Vapor Lock
drosera88
Posted 2016-05-28 12:02 PM (#512670)
Subject: Vapor Lock



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So on my recent road trip I encountered some very annoying vapor lock issues when I hit the high desert. It runs fine at the lower altitudes regardless of temperature and at higher altitudes during night time, but at the higher altitudes during daylight I experienced surging, loss of power, stalling, and an inability to restart if I let the car sit for a few minutes after it was warmed up.

I've insulated the lines, and it helps, but not much. I'm planning to wrap the pipes to keep the engine compartment cooler, as well as putting a spacer under the carb and maybe even insulating the tank to keep the the gas in the tank cooler.

Some people I've talked to said that adding a return line would be enough to prevent the vapor lock as the fuel would be constantly circulating. Some have also suggested using an electric pump near or in the tank either as an auxiliary that can be turned on via switch only when needed, or as an all together replacement for the mechanical one.

What would you recommend I do to resolve this issue? I'm gonna make the drive again next year in March when it is cooler, but I still want the added assurance that I won't have to deal with all these problems. All advice is greatly appreciated.
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Rebels-59
Posted 2016-05-28 12:16 PM (#512675 - in reply to #512670)
Subject: Re: Vapor Lock



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Deleted the other Duplicate thread as per your request
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Rebels-59
Posted 2016-05-28 12:19 PM (#512676 - in reply to #512670)
Subject: Re: Vapor Lock



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..When you say Vapour lock, do you mean in high climate the fuel tank is pressurising ,, If so have checked that your Fuel cap is athe Vented type and isnt plugged if it is
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Viper Guy
Posted 2016-05-28 4:24 PM (#512682 - in reply to #512670)
Subject: Re: Vapor Lock



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You will be safe with an electric fuel pump in addition to the stock pump. I suggest an external pump outside but near the gas tank - easy to install, easy to resolve any problems should they come down the road, not all that expensive, and they are usually audible when turned on and/or you can see a wiggling of your amp gage if you have one that shows it's working. It will not stop the gas from evaporating in the carburetor but will pump fresh gas to the carburetor to get your engine running much quicker.

We always used one on our race cars but I wouldn't do the following on your car unless you weren't concerned about the way your fuel line is routed under your hood. We routed the line from the stock fuel pump outside of the engine components to the carb rather than snaking it next to the block, etc. We wrapped the line with tin foil too thinking it would deflect or repel heat but not sure this really worked. Didn't look factory but for racing it was fine.
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drosera88
Posted 2016-05-28 8:11 PM (#512690 - in reply to #512676)
Subject: Re: Vapor Lock



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Rebels-59 Coronet - 2016-05-28 11:19 AM

..When you say Vapour lock, do you mean in high climate the fuel tank is pressurising ,, If so have checked that your Fuel cap is athe Vented type and isnt plugged if it is


That was the first thing I tried, and a new vented cap did nothing. It only has issues when it's warm and the altitude is high. Hot days at low elevations cause no issues, and night driving at altitude also causes no issues.

Viper Guy - 2016-05-28 3:24 PM

You will be safe with an electric fuel pump in addition to the stock pump. I suggest an external pump outside but near the gas tank - easy to install, easy to resolve any problems should they come down the road, not all that expensive, and they are usually audible when turned on and/or you can see a wiggling of your amp gage if you have one that shows it's working. It will not stop the gas from evaporating in the carburetor but will pump fresh gas to the carburetor to get your engine running much quicker.

We always used one on our race cars but I wouldn't do the following on your car unless you weren't concerned about the way your fuel line is routed under your hood. We routed the line from the stock fuel pump outside of the engine components to the carb rather than snaking it next to the block, etc. We wrapped the line with tin foil too thinking it would deflect or repel heat but not sure this really worked. Didn't look factory but for racing it was fine.


How should I install the pump in relation to the mechanical one? Should I put it in line with the mechanical pump so that the electric one pumps through it? Should I install it on a separate line that goes around the mechanical pump? Should I still have a return line? Should I have some sort of regulator to bleed off extra pressure into a return line?

As for line placement, I really don't care. I'm not trying to make this car into a stock restoration or anything; I'm trying to make what ever is under the hood practical rather than original.
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Mopar1
Posted 2016-05-28 10:27 PM (#512696 - in reply to #512690)
Subject: Re: Vapor Lock



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I was having some problems with my 331 hemi until I added a phenolic spacer under the carb, guess the gas is getting crappy, didn't need it on the last one.
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Viper Guy
Posted 2016-05-28 11:39 PM (#512698 - in reply to #512670)
Subject: Re: Vapor Lock



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How should I install the pump in relation to the mechanical one? Should I put it in line with the mechanical pump so that the electric one pumps through it? Should I install it on a separate line that goes around the mechanical pump? Should I still have a return line? Should I have some sort of regulator to bleed off extra pressure into a return line?

