A4 1.9TDi

shamwari

I looked at a 2000 A4 TDI (90bhp, code AHH) and I have a question for someone who has worked on the pump and injectors on these things and / or knows them inside out.

This one has all the symptoms of a fueling fault that could be a duff pump or an injector, and is something I haven't seen before. The car will start and ticks over absolutely perfectly. But flat out it will rev to only around 3400rpm. It is somewhat lumpy like a misfire and is putting out plenty of whitey blue smoke that smells very diesel-like. The car is not pressurising the crankcase or the cooling system, so it looks like this isn't a compression or a head gasket issue. Disconnecting the lift sensor from no3 injector caused the car to run worse. The diesel filter was replaced and there are no leaks in any of the low pressure pipework. A code scan shows no stored fault codes, and the live data showed nothing anomalous. Everything read ok and was in line with what I was expecting. The EGR is fine too.

I have a suspicion that either of the following are the cause:
1) A duff injector is failing under load
2) There is something amiss with the injection pump.

Has anyone seen same or similar fault before like this with a VAG power plant?

If not, I'll do a compression check on it and might get the injectors sent for testing. However I don't want to go too deep into this, especially if it is the pump because I don't have the space / time / to do it, and the age of the car mitigates against doing it in the first place. I want to avoid the owner the expense of getting me and an injector specialist involved if the pump is a certainty to be cream crackered.

Slidey

I haven't ever worked on the pump or injectors but have been around these yokes a long time.

My one question is, are you 100% certain the timing is not out?

shamwari

Slidey wrote: »

I haven't ever worked on the pump or injectors but have been around these yokes a long time.

My one question is, are you 100% certain the timing is not out?

I have seen timing out on these engines before but the tickover is also affected, if you are lucky enough to get it started! This one ticks over very very sweetly indeed. The owner said that the deterioration was gradual, and didn't happen all of a sudden. Originally I thought he had a fuel starvation problem. Getting at the timing belt is bumper off on these things......
:eek:

Slidey

Gradual worsening of the problem kinda rules out the belt. You could check the flywheel/cam timing without taking off the front.

Personally I have not seen issues with pumps/injectors but there is a lot of shyte diesel floating around these days.

If it was me I would rig up a can direct to the pump and see does the issue improve, it may be drawing air or have shyte in the tank

shamwari

Slidey wrote: »

Gradual worsening of the problem kinda rules out the belt. You could check the flywheel/cam timing without taking off the front.

Personally I have not seen issues with pumps/injectors but there is a lot of shyte diesel floating around these days.

If it was me I would rig up a can direct to the pump and see does the issue improve, it may be drawing air or have shyte in the tank

The first question I asked was where he bought his fuel, upon which, he produced his fuel card for a reputable chain. And he fills up there regularly! I cracked open the banjo bolt on the pump where the feed from the filter comes in, in case there was a micro-filter inside it (there wasn't) . The intake inside the pump was spotless too. I checked all of the hoses into and around the filter and they were good. There was no evidence of perishing and certainly no diesel seeping out. Even the leak-off pipes on the injectors were perfect!

I might drop a length of pipe into a clean diesel container and rig it to the pump to see what happens. Will post back the results.

shamwari

OK, update time. It looks like injector No2 might be screwed. We fired the car up and got it warm. In turn, we raised the revs up to around 2000rpm and slackened the high pressure pipe to each injector slightly. The engine almost died with opening the pipes to 1,3, & 4. On opening 2, the revs only dropped marginally and the excess smoke almost disappeared. The leak off of diesel around the slackened joints seemed the same on all injectors, so the pump looks like its fuelling each injector about the same, which is good.

All of the injectors have been removed and are going for testing tomorrow, with particular emphasis on no2.

More updates anon.

Slidey

Am I right in saying that this has a normal injector pump and isn't common rail

It would be nice if this was the fix. You could have swapped the injector with number 1 and see if it changed cylinders to be sure.

crosshair1

Would probably be worthwhile just moving no2 injector and ensuring the fault has moved cylinder.
What your describing could also be caused by intake restriction on no 2 cylinder

Plug

Did you do a leak back test?

shamwari

Slidey wrote: »

Am I right in saying that this has a normal injector pump and isn't common rail

It would be nice if this was the fix. You could have swapped the injector with number 1 and see if it changed cylinders to be sure.

Yep she aint a common railer, good old traditional rotary pump - albeit with some fly by wire bits!

crosshair1 wrote: »

Would probably be worthwhile just moving no2 injector and ensuring the fault has moved cylinder.
What your describing could also be caused by intake restriction on no 2 cylinder

Had this been an intake restriction, I would have expected the smoke to be more black than anything, but this is blue/grey and stinks of diesel. I didn't try moving the injector because (a) I didn't have any sealing washers to replace the old ones with, and (b) the owner wanted to chance whipping them out and getting the tested. In fairness he's desperate to get the thing sorted, and I'm making next to nothing for helping him.

Plug wrote: »

Did you do a leak back test?

She aint a common rail electronic injector jobbie, so a leak back might not be as conclusive as it would be on a newer engine. In any event, the test I did has pinpointed a significant difference with what's going on with no2, so off to the denzil workshop with it!!

shamwari

One A4 now resurrected and one happy owner. Injector number two was opening below its specified pressure and its spray pattern was very poor. The injector was overhauled and renozzled, and one of the other injectors was renozzled as well. The other two were fine and were cleaned.

For an 11year old motor with 200k on the clock, and just 90bhp on tap, it drove impressively!

Thanks everyone for advice and opinions. To be honest, I'm glad this one is sorted. The owner is a decent bloke who's hasn't had things easy in the past while, so I think he deserved a bit of good fortune with this one