I have an S5 TII. It has been running extremely rich at idle and I am quite sure it is because I put a Walbro 255 pump in it without further regulation. Question? I do not really want to put stainless lines in it with an aftermarket rail. Can I leave the stock FPR in the primary rail, disconnect or plug the vacuum hose to it and place an aftermarket FPR prior to the primary rail?

I guess that I am not sure that if I do this, that the stock regulator will be fully in the open position when it is capped so that the only regulation is done by the aftermarket FPR?

I had an old s5 rail that I tried to remove the FPR from and it was impossible to get out. I don't want to wreck the other one that I have.

 

The stock FPR would be partially open, and restricting pressure to what it would be when there is 0 manifold pressure (atmospheric pressure). With vacuum applied, it would be closer to being "open." Though, there's no way to make it see vacuum, but not have it see pressure changes as you accelerate.

Also, the walbro will definitely raise fuel pressure all around. I measured 46psi at idle, as opposed to 34psi with an FD fuel pump. Then 48psi at Atm vs. 41psi at Atm with the FD pump.

 

I read someone write about "flaming" the stock FPR. I wondered if this literally meant buring the insides out with a torch so that the regulator portion does not regulate anymore. Have you heard about this?

 

I think if that is possible, you would then probably need a way to seal the vacuum nipple off too. I've never cut one up to see exactly what's in there, and if it would burn.

 

Well......when I was trying to get the FPR out of the old rail, I applied a torch to see if I could break the "solder" that held it in. I used MAPP gas and it definitley burned the diaphram and other things out of there. Then I actually pulled the diaphram housing off (by cutting) and found that the FPR is actually pressed in and then "soldered" with copper. I could not get it hot enough to break the bond with the tube and remove it though.

 

use s4 fuel rails...the fpr is removable.

 

Sounds great. I assume they will still fit under the S5 UIM?

 

S3 shown

 

Will S4 NA fuel rails bolt up to the S5 manifold?

 

use s4 t2 fuel rails...you will need a couple washers to put under the mounts for the secondary rail as spacers

 

Thanks, I will try to secure some. Anyone out there have a set? I will look in the ads. Thanks,