During deceleration, fuel dumping out of the tanks vent line. What gives?

[fullmetaljacket]

So I have a custom aluminum tank in the stock location on my '65 Coronet. The tank has an Aeromotive 1000 in tank fuel pump and in tank filter along with baffles. 1/2 feed line with a 10 micron inline fuel filter on that. Return regulator and line and a coil vent.
here's what's happening. As I come to a traffic light or stop sign and slow the car down to a stop, fuel is dumping out the vent tube at a high rate. No trickles, DUMPING.
What's going on?

Thank you in advance.
FMJ

 

[toolmanmike]

Fuel pressure, regulator, and carb you ate running?

 

[fullmetaljacket]

So I have a custom aluminum tank in the stock location on my '65 Coronet. The tank has an Aeromotive 1000 in tank fuel pump and in tank filter along with baffles. 1/2 feed line with a 10 micron inline fuel filter on that. Return regulator and line and a coil vent.
here's what's happening. As I come to a traffic light or stop sign and slow the car down to a stop, fuel is dumping out the vent tube at a high rate. No trickles, DUMPING.
What's going on?

Thank you in advance.
FMJ

 

[QuickBpBp]

Regulator messed up and pressurizing the tank?

 

[1 Wild R/T]

Sounds like a vent issue... Can you pull the fuel cap off & take it for a drive?

 

[fullmetaljacket]

Sounds like a vent issue... Can you pull the fuel cap off & take it for a drive?

I guess I can. I have a Stant locking gas cap on it.

 

[fullmetaljacket]

Regulator messed up and pressurizing the tank?

I'm also running a Stant locking gas cap if that helps information.

 

[fullmetaljacket]

I'm also running a Stant locking gas cap if that helps information.

I guess I can change the regulator and see. The fuel pressure is at a steady 5.5

 

[1 Wild R/T]

If the tank is pressurizing pulling the cap will eliminate that... The end of the vent may be to low in the tank... I don't see how a regulator can pressurize the tank, it returns fuel to the tank but the fuel was sourced from the tank in the first place so there has to be enough room for it...

 

[fullmetaljacket]

If the tank is pressurizing pulling the cap will eliminate that... The end of the vent may be to low in the tank... I don't see how a regulator can pressurize the tank, it returns fuel to the tank but the fuel was sourced from the tank in the first place so there has to be enough room for it...

Perhaps the locking gas cap can be faulty after so long?

 

[QuickBpBp]

I'm also running a Stant locking gas cap if that helps information.

Is this a new set-up or an old one that is now acting up? Cap vented too?

 

[fullmetaljacket]

Fuel pressure, regulator, and carb you ate running?

5.5 constant fuel pressure. Aeromotive fuel regulator and a Thumper 950 based carb flowing 1000 cfm

 

[fullmetaljacket]

Is this a new set-up or an old one that is now acting up? Cap vented too?

Old set up that is now acting up. Stant locking gas cap. Got to go check if it is vented.

 

[toolmanmike]

5.5 constant fuel pressure. Aeromotive fuel regulator and a Thumper 950 based carb flowing 1000 cfm

Float level too high?

 

[1 Wild R/T]

Only if it's a vented style cap... But honestly I think the problem lies elsewhere... How's your fuel pressure? With an in tank pump if there were a pressure side leak inside the tank that just totally by chance was aimed at the vent it could pour fuel... I doubt thats the problem either... I tend to think there's something going on with the vent, it there a way to access the inside of the tank? Maybe with a bore scope?

 

[QuickBpBp]

If the tank is pressurizing pulling the cap will eliminate that... The end of the vent may be to low in the tank... I don't see how a regulator can pressurize the tank, it returns fuel to the tank but the fuel was sourced from the tank in the first place so there has to be enough room for it...

I agree. It's likely aerating the tank with amount of fuel returning so it will build pressure it's like shaking a gas can if not properly vented. Maybe the coiled vent is too small or the cap needs to vented too?

 

[1 Wild R/T]

I agree. It's likely aerating the tank with amount of fuel returning so it will build pressure it's like shaking a gas can if not properly vented. Maybe the coiled vent is too small or the cap needs to vented too?

Certainly an odd deal.... But what's new...

 

[QuickBpBp]

Only if it's a vented style cap... But honestly I think the problem lies elsewhere... How's your fuel pressure? With an in tank pump if there were a pressure side leak inside the tank that just totally by chance was aimed at the vent it could pour fuel... I doubt thats the problem either... I tend to think there's something going on with the vent, it there a way to access the inside of the tank? Maybe with a bore scope?

Typically the vents I have seen don't go into the tank but screwed to a fitting on the high side of the tank. Hope that makes sense..

 

[Daves69]

Put a gauge on the vent and check for pressure build up?

 

[fullmetaljacket]

Float level too high?

Float levels are at the half way point in the bowl window.