Kneale Brownson

No tachometer activity while cranking is a symptom of a bad engine speed sensor. The two sensors (ignition reference and engine speed) are not as exposed to heat on the I5 engines as on the V8s, but they're 25 years old in this case. Certainly worth testing.

a-talk

Also, you should pull codes from the ECU. Even in a no-start condition, codes can be pulled. If there is a hall sender or engine speed sensor issue, it will be logged.

audiqv8

Sound like both speed and crank sensor are failing. If the speed sensor fail while the engine is running then the engine will stop, if the crank sensor fail then the engine will not start. Both crank and speed sensors are magnetic sensors and as we all remember from high school physics, a magnet loses it magnetic property when heated. Once you stopped the car the heat under the hood, especially from a turbo engine will continue to climb. This will cause either the crank or speed or both sensor to fail. If this was my car I would replace both sensors.

BTW if the crank sensor fail while the engine is running , it will continue to run, but will not restart after the engine is turned off.

eventoday

Thanks for the info.
I will mention this to my mechanic.

He is really terrific with vanagons but I dont know if he knows the quirks of old Audis. Any info I can give him is great.

eventoday

Update: so just talked to my mechanic and he said when it won't start it is not getting fuel. He is not sure but says signs are leading toward fuel distributer. He is going to try and clean it.
Any thoughts?

audi_marv

Fuel pump relay. The underhood heat theory also applies to relays. This fault should come up when you run the codes. If you have the relay type with the fuse connector, when it won't start, put in a fuse and see if the fuel pump runs (you should be able to hear it). Messing with the fuel dizzy may open up another different can of worms...

yodasfro

This^Yikes tell the mechanic not to mess with the fuel distributor.

eventoday

New Update:

Hi Again,
So I got the car back from the mechanic today. Still kind of struggling finding the issue.

He purged the fuel system and changed air and fuel fileter.
Added some other fuel cleaning additives too.

He found out when it wont start if you hold the gas pedal to the ground (which he said keeps throttle body open) it will fire up after about 3-5 seconds.
I found out this is true today when it wouldnt start.

He told me to drive it for a week and see if anything changes.

He also mentioned it is not getting proper amounts fuel when the warm no start is happening.
I dont know what it is called but he said the plate underneath the fuel distributor in not operating correctly. He said he tested the sensor that operates it and it is working.

Am I making sense?

Any thoughts for me?

audiqv8

The plate underneath the fuel distributor is raised by engine vacuum, therefore verify the plate is not sticking and also check for vacuum leak(s).

eventoday

Thanks Audiqv8,
I will bring that up to my mechanic too.
One thing I failed to point out .

My secondary cooling pump does not work. I didnt think it really did anything ( i know its there for a purpose) but another member asked me if it was working.

Is that a part I can find easily? expensive?