Hey everybody. Living in Phoenix, I've been dealing with vapor lock on my 60 for a long time. I've taken a few measures to improve it - an electric in-line pump mounted low, shielding the hard line up by the head/manifold... But still have the occasional issue when I drive it on hot days. I understand an in-tank pump is the best solution, but one thing I haven't been able to find is anyone trying is a check valve. Putting a check valve just downstream of the pump should prevent the vaporized fuel from pushing the cooler fuel back past the pump... Right? It seems like a sure and easy solution, but then why hasn't anyone done it? I feel like I'm overlooking something. The valve would keep the pump fuel wetted and force the vaporized gas into the carburetor, which shouldn't be a problem, right? I'm not familiar with the fuel circuit... I don't believe there's any bypass back to the tank. Has anyone tried? I bought some good fuel-safe valves and might just do it unless someone foresees an issue. Thanks!
Check Valve to Prevent Vapor Lock (1 Viewer)
- Thread starter atxhaole
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I'm not in a position of good knowledge to answer your question directly but is your carb fan working as intended? I would be careful adding extra, non factory components to the fuel delivery system until you can establish root cause(s) of the vapor lock.
@atxhaole - Is your current electric pump mounted as close as possible to the tank? Electric pumps are always happier with cool, liquid fuel. If your pump is close to the tank, it seems unlikely that the vapors will ever push all the way back to the pump. If there are 2 fuel lines in the carb, you have a bypass fuel system with a return line (which I think the 60 has). I'm not against your check valve idea, but I'm not sure it will help hot soak/vapor lock issues.
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Man, quick responses. I love the ih8mud community. Yes it is. The fan works great, but when it's hot here in Phoenix, the fan just acts like a heat gun.
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Thanks for the quick response. Yep, it's mounted at an existing threaded hole on the frame cross member just forward of the tank. There's about 1.5 ft of fuel line between the tank and the pump, and the pump is about 4 inches below the bottom of the tank. I think with how hot it gets out here, and how hot things get under the hood (although the cooling system works great), it really does push down past the pump. I've been through a few pumps (probably because all of the cavitation from how bad it USED to be), and one of the previous ones was a pretty noisy pump. I could here a clear difference when it was trying to suck air when it was vapor locked and the second it "grabbed" liquid fuel and finally fed it up to the carb (the sound of success).
I think you're right about there being a return line, now that I look at a diagram. That makes me feel better about the idea of a check valve, giving the vapor a pathway to escape back to the tank.
Hmmm
I drove my FJ60 with a completely stock engine countless times in temperatures over 110°F and the engine always ran perfectly. Never a problem ever.
An electric fuel pump isn’t needed (or desired) on a normal 2F engine, nor a check valve.
It’s possible that fuel line vapor lock isn’t the root cause of the problem the engine is experiencing.
The stock fuel pump is diaphragm actuated. It can pump air just as easily as it can pump fuel. It doesn’t lose prime or become locked up if it gets air in it. It’s also always circulating fuel back to the fuel tank.
Maybe replace the fuel pump with the genuine Toyota pump.
The carburetor float bowl holds a fair amount of fuel and the jets are located on the bottom of it. If a few bubbles get pumped into the float bowl, they just pop at the top level. They’ll never make it down to the jets.
An air lock in the fuel line/fuel pump that makes the engine stall would empty the float bowl entirely before the engine conks out due to no gas.
That’s easy enough to check in the sight glass.
I drove my FJ60 with a completely stock engine countless times in temperatures over 110°F and the engine always ran perfectly. Never a problem ever.
An electric fuel pump isn’t needed (or desired) on a normal 2F engine, nor a check valve.
It’s possible that fuel line vapor lock isn’t the root cause of the problem the engine is experiencing.
The stock fuel pump is diaphragm actuated. It can pump air just as easily as it can pump fuel. It doesn’t lose prime or become locked up if it gets air in it. It’s also always circulating fuel back to the fuel tank.
Maybe replace the fuel pump with the genuine Toyota pump.
The carburetor float bowl holds a fair amount of fuel and the jets are located on the bottom of it. If a few bubbles get pumped into the float bowl, they just pop at the top level. They’ll never make it down to the jets.
An air lock in the fuel line/fuel pump that makes the engine stall would empty the float bowl entirely before the engine conks out due to no gas.
That’s easy enough to check in the sight glass.
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Sounds like your pump is in the right place, but you might install a can koozie around it or something to prevent it from picking up heat immediately from the hot AZ pavement.
Air getting into the system anywhere (at your pump or any inline filters) is evil. I had a tank switching valve that didn't leak fuel, but let air into the system, and it mimicked vapor locking.
Air getting into the system anywhere (at your pump or any inline filters) is evil. I had a tank switching valve that didn't leak fuel, but let air into the system, and it mimicked vapor locking.
Gotcha on the the ambient temperature topic but the fan pushes away the super hot air from the exhaust manifold so the carb doesn't heat soak from the exhaust manifold. Physics is your friend here via convection.
I'm in Tucson and I floated the idea of a inline fuel pump for my LS swap but didn't due to vapor lock. The pavement gets too hot and they're just not designed to deal with heat well.
If you're still running a carb there's no reason to be running an electric fuel pump, I'd switch back to a mechanical and then check your charcoal canister to make sure it's not clogged up.
I started my 60 series with the factory fuel pump and carb in hot weather this July and had no issues.
Also the return line is the bottom line that runs along the frame rail back to the tank
If you're still running a carb there's no reason to be running an electric fuel pump, I'd switch back to a mechanical and then check your charcoal canister to make sure it's not clogged up.
I started my 60 series with the factory fuel pump and carb in hot weather this July and had no issues.
Also the return line is the bottom line that runs along the frame rail back to the tank
Part of the problem is RFG - Even in metro Phoenix, which goes by the EPA standard of 7.0 RVP (Reed Vapor Pressure), vs. about 7.4 for Kalif. And this will vary with Winter/Summer blends. RVP roughly is a measure of how volatile a fuel is. The higher the RVP number, the less it evaporates (for emissions). That's why Kalif gas is actually still better for Carb'd vehicles than EPA standard as far as vapor lock goes; it takes a higher temp for it to boil. Overall, though, today's gas is more volatile for efficient Fuel-injection.
Normal mechanical fuel pump with METAL line from pump to carb and metal return line should be all you need. It is for me in Los Angeles Valley summers.
But if you want to try something else:
Normal mechanical fuel pump with METAL line from pump to carb and metal return line should be all you need. It is for me in Los Angeles Valley summers.
But if you want to try something else:
