Vapor-Locking... the bane of my existence.

[WileE]

The gasoline has changed since these cars were new.
Today's fuel evaporates much faster and therefore has a lower boiling point. If your car is all stock, you may be fine.
I had my fuel lines routed like stock and while the exhaust was nowhere near the fuel lines, I still had moments where it would heat soak after sitting or just buck and stall while idling in hot weather. The return line ended that.
The heat in the engine bay elevated the temperature of the gasoline. the return line lowered it enough to not be a problem anymore.
I'm not claiming that this is an a fix for everyone but the theory is sound. Yup.
I thought that even throttle body EFI systems used a fuel system with a return line despite having fuel pressures not much higher than carbureted cars.

I don't believe it's a one-way or no-way. You're absolutely correct, and many cars will require a return. Others, as in one of my cars, not. It's probably a case-by-case scenario. Some cars will benefit with the return system, others may not need it.

 

[Kern Dog]

The red car is the only one I have that has a return line but it is the fanciest car that I have. My other cars look straight out of Roadkill and they are not as pretty as the Charger.....

 

[Belvedere408]

The red car is the only one I have that has a return line but it is the fanciest car that I have. My other cars look straight out of Roadkill and they are not as pretty as the Charger.....

View attachment 1882227

View attachment 1882228

View attachment 1882229

The 67 Dart GT is awesome KD

 

[Kern Dog]

Thanks, man!
The Dart is all function, no beauty...or at least no "make-up".
It has a pretty peppy 360 and a 4.10 diff. stiff suspension and a Sure Grip. You watched Freiberger drift the General Mayhem around? I could teach that dude some moves with this Dart!

 

[Moparfever65]

I think a lot of maladies are lumped into the term vapor lock that don't belong there. Best to understand it. Sometimes it's the fuel in the carb bowls boiling off, causing the start to delay until the bowls are full. Fixed with a phenolic spacer and/or carb heat shields. It can also be a heat-soaked ignition coil causing weak spark. Here's a good description of heat soak: Ask Away with Jeff Smith: Understanding Vapor Lock--and How You Can Fix It! - OnAllCylinders

 

[Scotts]

I had the same problem with my 440. Solved it ultimately by running the fuel line into the wheel well thru the access cut out in the fender and into a large fuel filter canister and back out to the original routing up over the engine to the carb. I think the gas cooled enough in the well to make the final run to the carb without vaporizing. It’s been good for twenty years in the AZ heat.

 

[Road Grabber]

I had been tracking down an issue like this for years.
I finally discovered that the heat riser shaft on the exhaust manifold was leaking hot exhaust. The exhaust was pumping out a stream out towards the fuel line. There was a small hole next to the shaft for some reason. It was factory. Not a crack. Check out the area anyway.
It’s very hot down there so reaching down to check is a problem. I reached from underneath. You could also attach a sheet of paper to a rod of some kind and watch it flap.
I ended up plugging the hole up cause I don’t use the heat riser with braze but you could use your own method.
Once it was plugged- no more vapor lock.
This was after fuel pumps, carb spacers, changing fuel filter types with return lines and other stuff. Drove me crazy.

The heat shield around the line will help too but my main issue was the exhaust manifold.

 

[Mbrew]

The best thing ive found is a “paper” style carb spacer , Edelbrock has a couple different ones.
They were used on Fords a lot back in the day .
Getting the fuel line away from the engine is also a common sense thing too.

 

[artr8]

Good point RJ... I will put her up on the lift and check lines.

How many of you have added a tank return line?

On multiple cars, I have used an 80’s dodge fuel filter that has a 1/4” port return off the pressure side of the pump. The 1/4” line was plumbed back to the tank.
Then used phenolic spacer at the carb.
Never have had issues with vapor lock with these two fixes in place.

 

[toolmanmike]

On multiple cars, I have used an 80’s dodge fuel filter that has a 1/4” port return off the pressure side of the pump. The 1/4” line was plumbed back to the tank.
Then used phenolic spacer at the carb.
Never have had issues with vapor lock with these two fixes in place.

How about fuel evaporation after the car sets for a fre days to a week?

 

[Black_Sheep]

How about fuel evaporation after the car sets for a fre days to a week?

That doesn't bother me too much, the extra cranking to prime the carb allows the engine to build oil pressure before it lights...

 

[Kern Dog]

I had the same problem with my 440. Solved it ultimately by running the fuel line into the wheel well thru the access cut out in the fender and into a large fuel filter canister and back out to the original routing up over the engine to the carb. I think the gas cooled enough in the well to make the final run to the carb without vaporizing. It’s been good for twenty years in the AZ heat.

I’ve wondered if maybe some small change in temperature is just barely enough to result in a huge win.
In other words… reduction in temperature by day 15-20 degrees keeps the fuel just cool enough to solve an issue.

 

[autoxcuda]

Hey all,

1966 Charger with a 440 - New Edelbrock 750 AV2 carb. New mechanical fuel pump. - Total rebuild including the transmission.

