Vapor lock?

[Duskylady]

Greetings all! Does anyone have ideas on a solution for vapor locking?
 

I was out driving my ‘41 with stock flathead 6 today in 90° weather. I parked for about 20 minutes to grab groceries. Tried to start the car and no go. Carburetor wasn’t getting any fuel. Fuel pump looked full from underneath.  The engine bay was screaming hot.  I’m assuming it was vapor locked. The car sat for about an hour while I walked to get a gas can and some starting fluid. (Seems regular grocery stores don’t carry that stuff anymore and neither do small gas stations). The engine cooled off a bit. I sprayed some starting fluid in the carb with a few pumps of gas and she fired up. 

[Los_Control]

Seems adding a electric booster pump is a sure fire way to get through it.

The hot engine turns the fuel into vapor that a mechanical pump cant deal with ..... electric pump will push cool liquid fuel through the pump.

Is the go to for most people..

 

I'm going to try adding a return line on my tank to recirculate the fuel & keep it cooler.

When you are in traffic driving slow or stop & go, the fuel can vaporize as it sits in the line & heats up. .... At some point you may find this issue also.

Simply not using enough fuel, the float closes & the exhaust heats it up in the line. Turns into vapor.

When you stop at a grocery store, the engine heats up & turns the fuel to vapor in the carb.

Electric pump will fix these issues.

 

Modern cars with a return line are not affected by vapor lock with the modern fuels.

The fuel never sits in the line & heats up, excess is returned to the tank .... constant supply of fresh cooler fuel.

The cooler fuel can accept the heat soak from turning the engine off without turning to vapor .... will still rise 20-30 degrees temperature, but it was 20-30 degrees cooler before you shut the engine off.

Since I'm installing a new tank & lines on my project, a extra step to T the line before the carb & run it back to the tank is not a big deal .... I think.

Will it work? I hope.

[Duskylady]

That might work. Did you convert to 12 volt? This ‘41 is still all original 6 volt.  We did an electric pump with a return line to the tank in our ‘47 but it has a bored out 350. 

[Los_Control]

I am converting, many people here are 6 volt and use a 6 volt pump .... they will chime in on what pumps they use.

There are many threads here on vapor lock if you use the search function. ..... common problem.

 

My plan is to use the mechanical pump with the return line ...... just to see if it works for me here in West Texas heat.

I will install a electric pump if needed later.

I just want to know if a simple return line is enough for our old cars.

Edited July 26, 2023 by Los_Control

[Oliver Klozoff]

I kind of have the same thing in my 49 special deluxe.... drive for a while. Park. Starts chugging.  I'll be following this closely.

[Doug&Deb]

I use an Airtex E-8902 on my 52 Coronet with 6 volt system. I still have the mechanical pump. I use the electric pump for priming after the car hasn’t been started for a while and for hot starting. I wouldn’t recommend using starting fluid any more than absolutely necessary. 

[bacelaw]

I wrapped the fuel line that goes from pump to carb in a heat sink type wrap available on Amazon; I think it's fiberglass or something.  I drove today in 90 degree weather, started immediately after sitting for 20min or so.  

 

If that doesn't work, see Keith's video on an eletrical pump add-on...

 

 

 

[Sniper]

I routinely drive my 51 in 100+ degree heat with no issues and no vapor lock tricks.  I dunno.

[Bryan G]

I've had the vapor lock issue on several vehicles and "fixed" it each time with an electric pump. It's fairly easy to install one, and not something you have to think about. Perhaps with enough insulation around the line I could get away without it, but the only path my line can take up to the carb is rather crowded.

[Duskylady]

Honestly, I will be trying the electric fuel pump AND the wrap. It sucks getting stranded.  This car is supposed to be the grocery getter. Doesn’t do a good job if all the ice cream melts. Thank you all for the advice!!! I will reply here on the outcome. Now off to the interwebs!!!

[Duskylady]

4 hours ago, bacelaw said:

I wrapped the fuel line that goes from pump to carb in a heat sink type wrap available on Amazon; I think it's fiberglass or something.  I drove today in 90 degree weather, started immediately after sitting for 20min or so.  

 

If that doesn't work, see Keith's video on an eletrical pump add-on...

