39 Buick - Vapor Lock Problems

[WHSEWARD]

My 39 Buick Limited is having severe vapor lock problems. I live in Texas and routinely drive 40-50 miles each way to local car shows. Normally on an 85 degree day the temperature gauge will show 190-200ºF and the car runs fine, except that at those temperatures the (10% ethanol) gasoline is just about to boil in the fuel lines and if I stop in traffic even for a minute I run the risk of stalling with vapor lock. Pulling in to the car shows I have to stop in line and have stalled out in the last 3 shows I went to....not encouraging. Then it is 20 minutes or so before I can even try to start the car again. The radiator was recored about 4 years ago so I don't think there is a problem with it - I am running the original 4-blade fan. Sometimes I can keep the car running by kicking in the auxiliary electric fuel pump and auxiliary cooling fan but I really do not like to use the aux. pump for long periods because I am afraid I could damage the mechanical fuel pump by doing so.

I can think of two approaches to addressing the problem and would like feedback on either approach or on other approaches. #1: insulate the fuel lines from the mechanical fuel pump discharge to the carburetor - and perhaps wrap the carburetor; question: what to use? #2: ditch the 50/50 glycol-water mix and go back to straight water with a suitable corrosion inhibitor - the higher heat capacity of straight water should reduce the engine temperature (assuming the radiator works); questions: can I use Pencool 2000 or Napacool or similar, and since the problem appears to be heat transfer from the exterior of the block to the fuel lines, will this make any material difference?

Feedback will be much appreciated. Thanks

[ply33]

I started having heat related fuel problems on my 1933 Plymouth last summer when the ambient temperature was around 100F and the car had been driven for a distance at speed. For that reason I have been following any thread that mentions the problem.

I suspect that in my case, and maybe yours, the problem is in the pump itself getting too warm: The vaporization problem will be more likely on the suction side of the fuel system than on the pressure side. So insulating the line from the pump to the carburetor or insulating the carburetor may not be as useful as shielding the fuel pump from sources of heat. If your problem is that fuel is evaporating out of the carburetor and/or expanding when parked and filling the intake (hot restart problems), then keeping the carburetor cool would be useful.

But if it happens after you've come to idle after running hard (delayed by how long it takes to use the fuel in the float bowl), then my guess is the fuel pump is warm enough that fuel is vaporizing in there and the pump is ceasing to pump. This is what appears to be happening on my car and I am tempted to fit the fuel pump heat shield that later cars had onto mine.

[Owen_Dyneto]

I agree with ply33, the fuel line between the pump and carburetor always seems to be the first thing folks think about, wrap with insulation, attach clothes pins to, or whatever. Maybe because it's the first thing they see. But it's the least-likely place for vapor lock to originate because the fuel there is under slight pressure and thus has a more elevated boiling point. Always suspect the suction side first.

But your car running at 190-200 F. seems high, what rating thermostat are you using? Checked all the other likely suspects, collapsing hoses, dragging brakes, undersize or restricted exhaust, retarded timing, faulty water pump, slipping belt, fan to far from the radiator?

[Rusty_OToole]

I believe adding some kerosene to the fuel will help prevent vapor lock. The fuel your car was built for was "heavier" in the sense that it was lower in octane, and contained heavier or oilier elements than today's fuel.

Haven't tried it myself but it couldn't hurt anything especially on low compression engines built before 1955.

I would try adding 5% or 1 quart to 5 gallons just to try it. If your engine knocks or runs bad you can quickly add more gas to dilute the kerosene.

[Guest Julian]

My 39 Buick Limited is having severe vapor lock problems. I live in Texas and routinely drive 40-50 miles each way to local car shows. Normally on an 85 .........

hhmmm how bout the "old time remedy"... cloths pens on the fuel line

[WHSEWARD]

First, thanks for the quick and useful responses. Let me address a couple of them:

Ply33 and Owen_Dyneto, the fuel pump may indeed be the source of the problem, especially as switching on the auxiliary pump keeps the car running when it otherwise would have stalled. Is there a source for a heat shield for an AC Fuel Pump, Type "AB", or for a generic shield that would fit on such a pump. Or has someone made one of these?

Owen_Dyneto, I won't claim to have checked all of these things out, but the car was set up before I bought it and I haven't changed anything on it since then. It runs at 180ºF of below during the winter when the outside temperature is about 60-65º and only heats up over 180 when I run at 50 mph for more than 20-30 minutes. The vapor lock shows up at about 200ºF, which takes about 30-45 seconds if I'm waiting at a traffic light. I agree that the cooling system should be designed to handle the load, and I appreciate the listing of possiblities; I'll have to look at the spark timing when I have a chance. I suppose another possibility(which I'd rather not think about) is that the water pump impeller is corroded or that the radiator/block is full of crud). Anyway, thanks for the input.

