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Hello, I have a 2006 Subaru Impreza WRX STI, I am a technician but have hit a wall as I just can't work out why this car won't start.

So I had a compression issue with my engine but the car was driving and starting fine, I removed the engine to find the issue which ended up being a bad piston, I have just finished rebuilding the engine which has taken a couple of weeks, the engine is pretty much standard. The engine was back in the car and was ready to start, but upon turning the key the engine would only crank but not start. 

Now the compression sounds good and the engine is turning at an expected rate, I have no faults in the car, I can hear the fuel pump and have double checked the feal lines are the correct way around, I have also checked the spark, it would spark once just as I start cranking and then never again (this makes me believe the ecu is deciding not to start for some reason), I have unplugged the air mass sensor but still no joy, so moved on to checking the timing, that was all good, but I did unplug the cam sensors just to see if it would start, but again no, I have checked all my connectors which again are all plugged in, and have checked the fuses which are also ok.

I am now stuck, this isn't the 1st time I've had the engine out of this car and never had this issue before, so please any advice would be much appreciated.

Thanks Craig 

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  • 4 weeks later...

Have now found that bank 1 (cylinder 1 & 3) car sparking correctly but on bank 2 they spark only the once, have change the cam sensor that side but still no good, can't work out what would stop one side of the engine form sparking 

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  • 2 weeks later...

Does the other bank spark all the time or stop after a full rotation?


As I had a similar problem when I had a bent pin on the crank sprocket. It would turn over ,spark once and then cut spark once it noticed the bent sprocket pin 

Did you change any of the cam /crank ,pulleys/sprockets ? (UK, jdm pulleys can differ even on the same year )

Although you have compression due you have enough on all cylinders?

Double check the timing belt Mark's. 

If you have avcs and Tgv's are these plugged in correctly and functioning properly? 


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So i have found that the drivers side coils will spark as expected and will carried on sparking but the passenger side will only spark the once in the 1st rotation and not again.

I have double checked the cam sprocket which looks good, and the scope pattern from it looks good too, looking at the rest on the timing marks they are all bang on.

I didn't change any of the pulleys but they did all come of and then back on during the repair.

I haven't got a compression tester on it yet, but can't see how that would stop it from sparking, as these cars don't have a cylinder pressure sensor so it wouldn't know, but of course i may be wrong on this point.

The TGV's have been deleted months bore this repair.

It does have AVCS and they are plugged in, the control valve on the passenger side has been replaced not long ago and both are clean and moving freely. 

I have had a thought, is it possible that the AVCS cam pulley to be locked in a position making it so the cam is out of time although the pulley is showing it is in time? 


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