fusilier

My friend who owns a UrS4 is vacationing this weekend about 300 miles from home and his car wouldn't start this morning. It cranks and cranks, but doesn't seem to fire. He's also got a CEL light that came on last night for the last 2 minutes of his drive before he turned the car off. This is a well maintained urS4, 1994 with a bout 90,000 miles.

I'll report more info after he pulls codes.

jjm's quattro

my guess is the cam position sensor... but codes will tell you for sure.

UrS4boy

Fuel pump or cam position sensor. Based on the Check Engine Light (CEL) - which by the way is not meant to be ignored - its the ECU trying to convey some information to you - you have to listen - its probably the cam position sensor (CPS) While the CPS fails somewhat slowly and triggers the CEL, my fuel pump failure did not throw any codes - it was fine (or so I thought) when I shut the engine off - but pump was dead 5 hours later when I tried to leave my evening meeting at 10:30 PM - cranked like anything but no go. Had to be flat decked 40 km to the nearest Audi stealership (where I got royally hosed).

Good luck to your friend. He will need it (and VISA/American Expre$$)

Dave F.

fusilier

If it nothing that can be fixed over the phone, I'm taking my truck and trailer to pick his car up Sunday. Not going to leave it for the local vultures. After calling Fluhr, Pribble and the other local Audi gurus, we're thinking its fatal.

Owner is checking for any massive vacuum leaks on the turbo lines. Then we'll pull codes by jumping those plugs in the fusebox.

Thanks for the input guys.

fusilier

Will a cam position sensor work from another model 5 cylinder or is that a dealership only item? I'm guessing its the same thing from a 1994 100. Can someone verify a BTDT?

Anyone have a brief description on changing the cam position sensor on this car.

Mihnea

The UrS4 uses a cam position sensor that's behind the cam sprocket, whereas the cam position sensors on the other 5 cylinder cars is located in the distributor.

Sorry for that...

Mihnea

tt16v

part number 034 905 161 listed as a 92-94 100Q/S4
95-98 A6/S6. do you know anybody with a vag com? if not techtonicstuning.com has them, also you audi guys need to look into getting a copy of etka (elctronic parts catalog same one the dealer uses)

UrS4boy

As suggested above by others, the cam positions sensor (CPS) is the equivalent to the "Hall" (effect) sender in the distributor engines. It is basically a magnet (an expensive fridge magnet at that), that sends a signal to the ECU telling the ECU where No.1 piston is at. This in turn allows the ECU to figure out when to trigger the ignition and fuel injectors for all five cylinders. When the CPS fails completely (could be a bad magnet or just a broken wire), the ECU is not given the required timing signal and, hence, the ECU will not provide any fuel or ignition to the motor, i.e. you can crank forever (until the battery dies) and nothing will happen. Hmmmm.... this would be a good place to put an anti-theft switch into the loop. (But that's another topi c).

To replace the CPS, the cam sprocket that is driven by the timing belt must come off (Good Planning Mr. Audi engine design engineer (NOT!!). A good mechanic MAY be able to loosen the timing belt enough to just slip it off the cam sprocket and then (somehow) clamp the timing belt in a manner that it does move on any other sprockets or idlers. I have seen this done on a 30 minute cam swap on an 8V VW engine. Otherwise, you can use it as a sign to replace the timing belt, water pump, idler pulley, etc.

Don't you just love the fact that a little magnet can put your car totally out of commission until you inject $$$ back into the "system"? (NO?, I didn't think so - I hate it but whatchagonnado?)

Dave F.