Vingateo

Hello!
I have an B5 A4 from 1998 that sometimes wont start.
It always starts when it hasn't been running for a day or more, but when it has been running and then sitting for some hours it often doesn't start. When this happens, it ignites first time cranking but immediately dies and then it is dead and sometimes it is doesn't even ignite first time.

My guess is that it is a bad fuel pump, what do you think? How do I diagnose the problem?

Things I've replaced:
All spark plugs
Fuel filter

I appreciate all help I can get!

Thanks!
//Teo

Cybersombosis

Is the check engine light on? Have you scanned for codes? That would be the first thing I would do. If there are codes, post them up.

Intermittent starting has known to be a crank position sensor going out. When you crank when it doesn’t want to start, what is the tachometer doing? If it is erratic then that is a tell sign that it’s the crank position sensor. It is a fairly cheap check with that sensor only costing $11 at Rock Auto. They have been known to go out and not throw a code.

It is held in by one bolt and is close to where the engine meets the transmission on the NA driver’s side. Possible entry points are from the top, under the car or from the driver’s wheel well depending on how tall and long you are. I’ve done a slave cylinder from the top and it’s about in the same area. Good luck.

Doug

Vingateo

Hi and thanks for the answer!
The check engine light is not on except for when the car is not starting and I run the starter for about 7 seconds, then it starts blinking and a beeping sound goes on. This stops as soon as I stop running the starter.

Because of the model year, the car does not support OBD2, instead a special Audi/VAG tool is needed which I don't have and therefore I can not scan for codes.
I have not noticed anything odd with the tachometer when the car is not starting.
Another thing to add is that when the car is starting, it has a rough idle. The tachometer jumps in the range 850 to 950 rpm and sometimes the car almost dies when idling.

Teo

Cybersombosis

Does the EPC light turn on when this all happens? A 98 should be OBD II compliment. You should be able to scan the ECM for codes using a generic code reader but you won’t be able to log in to any other modules. Have you actually tried to scan or just assumed it wouldn’t work?

As a test, try unplugging your MAF and see what happens. When you do get it started and if it runs better with the MAF unplugged, then your MAF is most likely on the way out. The no start and rough idle may be two separate issues.

Another common thing to go is the coolant temp sensor which, in my experience, will cause erratic idle. Another inexpensive part that goes quite often and will throw a code.

Doug

Vingateo

Hi again!

No EPC light.

Since I live in Sweden and the car is Swedish where OBD2 was standardized in 2001, it isn't compatible. I did however try to scan it with a Bluetooth tool with no luck.
Is the car able to start without the MAF connected? I thought the MAF was necessary for the ECU to control the engine?

I will try changing the coolant temp sensor and the crankshaft position sensor and post the result afterwards!

Thank you!

Teo

clancy

I would revisit the fuel pump going out. If it has never been replaced it is due. Check to see if the fuel pump runs when you try to start the car. Lots of old threads about how to check this.

Vingateo

Ok!
Huge thanks for all the tips!
I will update!
Teo

Cybersombosis

The NA cars will run without the MAF plugged in. The ECU will use a default map when it doesn’t see a sensor. Don’t know about Europe though as you most likely have a immobilizer and we don’t.

Doug

Vingateo

I borrowed my friend's Vag-com scanner and pulled some codes with the Ross-tech vcds-lite. (I am a poor student and can't afford the real deal)

5 Faults Found:

16518 - Oxygen (Lambda) Sensor B1 S1: No Activity

P0134 - 35-10 - - - Intermittent

17967 - Shareware Version. To Decode all DTCs

P1559 - 35-10 - Please Register/Activate - Intermittent

17967 - Shareware Version. To Decode all DTCs

P1559 - 35-10 - Please Register/Activate - Intermittent

00561 - Mixture Adaptation

15-10 - Adaptation Limit (Add) Not Reached - Intermittent

16500 - Shareware Version. To Decode all DTCs

P0116 - 35-00 - Please Register/Activate

---------------------------------------------------------------------------
Tried clearing the codes and immediately got this one:

1 Fault Found:

16500 - Engine Coolant Temp. Sensor (G62): Implausible Signal

P0116 - 35-00 - -

---------------------------------------------------------------------------


Thanks,


Teo

Vingateo

Ok! Interesting!
I will try that then!
Thank you

Teo