Hi, does anyone know how to change the crank sensor on an 01 s4 manual. I think for sure this is what is giving me my starting problems when the car gets hot and sits for a little while or in the morning. The car will crank healthy but fuel pump does not fire up, after letting the car cool it will turn on perfectly. weird. But anyway i ordered one and i just need help if anyone has changed it themselves please give me advise and pictures. THanks!

 

I have a 2001 Audi S4 and am having the exact same problem. Car starts fine at morning and at night after sitting all day in my parking lot at work, but won't start multiple times if I run out to do errands. It's reassuring to know that you think it's the crank shaft sensor too as that's the conclusion I came to as well after replacing the temperature sensor and the car still not working. I have no idea how to replace it though-I've read that it's not difficult, just tight to get at, but there were no detailed instructions on how to do it.

 

crank sensor does not command fuel pump on, it gives the ecm a signal to know when to fire the injectors and igntion coils.. first find out whats missing, you need compression, fuel and air and fire.. obviously its not a compression problem because it runs good sometimes.. so its an intermittent fuel or spark issue.. see which one your missing and go from there...

 

but it is located right under the coolant reservoir sandwiched right between the tranny and the engine block.. its gonna be tough to get too, i think its under that plastic coolant tube that has the coolant sensors in it and connects the two heads and the auxiliary water pump if im not mistaken.. all on the driver side.

 

Hey gies, sorry for me not updating but I did replace the crank sensor it was really really easy it was a little tight but i got bigger arms and hands and was able to do it. You just need a 10mm wrench not a socket because that would not fit down there. You have to take off the coolant tank and move it away but be careful not to break the T splitter because I did its really brittle but i got a new one made of metal instead. Now you look straight down really deep down and its right next to a little open hole on top of the flywheel behind the engine the bolt will be towrd the front of the car and you have to do this all by touch because it is very hard to see but beleive me it is so easy to change. loosen the bolt and the sensor should come right out very easily you don't need to spray wd40 on it because its coated with a non sticky material. then the only hard part was to follow the wire back to the connector through the two heat fabric protectors. Ill try to post a pic for you soon. But hey it definatly fixed my problem with no fuel to the engine now car starts up every time. Oh and yes it does command fuel pump on by telling the ecu to turn it on hey I'm proof that this was the fix. if your car cranks healthy and it just feels that there is no fuel to the engine this is your problem. i thought it was going to be the ICModule but there are 2 of them on the 2.7t and i tested them by disconnecting 1 of them and vice versa and the car still turns on but runs like garbage so what are the odds that both go bad at the same time. Try the crank sensor it only cost me 63 dollars shipped off ebay (bosch sensor with Grey colored electrical connector) Hope this helps.

 

well im glad it fixed your problem but it still doesnt command fuel pump on.

 

Im not a pro on this sensor stuff so Im not 100% sure if it commands fuel pump on but. I had almost everything tested, the coil packs and plugs were sparking and starter was turning the only thing was no fuel to injectors. we pulled off the little valve on top of the fuel rail to see if when i crank fuel would sputter out and there was nothing. I was almost convinced it was the fuel pump. It was not, when i replaced the crank sensor...on came the fuel pump so I think from experience with this the crank sensor surely has something to do with sending a message to the ecu saying the engine is cranking go ahead and give spark and fuel. So i understand where you're coming from but understand where im coming from too.

 

again, im glad you fixed your problem. maybe it wasnt getting injector pulse or something like that.. im not sure.. but when you turn the key on the fuel pump is primed. at this point, you are not cranking the car, so the crank sensor is not relating information at that point, once the cranking begins, so does the injector fire and coil fire according to the info the ecu then gets from the crank sensor. but kudos for you for having a relatively cheap fix on your S4. icms are super high for these cars, coils and fuel pumps arent either. i hope the problem does not reoccur.

 

yeah i know the ICM's are like a 180 a piece thank god they didn't go out, fuel pump is like 380 from dealer... I see what ur saying now about the whole pump primed up before cranking. I understand now. Thanks for the input.

 

what does give the ecu the signal to prime the pump??? my pump and relay are good, but when i turn key, my pump doesnt prime!! and car just cranks and cranks with na start. i can manually jump my relay and pump works, but thats it.