ecu fault or inj pump?

[charlieb999]

a couple of days back my AFN 110BHP 97 A4 always started "on the button" just sunday I started it and just noticed it took a few more turns before it did so. thought little of it. made a short journey of aabout 4-5 KM & returned home.
shortly after this uneventful trip I had to go out again. put in key everything as normal immobiliser light did usual thing cold start light went out but turn turn turn over no start!!! the question is this upon checking if run/stop valve was receiving power found it did not next day by-passed it giving 12v direct to make it operate no joy do I suspect the ECU or the inj pump? should it start even if it then runs like a bag of bolts when the pump is by-passed if the ECU is faulty or is it just not possible to do this. i am an electronics engineer (linear) so can do a lot of diagnosis myself re electronics. but if it is a non run situ despite a by-pass where should I look next. ??

[green A8]

I don't know if this helps. I had an A6 TDi do the same thing to me.

Had the AA man scratching his head as he could find no faults with the car when he plugged his scan tool into it. He insisted that he could find nothing wrong. It turned out to be a blocked fuel filter.

Credit to the main agent, they had it up and running again less than an hour after the AA unloaded it off their transporter.
Birmingham Audi.
Kind regards.

Paul.

[charlieb999]

so do i take it yours was completely devoid of any life or did it tryn to start? cos mine behaves as if there is a completely dry pump not a hint of a firing cylinder at all. but will gladly take on board your advice & check the fuel line out. just thinking love a diesel car but do not like handling the stuff itself!!! but many thanks

[green A8]

so do i take it yours was completely devoid of any life or did it tryn to start? cos mine behaves as if there is a completely dry pump not a hint of a firing cylinder at all. but will gladly take on board your advice & check the fuel line out. just thinking love a diesel car but do not like handling the stuff itself!!! but many thanks

As you describe above no attempt at starting at all after being left overnight. I hope it is just a filter problem, maybe you ought to get it scanned for faults before you wade in renewing stuff. Good luck with it, hope you get it sorted at a minimal cost. Keep us all informed as to your progress.

As to handling Diesel, not my favorite part either, but make like a proper mechanic, wear gloves

Kind regards.

Paul.

[charlieb999]

I have tried the suggestion of fuel blockage that is a negative result. loosened a union on 3 injectors and cranked the engine plenty of fuel spilled out. so assume from this the pump is pumping fuel at what pressure not sure. so does not mean it is fully functional producing a good pressure from the injector. as I stated prior I am an electronics guru for mostly audio I do not have any way of reliably testing this.give me an amplifier I am your man my experience on engines is good but not that good. i need someone who is a VAG guru plain and simple, who knows it backwards any takers?

[charlieb999]

hmmm only left it sitting fo 30 mins or so had not even gone cold!!! not even overnight. so did not even need heaters. as for the checking it out at a diagnostics centre. heard it is poss to get some freeware & a cable on ebay to plug it in for error codes. what is this software called? anyone familiar with it?

thought I would buy this car due to my last one which as apoint of interest to all was an 80 2.8 used to be a VAG "showpiece" the guys at AFN west London had never seen one before!!! it had 2 exhaust systems complete they did some checking with Germany only to find out only one of 5 ever built. it did "Top Gear" in 92 a "Leanburn" V6 running on 2 litre running gear!!! used to drive the parts guys GSF bit nuts always pointless asking for bits just used to show them the parts like brake pads etc. so they could identify them. coz never put a spanner on it in anger in 5 years just service!!! but it got killed by a bus in Central london. fast, loud!! clocked it at 160mph so thought i will get another Audi after a few BMW 5's. got this in a hurry as a stop gap when my car got trashed front end. time to replace with a newer one I think

[abimogen]

Vagcom is the software, its around $99 to buy from ross-tech in the states.
The lead is an ebay effort, about £8.50 shipped and comes with free vagcom lite software. You can only read the fault codes (and i dont think all of them) with the free/lite software, so it takes some searching when you have them.

Good luck

[charlieb999]

well I ended up taking the ECU to bits to give it a visual check found a couple of suspect "drys" a quick re-work of same re-installed it on Sunday morning did a temp repair on the 60A fuse & holder which was more than a little showing some melting at one terminal cranked it up and wonders of wonders it spluttered into life!!! the fuse bit is a little strange and will need replacing alls well starts on the button every time as before. problem solved. btw although severely distressed the 60A fuse was still conducting and not reading high Z

so big thanks to all those that offered advice here