effect.
 
You're driving a 1.2. You either take it into your own hands or leave it. There are very, very few competent 1.2 mechanics.

If VCDS says nothing (and I would personally recommend CarPort and an AutoDia cable for €35) then you have a physical problem. Leak is very likely.

If you want to know standard values for something, I suggest you check over on the wiki at wiki.a2-freun.de or ask on the forum, as someone probably has them. Mankmil knows the 1.2 inside out (especially the gearboxes), Janihani and Mark (DerWeisseA2) are also more than competent. English is fine.

- Bret
 
audifan said:
Your Webasto will be on a lot but there again it probably was before. just trying to find reasons to increase fuel useage. Nobody is helping themselves to your fuel? Get under the car and really check for leaks from the tank all the way forward checking the fuel filter area very well, when was the filter last changed? In the engine bay check all fuel pipes and tandem pump. do all the checks first with the engine off then again with it running and get someone to rev up the engine not just at idle. At the same time use you scanner checking the injectors. Also look for leaks from Webasto. To double the fuel burn to me sounds more likely a leak. Remember the fuel is at high pressure after the tandem pump so a small leak from there will have a larger effect.
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I don't have a webasto, so it's not that.
I do leave my fuel cap door open a lot, the button is just in the right place to push with your behind, but then why did DIS calculate fuel efficiency almost right?
As far as I understand, it calculates it from injected amount, not from pumped amount.
I'll check fuel line under the hood, thanks. Not going to be an easy job tho :)


bretti_kivi said:
You're driving a 1.2. You either take it into your own hands or leave it. There are very, very few competent 1.2 mechanics.

If VCDS says nothing (and I would personally recommend CarPort and an AutoDia cable for €35) then you have a physical problem. Leak is very likely.

If you want to know standard values for something, I suggest you check over on the wiki at wiki.a2-freun.de or ask on the forum, as someone probably has them. Mankmil knows the 1.2 inside out (especially the gearboxes), Janihani and Mark (DerWeisseA2) are also more than competent. English is fine.

- Bret
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Thanks, I'll ask around on the German forum too! And again, I'm not sure if it's a leak (at least that this is the only reason), because DIS calculates mileage somewhat accurate still.
 
Shot into the sky; but have you checked wheels after driving if any of them are hot? Could be faulty bearing or brakes that hangs on?
 
Olerype said:
Shot into the sky; but have you checked wheels after driving if any of them are hot? Could be faulty bearing or brakes that hangs on?
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No, haven't even thought about it. It's winter, so temperature difference should be obvious. Thanks!
It can be a part of the reason, but still something is really wrong with the car for consumption to jump THAT high
 
audifan said:
Your Webasto will be on a lot but there again it probably was before. just trying to find reasons to increase fuel useage. Nobody is helping themselves to your fuel? Get under the car and really check for leaks from the tank all the way forward checking the fuel filter area very well, when was the filter last changed? In the engine bay check all fuel pipes and tandem pump. do all the checks first with the engine off then again with it running and get someone to rev up the engine not just at idle. At the same time use you scanner checking the injectors. Also look for leaks from Webasto. To double the fuel burn to me sounds more likely a leak. Remember the fuel is at high pressure after the tandem pump so a small leak from there will have a larger effect.
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No Webasto on any 1.2. They always had an electric cabin heater.

RAB
 
Thanks @RAB , forgot the 1.2 was super eco version so would not have a Webasto. Still leaning towards a fuel leak most likely post tandem pump. Any rough running, poor starting, worst cold or hot?
 
audifan said:
Still leaning towards a fuel leak most likely post tandem pump. Any rough running, poor starting, worst cold or hot?
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Yes, but you would have thought that that would have been spotted. Most likely a leak; under normal circumstances 9L/100km is impossible with a 1.2!

RAB
 
RAB said:
Injector seals? They WON'T show as a fault.

RAB
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How would I spot it with my eyes?


spike said:
Also worth checking coolant and fuel temp sensors are ok

Cheers Spike
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Coolant temp is couple of degrees higher than ambient after night, numbers close to oil temp when running, I think it's ok. Will check fuel sensor, thanks!


audifan said:
Thanks @RAB , forgot the 1.2 was super eco version so would not have a Webasto. Still leaning towards a fuel leak most likely post tandem pump. Any rough running, poor starting, worst cold or hot?
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It's a bit hard to start when temp drops below -5C, but it's a pretty worn battery that's culprit, I'm sure. Anything higher -- starts like a charm. Maybe sometimes it makes weird noise with starter clutch, but I don't think it's connected in any way.

RAB said:
Yes, but you would have thought that that would have been spotted. Most likely a leak; under normal circumstances 9L/100km is impossible with a 1.2!

RAB
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But wouldn't leak make my fuel system empty or just underpressurised while car is parked? My friend installed 42L tank on his A2 and had a small leak somewhere near a fuel filter. Car won't start for a couple of revs, then fuel got to engine and it worked until next overnight parking.
 
Until we get more information I am at a loss. Don't want to think the fuel is now in the oil due to engine problem. Are there injector return lines on 1.2 that could be leaking?
 
audifan said:
Until we get more information I am at a loss. Don't want to think the fuel is now in the oil due to engine problem. Are there injector return lines on 1.2 that could be leaking?
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I have some oil under the hood, around turbine, but a very little amount. Can't find any fuel tho. Will check more when it's not dark and raining.
I hope I'll get my VCDS tomorrow, what should I check first? I plan to get injection amounts from a working 1.2 and compare to my own. What else to compare? Air amounts, turbo pressure? I don't think I'll be able to get ALL the data, there's just too much! :)
 
If you can scan another good 1.2 and save its data you can compare it to your own. Not convinced a scan is the complete answer as not every part reports its status back to the basic computer in the A2. What is the mileage sorry Km on the car, how good is the service history, again when was the fuel filter replaced, fuel temp sensor will affect economy but not by that much. Have you run the car with the engine cover / insulation removed.? All fuel hoses are bone dry and no leaks below tandem pump?
 
WallK said:
How would I spot it with my eyes?

But wouldn't leak make my fuel system empty or just underpressurised while car is parked? My friend installed 42L tank on his A2 and had a small leak somewhere near a fuel filter. Car won't start for a couple of revs, then fuel got to engine and it worked until next overnight parking.
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Look at what is coming out of the exhaust. White smoke and/or soot would indicate failed seals. The engine may also run unevenly.

There are two parts of the fuel circuit. Fuel is drawn from the tank by the fuel pump on the end of the camshaft; this part is under vacuum and is therefore less likely to leak. The second part is the return from the engine to the tank via the fuel cooler; this part is under pressure and more likely to have a leak. The leak on the pressure part may only show with the engine running.

Also check for binding brakes.

RAB
 
@RAB is as per his title a technical specialist on the 1.2 tdi. I don't think many others come close to the knowledge he has on the 1.2 so he is far better at helping you on this issue than me. I can only point you in the direction, RAB will explain why.
 
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