Vapor Lock: Watch Fuel Boil and Learn Tips on How to Avoid It

Watch fuel boil and cause vapor lock! Prestige Motorsports installs clear fuel line to watch what happens during vapor lock. Then learn how to install Aeromotive in-tank fuel pump and return system. Also includes additional tips on how to avoid vapor lock.

Prestige Motorsports is a performance shop located in Concord, North Carolina. We offer custom built stroker engines, performance upgrades for all types of vehicles, car building and restoration services, and paint and body work.

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[A_Litre_of_Farva]

I've been dealing with ethanol issues on all the big 3 for years. The first thing to determine when having fuel issues: is the issue not enough fuel in the carb, or too much fuel? Not enough = vapour lock. Solution is electric pump and return line. An in frame Edelbrock works well. That set up in the Impala looks extremely expensive and prone to failure. I had a ford 460, 4100 series Motocraft carbed motorhome that worked flawlessly even climbing mountain passes in B.C. at 37 degrees celcius, loaded. NEVER percolated or vapour locked. And it had those two things.

Too much fuel/flooding = heat soak/percolation. The solution so far is a return line port as close to carb as possible, insulating lines, and as tall as possible Phenolic/wood spacer under carb. Also that big, hideous air cleaner is going to trap a lot of heat at the carb!

[pawpaw]

Hey guys, I am a small engine Mechanic - I`ve had the issue a few times of steel gas tanks needing holes drilled into them sometimes and I`ve come up with a 100% perfect solution to keep EVERY little speck of that metal debris/shavings from entering the gas tank - and THAT is to use one or several very powerful Ceramic "Rare Earth" magnets around the area where the hole or holes are being drilled, and you do NOT need to be in the awkward upside down position (and get a possible injury to your eyes and HOT shavings to skin areas making you jump from the burn reaction, possibly messing up the hole) to do the job. When finished with your cutting, drilling, de-burring?, simply *Slide* the magnet to the hole you just cut and remove the collected shavings. Another added suggestion would be to have a "Secondary" magnet set directly attached to the outside bottom of the tank directly below the drilled hole JUST in case SOME does slip past, when done?, you can (like " I " do) is to clean THOSE shavings at the INSIDE bottom of the tank where (IF ANY) that magnet was placed?, use a wood stick/Dowell with a Q-Tip like bundle on the end of it (DON`T use a telescoping magnetic pick-up tool to do this, it does NOT pick up those shavings because the area is MADE magnetic by the stronger magnet and chips WILL stay there) with a petroleum based lubricant to wipe/pick up any shavings after removing the magnet from it`s location. Hope this solves SOME headache`s with that issue.

[vintagethunderbirdrepair]

Hey Eric, great video. I restore old Thunderbirds and have had to deal with the vapor lock problem quite a bit lately mostly because of the crappy gasoline that is available today. I live at 7000 ft altitude so this altitude just adds insult to injury with regards to vapor lock. The problem you describe in the video, "not being able to restart the car after shutting it off, " I have found more attributable to the gasoline boiling or evaporating out of the carburetor while it is sitting there. For example, you go into the market and your car is sitting outside for 20 minutes or so and as the engine heats up from being shut off and no more cooling system action, the gas in the carb starts to boil and evaporates. When you go to restart it you have a "too rich" issue because of the excessive fuel vapors and the heat. I push the gas pedal to the floor and crank it until it starts, works every time. I do not pump the gas pedal. Pushing the gas pedal down to the floor and leaving it there until it starts opens up the throttle plates in the carb and allows air to rush in creating a lean mixture and allowing the car to restart.

The vapor lock problems I have experienced with the Thunderbird while driving is (390 or 428 FE engines), loosing power, bucking and surging, acting like it is running out of gas, not being able to reach speeds higher than about 40 mph, and all of the above when going up any kind of an incline. For me and my Thunderbirds, its never a restarting problem, its always a "while driving" problem. The cure was exactly what you did in your video with a few exceptions. You put an in tank fuel pump which Holley recommended as the number 1 fix. On a 1966 Thunderbird for example, the gas tank rest against the trunk floor on the top and back side. The fuel sender is on the front side facing the diff. Holley said that you need 3" of clearance between the tank and trunk floor to use their in tank fuel pump so that was not an option for me. The next best thing was to use an inline electric fuel pump as close to the gas tank as possible and level with the bottom of the gas tank. So I installed the electric fuel pump right next to the gas tank and level with the bottom and I ran a return line from the front of the car back to the gas tank via a Holley supplied regulator, and used the original fuel source fitting on the sending unit as the return. From the regulator back, I used steel fuel line because it does not warm up there like in the engine compartment, there is nothing to heat the lines up. In the engine compartment, I used fuel hose and I insulated it with thick foam insulation, the same stuff you see around water heater pipes. I eliminated the mechanical fuel pump completely. This worked out great and cured any vapor lock issues. The customer drove the car over the Rockies on Interstate 70 and went through the Eisenhower tunnel at 11, 000 feet with no issues while using 91 octane pump gas with 10% ethanol. They also drove around Utah, Nevada and California in 100 degree weather with the AC on the entire time. They had no issues what so ever.