 

 

 

Is it like the wrap for headers?

[bacelaw]

5 hours ago, Duskylady said:

Is it like the wrap for headers?

 

No, it's designed for thin fuel line.   Here's an Amazon link to what i used. AC PERFORMANCE 3/8" ID Silicone Coated Fiberglass Heat Shielded Fire Sleeve for Hose Line and Spark Plug Wire, 3/8 ID, 5 Feet (9.5 mm ID) https://a.co/d/akuKrXj

[FarmerJon]

11 hours ago, Sniper said:

I routinely drive my 51 in 100+ degree heat with no issues and no vapor lock tricks.  I dunno.

Does your fuel pump have the stock heat shield?

Do you have a functional factory exhaust heat riser?

Same for you, @Duskylady

 

There is also a factory heat shield for under the carb, I believe its from mid '50s cars. 

 

I have one of the under carb shields, from a '55, and 3 of the thick fiber carb gaskets stacked to add insulation. My exhaust heat riser is gutted, but my manifold is modified for dual exhaust. I do not have a fuel pump heat shield, for no good reason. 

I have minor heat soak/vapor lock issues, but nothing that has left me stranded.  When restarting hot, I usually hold pedal to the floor and crank. Do not pump or lift your foot until it fires up. 

 

[Sniper]

3 minutes ago, FarmerJon said:

Does your fuel pump have the stock heat shield?

No heat shield, don't think they were stock for everything

 

4 minutes ago, FarmerJon said:

Do you have a functional factory exhaust heat riser?

Yes, it does.

[keithb7]

My take on the electric booster fuel pump. 
 

https://youtu.be/d2pQW_LIdiE

Edited July 27, 2023 by keithb7

[JerseyHarold]

An inertia switch on the fuel pump feed wire is advisable so that the electric pump shuts off if the car is hit or jarred.

[Oliver Klozoff]

I think I'm going to install a 6v fuel pump and re route the lines further away from the engine.

 

My other option is a fuel filter with a return line, but electric pump seems to be an easier option

 

May also use those insulated covers as posted above.  

[JBNeal]

additional information - flathead fuel line routing and insulation

[Duskylady]

On 7/27/2023 at 6:37 AM, FarmerJon said:

Does your fuel pump have the stock heat shield?

Do you have a functional factory exhaust heat riser?

Same for you, @Duskylady

I do have the stock shield and heat riser. 

[Duskylady]

Thank you all for the good solutions and links. I’m finding parts to order right now. I’m probably going all out to squash this problem with an electric fuel pump, line wrap and split manifold. And my husband said to try wooden clothes pins on the fuel line while I’m waiting for parts. 

[Go Fleiter]

I use a 12 V fuel pump with 6 V (years ago I couldn´t find a 6V one) parallel to the mechanical one.

To only prime, fighting vapor lock,  it´s power is sufficient.

6V may not be sufficient to substitute a failure of the mechanical, however.

 

 

[Duskylady]

Update: As with most projects there is never enough time to do all the things. We are remodeling our house but I did tinker with the car a bit. Put some heat shield on the fuel line and ordered an online fuel pump (haven’t had time to install). Seems there are more issues I need to dig into. Now it’s not getting any fuel to the carb, perhaps this was the culprit previously and not vapor locking. I will post an update when I figure it out.  Thank you all again for all the help!

[Kilgore47]

On the 47 P15 the line from the fuel pump to the carb runs very close to the exhaust manifold.  What were they thinking?  Rerouted the fuel line away from the exhaust manifold and the vapor lock problem went away.  This car does have a heat shield at the pump.  

[Duskylady]

3 hours ago, Kilgore47 said:

On the 47 P15 the line from the fuel pump to the carb runs very close to the exhaust manifold.  What were they thinking?  Rerouted the fuel line away from the exhaust manifold and the vapor lock problem went away.  This car does have a heat shield at the pump.  

The ‘41 is the same! It has a heat shield as well. I will try rerouting the field line if this wrap doesn’t do the trick. Thank you! 

[Tom Skinner]

Put some old wood Clothes pins on the Gas line.

As Jackie Gleeson would say: And away we go!