Z-speed33

iTrader: (13)

I recently built the bottom end of my 2005 350Z. Pistons, rods, bearings, studs. I bought a local, lightly used turbo kit. I bought a lightly used AAM stage 1 fuel return system. I have the Walbro 255 HP pump and DW 600CC injectors. I'm also using Uprev for all my tuning.

I took it to be tuned by a buddy of mine and then dyno'd, we soon figured out that I need to go with the Uprev MAF because the OEM one is pinned at 5V, so I've order that and its on its way. However when I go to do a pull on the dyno at about 3000RPM it goes quick rich, about 10 on my AEM WB, and bogs out. Then we get up to 3500RPM and its all good again. Then from 4000RPM it progressively gets leaner and leaner. Till we get up to 6000RPM and its up in the 20s on the WB.

On my fuel pressure gauge right when it starts going lean I start loosing pressure. Drops from 40psi to 20psi.

Any ideas would be appreciated.
Thanks

terrasmak

iTrader: (8)

Sounds like you may need a return system with an aftermarket reg

Z-speed33

iTrader: (13)

^^^^^ Have one!

terrasmak

iTrader: (8)

Does you FPR have the vacuum hooked up to it ?

Z-speed33

iTrader: (13)

Yessir!

evilscorp

Have you done the walbro swirl jet mod?

Z-speed33

iTrader: (13)

i have not. i ordered a new pump and i was going to do that when i replace it. but i thought that was more for low rpms

binder

iTrader: (8)

You still need to modify it.

Sounds to me like it's running out of fuel pump. If your fuel pressure is only 40psi at high rpms then something is wrong with your fuel pressure regulator on that return fuel system. Your idle should be around mid 40's to 50psi. You should gain 1psi of fuel pressure per 1psi of boost if it's working. Your starting fuel pressure sounds too low to me.

Z-speed33

iTrader: (13)

okay so here is an update and a bit more information:
I drilled out the swirl jet valve and put it back in the tank. checked and still no change. running around 40psi and then going lean under boost.
But I am also having extended cranking (good like 15 seconds), I feel like it is because I have no fuel pressure when I go to start the car. So I thought there was something wrong with the regulator like it was not holding pressure, cause it should hold pressure even after I turn the car off. So I figured the fpr was toast, tested a friends one that we know is working and no change.
So I am fairly lost on where to go from here.

binder

iTrader: (8)

You might have a bad walbro. Sometimes the pressure relief valve on them can go bad and they leak pressure or you might have a leak where the walbro pump meets the fuel basket.

Did you install the walbro or did you purchase the fuel system already assembled?

I would use a regulated source of air and test the fuel pressure regulator. I suspect it is ok but it's always a good idea to test it with some air. Unplug the vac line and hook it up to a regulated source on an air compressor and with the car idling give it about 10psi and the fuel pressure should increase 10psi higher than what it is idling at. If not then you have a leak in your FPR. I would do this first since it's an easy test to perform.

Also, I always run a dedicated source for vac on my FPR instead of T'ing off of something else just to make sure it gets the proper pressure.

When you turn the car off the fuel pressure should drop down to zero since there is no fuel flowing to create a pressure.

If the FPR checks out just fine then you either have a bad pump or a bad seal between the pump and basket causing a loss in flow to the engine under load.

Z-speed33

iTrader: (13)

I got the walbro with the turbo kit I bought. It was already assembled but I did have it apart to make sure there was actually a walbro in it and to install the fuel return. I have ordered a new fuel pump just for the fact that I don't know where this one has been, so hopefully that will get here soon and will rule the pump out.

Would the check valve in the walbro going bad actually cause me to lose the pressure at higher rpms? That's why I figured the regulator, but its now rule out cause I've tried a known good one and I still have the same issue.

And yes I have a dedicated line straight from my SSV to the fpr.

