ok, still trying to solve the leanness problem.

I drive the car with the inline pump off (of course, I am not boosting it) and the fuel pressure reading is very stable. it goes up a little when I do a 1/4 throttle and it idles at 34psi.


now when I have both connected I noticed that at the same 1/4 throttle, the fuel pressure goes up higher as expected. but the needle of my gauge will bounce back and forth. my fuel p. gauge is 110psi max so I couldnt really tell how much it bounces.


Does this mean my inline pump is half dead?


thx

 

Sorry I dont completely understand what you wrote. You say at 1/4 throttle it barely goes up and idles at 34psi with the inline pump off. If so, thats perfect for NA/Idle and 1/4 throttle.

With both connected, the Fuel Pressure will be higher because of the inline. Same goes on an intank walbro 255lph. Your WOT FP on an oem pump is about 43psi. Your WOT FP on a walbro 255lph is probably close to 60psi. So your inline should be right around there.

I dont understand the part of the inline being possibly half dead. Almost seems like it is working fine.

Alright, here is something I just thought about as well, since you got an FP gauge now. Crimp the return fuel line going to the tank with a plier. With the inline and oem FP running, your FP gauge should read its max pressure of about 100psi (If that is what the inline can put out). If not, then your FP is bad.

Dixit

 

thx dixit for the reply.

the needle on the fuel pressure gauge is boucing with the inline and the OEM in tank. does that mean anything? I remember reading somewhere that fuel perssure should be very stable during idle and boost.

half dead fuel pump - can a pump be ok during normal driving but when under boost, it will start to deliver less fuel when too much fuel pressure is applied to the pump?

I will try your method tomorrow. but I went up to 100psi + with my inline and OEM in tank before.

 

Well sitting in your garage/parking lot this will show you when you crimp the return line, the FP should rise to in excess of 100psi as well. The pump really dont care/know when the car is boosting or not.

The needle should be stable at idle for sure. How much do you see it bouncing? Almost looks like a vacuum leak on the oem fpr or something part of that setup. Mine sometimes moves maybe, maybe 1psi when the car is idling up and down.

Dixit

 

Yes, try the crimp test as Dixit suggested. You will need to have someone sit in the car and watch the gauge.

Get an intank Walbro. It provides enough fuel for your needs.

 

as long as you use the proper FMU or ECU

 

guys:
I did the test today and it went up all the way to 110psi. soo....I dunno. I ordered a replacement pump and it's on the way. It's an inline pump with 60-70GPH. we will see.

dixit : I cant really tell how much does the needle bounce because my gauge goes up to 110psi and it is not very noticible until you park your car and stare at it. I think it is 1 - 2 psi at idle. but the gap gets bigger when I step on it. probably 5psi the most....I noticed that when I was driving.


thx all for your help.

 

So this means the pumps are definetely working. The fuel pressure gauge bouncing a bit isnt a big deal since you are not running an aftermarket fpr. That will help solve that issue, but your issue where it is lean is still boggling me.

At this point the only thing I can think of is the injectors are not working correctly. Almost seems as if they are not spraying enough fuel but getting the pressure. So that could mean they are clogged.

Dixit

 

Did you make sure the hoses were cleanly cut when you put in the FP sender?

Did you make sure no debris fell in the hose(s)?

 

that's what Alex (Icey2k1) thinks.

I dunno if excessive rail pressure is making the pump delivering less fuel. I called stillen to get the flow rate and pressure rating for their inline pump, but they wont give it to me. If the pump is designed to delivery, say 40 gph, then I am going to try another pump with higher fuel delivery.


maybe I should take off the injectors and take a look. but the ones in the rear will be a lot of work.

 

I just replaced the hose 2 weeks ago and they seems fine: the inner wall peeled-off a little near the sender tee and the pump but it was still in one piece.

I flushed the hose before I installed it. should be fine.

oh~ this is something that I noticed from replacing the fuel hose last time: It took me soo many tries to release the fuel pressure. I unplugged the fuel pump and the fuse, and I was still able to start the car for at least 10 times. Finally when it comes to the point that the car will die right the way...then I loose the fuel hose and guess what...there was still quite a lot of fuel spilling out. Does this mean the injectors are clogged and I wouldnt be able to push all the fuel to the engine when my pumps are off. That's why the car just wont die from lacking of fuel?

did you take a look at my dyno? It was lean all the way from 4000 to redline

 

Damn this is going to be a pain, cause removing the injector is not that bad, but actually testing it like what the FSM says about hooking it up and spraying it into a container to ensure correct atomization and flow I dont know how to do that. I mean I would have to rig the injector to open and then at the same time hookup a tube to the injector to spray the fuel from a fuel pump. Almost seems like more work than just sending it to RC.

I say if you got time and the funds, maybe send in all your injectors to make sure they are fine.

Dixit

 

My TWO guesses:

1)FP sender is restricting flow, yet measuring pressure.
OR
2)Some of that crap from the lines or junk or just being pushed too hard has clogged/fried the injectors.

The injectors are an electrical part that can be burnt up if really high FP is used with max duty cycles for long periods of time.

I say, pick up a set of injectors from a junkyard and give them a try, while sending in your stockers to RC Engineering OR buy RC Engineering 350Z 370cc injectors and an adjustable FPR.