Just splice the electric fuel pump in the fuel line between the tank and the stock mechanical pump and it will do the rest. No sense in making it too difficult all you want to do is get fuel into the carb. And yes, as Mopar! stated above, gasoline is pretty crappy these days and it is not a bad idea to put a phenolic spacer between the intake and the carb as it acts as a insulator.
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BigBlockMopar
Posted 2016-05-29 5:15 AM (#512707 - in reply to #512670)
Subject: Re: Vapor Lock



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An insulating spacer will help. But also (maybe more) will blocking off the heat-riser port in the intake manifold.
Especially if the original heat-riser valve in the exhaust manifold has been carboned up and is stuck in place (might want to confirm it's fully open by taking off the exhaust pipe and have a peak up inside the manifold).

The problem (I have) with electrical fuelpumps is, that if the engine might stall for any reason, that fuel pump keeps pumping fuel.
On a proper fuelpump installation there would be a pressure safety switch, which will remain triggered and power the fuel pump, as long as say engine vacuum or oil pressure is present (meaning the engine is running). It's only by-passed during engine start ups.
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udoittwo
Posted 2016-05-29 7:29 AM (#512713 - in reply to #512670)
Subject: RE: Vapor Lock



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IF you do add an electric pump, use the switch as another anti-theft device. Even though some would say "who would steal such a noticible car?". It happens all the time and it is such a simple thing to do if you are putting in a switch anyway. Personally, I would mount a hidden in-line switch and then the obvious one.

The N.E. is going through an early heat wave right now and the days are 90 and humid and my car has started having issues with really long cranking times after it has sat for a bit, so I guess i am getting vapor lock also? I don't know if this is a symtom also but I can feel it sort of surging or is it dying off a little while crusing steady?

So, what actually happens that an electric pump might fix and IF you added the pump, would you still need the mechanical? If you bypassed the mechanical one, then could you run your fuel line away from the exhaust more?

What actually happens, the gas gets real hot setting near the exhaust and then? What happens to the fuel in the bowl? Why wouldn't it start off that fuel? Does it vaporize in the carb/intake before it gets to the cyls.? Isn't that what the fuel needs to do anyway?

Sorry, I all my car and years of driving, I've never had the problem that I can remember, so I never wondered what was happening and what is the cure.

Karl.
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drosera88
Posted 2016-05-29 12:26 PM (#512731 - in reply to #512713)
Subject: RE: Vapor Lock



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udoittwo - 2016-05-29 6:29 AM

The N.E. is going through an early heat wave right now and the days are 90 and humid and my car has started having issues with really long cranking times after it has sat for a bit, so I guess i am getting vapor lock also? I don't know if this is a symtom also but I can feel it sort of surging or is it dying off a little while crusing steady?
What actually happens, the gas gets real hot setting near the exhaust and then? What happens to the fuel in the bowl? Why wouldn't it start off that fuel? Does it vaporize in the carb/intake before it gets to the cyls.? Isn't that what the fuel needs to do anyway?

Sorry, I all my car and years of driving, I've never had the problem that I can remember, so I never wondered what was happening and what is the cure.

Karl.


Sounds like your having exactly the same problems I have. I think (correct me if I am wrong) as the the car sits in hot temperatures, the fuel in the bowl and lines vaporizes. Fuel pumps don't pump vapor efficiently, and because there is such a long suction line between the pump and the engine, it takes quite awhile for the gasoline to to actually reach the pump and refill the bowl.

Liquids are not compressible, so even though the engine heats the fuel system up to much higher temperatures when you drive, vapor lock is less of an issue because there is no room for vapor in the system because the lines and bowls are filled with fuel; this is very similar to the way that the cooling system works in that if there is a leak in your cooling system, you start to over heat because there is now air in your cooling system and the water pump can't pump air. Unlike the cooling system though, the fuel system is not sealed, so if temperatures get high enough, vapor can work its way into your lines and pump causing you to lose power or stall. Also, as soon as you turn your car off, you relieve the suction that was created by the pump, causing the fuel to flow out of the lines and back into the tank. Since the car was running and is now hot, the effect is much more dramatic than a cold start, and you will have to wait until everything cools down.

