Classic Car Survival - Summer Is Coming And if You're A Car Guy It Means Vapor Lock Season Is Here!

Besides the addition of ethanol in today's pump gas, the basic formulation of the fuel we use has changed over the decades to match the evolution of emission laws and induction systems.
The biggest drawback to operating yesterday's tech on today's fuel is the phenomenon of vapor lock.
Here's a rundown on the history of the problem, fixes that have proven themselves to work, and a couple of examples of how fuel systems can be laid out to minimize the hassle of fuel percolation with your street car.
#engines #autorepair #maintenance #autoparts
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[adamrodenberg]

Thought I'd share my recent experience with vapor lock. I bought an old Chevy truck that would get up to about 215 degrees, then shut down with vapor lock, every time I drove it, even on the interstate with plenty of air moving through the grill... I also noticed after coasting to the side of the road and popping the hood open, the amount of heat under the hood was unbearable, forcing you to step back... First, I replaced everything in the cooling system, new radiator, new water pump, new thermostat, new fan clutch, and it still would get too hot and shut down... Then I tried insulating the fuel lines, blocked off the heat riser passages in the intake, and added a carburetor spacer, still got too hot... Then I started to notice a pattern where I could hear the fan clutch engage and start to pull more air through the radiator right before it would shut down at 215 degrees. So, I "recalibrated" the fan clutch by adjusting the little thermostatic clock spring on the front of the fan clutch. Only had to turn it like an 1/8 of an inch (think it was counterclockwise) and now the fan pulls much more air, but it still would get too hot and shut down... Then I did a little research and decided to check my vacuum advance... Then, the only changes I made were to switch the vacuum advance from a ported vacuum source to a manifold vacuum source, and adjusted the vacuum pot one and a half turns to maximize advance... That is what finally fixed it!!! Now the temperature gauge stays around 170-180 degrees even in traffic, in the hot south-east. My gas mileage got much better as well... Anyway, great videos!!

[speedy_pit_stop]

UTG is like an encyclopedia of motoring knowledge with a historical perspective like no other.

[guyjordan]

My only experience with it was on my 74 VW super beetle. My friend and I pushed that car for miles and when my dad got me back to it the car started just fine. That’s when he told me about vapor lock… proving an 18 year old kid can learn from his dad.

[x]

Just to get some of youse guyz tinkin', back in the 80's Mercedes used to run the fuel line up into the engine compartment, coil it about a dozen times around the cold side A/C line, and then on the the throttle body. So, if it was hot enough outside to turn on the A/C, presto you had cold gas going into the engine. Smart dudes them Germanz.

[kart]

Two other things, though, one commenter had touched on one. Electric cooling fans on a timer and pressure. The cooling fans do double duty. They reduce the heat soak in both the cooling system and the fuel system after the engine is off.
The pressure thing is kinda touched on, but not directly addressed on Bottle Rocket. Much like pressure in a cooling system keeps the water from boiling, so too will pressure help keep fuel from boiling. Having a high pressure fuel delivery system with a return style pressure regulator is ideal to reduce vapor lock.

[patricklynch]

I used the "eight dollar" cure on my '68 Fury VIP (318 2 bbl) by getting the same Wix fuel filter that would have gone on my '80 Cordoba (318 2bbl) and adding a return line that is hooked up to a tee at the tank. Also covered all my fuel lines under the hood with that slip on insulation from the carb to the filter, the factory fuel line down to the pump and also the return line from the filter down to the frame rail. Works great, no more problems after that.

[stephenG]

I swear to the almighty, your video might have just helped me figure out an issue I've been stumped on for 6 months now. I've got this 91 Camaro that was molested the worst I've ever seen a third gen butchered. I'll try and keep it short, It was gutted of it's electronics and had a 305 someone put effort into slapped with a Edelbrock 1406 on top, ran great without issue for the first 3 weeks into owning it. Throws a rod bearing, pretty sure the external balance flywheel they put on the neutral balanced engine was the culprit. They ran an inline pump mounted on the driver rear floor pan with specs saying it pumped 5psi to a regulator by the brake master cylinder with no return. I decided to spend the last 2 years restoring it, I put a crate motor 350 mounted to a T-5 and decided to put a posi/disk 4th gen rear end in it, figured I'd replace the fuel tank/sender/in tank pump while I'm at it so I have the option to convert it back to it's factory fuel injection. So I converted it from the dead head returnless to a return system with a quality regulator. Got it together, first 4-5 test runs ran perfectly, they were only 20 mins at most. First time I drove it longer about 45 mins in it's like it's starving for fuel as I'm cruising down the highway, pull over pressure gauge say 0, can hear the pump and see fuel in the inline filter, adjust it back to 5psi runs fine for another hour. I start it the next day it's pegging 14psi blowing fuel out of everywhere on the carburetor. Just a pack pressure held same thing 45 minutes in does it and I repeat this cycle several times, trying different things they'll finally I just say screw it and put a second regulator in line, It reduced the erratic fuel pressure but it still happens enough to be a problem. All right now realize I have about 3 ft of rubber hose probably two of it wrapping around the carburetor sitting on top of a GM 350 stove basically cooking the fuel past the second regulator and probably about another foot between the two regulators and the return line that sits within 4 in of an exhaust header. I am now thinking my problem is the heat soaking into the rubber fuel line is the reason why with fixed spring rate set at the regulators the fuel pressure is All over the place without rhyme or reason.
I'm going to try rerouting with Hardline avoiding the engine as much as possible and see if that fixes it running one regulator and if it does I'll have to come back with a big fat thank you for making this video.

