Vapor Lock on my Flatfender Willys Jeep

I thought I was done with this Jeep, but thanks to your suggestions I decided to try to fix the vapor lock issue it had. Using the premise of "scientific testing", I take this Willys CJ-3B out into the desert and cruise around for a while.

[@albatrosnh]

"add a wick" because.... Mobile Molotov cocktail!! Awesome as always!

[@LowBuckGarage]

Thanks! It ended up soaked in gas, but no catastrophe...

[@b-lopez394]

Low-Buck Garage, Because the mechanical fuel pump is mounted to the engine block, most of the heat transfer is transferred by conduction from the engine block. You can discard your mechanical fuel pump and replace it with 5 lb electric fuel pump to remedy that. If you incorporate a fuel filter with a return line and mounted as close as you can to the carburetor, I think, it should solve the problem. It solved my '76 Chevy van vapor locking problem when towed heavy load.

[@jonathanflatman]

Exactly what I was thinking. Blank off the engine fuel pump and put in an electric fuel pump and use a heat shield (old coke can?) to keep radient heat away. Or try the mechanical pump with a plastic spacer to reduce thermal transmission? In an emergency, could you wrap a wet cloth around the pump to cool it? In the UK, ethanol fuel is seriously messing up old outboard engines, motorcycles and lawn mowers. On the plus side, it rarely gets hot enough here for vapour lock but carb icing can be an issue. Love your dry humour.

[@butchs.4239]

Used to have a CJ-3A that had a F head swapped into it. Whoever did the swap also went to an Bosch electric fuel pump, mounted on the firewall. I never had any vapor lock issues with it, but this was before they started cutting gasoline with ethanol. Still, watching this video made me think this isn't a new problem and an electric pump is a tried and true solution to it.

[@dustcommander100]

That was an interesting experiment - especially about the low pressure readings - that was amazing. I'm still pondering that. Maybe the pump can't make pressure when the fuel vaporizes, and the vapors are condensing in the carb? I think the thermometers were probably responding to radio frequency noise generated by the ignition system. You might switch to resistor plugs or reroute the temperature sensor wires, but what you did is the most efficient cure: ignore the readings that jump around. I have a similar problem with my '47 Chevrolet, but in my case, the fuel percolates out of the carb when you shut it off on a hot day. The boiling fuel and vapors go into the intake manifold and create a sort of flooded condition. If the battery lasts long enough, you can turn it over and pump the fumes thru until it starts - otherwise you must wait about an hour for the vapors to dissipate - and then it starts quickly. Kind of embarrassing at times, because people don't want to wait an hour for you to move away from the pump at the gas station.

[@lunchbox2784]

First off, nice driving skills with those skinny bias plies and open diffs, that’s a challenge. Here’s some tips to help vapor lock off the top of my head: -fan shroud. This will help not only cool the engine block, but improve the efficiency of the fan instead of “slinging” air around, it will funnel air at a higher flow throughout the engine compartment at lower travel speeds (crawling up a hill or idling). -“seal” off your engine compartment. If you have a fan shroud, the idea is to direct air flow through the radiator via fan, across the engine, then straight down and under the firewall/trans tunnel. Radiator support should be sealed, as well as gaps between the frame rails and inner wheel fenders. Consider hood to fender and hood to grille seals. -try hood insulation. This should help in hot direct sunlight and will keep the hood cooler (the thick steel will only reflect the heat back to the top of the motor. -metallic fuel lines. Rubber will only insulate the warm/hot fuel, keeping it from cooling down (Only IF the ambient/flowing air is cooler than the fuel). Aluminum has an extremely high thermal conductivity (accepts heat fast, and dissipates fast). Copper is better yet. Steel is meh. -insulating fuel lines (only IF the fuel is cooler than ambient/passing air). -routing longer fuel lines away from exhaust and coolant hoses (gives fuel more time to cool before ending up in the carb). -header wrap your exhaust manifold. -fabricate heat shields out of aluminum and place them between fuel pump and exhaust manifold. Could also heat shield your fuel lines. -as you stated, non metallic carb spacer. Even though your carb appears to be running around 100*, I would wager getting it lower yet will help cool the fuel additionally. In your area, carb icing or running too cold shouldn’t be an issue. The fuel return is a great idea. This is one reason why it’s implemented on vehicles from the 1960’s and up, same with all the other ideas I’ve mentioned. I hope this helps!

