blk00ss

iTrader: (66)

First off I'll go ahead and give a run down of my setup.

2000 Camaro with LS2 404 and D1sc making 10-13lbs

Nasty nate Line and fitting kit, -8 feed/-6 return
DIY twin intank walbro's. The pump that runs all the time is a racetronix for a 99'+ car. And the second is just a regular gs340 walbro. The second pump comes on with a hobbs switch set at 4psi, and has 12 gauge wiring ran from the pump to a relay in the spare tire compartment. Then 12gauge wire all the way to the battery, with a 20amp fuse. Also the first pump has the racetronix plug and play hot wire kit. I have a aeromotive FPR which I have boost refrenced. I have the fuel pressure set at 50psi with the vacum line disconnected. So the FPR is anywhere between 43-50psi while normal driving. I also have 80lb injectors with MAST black label fuel rails.

So here is my problem. Just cruising around the pressure does good. As soon as it goes to "0" vacum the FP is 50. And if I slowly make a couple of pounds of boost it will rise up to say 52/53psi. But if I really nail it in a lower gear it will drop into the lower 40's/30's. Its almost like my second pump is not even coming on at all. But I can pressurize my hobbs switch with an air compressor and it will kick on instantly. And it sounds very strong and will take my FP straight to 50psi. My next course is to jump my hobbs switch and make the second pump stay on and I'll go make a pull and see if that helps.

But I am open to any and all suggestions anyone may have...oh and btw the fuel pressure was doing good and it kind of started doing this all the sudden while tuning on it a few days ago.

Lonnies Performance

iTrader: (16)

Not sure of the quality of your pump, or the way you have them connected, but a dual pump setup with a complete line kit, should have no problem with your engine combo. The fact that it drops pressure leads me to believe you have a major flow issue with 1 pump.

blk00ss

iTrader: (66)

Idk what you mean by the quality? One of them is a racetronix 255 and the other is a walbro 255 part number gs340. I know most people run two gs340's but I already had the racetronix so opted to keep it.

Racetronix

iTrader: (2)

.. or a DIY configuration problem. A F99-FPA is not designed to be paired with another pump or used in a modified bucket.

blk00ss

iTrader: (66)

Ok Im guessing the f99 is the pump I have? I made a effin thread before I did this, asking if it was ok to use a racetronix pump like this. I got no one telling me not to. So your saying that my pressure drop could be because because the racetronix is failing? Because it's not suppose to be in a modified bucket??

Racetronix

iTrader: (2)

Always contact our tech support dept. or a listed dealer as your primary source for information when it comes to Racetronix product. Public forums are not a reliable source of information.

It is possible that the F99 pump is the problem if you have cut holes in the bucket and / or eliminated the jet pump.

Lonnies Performance

iTrader: (16)

I was referring to the quality of the GSS340 pump that you used.... you did not say where it came from. There are many junk generic imports out there.
You get what you pay for with these pumps.

Also,
You are improperly using the 99 pump & may be starving it for fuel based on how everything is installed.

blk00ss

iTrader: (66)

Ok so I just went and tried a few things...first I jumped my second fuel pump to make sure it was comingon. Went for a drive and gradually got on it. It would make it to 55psi(sometimes) and start dropping like a rock.

So next I unhooked the vacum line from the FPR, and set my FPR to 58psi. Went for another test drive. As soon as I started driving the pressure dropped from the 58psi it was set at, to 56-57psi. And as I was driving and not even getting on it, the pressure would drop down to 50-52psi. And I would get it get on it some and it would drop to around 47-48 and hold there for a bit, then drop down into the 30's. I would immediately let out.

So it seems like this may be FPR related? I have a aeromotive 13101 FPR. I rememeber when I rodered my Nast Nate line and fitting kit, that he told me to stay away from the aeromotive FPR's. Said he has had problems with them not holding pressure...So should I look into getting another FPR or pumps? I just hate to start throwing money at a problem, unless I know for sure what the problem is.

Lonnies Performance

iTrader: (16)

Could be a lot of potential issues.

Since you built your own kit, did you use a rubber hose in the tank? It can be kinked or leaking, which is the problem 99% of the time.

First you will likely never exceed the capacity of 2 pumps at less than full thottle. The fact that pressure drops as soon as you get under load, I would think there is a weak pump, bad regulator or an internal line leak.

1. Drive with only 1 pump on at a time & see how easily pressure drops. You may be able to see if 1 pump has more effect than another. If they act the same, the pumps are probably fine.

2. Next plug the return line from the reg & quickly blip the key to prime the pump (using 1 pump only). Does pressure come up & hold. Do not start car or run the pump continuously as you could overpressurize the system. Just try to get 30-50psi. If it will not hold pressure, you likely have an internal leak.
Remember an electric gauge does not work with the key off, so you need a mech gauge.

3. If both pumps act roughly the same & they hold pressure, key off with the return blocked, the regulator is likely at fault.

blk00ss

iTrader: (66)

Yes I used the submergable fuel line. There are no kinks for sure. No visible leaks. I have been back in the tank twice to check over my hose clamps, ect. But I hve been having one re-occuring thought. I have to use 3/8" fuel line to fit onto my home depot t fitting. But that same line is loose on the pumps outlets. But I just hammered down on the hose clamps lol. There's no movement after I tightened the clamps. Maybe I'm getting a leak from here??

Lonnies Performance

iTrader: (16)

Are you taking into consideration the amount you compress the bucket when you install it? This often kinks the hose & either restricts flow or causes it to fail in this area.

blk00ss

iTrader: (66)

Well I haven't really thought about it. But I'll definately pull it back out and compress it as hard as I can and see what it looks like! Good call there Lonnie. Also how would you suggest I block off my return line?

blk00ss

iTrader: (66)

UPDATE: Well I believe that I have fixed my dropping fuel pressure problem. I went BACK into the tank for the third time to go over all my connections/ hoses, ect. I also replaced my "T" fitting with a "Y" fitting that I got from my buddy. He has an 03' Cobra, and they ahve the same problem with limited space inside the fuel tank. And he had a metal Y fitting that has 5/16" ends, the same as the Walbro's outlets. The T I was using was so big it needed 3/8" line. And obviously that was very loose around the outlets of the walbro's. I had to crank down so tight on the fuel line with hose clamps, that it was ripping and tearing the hose up. And I guess was causing a leak when under a load.

So anyways I replaced all my line with 5/16" submergable fuel injection hose, and replaced the T fiiting with a better flowing Y fitting. Now it doesnt drop pressure any time I'm at part throttle and higher. And rises pretty as you please with boost. All the way up to 60 psi(my base FP is 50). I beleive I am going to raise my base up to 55psi tho...

But I figured I would post up a fix to my problem so maybe it will help someone one day.