Ethanol is a big part of the problem. Ethanol causes the fuel to vaporize at lower temperatures than just pure gas. Fuel is also blended differently in different parts of the country, and though I am not 100% sure, I think that the gas in the north is slightly more volatile than gasoline down here in Texas. More volatile fuel vaporizes more easily. Winter gas is also more volatile than summer gas. You may also be affected by altitude as I was. My car has almost no issues down here in Texas, even when it's 100 degrees outside. But because fuel vaporizes and boils more easily at higher altitudes due to reduced atmospheric pressure, it has trouble on my trip to California, when I was driving through the high desert of NM and AZ. It was only about 90-95 degrees, but the altitude was around 3500-5000ft. I basically had to drive at night through the higher elevations due to this.
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ttotired
Posted 2016-05-29 7:23 PM (#512744 - in reply to #512670)
Subject: Re: Vapor Lock



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Without trying to be a science geek (because I am not), Your descriptions are a bit wrong.

The cooling system is pressurized to raise the boiling point of the coolant, not to just keep air out. You are correct about the water pump not being able to pump air and vapor locks can appear in a cooling system if air is trapped inside (some vehicles have bleed screws in the cooling system because the radiator cap is not the highest point in the cooling system)

What happens (and this happens in the fuel line as well) is that the vapor is made from a liquid that is expending into a vapor, so as it expands, it pushes the liquid out by building pressure, in the cooling system, it overcomes the spring pressure in the cap and coolant comes out, in the fuel system, it just pushes the fuel back to the tank

The fuel in the carby just straight up boils and generally, will spit fuel into the carby throat and evaporate. The fuel system is not really a pressurized system (on a carburetor system) as the pipe to the pump is open and the fuel tank itself is vented (or the cap is) and the carburetor fuel bowl is also vented.

The only pressure area in the fuel system is between the pump and the needle and seat and that is pressurized only enough to allow a good flow of fuel into the fuel bowl when the needle valve opens

My car (318 poly with 2x4) was having quite a lot of dramas with fuel boiling out until I fitted 1" phenolic (plastic) spacers to heat insulate the carby's a bit

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drosera88
Posted 2016-05-30 1:39 AM (#512762 - in reply to #512744)
Subject: Re: Vapor Lock



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ttotired - 2016-05-29 6:23 PM

The cooling system is pressurized to raise the boiling point of the coolant, not to just keep air out. You are correct about the water pump not being able to pump air and vapor locks can appear in a cooling system if air is trapped inside (some vehicles have bleed screws in the cooling system because the radiator cap is not the highest point in the cooling system)

What happens (and this happens in the fuel line as well) is that the vapor is made from a liquid that is expending into a vapor, so as it expands, it pushes the liquid out by building pressure, in the cooling system, it overcomes the spring pressure in the cap and coolant comes out, in the fuel system, it just pushes the fuel back to the tank

The fuel in the carby just straight up boils and generally, will spit fuel into the carby throat and evaporate. The fuel system is not really a pressurized system (on a carburetor system) as the pipe to the pump is open and the fuel tank itself is vented (or the cap is) and the carburetor fuel bowl is also vented.

The only pressure area in the fuel system is between the pump and the needle and seat and that is pressurized only enough to allow a good flow of fuel into the fuel bowl when the needle valve opens



^^This. That's a better explanation than I gave. I forgot that the radiator cap is meant to release and return fluid to the cooling system as it pressurizes, and that the pressure raises the boiling point of the coolant.
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udoittwo
Posted 2016-05-30 9:50 AM (#512780 - in reply to #512744)
Subject: Re: Vapor Lock



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I had a 67 GTO for 20 years before the Plymouth and the intake sat above the block so the carb temps had to be a lot lower and never had vapor locking with it. I MAY have this issue with my first 57 Chevy[283 2 BBL] now that I think about it but that was over 45 years ago. All of my classics from my 2nd 57 Chevy in 1970 until this Plymouth were quadrajets or aftermarket 4 BBLs. Were the 4 BBLs less prone to vapor locking than this 2 BBLs?

So, its not as much an issue with the fuel lines but the carb itself gets too hot and just insulating the carb from the intake seems to be a big help? Plenty of clearence, so 1" would be fine. Does it seem to have any affect on the running? Are these spacer/insulators readily available or would I need to make one, if i were to go that way?

Apparently insulating the fuel lines will help some also? Would runnng fuel hose in the engine compartment be better other than longevity or possibly slipping a larger size fuel hose over the steel tube help?

Karl.
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Viper Guy
Posted 2016-05-30 10:30 AM (#512781 - in reply to #512670)
Subject: Re: Vapor Lock



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Any type of insulation from heat will help whether it be location or materials. Keep in mind though that the carburetor is what feeds the fuel to the cylinders through the intake manifold. It is the carburetor that has to have the liquid fuel that is sprayed into the manifold along with air. If there is no liquid fuel in the carburetor because of evaporation (due to heat of course while the hot engine is not running), the fuel in the lines and fuel pump has to be moved to the carburetor and fill the float bowl(s) so the accelerator pump in the carburetor can squirt the liquid fuel from the carb into the intake.

