Im scratching my head a bit. This is a procharged car with piggy back booster pump for reference. Once the booster puml kicks in we are good

I have a fuel pressure gauge in the car and idles around 52psi. Recently if I cruise oit of boost(so 2nd pump is off) my psi will sometimes drop to as low as 43and leans out to 16afr. Of cpurse if I mash the gas and the booster pump kicks on we are solid again.

Is this a sign of a failing in tank pump on this platform?

Im assuming the pump was never changed out before I bought it

 

I dont know that pumps fail like that … from my experience they are either 100% go or 100% no-go …

I would open up your fuel pump basket and check to ensure your gromet inside the fuel basket is 100% sealing up…If this is the issue, I suspect you have a very small leak in the grommet but the pump has enough flow to overcome it at low load/low rpms and still supply fuel to the engine at 52psi.

As soon as you demand throttle / boost your injectors are staying open longer and consuming more fuel and more fuel flow and this is why you are seeing a dip in your fuel pressure and AFRs. Then, as you mentioned, the second pump kicks on and supplies ample fuel pressure.

It may be wise to replace your primary fuel pump while youre in there? Just a thought.

 

I still have the whole return system I got from you that Ive been too caught up with other stuff to install. Guess now is a good time to do so.

 

I still have the whole return system I got from you that Ive been too caught up with other stuff to install. Guess now is a good time to do so.

 

Follow up... after reading a bunch youre probably correct on the grommet... i would bet the booster pump furthers the wear on things as its pulling more fuel faster boosting pressure through the roof.

Just to test something is there a limit on pump size the stock system can handle? I know on dsm if you go over 255 you start over running the stock regulator.

 

Get the return system installed and see where you end up…it very well could solve your problem. And/or take your fuel basket out and visually inspect. I only know this because it’s happened to me on my car and customer cars (during the UP days). I try to keep a extra grommets on hand for this exact reason.

We dont have OEM / stock regulators as they are not turbo’d from the factory and there would be no reason / no need to adjust the OEM fuel pressure. What youre refering to is a pulse dampener.

Im sure there is a limit to what the OEM setup can handle but plenty of people have run 340lph, 450lph, and 525lph with the OEM basket … whether pressure or flow I think the stock setup can take whatever you throw at it.

I suspect your grommet aged-out and got slightly compromised and every time you run the car it probably got a tiny bit worse and you are now seeing the ramifications of it. No big deal, order a few fresh ones and you’ll be good to go.

 

Newest update.

Got the grommet replaced and still an issue. Thought with the old one swollen as it was I had found my issue

But still having the issue with a slow preasure bleed. Slowly went to 4k and this happens

 

Coming back with the problem solved. Cj motorsports was super awesome to talk with and trouble shoot.

I went ahead and got a wally 255 pump and new basket assembly. CjM said that the baskets have internal filters that are non serviceable as Nissan assumes when its time to change the pump the basket would be changed thus your filter as well.

I followed the directions on the wally 255 to a "T" but I should have made the regulator hole just a hair bigger. I can live with it but the fuel pressre is around 57 instead of the original 51. Haltech can easily tune that out. Im a point and a half richer at idle on that pressure.


RESOLVED

 

Im happy it’s fixed but where is the filter element in those baskets?

 

i may cut mine open to find out and chronicle for the good of the Z community... its a cellulose element, Ive seen them in the 370z baskets

 

Here is your element built into the basket