OK...I've got an 81 FJ40 that is bone stock that I have owned since 1988...still has emissions junk. Over the last year or so I've started to experience dreaded carb bowl drain when it sits for a day or two. So I started doing some research. In fact, before somebody calls me out for not searching the forum for previous threads let me assure you I have read every one. But from what I can tell a cause/fix has not been determined. There are plenty on theories though. Which I have investigated and have come to the conclusion that nobody really knows what is going on even though the most respected LC gurus have weighed in. For those who don't have time to read all the posts...let me summarize some of the ideas:
1. Evaporation - doubt it. Carb fan works fine and it's 30 outside. Plus lived in Phoenix for 3 years and drove it everyday without a problem
2. Ethanol fuel - doubt it. Been running it for 30 years no problem...tried non-ethanol with same results.
3. Fuel bowl "O" ring - Not sure exactly what the result would be...would fuel leak inside carb or outside...no evidence any where on carb of fuel leak
4. Plugged air vents - maybe, but once fuel is pumped back up to carb starts and runs fine
5. Siphoning into intake due to vacuum produced by differential pressures as the engine cools. Sounds very scientific, but if true why did it not drain for the first 30 years I owned it?
6. Kind of "wicking" action due to surface tension causing leak past idle solenoid. Maybe. But once again 30 years worked fine.
7. Fuel pump/filter - both new.
Conclusion: Like I said unsolved mystery. However, seems like a very common problem not just with 2F, but 22RE engine in Toyo trucks, etc. Since mine ran fine for 30 years, I believe it has to be related to internal wear or contamination. What I don't understand about that is even after rebuilds it still happens sometimes. Seems like mine loses fuel all the way down to fuel pump since I have to crank it over for about the same amount of time as after a pump change. Maybe somebody will solve it, until then I guess I'll live with it. I wouldn't be surprised if someone figured it out...I've got so many fixes from really smart guys on here already.
1. Evaporation - doubt it. Carb fan works fine and it's 30 outside. Plus lived in Phoenix for 3 years and drove it everyday without a problem
2. Ethanol fuel - doubt it. Been running it for 30 years no problem...tried non-ethanol with same results.
3. Fuel bowl "O" ring - Not sure exactly what the result would be...would fuel leak inside carb or outside...no evidence any where on carb of fuel leak
4. Plugged air vents - maybe, but once fuel is pumped back up to carb starts and runs fine
5. Siphoning into intake due to vacuum produced by differential pressures as the engine cools. Sounds very scientific, but if true why did it not drain for the first 30 years I owned it?
6. Kind of "wicking" action due to surface tension causing leak past idle solenoid. Maybe. But once again 30 years worked fine.
7. Fuel pump/filter - both new.
Conclusion: Like I said unsolved mystery. However, seems like a very common problem not just with 2F, but 22RE engine in Toyo trucks, etc. Since mine ran fine for 30 years, I believe it has to be related to internal wear or contamination. What I don't understand about that is even after rebuilds it still happens sometimes. Seems like mine loses fuel all the way down to fuel pump since I have to crank it over for about the same amount of time as after a pump change. Maybe somebody will solve it, until then I guess I'll live with it. I wouldn't be surprised if someone figured it out...I've got so many fixes from really smart guys on here already.
