old_man
NAXJA Forum User
- Location
- Loveland, Colorado
I've had a hard to diagnose fuel smell problem for quite a while and finally figured it out. First I had a leaky gasket on the fuel tank, but that didn't make the problem go away. It happens when it gets hot, or pulling hard on the highway, and was worse at a half tank and below.
As it turns out it had at least a small part to do with having a snorkel. I am running a 4.7L stroker. When I installed it, I pulled the venturi from the air box. As it turns out, that venturi is not there only to reduce intake noise. It creates a small vacuum that is used to purge the fuel vapor canister. It probably isn't a big deal on a normal intake, but with the snorkel, going down the road at speed, a positive pressure is generated in the air box instead of a small vacuum. That leads to forcing gas out the vapor canister instead of sucking the fumes back in and burning them.
I am going to try and put the venturi back in and see if that helps. If not, I will need to tap a small amount of vacuum to purge the canister. You can't just run straight manifold vacuum because it is too strong and might collapse the fuel tank.
Has anyone else seen a similar problem?
As it turns out it had at least a small part to do with having a snorkel. I am running a 4.7L stroker. When I installed it, I pulled the venturi from the air box. As it turns out, that venturi is not there only to reduce intake noise. It creates a small vacuum that is used to purge the fuel vapor canister. It probably isn't a big deal on a normal intake, but with the snorkel, going down the road at speed, a positive pressure is generated in the air box instead of a small vacuum. That leads to forcing gas out the vapor canister instead of sucking the fumes back in and burning them.
I am going to try and put the venturi back in and see if that helps. If not, I will need to tap a small amount of vacuum to purge the canister. You can't just run straight manifold vacuum because it is too strong and might collapse the fuel tank.
Has anyone else seen a similar problem?