[@LowBuckGarage]

Thanks for the info, that gives me a lot more food for thought! I'll do an update in the summer when ambient temp is over 100F, and incorporate your ideas. I'll start with the fan shroud, and then go from there!

[@1984xlx]

I've been kind of binge watching your videos since I came across your channel. It is rapidly becoming one of my favorites! Keep up the great content.

[@thirdcargarage2951]

Adding the wick made me laugh out loud. My sleeping wife beside me found it less funny….

[@LowBuckGarage]

My apologies to your wife, but I'm glad you enjoyed it!

[@farmerjim-fat-man-do]

The falling pressure on the gauge is not a pump or fuel delivery issue, its a gauge issue. There is a Bourdon tube inside most fuel gauges, dry and liquid filled. As pressure increases the tube uncurls and it acts upon a little rack and pinion like gear that moves the needle. In a dry gauge, heat will cause the tube to curl back up and reduce the pressure shown on the gauge. An oil filled gauge will react just the opposite, pressure increases as it gets hot. This is due to the glycerin inside the gauge expanding due to heat which results in extra pressure on the tube which makes the gauge read higher. moving the gauge away from the engine will help prevent effects of ambient temperature. Taking steps to cool the fuel like recirculating as you did will also help the gauge read correctly and help reduce vapor lock. There are liquid filled gauges available that have a pressure equalizing valve so they will reed accurately regardless of temp. but they cost considerably more than a parts store dry gauge. Bottom line…if it’s running you know there is fuel pressure.

[@LowBuckGarage]

Great info, I had never thought about that! I think I'll move the gauge to the end of the return line, right before the flow control valve. It will still see system pressure, but be at ambient temperature. Also, I can see it as I drive to see what RPM/load does to it. But as long as it keeps running, I'm happy!

[@Freedbird]

I have been watching for about a year. Lately, I have been watching your older stuff. It's pretty awesome the vehicles, tools, techniques and your calm attitude. I have unsubbed from "popular" channels, because they are flakes, so I appreciate you. The Only thing I don't like is getting all wound up and no money or stuff to work on. Oh well. It's spring, so time to change the oil in the riding lawnmower!

[@Earlywinters09]

Love the flat fender Jeep!

[@yager4092]

You are absolutely reading my mind these are some measurements I have been wondering about myself thank you for your video

[@LowBuckGarage]

Glad it was helpful!

[@leonjohansson6542]

My guess on the pressure gage is that it only measures the pressure of liquid. When it sees vapor it won't give you an accurate reading.

[@mountainfarmer8766]

Ethanol boils at a higher point than gasoline. I use a bypass style fuel filter so it always circulating.

[@michaelranasinghe3774]

Love this jeep, great video man.

[@LowBuckGarage]

Thanks! 👍

[@davevanatta1965]

luv how ya narate ya videos ty

[@jacobjohns6047]

Great video as always keep it up!

[@LowBuckGarage]

Thanks, will do!

[@huskyflylangley6053]

I've used a couple clothespins clipped to the steel fuel line close to the carb, it acts as a heat sink and radiator. Might seem hoakey , but I learned from an old depression -era trick.

[@christophernoffsinger4316]

When I was much younger. I had a 65 Mustang Fastback. It kept vapor locking on me in the hot summer days of Oregon. We had an old mechanic friend and he put wooden clothes pins on the gas line between the fuel pump and the carburettor. I have no Idea why, but for the next 3 years I must have lost or replaced them many times. Why it worked? but it changed everything!! no more vapor locking!!!!!!!!!!!!!!