The phenolic insulator between the carb and the intake manifold is usually available but can also easily be made. They are generally at least 1/4 inch thick but most are 3/8 to 1/2 inch. Also blocking off the heat crossover in the intake manifold will help as well as eliminating the heat riser on the exhaust manifold but both of these aid in initial engine warm-up after a cold start to open the choke. Once the engine is hot though and is shut off, the heat is already there and will still evaporate the fuel, as with any fuel line materials, that conduct heat to the fuel where ever the location is. But it will take longer to do so and sometimes that time is just long enough to still have fuel in the carb when the car is started after sitting for awhile when hot.

One final thought and that is if you can find gasoline without ethanol, buy it. Many stations state on their pumps that their premium does not contain ethanol. Good luck and keep us posted as to your success.


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big m
Posted 2016-05-30 11:15 AM (#512784 - in reply to #512670)
Subject: Re: Vapor Lock



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On my cross country trip last summer, the higher the ethanol content the worse the problem was. Initially I thought I had the floats set too high and the fuel was bleeding over, but after removing the air horn and checking float level, I found it not to be the case. Pulling into a fuel stop, I removed the air cleaner, and after a few minutes went by, could see fuel percolating out into the intake.

At Carlisle, Pa. swap meet, I purchased a 1/2" phenolic spacer and mounted it beneath the carb, [361 engine, 4-barrel carb] before the return trip of 3500 miles. If the outside temp was 85 degrees or below, there was little of the percolation of fuel. However when I got back to hotter weather, the problem persisted. I bought a valley pan intake gasket that blocked the exhaust crossover port beneath the carburetor, and it has solved the problem completely. When cold, there is a bit of hesitation and stalling if the engine is not allowed to warm up a bit before taking off, but I can live with that as the climate here is not extremely cold.

---John
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Mopar1
Posted 2016-05-31 10:54 AM (#512849 - in reply to #512696)
Subject: Re: Vapor Lock



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Mopar1 - 2016-05-28 9:27 PM

I was having some problems with my 331 hemi until I added a phenolic spacer under the carb, guess the gas is getting crappy, didn't need it on the last one.
This is with the OEM 4 bl intake, alloy adaptor plate & Edelbrock carb, no problems after adding the phenolic spacer on top of the adaptor.
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56D500boy
Posted 2019-06-07 9:11 AM (#583062 - in reply to #512849)
Subject: Re: Vapor Lock



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Any updates on solutions to vapor lock or does this thread contain them all?

These:

1. Non-ethanol fuel if you can find it.
2. Block off the heat passage from the head to under the carb
3. Phenolic spacer under the carb
4. Wrapping the fuel line between the pump and the carb
5. Install a recirculating fuel pump and a return line (sounds potentially dangerous)
6. Installing an electric fuel pump in line, near the gas tank, to feed the pump (needs a safety shut off for emergencies)

And/or ???
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Stroller
Posted 2019-06-07 2:06 PM (#583071 - in reply to #512670)
Subject: Re: Vapor Lock


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It was said to the point. Vapor locking is the fuel boiling into a vapor. There are some other old timey tricks like wraping your fuel line in coil and putting it in a coffee can filled with ice, put close pins on the fuel line. Something I have found in some of travels is that sometimes the old ignition systems would falter a tad in less air, higher altitudes( less air). Remember all carbs from factory are jetted at sea level, but changing jets is a science or a real tricky tune. The crappy gas is something I agree with, might work for new cars ok. I still add lead aditive and buy pure gas, it's worth it to me. The electric fuel pump will help as well as anything.
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normsclassicradio
Posted 2019-06-07 6:00 PM (#583081 - in reply to #583071)
Subject: Re: Vapor Lock



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Stroller - 2019-06-07 12:06 PM

It was said to the point. Vapor locking is the fuel boiling into a vapor. There are some other old timey tricks like wraping your fuel line in coil and putting it in a coffee can filled with ice, put close pins on the fuel line. Something I have found in some of travels is that sometimes the old ignition systems would falter a tad in less air, higher altitudes( less air). Remember all carbs from factory are jetted at sea level, but changing jets is a science or a real tricky tune. The crappy gas is something I agree with, might work for new cars ok. I still add lead aditive and buy pure gas, it's worth it to me. The electric fuel pump will help as well as anything.


Back in the 80's I had a VW with CIS. it would vapor lock if the temp got near 100. I got tired of a wet rag oveer the external fule pump. My brother was a logger told me that they had the same issue with chain saws, and recommended adding a little diesel to the fuel to raise the boiling point. I put a gallon in a full tank of gas and had no more problems. I think they had to much ethanol in our gas back then.

Edited by normsclassicradio 2019-06-07 6:01 PM
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