[vincentbryan]

Damn that’s a lot of work. I fixed vapor lock in my 62 impala for about $50. Purchased return hose and 3nipple fuel filter before the carburetor. Also used some heat shield wrap over the fuel lines in the engine. I drilled into the filler neck so I didn’t have to clean up or mess with the gas tank at all. I live in texas with 100+ degrees all week. I drive my old school every single day:) after I did that fix my car never had any problems after that. I even went to car shows driving for 4+ hours with the car on and sitting in the summer :)

[claytoncherry]

My 69 camaro with a quadrajet has a return line to the tank from the factory. GM had this issue in the 60s and quadrajets are very sensitive to it. If someone wants to stay original this is the easiest solution. Just add a fuel filter with a return line and a 1/4" line to the tank and use a sending unit with a return line on it or tap in a fitting to the tank.

[johnbeer]

uncle Tony's Garage got a cheaper way simpler way to do it 👏🏌with a filter😁✌

[prun]

One of those filters with 3 fingers (Wix 33041), a return line to the tank, insulate the feed line in the engine bay to the carburetor with ceramic fire insulation wrapped in foil tape, get rid of mechanical fuel pump and replace with an electric, a phenolic carb my vapor lock....even on 100F days in Colorado altitude on 89 octane ethanol gas. Find a sender with an inlet along with the outlet and switch it out. Don't cut a hole in the tank.

[whatsinaname]

Geeze, what a complicated and expensive way to fix a problem a $8 napa filter could fix. Again, learned it from Uncle Tony.

[MrPreacher]

i had that same problem, turned out someone in the past had installed a non vented gas cap, i put a factory cap back on it and problem was solved

[VintageMoparnut]

I know this video came out in 2016 but Here's another tip i picked up back in the day in a issue of hot rod magazine: 101 tech tips. If you have a metal gas tank prep the metal surface for primer / paint . Used high temp header primer and paint with the ceramic in VHT or dupli color . But use the header aluminum paint. It will insulate the tank from heat coming off of the motor / car / pavement and keep the gas cooler. Also if you use a mechanical or electric fuel pump always use a vapor return line to get rid of a lot or all of vapor lock.

[tarlachx]

Yes to look up Tony's garage way simpler way cheaper works wonderful...

[JimmyLoose]

LOL, "Prestige" Motorsports. Made me bust up laughing because all I can think of is Prestige Worldwide from Step Brothers. "Boats and Hoes!"

[ASuperBee]

Save your self some $$ and just keep the stock mechanical pump in place and "tee" it back to the tank with a return loop. Don't even have to drop the tank or "shim" it up! Simplicity holds much merit even today!

[tomoconnor]

I bought a f 800 fire truck with 11k on it. They said it sat in the back of the fire hall for 20 years bc it wouldnt stay running. 429 bb industrial. and it runs fkin great when shes cool but when its hot kikin and buckin. SOOO i found a factory fuel tank that would except a high volume low pressure in tank oem pump and added a restricted return line to get the pressure back to 6 psi and never had a problem since.

[bryanhinds]

cut out the center with a hole saw upside down so minimal shavings get in the use a die grinder and sanding roll right side up. 🤦‍♂️😂😂😂😂😂😂😂😂

[human]

Yep go to uncle Tobys garage channel, he fixes it with a wix filter 33040 ? ( just get a 3 outlet fuel filter with a small hole for back pressure in the run outlet to the tank ) and with the third smaller outlet on top or north of the filter run a line back to the tank, sometimes the tank has the hole in it at the connection for the return line, where did the idea of running fuel line to the carburetor only come from ?

[danhalfhill]

FYI, cutting/grinder bits cause sparks. Sparks and gas fumes cause boom.

[keything]

Or just add a 3 head fuel filter witha return line to

[mauriziopescatori]

The idea of a clear tube is excellent to show *how the problem manifests itself* but your video does not explain *where the problem occurs*. Furthermore, it is not always feasible (nor desirable) to fit a system such as the one described.
Rather, how can I fix the problem on a vintage car with "vintage good ideas"?
THAT was my expectation in the viedo, but sadly did not find it :(

[DoctorBrodski]

I wonder if fuel pressure regulators make any difference. One guy I know fitted one to his seventies coupe to cure the hot starting problem where fuel surges in and floods a hot engine after it's turned off. I know you can buy cheap 'n' cheerful regulators on EBay from China or a pay a couple of hundred for a quality one from Edelbrock or somewhere. But I won't go to the trouble of installing one unless I know it makes a difference.