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  #31  
Old 07-27-2013, 03:13 PM
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Originally Posted by JadeRunner View Post
Nice trip ad write up. Dan's not afraid to wheel that stock 3rd gen.



Jeff, help me understand this. It could have been dangerous for a novice in a large group on that hill. I have seen this before on older rigs and always thought it was a carb setup issue or maintenance issue causing that problem. Some older rigs don't have that issue on high altitude hills. I know that you have a properly built carb and maintain your stuff. So just help me understand what else you could do to prevent this in the future.
Use actual gasoline that doesn't have ethanol in it so it has a lower vapor pressure, or maybe some additive as has been suggested, which would lower the vapor pressure of the fuel. The other thing that could be done is to install an electric pusher fuel pump back at the fuel tank. That would increase the ambient pressure in the fuel line.

You see, mechanical fuel pumps are located on the engine, which is convenient from a mechanical engineering point of view.

But they have two disadvantages in these particular situations. One is that they get hot because of being attached to the block instead of being immersed in cool fuel inside the fuel tank as is found in newer fuel injected vehicles. The huge disadvantage of the latter arrangement is that it is usually a huge PITA to replace a faulty pump inside the tank, and on many vehicles the tank must be drained and removed from the vehicle to get at the access port on the top.

The other is that they must use suction (AKA vacuum or negative pressure) to pull fuel from the tank, and a good bit of it when on a steep incline. The definition of boiling in chemistry is when the vapor pressure of the liquid equals or exceeds the ambient pressure. When using negative pressure (vacuum) to pull fuel from the tank, we have just lowered the ambient pressure and thus lowered the boiling point of the liquid. The liquid turns to gas (not gasoline, but gaseous state) and the fuel pump cavitates and is pretty ineffective at pumping. "Vapor Lock" is an incorrect term but is widely understood - it isn't really locked, it is just that we don't have liquid fuel to pump.

60s are more prone to this than 40s partly because the tank is lower relative to the pump, and farther back, which causes issues when on a steep incline like this. Once I was on level ground at the top I had no issues whatsoever. I didn't have any further problems later during the day because we didn't have any uphills that were as long as Radical Hill was. And it was cooler outside, which helps a bit.

It was reassuring to know what was going on so as not to worry or waste battery trying in vain to crank it over. I started pulling the fuel line downstream from the pump to verify my suspicions, but stopped when it wasn't super easy, and we were pretty confident we knew what the problem was and what the remedy was. In a situation like this, the mantra is "Patience Padiwan".
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  #32  
Old 07-27-2013, 09:20 PM
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Jeff, when I had vapor lock issues on Argentine Pass with my 40, Justin from Redline suggested installing an electric in-line fuel pump before the manual pump. He said the manual pump would then act as a regulator, keeping the fuel line pressure to spec, but the electric pump would eliminate the vaporizing issue. My question is this...why do you suggest an in-tank one instead of this seemingly less complicated alternative?
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  #33  
Old 07-28-2013, 05:48 PM
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Originally Posted by nattybumppo View Post
Jeff, when I had vapor lock issues on Argentine Pass with my 40, Justin from Redline suggested installing an electric in-line fuel pump before the manual pump. He said the manual pump would then act as a regulator, keeping the fuel line pressure to spec, but the electric pump would eliminate the vaporizing issue. My question is this...why do you suggest an in-tank one instead of this seemingly less complicated alternative?
I did not suggest an in-tank one for an FJ60. I suggested a pusher pump at the tank, but not inside it. My daughter's 60 has such an arrangement. It would be a huge PITA to modify the tank to accept an in-tank pump such as is common for fuel injected rigs.
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  #34  
Old 07-28-2013, 06:08 PM
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Yes you did! Thanks for the correction. Someday I will probably do this to my 40.
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  #35  
Old 07-28-2013, 06:15 PM
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Yes you did! Thanks for the correction. Someday I will probably do this to my 40.
It shouldn't be as much of an issue for a later 40 since the tank is both higher and closer to the motor. I think the big thing on older 40s like my 71 is not having any kind of return to cool the fuel.
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  #36  
Old 07-28-2013, 07:11 PM
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Sascha, on our 77s it shouldn't be as much of a problem as Jeff said because we have a fuel return on our carbs. The PO apparently had an issue because when I bought the rig it had insulated soft lines running to and from the carb. I swapped them out with the factory hard lines, but have never had a problem either before or after. Can't explain why though since I run the same gas as everybody and go to the same altitudes at the same temperatures. Wish I could be more helpful
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  #37  
Old 07-29-2013, 08:17 AM
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Originally Posted by nattybumppo View Post
Jeff, when I had vapor lock issues on Argentine Pass with my 40, Justin from Redline suggested installing an electric in-line fuel pump before the manual pump. He said the manual pump would then act as a regulator, keeping the fuel line pressure to spec, but the electric pump would eliminate the vaporizing issue. My question is this...why do you suggest an in-tank one instead of this seemingly less complicated alternative?
the FJ60 tank actually has a spot for a hole to be cut for an in tank pump (like the FJ62 tank).

Or you could swap a 62 tank.

not a suggestion, just and FYI.
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  #38  
Old 07-29-2013, 10:49 AM
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Great pics guys and great discussion.

My '76 FJ40 vapor locks terribly during the summer. I have thought about going with the inline electric fuel pump as well. When I shut down the engine after driving this time of year, the fuel vaporizes and takes about 30 minutes to cool down and turn back into liquid. Then I can start it and drive right off again. Very annoying sometimes.

When you guys take your carbureted rigs on these trail runs (like the 40s only run), is this not an issue with nearly every truck with the original OEM setup?
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  #39  
Old 07-29-2013, 04:02 PM
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Originally Posted by rover67 View Post
the FJ60 tank actually has a spot for a hole to be cut for an in tank pump (like the FJ62 tank).

Or you could swap a 62 tank.

not a suggestion, just and FYI.
While I was changing the oil in the 60 today, I took a close look at the fuel routing. Then I slapped my forehead. D'oH! There is only one line to the carb. There are two lines from the frame to the fuel pump (one with filter is obviously the inlet). Obviously the return is between the pump and the tank, not the pump and the carb. This would make the fuel in the line between the pump and the carb hotter, but it is under pressure so it shouldn't boil as readily as the inlet between the tank and the pump which is under negative pressure.
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  #40  
Old 07-29-2013, 04:05 PM
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Originally Posted by cbmontgo View Post
Great pics guys and great discussion.

My '76 FJ40 vapor locks terribly during the summer. I have thought about going with the inline electric fuel pump as well. When I shut down the engine after driving this time of year, the fuel vaporizes and takes about 30 minutes to cool down and turn back into liquid. Then I can start it and drive right off again. Very annoying sometimes.

When you guys take your carbureted rigs on these trail runs (like the 40s only run), is this not an issue with nearly every truck with the original OEM setup?
I have never had either of my 40s stall while driving, but my '71 will occasionally be difficult to start at high elevation within 2-15 minutes after being shut down and is being heat soaked. If it is less than about 2 minutes, or greater than about 15 minutes then it is fine.
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