Rusty: I've heard that suggestion elsewhere and I'm tempted to try it. Even if it works, I guess it's still addressing the symptom rather than the cause. In Texas it is not so easy to get fuel oil as in the North, and I'd rather not go with diesel (heavier than kero), so I guess the question is, where do I go to buy say 5-10 gallons of kerosene?

As another piece of information I checked the routing on my fuel pump suction and the line is not close to the block until it comes right up to the fuel bowl. Also the discharge lines do not touch the block but stand off at least 1 inch. However the lines do not run uphill continuously to the carburetor so there is a low spot where bubbles could collect and block the line at idle, but it's a good sized line 1/4-3/8" OD so should be swept out when the pump is operating at driving speeds.

Thanks again for the inputs.

[Guest Jim_Edwards]

I don't think your problem is vapor lock. If the three shows you are taking about have taken place this year, it hasn't been hot enough even here in Texas so far this year to cause a vapor lock related to ambient temperature.

The fact an electrical fuel pump will get past the problem would indicate to me that the mechanical fuel pump has an issue with delivering sufficient fuel at low engine RPMs. I'm not intimately familiar with the fuel pump setup on your engine, but if it is push rod driven I'd be more than willing to bet wear factors with the push rod and/or the pump arm are the culprit, not temperature.

Jim

[FLYER15015]

Bill,

I had this "vapor lock" problem on my '40 LTD too.

My solution was to reroute the fuel line. I know this will drive "restorers" nuts, but I routed mine, which is 1/4" copper tube, up from the pump to just under the cold air 4" intake flex tube and clear back to the firewall, over the rocker box (valve cover) with a metal brace (14ga x1-1/4" sheet metal bolted to the rear nut on the rocker box, that holds the fuel line tight. Then a gentle 90 degree bend to the glass bowl filter aft of the carb. I also covered the copper line with rubber fuel line 1/4"I.D.

Best Regards,

Mike in Colorado

BCA#45728

AACA#994416

[Rusty_OToole]

First, thanks for the quick and useful responses. Let me address a couple of them:

Ply33 and Owen_Dyneto, the fuel pump may indeed be the source of the problem, especially as switching on the auxiliary pump keeps the car running when it otherwise would have stalled. Is there a source for a heat shield for an AC Fuel Pump, Type "AB", or for a generic shield that would fit on such a pump. Or has someone made one of these?

Owen_Dyneto, I won't claim to have checked all of these things out, but the car was set up before I bought it and I haven't changed anything on it since then. It runs at 180ºF of below during the winter when the outside temperature is about 60-65º and only heats up over 180 when I run at 50 mph for more than 20-30 minutes. The vapor lock shows up at about 200ºF, which takes about 30-45 seconds if I'm waiting at a traffic light. I agree that the cooling system should be designed to handle the load, and I appreciate the listing of possiblities; I'll have to look at the spark timing when I have a chance. I suppose another possibility(which I'd rather not think about) is that the water pump impeller is corroded or that the radiator/block is full of crud). Anyway, thanks for the input.

Rusty: I've heard that suggestion elsewhere and I'm tempted to try it. Even if it works, I guess it's still addressing the symptom rather than the cause. In Texas it is not so easy to get fuel oil as in the North, and I'd rather not go with diesel (heavier than kero), so I guess the question is, where do I go to buy say 5-10 gallons of kerosene?

As another piece of information I checked the routing on my fuel pump suction and the line is not close to the block until it comes right up to the fuel bowl. Also the discharge lines do not touch the block but stand off at least 1 inch. However the lines do not run uphill continuously to the carburetor so there is a low spot where bubbles could collect and block the line at idle, but it's a good sized line 1/4-3/8" OD so should be swept out when the pump is operating at driving speeds.

Thanks again for the inputs.

I don't know where you by kerosene in Texas but around here every hardware store sells it.

[Guest Jim_Edwards]

I don't know where you by kerosene in Texas but around here every hardware store sells it.

Where Bill lives in Katy, Texas there should be a Tractor Supply Store (TSC) which has Kerosene. Only problem is they only sell 5 gallon cans and the last time I priced it at one of their stores by the time sales tax was added it would be around $40.00 per can. Probably more today.

I buy kerosene from a local fuels distributor for heaters and it runs a lot less using my can. But then I live about 70 miles West of Katy and it's farm and ranch country with a lot more demand for kerosene I'm sure than in what is basically West Houston.