[@StewsChannel]

Testing in the name of science, sounds good to me! :) Love the Jeep!

[@LowBuckGarage]

Thanks!

[@TJEssary]

A theory on the zero pressure: I keep hearing that pumps don't really make pressure, they just make flow,, and the "restriction" of the size of the line is what creates the pressure. So, if the needle valve on the carb is staying open while the engine is running, perhaps the pump is actually working just fine but there is no "restriction" to create the pressure to be measured by the gauge, especially at such low pressures.

[@cdeprima1209]

I have had good luck with carb heat shield; also fuel pump return works good, heat shield for fuel pump and wires; a good fan clutch; I like the closed cooling system so radiator can stay full, air chamber above radiator made from heater hoses for ~3% expansion like in BMWs; mostly water in radiator with just enough coolant for corrosion resistance. Good luck! :)

[@ronaldrey8474]

3-tube mech. fuel pump like on Mopars. 3rd tube is a vent to stop vapor lock. Learned from UTG

[@notsogreat123]

You still should consider an insulating spacer gasket on the carburetor. I think the carburetor should be running cooler yet.

[@tundramanq]

If I still had my 62 Chevy 327 with Holley spread bore, I would try the return line thing. I tried many things (fuel pump, carburetor spacers, electric fans ) even moving the line outside the frame rail and insulating the steel fuel line where near the headers. It would still die in the summer sitting in traffic idling.

[@dustytrailscactusron]

I sure appreciate you working on my 3B! ;-) Hey, so interesting issue. I had exactly the same issue with my old 3B. My solution was to plumb the fuel line with copper instead of rubber. Well, I don't know if that was the actual solution, and sounds counter intuitive. All I know is, once I did that, I could drive it in these Hell-hot summers with no vapor lock. I still don't know why, and remain unconvinced that vapor lock was the problem, and copper was the solution. Weird. But, I do know this: those engines went through many years of service, this can't be an isolated issue. Surely someone out there knows the skinny on it. Hey, may I make a suggestion? (Unrelated to fuel) Put in a couple of lunchbox lockers on that thing. You won't beat it up getting up those hills. (And also, maybe air down to like 15psi in those tires) I'm sure you know all this already. In any case, I love your videos! Make more! ... and let's go wheeling some day.

[@LowBuckGarage]

Thanks! From what I understand, it wasn't as much of a problem when these were in regular use because the gasoline then was formulated to work with carbs. With fuel injection being common now, a low boiling point is not a problem because the high fuel pressures used in injection prevent the formation of vapor. I have heard of return lines mentioned a few times, and it does seem to be a good solution. I hadn't heard of running copper lines before, but copper is a funny metal. It reacts differently than most metals in some situations. Getting a cut from working with copper is way different than steel or aluminum! It could even have been a chemical reaction that helped stabilize the fuel. I actually just scored a set of "junk" Jeep axles, and come to find out they had limited slips both front and rear! Not sure which one to install them in yet, though, they might end up in a new build I'm planning... This CJ-3B is not really set up well for serious off-roading, those tires are so stiff that they were at about 17psi in this video! This is my most roadworthy Willys, one of the others will be more trail oriented. And yes, wheeling sounds fun! I keep an eye out for your Jeep when I'm out there, so I'm sure I'll run into you at some point.

[@dustytrailscactusron]

@@LowBuckGarage Right now I'm installing new gears in my YJ, but as soon as that's done and I can safely call the new gears broke-in, I'll be out there (searching for a certain white 3B) Have fun!

[@dustytrailscactusron]

Oh, and, this thing about low boiling point sure makes sense. The time I'm talking about is the late 70s when we still had leaded regular gasoline. Interesting!

[@mikemorone193]

I put a Chevy 4.3 in a cj7. As soon as the weather warmed up, it vapor locked. I added a fuel filter with a return line back to the tank, and that cured it for good.

[@LowBuckGarage]

It does seem like a good solution, glad to hear you confirm that it might be the cure!