In the garage, it starts and runs great. On the road, until it heats up, it runs great. Run a mile and stop for a bit and it is obviously vapor-locking. The see-through fuel filter actually bubbles. Let it sit for an hour, and it starts great. The filter sits, as it has always sat, next to the carb. An anti-vapor lock filter is part of the answer though this breed of car never had one before. Should that filter be placed BEFORE the fuel pump or after?

Any suggestions would be well received.

Thanks in advance...

Could you show pictures of your fuel line from frame rail near footwell to carb.

Seeing is much better than taking shots in dark.

Lowing your float level 3/16” could make a difference too.

 

[moonshine_mike]

Could you show pictures of your fuel line from frame rail near footwell to carb.

Seeing is much better than taking shots in dark.

Lowing your float level 3/16” could make a difference too.

I'm really late to this thread, sorry.
I have a number of MOPARS here is southern AZ. Scorching heat. Had a "vapor lock" problem for multiple years on one car. Blamed numerous things, then finally found the issue. Simply needed a gas cap that could breath. Since that discovery, I have run 340s up to hemis and 440 six packs, with no need for any heat shielding, no need for return fuel flow to tank, just the correct gas cap. We run up to 95 deg outside temp, not because the cars have issues higher than that, but because I have issues at higher without AC.

 

[threewood]

Well explain how millions of cars performed flawlessly....without a return line.

Better gasoline.

 

[Road Grabber]

I haven't seen a picture of the fuel line route but make sure the fuel line is away from the heater and radiator hoses. Check that your fuel line is not near the exhaust system back by the tank and muffler. Also in the rear wheel well where it goes from the frame to the tank.

If you have a stock system without headers vapor lock should not be a problem. If there is a problem it's usually caused by ourselves. I'd start with the solutions mentioned that don't cost money and go from there.

If you have clearance away from the exhaust in the engine bay inner fender up to the fuel pump, it's an issue from the pump to the carb. Try to create space from the block and heater hoses if possible. I know it's tight there for sure and yes you should have the filter vertical just below the alternator. When you adjust the alternator sometimes the fuel line gets pushed around and leans up against the block or heater hose.

If your problem happens that quick though I think it's getting heat from the exhaust somewhere because that gets hot right away.

I may have missed it but make sure you check your float bowl height too in the carb if you need to fine tune. IMO those spacers are a band aid and you shouldn't have to use them.

Good luck

 

[savoy64]

I had similar issues for a long time and tried lots of tricks including the vapor canister filter and a new pump. None worked well. Ultimately I put an electric pump on it. Poof, vapor lock problems gone.

In hindsight I think my fuel pump pushrod may have been worn. But the electric pump was so nice I never bothered trying to go back to a mechanical one.

Ditto! My 522 stroker endured the same issue. I insulated the fuel line, used a carb spacer etc. Installed a Carter electric pump back at the tank and took off the mechanical pump. Problem solved even in this heat wave were having now!

 

[savoy64]

You are lucky. A friend was having excessive pressure with his mechanical pump, bought a new one from Car Quest and it was worse. Over 10#

I didn't run a return line. I'm using a Carter electric pump that regulates at 5-7 psi. It stays around 5 psi ( no fuel pressure regulator). No problems after 5 years

 

[GassMann]

Hey all,

Sorry for the delay in following up with this. I have been out of town and this is my first weekend back and under the car.

I just finished wrapping DEI Fireline around the fuel line. I also installed a vapor separator filter and was running the return line. Got almost all the way to the tank when I noticed, just above the axel where the fuel line follows the contour of the body to the tank, a !@#$!@ kink in the line. It looks like it has been there for ages. Covered in grease and undercoating, the kink almost shuts off the fuel flow. My guess is the original 318 with a 500CFM didn't need as much fuel and so no problem. But the 440 with a 750CFM is fine at idle but under load, the kink is restricting the fuel.

I know it was vapor locking as well so I will leave the filter as it is. I may take out the vapor separator and go back to a simple inline filter, fix the kink and see how I get on. Curiosity is driving this more than anything. I want to know how the DEI fire line helps with the heating fuel.

Lots of great advice here.

Here are some pics of the fuel line today. Last pic shows the crushed line, and it looks like maybe the old exhaust did it. I think I know how it happened, but I have to go back 46 years. That was the side when, as a 17-yr old kid, I had single exhaust and, hitting a 90 deg corner on a Puyallup farm road at 55 MPH, I blew the bead off my stupidly wide rimed tires. The tire blew, dropped the rear passenger side axel into the gravel, destroyed the rims and stretched the leaf spring by an inch. I didn't realize the exhaust moved up that far and crushed the line. In hindsight, I was lucky I didn't roll my Charger.

The crushed line is about 15" from the tank. Do you think it would be OK if I just cut the pinch out and ran a longer fuel line to the tank? Or should I replace the entire line?

 

[GassMann]

Ditto! My 522 stroker endured the same issue. I insulated the fuel line, used a carb spacer etc. Installed a Carter electric pump back at the tank and took off the mechanical pump. Problem solved even in this heat wave were having now!

With the electric pump, did you have to install a return line???