Vapor Lock

DanBronco66
Aug 15, 2020

Rank III

Aug 15, 2020

Hello

I have a 1966 Ford bronco, over the last year I’ve been experiencing a vapor lock and I’ve tried a number of things to resolve it with no success. Installed a new fuel pump, we directed my fuel line, and a spacer under the carburetor.

I was hoping someone else would have some suggestions.Thanks and advance

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Last edited by a moderator: Aug 15, 2020

Rank V

Aug 19, 2020

#20
The strange things is nothing changes that I can put my finger on. A few years ago I put a new carb on but it ran great for two years before this started. When this started I replaced the fuel pump, thinking the old one was very old.... I got it thru one of the Bronco sites that I get my parts. It was just a standard fuel pump. I also started running leaded gas in the Bronco Vs unleaded gas.
The metal fuel line been on for years. I was thinking of replacing it with high end fuel line.

The fuel line from the tank Has a fuel filter (clear filter) before the fuel pump, when the vapor lock Happens there is no fuel in the fuel filter. 20 to 30 minutes later you can see fuel in the filter - crazy
Thats not crazy since vapor lock or cavitation occurs when excessive heat or exhaust boils the fuel in the lines and when it cools it draws again. Sounds like it takes 20 - 30 minutes for it to cool enough to fill the filter cup.
It’s time to live again but never forget the ones we lost!
Deano Bronc
Moderator

Rank III

Aug 20, 2020

#21
The strange things is nothing changes that I can put my finger on. A few years ago I put a new carb on but it ran great for two years before this started. When this started I replaced the fuel pump, thinking the old one was very old.... I got it thru one of the Bronco sites that I get my parts. It was just a standard fuel pump. I also started running leaded gas in the Bronco Vs unleaded gas.
The metal fuel line been on for years. I was thinking of replacing it with high end fuel line.

The fuel line from the tank Has a fuel filter (clear filter) before the fuel pump, when the vapor lock Happens there is no fuel in the fuel filter. 20 to 30 minutes later you can see fuel in the filter - crazy
I don’t buy into the vapor lock theory, specially since you haven’t changed the exhaust, fuel line, etc. and it’s a new problem. Maybe there’s trash in the tank? Will it sit and idle for longer then the 30 minutes it takes it to run out of fuel when you drive it?
I think its a fuel blockage/restriction.
Couple things to try:
Let it idle for long period of time, see what happens. Keep in mind, at idle it doesn’t use as much fuel as it does while driving.
The next time it doesn’t get fuel, disconnect fuel line at fuel pump and blow compressed air through the fuel line into the fuel tank. Reconnect fuel line and see if problem is still there.
Good luck
pilonfx, Deano Bronc

Rank III

Aug 20, 2020

#22
I don’t buy into the vapor lock theory, specially since you haven’t changed the exhaust, fuel line, etc. and it’s a new problem. Maybe there’s trash in the tank? Will it sit and idle for longer then the 30 minutes it takes it to run out of fuel when you drive it?
I think its a fuel blockage/restriction.
Couple things to try:
Let it idle for long period of time, see what happens. Keep in mind, at idle it doesn’t use as much fuel as it does while driving.
The next time it doesn’t get fuel, disconnect fuel line at fuel pump and blow compressed air through the fuel line into the fuel tank. Reconnect fuel line and see if problem is still there.
Good luck
Thanks for the response - I will give that a shot.
pilonfx

Rank VI

Aug 24, 2020

#23
My recommendation is to install an electric pusher fuel pump at the gas tank. This will push liquid fuel through the vapor lock area to the mechanical pump. IF you really have a vapor lock issue. If the electric fuel pump solves the issue, then it was vapor lock. If it does not solve the issue, then you have a different issue. An electric fuel pump is good to have in the base case. Wire it switched so you can use it when needed.
2022 Bronco BadSquatch, 1974 Bronco Ranger, 1976 Bronco Crawler, 1978 Bronco Custom
Deano Bronc, Big Mike
NC_Pinz

Aug 24, 2020

#24
Welcome to Bronco ownership. Most have a vapor lock issue if you drive them in the summer especially when you are just doing around town stuff. They were that way new out of the box. Maybe some folks don't experience it but I have for 45 years, give or take.

Rank 0

Aug 26, 2020

#25
How about adding a inline cooler on the return line. I have this on mine and have had no issues. Was this happening before or a new thing?
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Rank III

Aug 29, 2020

#26
How about adding a inline cooler on the return line. I have this on mine and have had no issues. Was this happening before or a new thing?

thanks for the ideas -

Answer - this really started happen out of nowhere, that was the confusing part of it .

what in-line cooler product are you using ??

Rank II

Aug 14, 2021

#27
"...when the vapor lock Happens there is no fuel in the fuel filter...."
Run metal line as much as possibe. Use the standard routing, this 1 looks off. Put the F.pump on right side up (flip it over. If U wanna have 2 filters have one right there, the other is almost part of the carb.
Not "vapor lock". That happens when fuel races thru the carb venturi and the water freezes out to clog that area. Feel carb (is it a humid day? is the throat cold? Water in the humid air also 'locks' (frez) as it comes into that area.
Right after pump (plez rout lines correct, that may B prt of problem) pull line or hose'n place bucket under. What's the rate of drip? Is the bent8 a 3 gal a min spec? Try after filter - same? During problem also look down throat, flog throttle'n C if it's "getting a shot" there.
Chad - '70 LUEB on '77 frame (i.e. PS, D44, trapezoidal BB 9", 4.11) '69 4.1, NV 3550 & DSII, "T" D20 [email protected]~

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