fuel tank depression causing spluttering?

[Johnerz]

I posted a wee while ago about my car stuttering completely and not boosting at all, just spluttering, hesitating and backfiring.Took the car to the mazda dealer who did a compression check and also a vacuum check and found no problems.  they tested the fuel tank and said that the breather may be faulty, causing a depression in the tank and that in turn is causing the problems (fuel pump not being able to get fuel thru, etc)He asked if there was a sudden hiss when i took the petrol cap off after driving - answer is yes - he said that was the tank sucking air in.now the best bit is the car WONT FIT on the dealers ramps...apparently the bar on the ramp is right under the rear axle and so they cant drop the tank out.  they were as helpful as possible and loved the car just cant fix it :(i rang a guy here who works on rotaries/supras, etc and he thinks its a solenoid/actuator/turbo, rather than that.  but the car is running fine every time if i do the whole petrol cap thing.anyone else agree that is the most likely cause??cheers

[FD3SNuttah]

my car makes a hiss when i stop at the petrol station and i dont have any spluttering problems?? maybe you have a dodgy fuel pump or crap in the fuel lines.

[JBerg]

All the cars ive owned make a hissing sound when you open the fuel tank...its just relief of fuel pressure?? or something like that iirc.

[nikp]

Mine makes a hiss too, i don\'t have any issues.

[CraigWWW]

Yep mine hisses too, the emptier the tank the bigger the hiss! No running probs tho!

[banned advertiser]

It might be the fuel filter, I better there are lots of 10-12 years old cars with original fuel filters in, as they are not the easiest things to change.
But could fix your problem or worse still stop fue starvation.
http://www.rotaryart.uk.com/acatalog/Blue_Print_FD_RX7_engine_parts.html

[Johnerz]

thanks for the info folks.  seems strange i havent had any issue since i started releasing the pressure when i turn the car off.  it might just be part of the problem tho, now im sure it wasnt a boost problem as they did the vacuum test ill see about looking into the fuel line/pump/filter, etc.nothing worse than going out and starting the car to have it splutter up the road with barely any power!

[Evil Twin]

Hi

As a test you could buy one of those cheap push in fuel caps and drill a couple of small holes in it. Install it and try running the car. This would equalise the tank with the outside atmosphere and prove the garages theory.

I wouldn\'t make any wild turns though, you might end up with some fuel finding it way out.

[Martiny]

Doesnt the vapour go to the charcoal canister, and that is supposed to vent the right amount? So , if running a vented cap sorts the problem, we should look at that system.

[Johnerz]

im picking the car up from the sprayers tonight and he had suggested either drilling some holes in or else just leaving the cap off (not on full tank) and just putting a thin cloth over the gap with an elstic band to check.  ill let you know how i get onthanks again for all your help.  appreciate it!