What I was wondering from the title is in my 1990 JDM fc3s, or in any S5 TII to my knowledge.

I've changed what I believe was everything. The fuel filter against the Firewall feeding to the regulator / rails / injectors.

I've changed the in tank pump assembly.

But I noticed a small white factory pill style filter you see often in cars located under the tank behind the rear *Sub-Frame* while I was adjusting. (white non translucent - one in one out)
The lines are going in the direction to make me think it's fuel related. (can't trace the lines to well)

It's the only one I've seen on the car in that underbody, I also never found anything online for FC3S filters regarding this. It's original to the car from it's appearance and stamps.


Even a part # or picture may help me. I want to replace it.

 

This is 100% a guess, but is it a check valve for the evap system so it only lets fumes through it?

 

Looks and sounds like what it is...

I have issues with over-pressurizing in my tank during track days, and fluid being pressurized out of the cap. Most likely after years of sitting it's probably blocked within some reason.

I don't think it has anything to do with brakes or fluids in the rear end, and the design of the 1-2" filter suggest flow of air/vacuum.

Thanks for the input I'm sure it's correct.

 

Did you do an emissions delete and take out the Charcoal cannister in the engine bay?.It is related.

 

Yes, track car and the canister was removed, I believe I have not replaced the line and used a rubber cap instead on both hardlines. I see your concern now.


If your right I may need some assistance to figured out which line was removed and replace it with a suitable hose.


It's funny as I had time to work on it again, I believe your right and this is a check-valve for that said system. It located between the tank and rear axles, and I will upload a picture.

Soon as I saw your name I realized something may be off, funny for me at least.

Currently I saw it ran into the pump assembly and hard-lined to the engine bay.
This would be it. FC3S check valve?

 

I was going to show a video until I realized I need permission, but it's located behind the trailing coil pack on all Rhd FC3S .
This is an image of mine and the line going to it.



I see the issue now, the line as you see between the blue *Loom* and the wiper motor connector has a cap and a hose clamp around it.

Issue solved?

 

Take the Cap off the lines and run the car for a bit..See if that changes things.

My Guess is that IF you capped the lines to the cannister and that hose goes from the "pill" to the cannister to help vent the tank,then the only real Vent now is the actual Gas cap.So that would lead me to believe that is your problem.

I had the cannister removed in my S4 TII swap and never touched the lines inside the engine bay.I just folded it down out of sight.It still acted like a Vent hose all the way from tank to bay but never actually went to the cannister as it was removed.

 

I removed it right after your first reply and it hissed for a good while, It's the same for JDM, just the line runs slightly shorter. *Tank to the one way valve/filter to the canister*

Long story short, the design doesn't effect anything until pressure builds up from hard cornering and half tank to empty. On a full tank there literally is no sign of change from having it capped in my case.

If anyone else comes across this thread, I would just grab a hose and vent it down and out for vapors away from any heat source. In my case RHD it vents away from turbo and exhaust so leaving it pointing toward the firewall with a little bend of the hard-line. Works just fine for me.