S3 boosting issues / petrol tank hissing

[Shawny-S3]

Hi all first of all il tell you a little about my car my old engine broke through low oil pressure which also cleaned the turbo out to so I've fitted an agu engine and also had my turbo rebuilt. Now the car pulls like a train alot better than it ever has its has the legs on most astra vxr,s but I'm finding that when I get up to speed like late in the rev range in 5th gear and 6th about 5k on the rev counter theres no boost its like it boost cuts does and body have any ideas ? Also I don't know if these problems are related but my petrol tank seem to be pressurising hisses for a good 20 seconds when I loosen the fuel filler cap any ideas would help greatly.
thannk you for your time ,
shawn

 

[<tuffty/>]

Have seen this before when a customer had done all the usual PCV and pipes delete stuff and re-piped the evap wrong... loud hiss from the tip on idle IIRC and a pressurised tank...

He had forgotten the check valve for the pipe that goes over the back of the engine bay from the TIP to the evap canister and the tank was getting pressurised under boost...

I think it affected top end power too but can't remember the exact details...

<tuffty/>

 

[badger5]

done n249 or any bypasses ?

 

[sportstractor]

Does sound like a charcoal canister problem.

I don't really understand how they work, but today I noticed my fuel tak was bubbling, like air was being pushed in and bubbling in the tank, which increased when I loosened the filler cap? What would this indicate?

Sorry to hijack

 

[Shawny-S3]

Haven't done any recently but I have had the pipes off and stuff for the turbo removal but yes I have done the n249 bypass

 

[Shawny-S3]

Haven't done any recently but I have had the pipes off and stuff for the turbo removal but yes I have done the n249 bypass

but i havent fitted a check valve or anything should i have ?

 

[<tuffty/>]

but i havent fitted a check valve or anything should i have ?

Not on the N249 bypass no... have you checked the evap pipes yet? there is one coming off the top of the throttle body and the other goes to the TIP... they both need a check valve... this would be the only way pressure could get into the tank tbh...

<tuffty/>

 

[Shawny-S3]

to be honest tuffty i havent checked them no. doesnt that have a check valve fitted to it already though ? i cant see how i could of messed it up but i could of done it when i fitted the engine and ive only just noticed the issue as its the first time ive been able to drive it properly since the fit

 

[<tuffty/>]

Its easily done... check those pipes and valves... no boost pressure should be getting to the tank if done right

<tuffty/>

 

[badger5]

Does sound like a charcoal canister problem.

I don't really understand how they work, but today I noticed my fuel tak was bubbling, like air was being pushed in and bubbling in the tank, which increased when I loosened the filler cap? What would this indicate?

Sorry to hijack

did the tank inhale or exhale when you undid the filler cap?
its vent goes to the charcoal cannister in the engine bay with n80 evap valve on it.
If its blocked or check valve is wrong, failed or not fitted etc then the tank breather wont function properly..

 

[Shawny-S3]

Its easily done... check those pipes and valves... no boost pressure should be getting to the tank if done right

<tuffty/>

ive checked the 3 pipes going into what i presume is the fuel filter now correct me if m wrong but the pipe with the blue clip goes to the blue male adapter the pipe with the white clip goes to the white male adapter pipe and the pipe with the black clip goes to the black pipe if thats correct i had them on the wrong way round and there the right way round now hopfully

 

[<tuffty/>]

Looks bit like this...

Photos would be useful...

<tuffty/>