Fuel Tanks Question ?

[switta]

Hey guys new here to the GTM side of things , built a 33 hot rod back in 2010 and i have now bought a finished GTM .
so im trying to figure out how this fuel system works with the two tanks ? i had the front of the car jacked up to bleed the cooling system and after about 10 min i smell fuel ? look around the back passenger side and there was fuel all over the garage floor ? ( the day before i put 5 gal in each tank ) could not see where it was coming from through the engine bay so i shut things down and by the time i got the rear wheel off and inside access panel in front of the wheel things were dried up and could not tell where it came from ? started the engine again and could not replicate the problem ?
so on the passenger tank there is a large braided hose i would say at least 1-1/4 at the top left of the tank that comes down under the engine to the bottom of drivers side tank . there are the two solid lines under the engine between the two tanks that tie them together . over night the two tanks will even out when i check them switching the sending units rocker switch back and forth but when running the passenger tank will read way over full on the gauge and the drivers about 1/4 to 1/2 ? my thought on this and i may be way wrong but is the pass tank the main tank with the pump and the drivers is auxiliary tank ? does the fuel return go to the pass tank and fill it full when running and the large hose transfers fuel from the top of the pass to bottom of drivers ? not being able to replicate the fuel leak has me a bit concerned on where it came out of . i guess this is one of the drawbacks of not building it my self so any help would be much appreciated on how this system works . engine is an LS1 out of a 2004 corvette single feed fuel from filter , car has 11k miles on it and im sure the fuel system has been like this from day one . car runs and drives great just this strange fuel situation that just happened working on the cooling system today ?

Thanks in advance
Dave s

[beeman]

The passenger side GTM tank is the driver's side Corvette C5 tank. This houses the fuel pump, fuel return, and the jet pump. The jet pump keeps the fuel tanks relatively equally full in the Corvette, but is capped and not used in the GTM setup because in the corvette, there is a large crossover tube that connects the tops of the tanks to help keep them balanced. This can't work in the GTM because the tanks are swapped side-to-side, plus there's now an engine between the tanks.
To work around the loss of the jet pump and crossover tube, we have to drill holes in the bottoms of the tanks for the braided crossover tube you saw. These are prone to leaking, it's a less that perfect design but how else are you going to keep the tanks balanced?
The leaks occur where the AN fitting is mounted to the hdpe tanks. Guys over the years have tried aircraft grade sealers, etc, but most sealers break down from the gasoline. Do you see any thick sealant gooped around the AN fittings on the tanks? I opted to purchase the inexpensive kit from vraptorspeedworks which I believe is a superior design.

[beeman]

http://vraptorspeedworks.com/fuel-tank-budget-cross-over-kit-97-03/

[switta]

Thanks for the reply beeman , so i looked through the manual and verified all my fuel lines are plumbed as the manual listed the only thing i did not see was the large 1" braided cross over tube ? mine is routed to top of passenger side looks like they used existing factory fill tube that points toward the engine and then goes to bottom of drivers side , i would think it should be on the bottom of both ? it would equal out the tanks better , but having the braided hose on the top of the passenger side does keep that tank full when running . do you think that is something i should change or leave it the way it is ? i could order that fitting you suggested drain the system and move it to the bottom of the passenger side instead of the top .
also there are no leaks on that line , still not sure where the fuel came from ? i did have it lifted on the front left corner so the fuel could not get the large cross over line and may have come out of an open vent tube on top of the tank ? i need to look into that , i would not think there would be one there as the drivers side has the charcoal canister .


Dave s

[beeman]

There are some differences with the 2004 tanks, but I'm not not sure exactly what, but I'm not aware of any high crossover setups, maybe others can chime in on the 2004 differences. You do have the black plastic oem corvette tanks and not aluminum aftermarket tanks, correct?

[switta]

yes stock black plastic

[VRaptor SpeedWorks, LLC]

Sounds like someone intentionally plumbed it to keep the passenger side tank full. Here's the full story:

In the beginning, FFR had the GTM set up with just the 2 hard lines between the tanks for the jet pump. The jet pump uses the fuel pressure from the pump to send a small amount of fuel to the driver's side tank which basically runs thru a venturi to suck a larger volume out of the driver's side tank and pump it over to the passenger side, since the pump is in the pass side tank. The problem is that under normal driving, the jet pump pulls more fuel from the driver's tank into the pass tank than is being used by the engine.....so eventually, the pass side tank overflows out of the filler neck and dumps fuel all over the ground.

FFR did a "recall" of sorts and sent out the -12 AN hose and fittings. That AN crossover hose was meant to REPLACE the jet pump hard lines. So instead of a jet pump constantly filling the pass tank, you just had the AN hose, which is supposed to run from the BOTTOM of the drivers tank to the BOTTOM of the pass tank so that gravity keeps both tanks at the same level. All of the jet pump fittings get capped off in this scenario.