Z-speed33

iTrader: (13)

So latest update... I got my new fuel pump, another walbro 255. Installed it into the assembly. Tested and my pressure is still to low and will not change when adjusting the fpr. I have no idea where to go from here now, like the pump is new so it can't be losing pressure through the check valve, regulator is good so it can't be leaking past the diaphragm. Not sure what's wrong with this...

binder

iTrader: (8)

do you mean low at idle now?

Did you run through all the tests I suggested and watched the fuel pressure rise with putting air pressure on the FPR?

If that checked out then you are losing pressure in the basket. How hard was it to click the back cap onto the fuel pump? it should be quite hard in order to seal that fuel pump against the basket.

Z-speed33

iTrader: (13)

It always been low at idle. it idles around 35psi. and i cant adjust it any higher. i replaced the fpr with a know good one, but I have not applied pressure to it, just left it to vac/boost.

I thought maybe I didnt have enough current going to the pump, so I used my powerprobe and applied a direct 12V straight to the pump while the car was running and it didnt affect it at all.

And when you turn it off it should still hold pressure, so that when you go to turn it on you already have fuel at the injectors, I loose my pressure and then I get a 15-20 second crank.

str8dum1

iTrader: (11)

if you cant raise your fuel pressure above 35psi, you have a leak, esp if you tried a different regulator.

Your fuel line hose is leaking inside the basket, or something you missed since you have a new pump.

With a properly setup system, when you crank down on the FPR adjustment screw, you should be able to run that fuel pressure up to 70psi.

And given the fact that its practically impossible to get base fuel pressure below 40psi on the stock basket setup, even more points towards a leak

binder

iTrader: (8)

+1, most aeromotive style regulators won't allow less than 40psi on a functioning fuel system. It should raise when you turn the screw in on the FPR.

and no, if it holds pressure then your return line has something backing it up. Mine used to do that and I had all kinds of fuel problems. Since getting everything working properly my fuel pressure drops right down to 0 as soon as the car is off. There shouldn't be any restrictions past the FPR to hold fuel from draining back to the basket.

Z-speed33

iTrader: (13)

Yeah I figured 35psi was really low for the system because that's not even as high as stock pressure.
And yeah my pressure does drop off right away. but the gauge for the fpr is on the pressure side not the return side, correct? if it is on the return side then yes I agree it should drop off right away. but the pressure side should keep pressure, which mine is not. which is why I am getting extended cranking, and could be why I have low pressure?

str8dum1

iTrader: (11)

my guess is you are leaking internally in the basket

Z-speed33

iTrader: (13)

FINALLY!!!!

So I basically took it all apart and went over everything.... and I found something very interesting that I didn't notice before. I was re-installing everything, carefully doing ever step the instructions (that I got online) said to do. Then I notice in the picture in the instructions that there was two o-rings on the plug that replaces the pressure relief valve. My kit (remember it was used) had the end cut off so it was missing the groove for the second o-ring.

Here is the picture from the instructions, mine was cut off about where the red line is.





So really I was pumping fuel into the pressure side and the return just equalizing the pressure at 35psi. I had a kit of universal o-ring and I just slide one on, it sits right at the bottom so I may end up having some issues down the road, but then I gave it a try.

It holds pressure on the pressure side when I turn it off now, I can adjust pressure and it increases with boost. Now off to the tune/dyno!

Thanks for all your help guys! Really appreciate it.

binder

iTrader: (8)

silly AAM. I never understood why they have such a strange setup. CJM is simple and to the point.


I'm still confused how your fuel pressure holds after you turn the car off. On a returnless system it will because it's closed but on a return system there should be no restriction back to the tank so pressure will drop. On every car I've done work on or tuned the gauge at the FPR goes to zero when the car is off on a return style system.

EDIT: except once on mine when the FPR diaphragm tore and pieces of it clogged up my return port on my basket. Then my fuel pressure was staying when the car was off which confused me so I tore it down and found the problem.