I'd like to get a better understanding of the Turbonetics fuel pump assembly mod. (drilling holes into the basket, drilling out the FPR & yellow sipon jet) What exactly does this accomplish? Can anyone go into detail on it please?

I did this when I installed my Walbro fuel pump, but never really understood it fully.

 

Its intent was to ensure the fuel pump was able to draw in as much fuel as it needed. phunk has since posted that doing so disables the small surge tank in the assembly. I have never had an issue as a result of doing it though..

 

yeah I'm a bit worried b/c the original instructions said to discard the yellow siphon jet, which I did. But now I read to just drill that thing out.

What purpose does the small surge tank in the assembly serve?

 

well a lot of TN kits when they go under 1/4 tank will buck and misfire. we have figured out that it is because of that yellow piece missing. we have tested and tested it and thats the issue. so drill it out a bit bigger and put it in. then it wont do that...

 

I have the Walbro and did not drill out the FPR. As a result my fuel press is around 80 psi normal non-boost conditions..Under boost the Vortech FMU/Aux fuel kicks in and press goes up and up and up..I also have 440 inj's. I have not experienced any problems with fuel delivery but 80 psi with the Vortech fuel lines up to the FMU scares me..The drilling mod brings the fuel press down to around 50 psi I believe..

 

can you please elaborate a bit more??

 

i wish someone would just send me a completely stock fuel pump assembly so i can make an end all video to how it works and how you should and shouldnt do certain things to it

 

just throwing a walbro in there doesnt raise it to 80 psi, we have tested it with a fuel pressure gauge on two different cars and it was usually mid 50s at highest.

 

Please don't tell me what my Fuel Pressure is reading..80 PSI..

 

stock psi is like 55psi at idle...80 should be more like wot....

 

stock fuel pressure is 51 psi.

its 51 psi at idle, its 51 psi at full throttle. its always 51 PSI, because its a returnless system without vacuum reference.

if fuel pressure is higher than 51 psi, than there is a blockage in the internal regulation system.

if the pressure is less than 51 psi, than the regulator is failing, the pump is failing, the internal filter is clogged, or there is a low voltage condition.

if you upgrade to a walbro GSS342, the internal regulation system becomes a restriction and fuel pressure at idle will be inconsistent. this is because the fuel that is relieved from the pressure side by the regulator is fed into 2 very small and restrictive venturi jets. one for the fuel transfer from one side of the tank to the other, and one to fill the surge can (i will call this the swirl jet, or the fill jet, or the fill siphon, whatever its all the same). you cannot get to the transfer venturi, but you can get to the fill venturi. the fill venturi is the yellow part on the bottom of the can that people that dont know what they are talking about will tell you to remove.

there is no guessing what your pressure will be when it is being regulated by restrictions rather than the regulator. voltage, idle rpm, and injector atomization quality, and injector pulse width will be the new determining factors in what your new idle fuel pressure will be, but it will float around anyway. a simple rev of the engine and the pressure should go back to normal. raise the idle rpm to help the situation too. or, do it the right way.

the regulator itself has to be able to support the new quanity of return fuel at idle. supposedly you have to drill its outlet or something... i dont know, i dont play with the stock regulator.

aside from the regulator, the internal passages in the pump assembly now have to be able to support this amount of fuel. this is easy. remove the fill jet, drill it to a slightly larger hole, then reinstall it.

if you do not reinstall it, fuel pressure will be fine, but you will be removing the surge cans ability to provide better fuel control for the fuel pump, and at lower tank levels you are promoting fuel starvation.

do not put holes in the side of your fuel surge can like turbonetics says. this is the most retarded thing i can imagine, as it serves no purpose. its only purpose would be to help fuel get to the pump after you made the mistake they used to tell you to do which was removing the fill venturi. if you keep your system how it was originally designed by nissan, you do not need to make such mistakes and take such risks by reducing your fuel pump assemblies ability to control the fuel and provide a quality supply to the fuel pump pickup.

so... these are the basic rules.

if you have a stock fuel pump, do not do anything at all, you can only make things worse.

if you have a GSS342, DO NOT DRILL HOLES IN THE SIDE OF THE CAN, AND DO NOT REMOVE THE YELLOW VENTURI ON THE BOTTOM OF THE CAN. BOTH OF THESE IDEAS ARE DESTRUCTIVE and make you worse off than you started.

if you have a GSS342; ***DO*** drill out the oriface in the venturi jet to 070" - .100". this is a **must** unless you live where the laws of physics cease to exist, or you car idles at 1200+ rpm and/or has crappy injectors dumping skittle sized droplets of fuel in your engine and/or has a bad alternator/charging system.

secondly, if you have a GSS342; ***DO*** make one of two changes to your regulation system. You either will modify your stock regulator as some people will tell you to do so that it flows enough at idle. REMEMBER, IDLE IS WHEN YOUR FUEL REGULATION SYSTEM IS WORKING THE HARDEST. this is because your engine is hardly using any of the fuel that the pump is sending, therefore it nearly all must be bypassed and returned to the tank. Or your second option is to get a proper return fuel system that INCLUDES a SIPHON FITTING to send your return fuel to back into where the stock regulator was in order for your transfer siphon and fill siphon to still function.

 

putting a walbro GSS342 fuel pump in an otherwise completely stock fuel pump asssembly in a car that has factory idle rpm will yield up to 80psi of fuel pressure at idle. this has happened a tons of people... this is why i originally started tell people to oversize the fill jet on the can, this is why APS eventually added to their instructions to do this as well, its probably why turbonetics originally removed it to begin with, and its why tons of people have called me and complained of high fuel pressure at idle after doing their fuel system and then they call me again to tell me the problem is gone after they oversized the fill jet like i told them to.

 

and on my 06 I did not do any drilling, only swapped out the pump for a walbro 255 and I had 52 PSI without modification. I too have 440's

 

what is your engine vacuum at idle, full temp? what is your idle speed? also, how many miles on your car?

 

the two cars we had were both bone stock cars , fuel pressure was pretty normal at idle and driving too. i can see where people would have high fuel pressure because of the pump change for sure, just wasnt the case with the two setups we did.

nice write up charles!!

 

Cool I will follow phunks instructions when upgrading my fuel pump.

 

around 20 In. Hg and idle speed is set to 900, but is usually around 1k-1.1k. 16k miles on the car

 

the higher idle is likely how your car doesnt have a fuel pressure spike at idle. you dont have enough miles for it to be very likely that a clogged filter could be reducing the output of the pump.

 

I have one i'm fixing to do up and a walbro pump too. i'll send it and pay shipping both ways if you want to make the video. i'm sure i'll blow my house up hosing around with this stuff.

lemme know.

 

I have a GSS317 and didnt modify the stock assembly at all. I am running the stock injectors and won't be running the FMU. Will I run lean? Should I use the FMU with the fuel pump?