Brian Dubois

Hi- My son has a 2001 A6. Was running fine, but one day he went to start it and it would just crank and crank but never start. We tried to start it several times over the course of a few days with no luck., then one day it started right up and ran fine. He drove it for a few days and he went to start it one morning and it wouldn't start again! It would just crank. We had it towed to the repair shop and when they tried to start it, it started right up, so they could not diagnose the issue. We drove the car home and my son drove it for a few days with no issues and then one day it didn't start again. I pulled the fuel line in the engine compartment and it is getting fuel. It only happens on occasion, not every time. When the car does start, it runs just fine. It is sitting now and not able to start at all this week. Has anyone heard of a similar issue? I am just puzzled. It starts right up sometimes and sometimes it just cranks and never starts. We did bring it to the auto part store to check for codes and it did say that it needs an O2 sensor. But the car was running at the time, so I do not if it would pick up the correct issue? Would an o2 sensor cause an occasional non start and just crank? I'm puzzled! Any help would be appreciated!

johnkk

O2 sensor usually won't cause a non-start. Could be lots of things. Was the car not starting when you checked the fuel line? When my fuel pump failed, the car behaved like that. I could get it to start by whacking the floor under the rear seat bench where the pump hides. Pump motor had dead spot and whack got it going.

Also might be crank position sensor, but they usually show symptom of starting fine cold, but not restarting when warmed up.

4Driver4

Has anyone pulled any codes?

If spitballing, I'd agree with the crank sensor comments. Another guess would be a coolant temp sensor.