Jim

[WHSEWARD]

Everyone, I really appreciate the responses.

Jim, I'll look for the tractor supply store in Old Katy - with kero at $8/gallon - $2 a quart - I can at least afford to try it out for a while. I think I will also check out the bypass valve below the thermostat to see if it's sticking open when the thermostat does.

Mike, I'll also keep the fuel line reroute as a possibility but maybe try to insulate the fuel pump first to see if that keeps me out of trouble.

I also verified that the Katy NAPA parts store carries Napacool so if I need to switch to all water that option is also open.

I'll try to keep all of you posted on this thread as to what is working for me.

Thanks,

[rons49]

Bill, all good answers. Temp seems warm, I agree about the water pump impellar( cause on my 50 Caddy) at speed. 39 Buicks also have a air circulation problem more so than some others due to the grille design. Get a infra red temp sensor. Check the water temp in the radiator, AND the temp of the fuel pump. Gas will begin to flash at @145 degrees with summer gas. If any winter gas is in the tank is will flash off at an astounding 105. What part of the country is dependant,of course. A steel shroud can help, or at least postpone the inevitable. Fuel pump may be beginning to fail, what is the suction and pressure? If the electric works, then the mech pump is probably the culpret. The electric pump (located near the tank as far as possible) will push gas through hot spots better than a mech can suck it through. Carb could be getting hot too. Is the electric in series? That could require the weak mech pump to work too hard to pull gas from the tank. How much fuel is getting to the carb, there is a test for that. Jim is also correct. Not yet vapor lock, it is called fuel starvation. So what we have is a combination of circumstances, each has to be eliminated. Run a rubber dummy line way far away from a heat source, after you check suction& pressure on a cold & then a hot engine. Best is to run the line where you can watch the gauge. Thats fun!

[WHSEWARD]

Hi, everyone...please forgive the very long post.

I found on the Internet that summer ethanol-free gasoline is supposed to have a maximum Reid Vapor Pressure (RVP) of 9.0 psia. Adding 10% ethanol raises RVP by about 1 psi (pound per square inch). RVP is measured by a specific lab procedure but can be converted to True Vapor Pressure (TVP) at a given temperature. When the TVP of a liquid equals the actual pressure, it begins to boil (the TVP of water at 14.7 psia is 212ºF). If we know the pressure in a gasoline line or the fuel bowl, we can predict at what temperature it will begin to boil. (I can furnish my references for whomever is interested.)

I calculate that for a 10 psi RVP gasoline at atmospheric pressure(in the fuel pump suction, say), it will begin to boil at around 118ºF, while at the carburetor inlet at say 3 psig (17.7 psia) the same fuel will begin to boil at 129ºF. So it's correct to say that the fuel should be less likely to boil on the discharge side of the fuel pump than on the suction side, at the same temperature. But if the fuel in the carburetor feed lines is much hotter than the fuel in the fuel pump, it may begin boil first.

I took two kitchen thermometers, strapped one to the carburetor inlet line and the other touching the top of the fuel pump. Both intended to read the surrounding temperature, not the fuel temperature. Started my car and got it up to near steady-state temperature, around 165-170ºF per the dash gauge reading. Quickly opened the hood and read the thermometers. The thermometer at the carburetor read 160ºF, while the one on the fuel pump read 100ºF.

The way my Buick is designed, all the air from the fan has to go out the bottom of the car (no louvers). The heat from the exhaust manifold rises and is trapped under the hood on the driver's side, and that's right where the fuel line comes across to the carburetor. Also, the shroud (either for the flywheel or the water pump) on the passenger side partly shields the fuel pump from the fan exhaust, so the source of the heat for it is just from the bottom of the block itself.

So I conclude that the fuel may be more likely to boil in the fuel lines to the carburetor than in the fuel pump, even with the higher boiling temperature in those lines than in the fuel pump, because of the much higher surrounding temperature in that region compared to the region of the fuel pump. Whether or not this actually happens, depends on the mechanism of heat transfer between the air and the fuel in each place. But I would conclude from this that wrapping the fuel lines to the carburetor, or the exhaust manifold, may actually be effective in mitigating vapor lock.

AS I said, please forgive the very long post....I would appreciate your feedback and comments, and I will be getting more data during the upcoming Texas Tour, since I will be driving at speed for several hours to get there, and also during the Tour.

[Owen_Dyneto]

Can't argue with your science or math, I can only wish we could get ethanol-free gasoline in the summer in New Jersey. Nice piece of analytic work. Are you now prepared to tell me how the wooden clothes pins on the fuel line solve the probem?