[happyrootsfamily]

My grandfather used to keep clothes pins on his line to draw heat out

[stevelacker]

One other thing about modern fuel… they actually CHANGE the boiling point of the fuel twice a year. They lower the boiling point (raise the equilibrium vapor pressure) in winter, allegedly to lower emissions by getting the fuel to vaporize better for clean combustion. Then they raise it in summer to prevent unburned fuel emissions from gas evaporation out of car gas tanks and gas station storage tanks. The result of that is that you are now more likely to get vapor lock on a warm day in winter than on a hot day in summer… and it’s really bad on cars that are rarely driven and can get all the way into late spring early summer and still have winter gas in the tank.

[spankyham]

You are far more informative than my ASE teacher was 20 years ago. You really are a wealth of knowledge!

[VWbusmarketcrash]

Late 70’s and early 80’s Datsun Z’s with the inline 6 had a small fan on the side of the engine with plastic ducting that would turn on after the engine was shut off. It would kick on maybe 30 seconds after the key is shut off and would run for a few minutes. The air would come from the cooler side of the engine and blow over the fuel rail, to keep it cool for that first few minutes after the key was shut off, so that you could restart the car if you only stopped for a minute. Even some recirculating fuel systems had vapor lock issues.

[emmett]

The fuel injection returnless systems have this topic covered. The method is to vary fuel pump speed based on fuel rail temp. At higher fuel rail temp, fuel pump output is increased, increasing rail pressure, raising boiling point to prevent vapor lock.

[frednerk]

Allied forces during WW2 behind enemy lines in Africa(Long Range Desert Group - look it up), used to, when they stopped, turn their trucks/jeeps into the wind and lift up their bonnets (hoods) to get the latent cooling while taking a break.

[glennhales]

My Dad was a woodworker and had a guy buying carb spacers made of oak, as he said they were the best insulators available.

[floydpack]

This guy has learned me more in the last 3 hours then any asshole wanting my money when they see my old k10 come beating the earth when I pull into the shop. I'm new to the SBC game and I can tell you Everyone needs a uncle tony.

[BackyardClunkers]

A few ideas that help in this issue of vapor lock: like your brake lines'coils next to the master cylinder: Coil/ spiral your steel fuel line.. this technique disperses heat (remember why the brake lines are like that by the master cylinder, & very close to the exhaust manifold/ header: to disperse heat: boiled brake lines= no brakes.
Another idea: coil up/ spiral up your fuel line away from headers/ exhaust piping & have it inside a metal coffee can: if need being on certain occasions now u can fill that coffee can with ice.
Another idea: use a brand new "universal trans cooler" plumb your fuel lines through that, then to fuel pressure regulator/ carb, & so forth. Header wrap exhaust stuff, & coolant hoses if need being. You'd be surprised how well a combination of these techniques work well.

[stevelacker]

There’s actually a technical service bulletin for vapor lock on the Jeep 4.0. It is mostly a problem with the 2000 and later engines that had iron exhaust manifolds and the two pre-cats up close to the manifold below the engine, rather than back under the floor. The “fix” is insulating socks over the fuel injectors (especially #3). It definerky helped on my 2000 Cherokee. My daughter’s 99 Cherokee never had the problem, since it had the older exhaust design.

[bobsmith-mhxz]

I use a plywood spacer under my quadrajet.. yes... Wood .. helped a lot with heat soak ..

[MrChevelle]

Having delt with vapor lock over many times, ive went to a home made bypass fuel system using an electric fuel pump. Lots of examples to look up and copy, I route the lines away from the heat as much as possible, it works great when properly setup to keep your good ol simple carb system going on the dishwater crap fuel we have to run, I used non eth gas when I can but its just not available everywhere.

[The_Kman]

My dad had an old pontiac that vapor locked frequently. He fixed it by clipping a bunch od spring type wooden cloths pins to the metal gas line between the fuel pump and carb. Every time a mechanic saw them they would always ask about the cloths pins!😂