Just wanted to give an update on my dual walbro setup. I recently was having some unexplained missing in my car. When I checked my pump setup I found that the tank was not pressurizing like it should. My JB weld was not holding pressure where the wires enter the tank.

This was causing the fuel pump to cavitate or make air bubbles in the lines. I put a Nylon bolt fitting and O ring like shown earlier and sealed it with ultra copper and now the problem is fixed. Apparently the tank must pressurize to 5psi to allow the pumps to not cavitate.

 

Thanks for the bit of info 97WS6Pilot. I think I may be in the same boat as I swapped sending units and had to remove the wiring and reinstall and it wasn't quite as snug as the original setup.

 

So what is actually pressurizing the tank? This may be the problem I am experiencing (stumble in upper RPM's). I don't have any of the EVAP lines hooked up anymore. How is yours?

 

My tank evap system is hooked up and has a stock pressure relief valve that opens at approximately 5 psi. After you run your car for about 10 minutes you should hear a hissing sound when you remove your fuel cap if it is pressurizing properly. I'm pretty sure that the muffler that sits up underneath the fuel tank is the main source of pressure. It heats the fuel causing it to pressurize the tank.

I know on turbine engines there is always a fuel boost pump to aid the main engine pump and prevent cavitation. I think in this instance GM pressurizes tank to aid the fuel pump and also to prevent so much fuel from vaporizing in the tank. More pressure = less vapor.

 

how did you know you needed to run two pumps? i'm running 8psi with 42lb injectors and one 255 walbro. when my 355 is done i plan to raise boost to 10-12lbs. will i need another pump to supply enough fuel?

 

I'm wondering this as well. I'm already running 12 psi with 42 lb injectors but can't seem to put down any good times. Wondering if I'm running out of fuel. Running a stock in tank pump with a T-Rex. Not sure I want to blow $500 on the dual pump setup....I just need some prodding, I guess...

 

yeah thats alot of bills....

 

I have a wideband commander and a fuel pressure guage mounted in the car. When I hit about 5500 and WOT the fuel pressure would decrease and the AFR would start climbing. I've found a good 3rd gear pull will give you extemely accurate info. I tried adding fuel to the RPM vs PE table to no avail. Time for fuel pump upgrade.

 

the real deal..racetronix set up

 

More pics of the real deal

 

blown383 tell me that was fun trying to get that sending unit back in the tank. LOL! It took me a 1/2 trying to get that thing back in.

I had to go back to my old sending unit as I jacked up theirs trying to modifiy the y-block. That yellow was a pain removing and putting on my old sending unit. OMG! Now I'm worried if it isn't sealed as tight as theirs will it cause a pressure problem? I got it on there snug but not dead tight as his.

 

Now the question is where can you get the factory style corrigated clear fuel hose? Seems like that's the only stuff out there that does't get softened by all the ethanol they're putting in gas now.

 

I used some stuff from Carquest that's fuel line rated for in-tank use. It's special order and sold in 6" sections... Earlier in this thread lists a place that sells that flex hose, but the place only sells them if you buy a pump. He does let you order as many as you want with one pump order though.

dealerships don't even sell that flex hose separate...

 

It wasn't too bad but I had to maneuver and angle that thing for a while before it would seat properly. Even then it was still wasn't seating properly. I have to redo my entire fuel system because the stainless braided line I have was actually Teflon instead of the CPE rubber. So now all of the hose ends and fittings that I bought won't work!!!! Now I have to measure and cut the lines so that the fitting shop can hydraulically crimp the proper fittings on. So there is no chance of leaks.

-B

 

That y block and flex tube looks sweeeet. How is it attached to the metal feed line? Compression Fitting?