Vapor lock

[austinsailor]

A month or so ago we were talking about vapor lock. Some thought it didn't exist, some had various ideas about combating it, I thought it was a problem now mainly due to the crappy gas we get.

I bought some octane booster, which also is supposed to raise the boiling point of gas quite a bit.

After trying it for several trips I've found that I completely got rid of the problem. Before, it was very predictable where and how I would stall. With the booster added to the same gas it has had zero problem, even under the same circumstance, same distance and temps.

There is one place here that sells premium with no alcohol and my father tried it in his 41 Chevy but it didn't change, he still gets stalled. I may try it anyway, his problem was much worse than mine.

When I get time I'll get some avation has and try that. It'll be more expensive than the additive, but it might be another solution.

[desoto1939]

Instead of spending the extra dollars for the fuel additive and the aviation fuel you can purchase an electric fuel pump for around $50. They are listed on ebay for $48.

Install it as close to the gas tank as possible and have a toggle switch to turn it off an on only whenthe iginition is turned on.

This electric pump is well wortht he investment for several reasons:

1. Since you are getting vapor lock all you then have to do is flip the switch and the electric pump will pump the gas trought the mechnaical pump up into the carb and the vapot lock is gone and you can continue on your merry way.

2. BAck up to the mechanical pump. If the mechanical fails then you can use the electric pump to get you home since it will pump gas to the carb.

3. After the car has sat not running for several days or weeks you then do not have to grind the engine to get gas upto the carb and then wear down the battery. Runthe pump for about 5 seconds check to see if you have gas in a filter installed just before the carb. Then start the car It will start right up. Also now you do not get any metal wear on the cylinders. If you use a spray starter fluid this is bad. If you do not get the car to start the fluid strips the oil off of the cylinder walls and then you have bare metal to metal.

This is just my 3 cents onthe topic but I have the new Airtex pump in my 39 Desoto and I recommend everyone to have one in their antique car or truck.

Rich Hartung

desoto1939@aol.com

[Merle Coggins]

I agree with Rich. In fact I agree so much that I've already added an electric pump and it has saved me during a brief vapor lock type issue a couple of weeks ago.

Merle

[JBNeal]

The electric fuel pump as a back-up to the mechanical fuel pump as well as a mfp primer...I reckon that is going on the upgrade list, along with bigger rectangular mirrors, radial tires & turn signals.

My '48 stalled a couple of summers back at the controlled intersection of two farm highways in between two small towns. As I sat in the truck at the green light, waving the sporadic drivers to pass, I spied a rapidly approaching F250 with a contractor just a yappin' on his cell...I was getting ready to bail out of the truck when he finally saw me stopped in the middle of the road and swerved to avoid smashing into me. This prompted me to get out & push the beast into the ditch, where we sat for another 1/2 hour (it was well over 100 that day) as the truck cooled off, both hoods open. I reckon the electric fuel pump would've negated this story and the near-loss of my wits that day, so that's good enough reason to bite the bullet.

[41/53dodges]

i just completely replaced the mechanical, and i have the pump running off the key (in a roundabout way). my mechanical started making oil, so that had to go. let the truck sit for 6 months empty, dumped gas in the tanks, fired right off!

[SteveMelchiorre]

You sold me on it. I'll be putting one in this summer.

If I may ask where did you guys mount yours? (the pump)

Steve...

[Dave72dt]

Electric fuel pumps are designed to push the fuel and don't suck well. Mount as close to the fuel tank as possible.

[Mustang6147]

That is intresting. It must have somthing else to do with it, because years ago you could redily get high octane gas. Now the most commonly found is 94 at Sunoco. Have you tried racing fuel? perhaps 116 octane? I did try 110 in my 41 plymouth. It has a 49 dodge truck 230 in it, and boosting the octane made no difference, but I rerouted the fuel line away from the engine, and used an electrical pump back by the tank and that is what got rid of it for me.

[ChrisCoccia]

Does anybody know if a 6 volt electric fuel pump is available?

[JBNeal]

Q: if an electric fuel pump is installed, does a return line from the carb to the fuel tank also need to be installed? My concern is the psi from the electric pump will crack open the float needle valve and flood the carb...

