There isn't a pressure regulator on the OE fuel rail. The RX-8 has a dead-head fuel system and the pressure is regulated at the pump.

KG Parts makes a rail that fits the factory injectors.

 

The thing on the OEM fuel rail is a pulsation damper...as MM said the regulator is in the pump

 

Hmm so what does the Saucer thing do on the stock fuel rail and why do the aftermarket rails don't use them? I'm going lean on WOT runs currently and I am unsure that it is the tune.. I replaced the stock fuel pump with a walbro knock off 255 pump and it reads 60 psi on the digital fuel pressure gauge but after some driving it drops under 20 then just cruising around the numbers are in the negative! Dunno what exactly is causing this and I am going to buy an inline 255 pump and put it under the hood and run 2 pumps to compensate.. I don't really want to run a return line back to the Fuel tank either.

 

If you can't hold fuel pressure you are going to have problems. and make it impossible to tune. In a returnless system you should see a very stable pressure on a gauge...only varying about 2-3psi.

By the sounds of it you need to make sure the gauge isn't the problem I would use a decent mechanical gauge to check that your electronic one is working

You can't run a pump under the hood without a return line anyway ( there will be no way to regulate the presure)...so you might as well do it properly if you are going to do something like that. You will need fuel rails and an external FPR.

PS: The "saucer thing" is a pulsation damper...it helps smooth out the fuel pressur pulses when the injectors open and close and acts like an accumulator to help stabilize the fuel pressure

 

well there is no relay currently on the FP switch and I notice the cables and switch get a little hot after a couple miles then the Fuel Pressure drops, so it is either a current draw when they get hot that the Fuel Pump cant operate properly under or a shitty Fuel Pump 255 lph I got off Ebay.. Either way I bought an inline 255 pump today at Murrays Speed shop for a hundred bucks and planning on putting it in today triggered via DPO above 5000 RPM's to give it a lil extra pressure on the high end, a great MOD if yer Boosting..

 

Sounds like you need to do a few things then

If you add an unregulated pump you may have problems depending on how you do it. The stock regulator may work correctly...or you may back up the system and end up with really strange FP problems

If the wiring is getting hot that fast you need to fix that BEFORE you get an electrical fire...so that would be the best place to start....Use at least 12 ga wire and run a relay

If that doesn't work then you will need to get another pump......

 

Yeah it was my mistake not running a relay I just wired one in tonight, along with one on the secondary Fuel Pump.. The issue is that the fuel is not flowing thru the secondary pump unless it is on as well so tomorrow I'm riding out to Ace Hardware and getting 2 Y pieces 3/8" and running a line right next to that 2nd FP to allow the fuel to get to the Fuel Rail at All times from the Primary Pump..

 

WTF? You need to take a break and study this stuff for a while. If you don't fundamentally understand why that wont work, you are really playing with fire.

 

What would you suggest? That is how dual Fuel Pumps are run.

 

Something like this is what I had in mind... http://imageshack.us/photo/my-images...22eh1.jpg/sr=1

 

That isn't what you were saying you are going to do.
You were going to run a bypass around the secondary pump. Think about that for a minute.

You've already run the pump directly through a switch. That is incredibly bone-headed. You are going to set yourself on fire.

Spend a day or two and read up on how this stuff is done. There are reasons for the methods that have been properly implemented in the past.

 

..failure to communicate.. I pray no one ever catches on Fire... A Switch is just a Flick away to Safety in case of an Emergency..

 

Ever tried to shut off a melted switch? Hopefully you fused it correctly

 

I've watched a guy try to turn of an actively burning switch before.
It was excellent.

 

Yep...seems to be missing the point A bit of remedial wiring instruction seems to be required

 

There is a fuse inline..

 

Just for fun....where?

 

Inline on the constant 12v prong off the Relay for the Fuel Pump switch..

 

Best place for the fuse is on the power source for the pump as close to the source as possible. Otherwise you will have a long unprotected run of live wire before the fuse. If you use a fused ign wire for the relay trigger you don't have to fuse that side

 

I got the Fuse a couple Inches away from the Power Block up front in the Engine Bay..

Dunno why but the Fuel Pressure drops drastically after the car has warmed up and drove around for a few.. Even with both Fuel Pumps in there (When the secondary kicks in PSI raises to like 30 from 0 or negative 5 where it stays after cruising for a while)... I think the Fuel Pump Housing Assembly Syphon Surge Valve thingie is NOT Staying close after all.... I really DUNNO another reason why the crazy drop in fuel PSI..

 

You either have a regulator problem..or a really bad fuel pickup problem..... Or your gauge is FUBAR

Pinch off the return and see what your pressure does

 

WHAT Return? And the Regulator is that Saucer thing right? That is why I was asking about it.. I might just rip/cut that UFO thing out and weld/cover it.... The Digital Gauge reads fine.. Fuel Pick up Perhaps or something in the Fuel Pump Assembly..

 

What are you using for a pump? Is this in your Starquest conversion? How do you have the fuel system plumbed? There must be a return/regulator someplace. In the stock RX-8 it is all in the pump.....

 

I am running the RX8 Fuel Tank with the StarQuest Fuel Lines but only using one Send line for the RX8's system... I DO have an AFTERMARKET 255 lph fuel pump I bought on Ebay that FITS in the RX8's Fuel Tank.... All InTank FP's Should regulate themselves right? And I have done the Fuel Pump Assembly Syphon closed valve Mod as stated before.....

So I just drove to Winn Dixxie to get me a 24 pack of King Of Beers with my friend and the Fuel Pressure did NOT drop this time.... Stayed at 60 psi strong for the whole ride, Floored it once and went up to 120 lol so no power loss of PSI this time.... Hmmmm

 

The pumps are not self regulating...the RX-8 regulator is in the pump assembly in the tank...the little mushroom looking thing that is on the line after the pump outlet.There is no way you should be seeing spikes in the line pressure like that unless you have the accessory pump plumbed in unregulated.

Once again the saucer thingy on the fuel rail is NOT a pressure regulator..it just smooths out the bumps in the pressure when the injectors open and close