[@jamessnyder1175]

Back in Little Rock Air Force base, my dad was a aircraft mechanic. We used aspestos tape to wrap the fuel line. They don’t make that style of tape. So you can wrap the fuel line with another heat prevention tape

[@motownXJdad9565]

old video, but im binging this series on your channel. when you put that motor in the Jeep you used a Cherokee XJ factory thermostat. thats a 195° thermostat. my guess is that may be too hot for the F head motor. i kinda thought that on the first video.

[@CDNBVR1]

I liked the extra 15 HP that those F heads had over the L heads. I put a F head in my 1947 CJ 2A. The only problem I had was , I had to cut a hole in the hood for the carb to stick through. Having that Jeep was a great learning experience. I don't think I ever had vapor lock, but then, it never was that hot in southern Ontario in the mid to late 70's either.

[@LowBuckGarage]

I'm planning on doing an F-head swap into my yellow CJ-2A, I found a very short carb so I think I may be able to avoid the hood clearance issue. Hopefully I'll have the video done sometime next year.

[@CDNBVR1]

@@LowBuckGarage I wish you good luck. I no longer have either my 1947 CJ2A or my 1949 CJ3A. I miss my 3A the most. I just have a 1992 YJ now.

[@jayjenkins4721]

Drove my 48 2A L134 (still 6v) to town the other day to get titled. Warm day (70s), ran 45-50ish mph for about 6-7 miles on country roads and in town, parked for about an hour waiting on LE to run my VIN since out of state purchase, and made it about 2 miles toward home before she stumbled and died. After towing it home and scratching my head I originally thought my timing had slipped since I was getting some back firing when I tried to start...but now wondering if it was vapor lock. She didn't seem like she was getting enough fuel, so once I advanced the timing a little I did drive it into my garage where she's parked now...waiting for me to figure out WTH is going on...lol. I do have the riser on the WO carb, and mechanical glass bowl fuel pump bolted onto the block. Haven't tested for heat yet, so this gives me something to look at.

[@LowBuckGarage]

Definitely worth a look. If you dump a little gas in the carb and it starts right up, its some kind of fuel supply issue.

[@shawnwhitman5482]

If you measure the air temperature at the base of the carburetor or the temperature of the air inside the intake it should be really low perhaps around 35°~ 40° keeping the fuel moving will cool down things

[@Dancing_Alone_wRentals]

15:50 Be careful out there by your lonesome, Any minute Rat Patrol could come sailing over those hill sides. Don't get run over!

[@Dancing_Alone_wRentals]

" Where does he get all those wonderful toys?"

[@RH-in-UK]

Shouldn't the water pump fan be sited within a radiator shroud?

[@kornami8678]

Is your fuel line resting against the top radiator hose? Separate them.

[@yager4092]

Once the carburetors fold the fuel pump don't need to pump anymore

[@nickpanhead7209]

Could it be your gas line with guage installed in it. Going across your radiator hose ?

[@LowBuckGarage]

I should have done a "before" shot, but the line only went across the radiator hose after I added the pressure gauge. Before that, the line was routed away, and that was when I had the most vapor lock issues. However, you bring up a good point, thanks! I'll move a temp gauge to that line and see what it reads just to be sure.

[@nickpanhead7209]

@@LowBuckGarage yeah seen that just figure I mention it. But you seem like you know what your doing. Cool jeeps, I'm looking for now myself

[@kornami8678]

Would a change to an electric fuel pump fix the problem? Or is that too easy for a great guy who loves to do things the lazy way.

[@thirdcargarage2951]

I love science…..

[@flight2k5]

It’s your religion

[@retiredafce3373]

Ever want to sell it?

[@MartinLopez-ys5dm]

Check the thermostat...

[@LowBuckGarage]

Its been running consistently at a coolant temp of about 170F, so I think that the thermostat is good, or at least good enough.

[@greywolfwalking6359]

Jus sayin 🤷...you wanna fix the problem... " Stay out of the sand"!!!! ORRRRR, take the red jeep n play!!!????Or---> Stay on road!!??