[greg g]

Last night I was looking at a 50 pontiac straight 8 equiped. I spoke to the owner for a bit ad he said he usually doesn't drive it when its hot because of VAPOR LOCK. When I asked him a bit more about how it manifiested itself, he said it didn't like to start afer a shut down. He figured hw was safe (it was in the high 80's) because he would be parked for a couple hours after driving. I aksed hi if he knew the actory recommended procedure for starting a hot engine? He said, "NO". I then asked him if he knew the procedure for starting a floded engine? He looked at me like I was nuts. then I asked him to open his hood. After the breeze blew the gas vapor smell away, we took a look at his carburetor. The base of which along withthe heat shield and the top of the intake were wet with gas. He tought he had a leaky in the carb. When I showed him that the raw gas was coming from the throttle plate pivot and leaking out the top gasket. So I then asked him to pull his dipstic and smell his oil. Gassy also. I aked him if he had a screw driver and if he was willing to make an adjustmet to his float? He said sure. So off came the top of his carb, and sure enogh the float bowl was over filled. So I expained float level, perculation, flooding from perculation and we adjusted his float to close the needle and seat a bit lower the the top of the float bowl. Then I told him wet throughthe hot start floded engine routine, and he was surprised that the car started after only about 4 or 5 turns.

He said he would change his oil, and I will hopefully see him tonight to see if the fix is still in.

His owners manual, which he had never read, says to restart a hot engine, to depress the gas pedal to 2/3, 3/4 open before engaging the starter. He was just cranking the starter.

the next paragraph covered starting a flooded engine.

Folks are just so used to starting Fuel Injected cars these days, they assume carbureted cars act the same way.

As for electric pumps buy one that puts out max of 7 lbs pressure and it shouldn't be a problem. Unlike modern cars with pumps in the tank and 40 to 60 lbs for FI, universla pumps will shut off when the line is pressurized. If you can'tfind a 7 pounder you will need to put in an adjustable regulator.

Edited July 15, 2010 by greg g

[Young Ed]

Greg the little neighbor kids remind me of this fact all the time. If one of my old cars doens't start on the first 2 rrr rrr's they ask me if its broken.

[Zeke1953]

An electric fuel pump sounds like a great idea for all the reasons mentioned here. The only concern I have is whether we need some kind of emergency automatic shutoff switch in case of an accident (God forbid!) or a broken fuel line. In either case, won't the pump just keep on doing its job until someone can kill the power? Zeke

[jd52cranbrook]

An electric fuel pump sounds like a great idea for all the reasons mentioned here. The only concern I have is whether we need some kind of emergency automatic shutoff switch in case of an accident (God forbid!) or a broken fuel line. In either case, won't the pump just keep on doing its job until someone can kill the power? Zeke

That's always been my concern with one. I do have a pressure switch on a oil bung on my block for a idiot light on my dash that would shut it off if oil pressure drops below 20lbs. But that would not help me on starting the car.

[Don Coatney]

Instead of spending the extra dollars for the fuel additive and the aviation fuel you can purchase an electric fuel pump for around $50. They are listed on ebay for $48.

I must ask what the folks did about this problem in 1940, or 48, etc? Looks like Greg already ansewered this.

Last night I was looking at a 50 pontiac straight 8 equiped. I spoke to the owner for a bit ad he said he usually doesn't drive it when its hot because of VAPOR LOCK. When I asked him a bit more about how it manifiested itself, he said it didn't like to start afer a shut down. He figured hw was safe (it was in the high 80's) because he would be parked for a couple hours after driving. I aksed hi if he knew the actory recommended procedure for starting a hot engine? He said, "NO". I then asked him if he knew the procedure for starting a floded engine? He looked at me like I was nuts. then I asked him to open his hood. After the breeze blew the gas vapor smell away, we took a look at his carburetor. The base of which along withthe heat shield and the top of the intake were wet with gas. He tought he had a leaky in the carb. When I showed him that the raw gas was coming from the throttle plate pivot and leaking out the top gasket. So I then asked him to pull his dipstic and smell his oil. Gassy also. I aked him if he had a screw driver and if he was willing to make an adjustmet to his float? He said sure. So off came the top of his carb, and sure enogh the float bowl was over filled. So I expained float level, perculation, flooding from perculation and we adjusted his float to close the needle and seat a bit lower the the top of the float bowl. Then I told him wet throughthe hot start floded engine routine, and he was surprised that the car started after only about 4 or 5 turns.

He said he would change his oil, and I will hopefully see him tonight to see if the fix is still in.

His owners manual, which he had never read, says to restart a hot engine, to depress the gas pedal to 2/3, 3/4 open before engaging the starter. He was just cranking the starter.

the next paragraph covered starting a flooded engine.

Folks are just so used to starting Fuel Injected cars these days, they assume carbureted cars act the same way.

As for electric pumps buy one that puts out max of 7 lbs pressure and it shouldn't be a problem. Unlike modern cars with pumps in the tank and 40 to 60 lbs for FI, universla pumps will shut off when the line is pressurized. If you can'tfind a 7 pounder you will need to put in an adjustable regulator.

Thanks for posting Greg!

An electric fuel pump sounds like a great idea for all the reasons mentioned here. Zeke

I dont believe an electric fuel pump was available when your vehicle was new. Why does it sound like a good idea now?