Sounds like whoever built your car wanted the best of both worlds, so they installed the crossover tube from the TOP of the pass pump tank to the BOTTOM of the driver's tank....so that the jet pump is still pumping fuel into the pass tank from the driver's tank, but the excess would drain back to the driver's tank once the pass tank was full.....and in theory, I don't see why that wouldn't work.....unless they don't have the tanks properly vented and the fuel can't drain back thru the AN crossover hose because the driver's side tank is air-locked somehow?.....or the crossover hose is kinked somewhere and can't flow enough fuel to keep up with what the jet pump is supplying?....or the crossover hose is installed so high on the tank that the tank is already overflowing out of the filler neck by the time the fuel level reaches the crossover hose? Since the crossover only relying on gravity to return the excess fuel from the pass tank to the driver's tank, it would have been better if they had installed the AN crossover something like half way up the tank. That would keep the pass tank at least half full all the time and if the jet pump pumped the pass tank to 3/4 full, then you'd have all of the weight of that fuel above the crossover forcing the excess fuel back thru the crossover to the driver's tank. My guess is even then, if you just filled up the car and both tanks are full, you still have the jet pump moving fuel to the pass tank and now it can't return to the driver's tank, because it's also already full (gravity can't push the fuel back into the driver's tank because the crossover hose is already full of fuel and so is the driver's tank) and you'd still get fuel puking out of the pass tank.

My advice would be to plug off the jet pump and install the crossover hose in the bottom of the pass tank where it's supposed to be and be done with it.

[switta]

VRaptor-SpeedWorks-LLC thank you so much for this reply that explains a lot and yes i totally agree with you , i dont like all the weight on the passenger side and im sure it over filled when i had the front left jacked up and fuel could not get to the cross over tube in the upper left hand corner of the tank . i will change the line from the top of passenger tank to the bottom , i am not sure where the plug is for the jet pump on the drivers tank i will have to do some research on that ?
thank you guys for the help i will report back after the fix .

Dave s

[beeman]

They are quick disconnect fuel lines, just get an AN 6 fuel disconnect adapter, and an AN 6 cap. I can't remember if that line is 5/16 or 3/8?

151302

151303

[crash]

I have not read this entire thread, but DO NOT use the adapter that is pictured here. This is the exact same style connector that caused the FFR PDG GTM to burn down during a race. There are ones that have been redesigned with a screw in lock that seem to address the issue of the plastic part eventually breaking, but make no mistake, you DO NOT want to use that pictured adapter under any circumstances. EVER!!


They are quick disconnect fuel lines, just get an AN 6 fuel disconnect adapter, and an AN 6 cap. I can't remember if that line is 5/16 or 3/8?

151302

151303

[switta]

Thanks for the info crash , the car i bought was built by PDG it's the red one on this page http://www.pdg4.com/articles.html
, i am basically re plumbing the entire fuel system , after i got into it there are several issues i dont like .
i will be sure and not use them fittings .

Dave s

[beeman]

OK, was not aware of that, are you aware of failures other than the one you personally experienced? Seems like they are commonly used, and I use the oem inner plastic clip, not the Chinese one that comes with the fitting. Yes, the OEM clip is probably made in China or Mexico.
What's the alternative? Use the entire OEM plastic QD with injection fuel line as per the manual? This is actually how I did it on my GTM for the lines seeing fuel but I did use the above AN adapter and cap for the jet pump fitting. I used the aluminum AN adapter on my Lotus build though...

[switta]

I'm curious about the factory quick connects that are used on the pump lines now out of the tank fittings ? are they safe ? or is there updated ones that should be used , my system is empty and now would be the time to change them if needed .
maybe change to these ? Earls 751156ERL O.E. Fuel Line EFI Quick Connect . cant figure out how to post picture ? but these look pretty safe i would just make a new line from the pump to the filter regulator the return line would be low pressure after that regulator correct ? and i would just plug the 5/16 line going to the jet pump on the left tank , there would be no pressure there after eliminating the Y hose . am i thinking this through right ?

Dave s

[beeman]

I think those are the style that Mike is saying are not safe? The only thing I can think of is that movement and vibration over time causes the solid aluminum body of the fitting to wear into the inner plastic clip and cause it to fail? Mike could have you clarify your concerns?

[switta]

these appear to screw together not push on like the others ,
https://content.speedwaymotors.com/ProductImages/425751156ERL_L_6ba08471-0a96-4a1f-94ba-878f9b3675dd.webp

[beeman]

Ah, now I see, yes that must be the ones he recommends.

[crash]

these appear to screw together not push on like the others ,
https://content.speedwaymotors.com/ProductImages/425751156ERL_L_6ba08471-0a96-4a1f-94ba-878f9b3675dd.webp

Yes this is what I was recommending. If you look at any of the reputable manufacturers, you will notice that they have gone to this style fitting. And yes there were quite a few other instances of there being problems, which is why the companies went to this new design. THis new design does not rely on the plastic to hold the part on the tube.

[beeman]

I forgot to add, if I was doing the OEM tanks again in the GTM, I would consider this device for the crossover line on the fuel pump tank, then Shane's plate on the driver side tank, assuming the AN fitting size is adequate, I think it's a size down from the supplied FFR line, which may slow fuel fill-up at the gas station a little. It's designed for an external fuel pump but looks like it would work for a crossover.

https://s20.directupload.net/images/210812/59x8z33a.jpg

https://s20.directupload.net/images/210812/ngm73lvc.jpg

[VRaptor SpeedWorks, LLC]

Nice find! I have never seen those before. And yes, the plate I make for the non-pump tank is set up for the -12 fittings for the crossover, but could easily be drilled out if you wanted to go bigger.

[Erik W. Treves]

https://eastcoastsupercharging.com/product/ecs-c5-fuel-block-97-to-03-corvette-3-50-08-06/