1994 A6 2.5TDi Cold starting


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Apr 22, 2007
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Hi all. New here so be gentle...

I have a 1994 A6 5 cyl 2.5TDi (AAT 115) auto Avant with 150k on the clock. It has been fine since I got it last summer, (done 15k miles) but in the last week it has developed a cold start problem. The glow plug light goes out (from cold) after a fraction of a second as it does from hot, but on cranking, nothing happens. If I leave the ignition on for 20 seconds or so (to get the plugs to temperature), it starts grudgingly with a foot load of throttle and a driveful of black smoke. For the rest of the day it starts fine. I've checked the plugs and they all work.

The other curiosity is that if I crank and crank to get it started from cold, the ABS warning light comes on, and the digital display thingy beeps and I get the brake symbol with the excalmation mark in it making a positive fiesta of warnings. It eventually starts (with the same gobbet of black smoke) and has done every time. But it's not very dignified, and I can't see the battery coping with much more of this punishment. Plus there's a big black patch of soot on the drive. Any help would be gratefully recieved, thanks in advance...

Get the car plugged in and it will reveal all, possibly your fuel pump or crankshaft positioning sensor
I'm trying to avoid taking it in to get it fixed - I should be able to do it myself...

Currently chasing wires, and it seems that the glow plugs aren't operating. I have found the whopping 80A fuse, which is intact, so now I'm looking for the glowplug relay. But I'm ******** if I can find it. Please point me in the right direction (or even better, tell me where it is!) If that is okay, I'm looking at paying a garage. Would it need to be an Audi/Bosch specialist?


Hi All.
I also have an A6 estate, 2.5 auto (1995) that is recently having the same problem - slow to start. Glow plug light only comes on for a split second when the ignition switch is turned on. Checked plugs and 80 amp fuse - all ok. Then located glow plug relay(far right of relay bank that's behind panel under steering) and it is fine. Checked glow plugs while cranking and they operate correctly. I'm thinking temperature sensor but which one and where? Greatful for any help.
Thanks in advance
Hi all
Still having this problem....any ideas?