i must be blind but i can't see where you modified the hanger




nvm i see it now

 

Heres one for ya....this happened to me....!

Due to the higher pressure of the FB-340 pump, at the top / near redline rpm, the pressure was great enough to actually expand the OEM hose clamps coming off of the small 2" fuel line on the in-tank pump. This was causing a huge fuel pressure drop at higher rpm's....and leaned out / misfire if thats what you're describing

To fix the issue we swapped out the OEM squeeze style clamps for the type that screw down. This completely fixed the fuel pressure drop at high rpm issue....now the FB-340 pump holds steady all the way through the rising rate to 85-psi WOT @ full boost.
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Thanks, this will help people.

 

Heres one for ya....this happened to me....!

Due to the higher pressure of the FB-340 pump, at the top / near redline rpm, the pressure was great enough to actually expand the OEM hose clamps coming off of the small 2" fuel line on the in-tank pump. This was causing a huge fuel pressure drop at higher rpm's....and leaned out / misfire if thats what you're describing

To fix the issue we swapped out the OEM squeeze style clamps for the type that screw down. This completely fixed the fuel pressure drop at high rpm issue....now the FB-340 pump holds steady all the way through the rising rate to 85-psi WOT @ full boost.
[/quote]
I have already replaced them with the screw down clamps and have also rewired the pump with 10 gauge wire as well :/

The bigger wire helped to lower my duty cycle about 4%, but thats it.

 

Ok I modified the hanger to raise the pump up to the level of my old pump and still it is flowing worse than my full blown. I then switched the filter out for the filter off of the Full Blown pump and positioned it exactly how it is with the Full blown pump in stock configuration and it was a bit better, but still worse than the Full Blown. I'm about to replace my whole damn fuel system :/

 

I don't remember, did you say you have rewired your pump? what's your fuel pressure ?

 

Just dual 340 it and be done

 

Yes it is rewired with 10ga wire. Fuel pressure is 65psi base. On the dyno it was jumping up with boost like it should, but by redline was dropping to below 65psi leaving me with a base pressure across the injector of way less than 65psi!

I am going to wire in a pressure sensor hopefully this week so I can monitor fuel pressure all the time and see what it is doing with this 400 pump.

 

What size injector are you running, sohc?

 

ID1000

 

I went through a very similar situation this summer trying to get my car tuned and running right. I tried both of the new 340lph pumps, but was dropping fuel pressure with both.

First setup:
FB340 w/brand new OEM sock filter -> hardwired off battery in trunk -> stock fuel rail -> stock FPR

Didn't have a fuel pressure gauge, but car was going lean over 7K rpm's. Was on the dyno for over 3hrs, tuner couldn't get it running right no matter how much fuel he dumped in at high rpm.

Second setup:
Aeromotive 340 w/OEM sock filter -> hardwired off battery in trunk -> AEM S2000 fuel rail -> AEM FPR (using small internal orifice that came installed) -> K-Tuned 100psi fuel pressure gauge.

Car seemed to run a little bit better with this setup, but ran into the same issue on the dyno. With the fuel pressure gauge, we watched the fuel pressure rise from 50psi (base) to ~65psi then just drop to around 40psi at redline.

Tuner started talking crazy talk with me...dual pump setup, surge tank, etc. I knew I didn't need all that for 12-14lbs of boost on 91 pump gas, sooooo I went to another tuner.

Next/New dyno session with new Tuner
Third Setup:
The only thing I changed was pulling the pump out (again) and adding fuel line specific hose clamps on the hose in between the pump and pump hanger.

Once again, car ran great on partial throttle pulls but lost fuel pressure at high rpm's

Forth setup:
Went back to my tried and true Walbro 255 w/another brand new OEM sock filter -> new fuel hose between pump and hanger w/fuel line specific clamps -> brand new OEM pump hanger -> AEM fuel rail -> AEM FPR (switched to medium sized orifice) and dropped fuel pressure down to near stock ~45 psi IIRC

Also, the shop had me drill a few holes into the fuel supply fitting on the fuel rail to allow fuel to flow into the rail faster




Sure enough, fuel pressure held strong all the way to redline with this setup.
Not sure if it was the pump or drilling out the fitting (or combo of both).

Hope this helps some of you out. I know how frustrating (and expensive) these issues can be.

Scott-