[JBNeal]

I reckon the oil pressure switch can also be routed to a relay that feeds the ignition coil...a manual override switch with a trigger guard could be put under the dash.

[grey beard]

When I overhauled my engine, I pulled the mechanical pump, drove the pin out of the arm and took it off. Put the pin back in and used the dead pump for a block-off plate for the hole in the block. My electric pump sits on the crossmember, immediately at the front of the fuel tank with a short rubber fuel inne just long enough to include a fuel filter,. From there the new steel line goes to the carb with a flex line down close to the origihal pump. No fuel passes through the old pump. I guarangtee this is one mechanical pump that will never make oily gas . . .

It starts quickly after sitting a long time, and runs nicely, and has never been a problem . . . . . . ever since I finally found a good 6-volt pump. The cheap stuff is just that, and will last only a short while. Go to NAPA and buy a Carter heavy duty six-volt pump - they're about sixty bucks - and it'll never die. The ohly down side is that they are a tad noisy - I can hear it at idle . . . Never had a vapor lock in the past two summers with this setup.

Good Luck

[41/53dodges]

Electric fuel pumps are designed to push the fuel and don't suck well. Mount as close to the fuel tank as possible.

this all depends on the type of pump, if it is a regular automotive pump, then this is true. the "diddle" pumps i use are diaphragm and work perfectly fine under the hood, mounted on the inner fender across from the alternator.

P.S.

these "diddle" pumps are built with a governor of sorts built in to only make about 8 pounds max.

[Don Coatney]

I do not have an electric fuel pump and to date I do not see the need. My mechanical pump works great. If my car has been sitting for an extended time I simply crank the starter in short 3-4 second bursts to prime the carburetors and my engine will light off.

I am a non believer that this thing called vapor lock can physically happen to a Mopar flathead engine. My engine has never given me a bit of fuel trouble even on the hottest of days. I did route my fuel line from the pump to the carburetors in front of the manifold and I do not have a heat sheild.

[41/53dodges]

it looks like you are using aluminum tubes, those are much better thermally than steel or rubber.also, being in front of the manifold, the radiator fan sends the air behind the tubes, it does not come near it when running

[Zeke1953]

I dont believe an electric fuel pump was available when your vehicle was new. Why does it sound like a good idea now?

As far as I know, electric fuel pumps, disc brakes, radial tires and chrome wheels were not available when our vehicles were new. But if the addition of any or all of these increses your enjoyment, safety or just plain peace of mind, why not do it? I've never experienced vapor lock in my truck but I did once in another vehicle and it was not a lot of fun. Zeke

[Don Coatney]

it looks like you are using aluminum tubes, those are much better thermally than steel or rubber.also, being in front of the manifold, the radiator fan sends the air behind the tubes, it does not come near it when running

My fuel lines are not aluminum, they are shiney new steel. Also I do not use a belt driven fan. I have a thermostatically controlled electric pusher fan in front of the radiator.

[Don Coatney]

As far as I know, electric fuel pumps, disc brakes, radial tires and chrome wheels were not available when our vehicles were new. But if the addition of any or all of these increses your enjoyment, safety or just plain peace of mind, why not do it? I've never experienced vapor lock in my truck but I did once in another vehicle and it was not a lot of fun. Zeke

Zeke;

You are correct! Electric fuel pumps, disc brakes, radial tires and chrome wheels are not required. My point was simply that mechanical fuel pumps are dependable.

Vapor lock in other vehicles is real. Ford flatheads in particular. Reason being the fuel pump is elevated higher than the gas tank. On Mopar flathead engines the fuel pump is almost level with the gas tank. This vapor lock issue has been cussed and discussed many times on this forum. Use the search feature keywords "vapor lock" and you will get many hits.

[desoto1939]

Does anybody know if a 6 volt electric fuel pump is available?

Chris if you look on ebay there are 6v electric fule pumps they are from Airtex I think the model is Em0011. They cost around 45-50 dollars. This is the 6v model.

If you get this model and this is the one that is most readily available and you still have the positive ground system Here is what you need to do to hook up the pump.

It should be mounted as close tot he tank as possible and mount onthe frame rail.

The wire that is brown and marked as positive becomes you ground wire since the car is Positive grounded.

The black wire which would be the negative wire is the one that gets connected to the poswer supply. I connected this to a toggle switch that is connected to the ignition switch. The pump can only run whenthe key is turned on. This prevents the pump from running and drawing power.

The pump does not have an automatic shutoff so after you have primped the car or cleared the vapor lock then turn off the pump and run on the mechanical.

Rich Hartung

desoto1939@aol.com

[austinsailor]

Would this be the type you guys are using?

ebay 300440946332