1.4 AUA Won't start, please validate my diagnostic

ds20prefecture

ds20prefecture

Member
Hey folks, long time no post as the A2 has been flawless for ages. However, it won't start at the moment.
  • Battery is good - Starter motor turning over the engine strongly. I believe this eliminates the immobiliser.
  • Can see strong spark when I removed #1 and turned over. Coil pack/distributor is less than 1 year old so assuming with a good spark i've eliminated ignition.
  • I can hear the pump running with ignition on and then it stops (presumably when pressurised). I think this eliminates the fuel pump relay as the source.
  • No engine faults showing on OBDEleven
  • It almost catches so I think it's starved of fuel
I think the fuel pump needs to be replaced. I can hear it whirring and stopping after a couple of seconds. I think this means it had built pressure but maybe I'm wrong.

Does this diagnostic look correct to you or should I look at something else?
 
When was the fuel filter last replaced? While I am not a great believer in starter fluid, at least if the car runs after a couple of short squirts of fluid, then you are not getting fuel to the engine. So could be pump, filter or blocked fuel line or injector(s).

When you put the key in the ignition and turn on to warning lights does the immobiliser lamp go out? Have you dropped the keys and perhaps broken the ID48 chip?
 
Thanks for the reply @audifan
Hadn't considered the pump. Will try to use some starter spray. Can you tell me where the filter is located?

My understanding is that the engine won't even turn over without the immobiliser - is that not correct? I added a key last year and both keys were working before I stopped and the car shows the same symptoms with both keys now. New CCM last year too.
 
ds20prefecture said:
Thanks for the reply @audifan
Hadn't considered the pump. Will try to use some starter spray. Can you tell me where the filter is located?

My understanding is that the engine won't even turn over without the immobiliser - is that not correct? I added a key last year and both keys were working before I stopped and the car shows the same symptoms with both keys now. New CCM last year too.
Click to expand...
Be a bit careful with the starter spray, it burns very hot and repeated use can damage the engine.
Mac.
 
If nothing of the above apply, just start unplugging sensors to make it run as default as it can. MAP is the first one that i would have tried. It might was a sudden state change and can not be registered through the cranking phase of the engine. Also try to readapt the throttle body in case it failed and is not letting enough air in or moving at all.
Rooting for the fuel pump tbh, when mine let go, it was still making some pressure but not enough to make the car cough more than once and it needed to sit for a minute to do that every time.
 
Update: Replaced pump and filter, but the problem persists.
Confirmed that immobiliser light goes out
will try starter spray
 
ds20prefecture said:
Update: Replaced pump and filter, but the problem persists.
Confirmed that immobiliser light goes out Does
will try starter spray
Click to expand...
When you try to start it, quickly take a plug out, to check if you have fuel being injected.
Does the rev counter show engine speed when cranking?
If not, probably crankshaft sensor
Mac.
 
Sorted now. I put a jump starter on the pack and I replugged all of the spark plugs and it started rough 750-900 idle then evened out. Driving fine now.

I reckon the jump pack lifted volts above 13. A mechanic friend says that if the engine turning speed is too low camshaft sensor won’t read properly which fecks up the timing. Maybe.

I had charged the battery twice and jumped off our Seat and that didn’t help so I don’t feel too thick 😁
 
I reckon the jump pack lifted volts above 13. A mechanic friend says that if the engine turning speed is too low camshaft sensor won’t read properly which fecks up the timing. Maybe.
 
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