How do you check cold start valve (5th injector)

[rhencullen1989]

Hi, still having problems with my audi 80 2.0 litre 8 valve 3A engine when starting from cold, it seems to run ok for literally 1 or 2 seconds(1000 rpm) then the revs drop to 400-500 and it stalls, trying to give it some throttle seems to make things worse. I have been told to check the cold start valve BOSCH KE MOTRONIC FUEL INJECTION SYSTEM, I have removed the valve and started the engine but there is no fuel spray, the coolant may still be too warm as i only left the car for a couple of hours. There is a coolant temp sendor that operates the valve (i assume) the aluminium knuckle on the end of the top hose near the engine block has a sensor top and bottom, the top one does the temp gauge in the car, is the bottom one the one for the cold start valve? if so how do i check it is working ok. What else could i check. I have cleaned out the idle stabilisation valve (canister type thing at back top of engine) with carb cleaner but no difference. Please some help, Thanks............

[scotty33]

Hi

The top switch should be the thermotime switch for cold starting, brown, 2 pins 034 906 163 (15 deg C) or 043 906 163A (35 deg C) I'm not sure what the readings should be, but you could check resistance hot and cold, there should be a difference.
The bottom switch should be 2 pins white, 049 919 501B, it is rated 120 degrees C and has a switch, I guess it could be for an overtemp alarm?

I changed an engine for father in law in a passat 16v once, the thermotime switch sheared off, I could no get the right part. After that he found that his cold enrichment would operate ok, until he touched the accelerator, it would then run weak/lumpy until warmed up. Have you tried starting yours without touching the accelerator?

[Crasher]

With the engine cold, remove the injector and the centre HT lead which MUST be clamped to a good earth to prevent sparks. Point the injector away from the car (have a fire extinguisher to hand) and crank the engine over, the injector should spray for at most 12 seconds at which point the thermo time switch will heat up internally and cut the power to the injector. The most common problem I see with the 3A is a faulty engine coolant temperature sender.

[rhencullen1989]

Thanks for the advice, which one is the coolant temp sender? where is the thermo time switch? It seems to start and run ok for a couple of seconds even when cold before it starts playing up, does this sound like a faulty cold start valve?

[Crasher]

The Thermo Time Switch is a large brass switch with (I think) a 24-mm spanner size body and a brown top with two pins and is on the head water flange. The Coolant Temperature Sender is a smaller brass switch with a 19-mm (again, I think) spanner size and a white top and I think the part number is 026 906 161. Sorry to be slightly vague but it is a while since I worked on a 3A. I think you should get a fault code read done even tough the fault code abilities of that ECU are rudimentary and you will need someone with equipment capable of communicating with it, if I remember rightly VAG-COM struggles on these and I usually end up getting out my old Omitec scanner from years ago.

[rhencullen1989]

Hi, my cold start valve is definately not spraying fuel when cold, the part number of the top sendor is 049919501E (or B) and works the coolant gauge in the car its 22mm hex. The bottom sendor is part number 0280130040 and is 19mm hex,and i think its this one giving me grief, i.e sending the coolant temp message to the ECU, (or not as in my case!)Went to my local audi specialist this morning and it seems that part number 0280130040 has been superseded with 026906161, so i have ordered one of those and hope that fixes my problem. By the way, depending weather you have a 4 or 5 cylinder or carb, they seem to swap the position of the sendors over, so a top sendor on mine that does the gauge in the car is probably a bottom sendor on a 5 cylinder. If not sure, get gauge in car to register a temp, switch off ignition remove connector and turn ignition back on, see if gauge works or not. Can anyone tell me if i have the correct information, thanks.

[Crasher]

I am just bumping this so I remember to read it when I get home.

[rhencullen1989]

Hi, just to say i have replaced the temp sendor audi part no 026906161 (bosch part no 0280130040) and my car now starts and ticks over a treat, even on a cold frosty morning, thanks to everyone for their help especially crasher. Ta.

[jimbojangles]

Long live the cold start sensor