[WHSEWARD]

Owen_Dyneto...I have absolutely no idea. Unless you completely cover the entire line with them so they act like an insulating blanket. I had a fellow tell me, at a prestigious car show, that his dad was a Packard dealer, who said that the answer to vapor lock was to put half an orange on top of the fuel pump. Never said how often to change it, though.

I wish someone would verify the airflow through the engine compartment at 50 mph and zero (stuck in traffic), I'd sure like to see the data. At low speeds, the engine-driven fan doesn't pull in as much air, so the under-hood temperature should be higher than at higher speeds. Also, the fuel flow rate is lower at idle, which gives the fuel more time between the pump and the carburetor to get to boiling temperature. I will take the car out on the road and measure temperatures after at-speed driving to see the difference.

One other thing I found, is at the carburetor, the bubble point of no-ethanol (9 RVP) gasoline is about 138ºF while the 10% ethanol gasoline is 129ºF. That 9ºF may be the difference between vapor lock or no.

Lower RVP gasoline (summer blends) has an even higher boiling point. rons49, your 145ºF seems to correlate with a 6 psi RVP gasoline-is that about what you were thinking?

Anyway, I think the real issue is finding a way to keep the heat off the fuel lines. Has anyone out there tried wrapping the exhaust manifolds? I hear that's done on the racing circuits and on motorcycles a lot.

Flyer15015, your fuel line reroute might just be a good answer for those who don't worry about originality.

It will be interesting to see whether people's vapor lock problems are worse in the winter or summer and whether it depends on the car. Owners of 37 and 38 Buicks might be able to provide some input on that. Grab your thermometers, folks, and let's get some data!!!

[Marty Roth]

Last summer on my 1937 Roadmaster, we re-routed the fuel line - Flyer15015 did the same thing.

We also added the electric fuel pump - the turbine type, rather than the cheaper "pulse" type.

One more thing I did was to add a fuel filter just before the carburetor, BUT....

this is a modern type with a 3rd "bypass" fitting. Fuel is bypassed to a return hose, and excess fuel is rerouted back to the tank via a nipple fitting on the filler neck.

This way, fuel does not sit still in the engine compartment, absorbing heat - it is in motion, either to the carb, or to the tank.

I will also use 10% diesel (at times up to 20%) to lower the octane and this helped even in my big block 454 Chevy Suburban, pulling a trailer across the Texas Panhandle in the 110-plus days of summer.

[Owen_Dyneto]

WHSEWARD, please supply details on the orange, country-of-origin, size, seedless or seeded, etc.

Seriously, I'm almost completely unfamiliar with Buicks but for comparison with Packards many (most) had a heat shroud around the fuel pump to capture and direct the fan blast around the pump. The 41 and up senior models used a heat shield at the base of the carburetor. 33-39 Eights (most models) also had an upper heat shield around the carburetor fuel bowl where it was in close proximity to the exhaust manifold. Many older models wrapped the exhaust header with asbestor wrap. Lower engine compartment splash pans pretty much insured that much of the air blast under the hood remained at engine level and exited at the rear. Those Packards remain, for the most part, pretty immune to vapor lock so perhaps you're onto something important with underhood air flow and temperatures. Perhaps a couple of air deflectors would help, though there is the authenticity issue if that's important to you. Looking forward to more data.

[rons49]

Bill, did a similar test with my Hornet. I used an infra red thermometer fired it a the fuel pump. Arizona air temp @95. water in radiator 165, temp of the fuel pump 157. Too hot! I tried a fuel feed back last year. Don't forget a restictor in the return line (.030) to maintain pressure. Helped but starvation returned, albeit at a longer duration. March 15 gas stations go to summer gas. they add it to what is in their tanks( and yours). One good hot day of over 90 and you better have an electric pump. At 105+ even the electric can be weak. Does any one notice plug fouling by adding kero or diesel or any other adverse effects?

[DavidMc]

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]--> Very interesting link on the theory behind the problem of fuel (petrol) vapor lock. Note that it has nothing to do with octane rating, its all about the boiling point of the fractions in the fuel. In response to one of the comments I have been using kerosene in the fuel for years and have not detected any change to performence, plug fouling etc. I have also found kerosene to be far more effective than diesel

http://www.bp.com/liveassets/bp_internet/australia/corporate_australia/STAGING/local_assets/downloads_pdfs/f/Modern_Petro_in_Vintage_Cars.pdf

[Rusty_OToole]

WHSEWARD, please supply details on the orange, country-of-origin, size, seedless or seeded, etc.

Seriously, I'm almost completely unfamiliar with Buicks but for comparison with Packards many (most) had a heat shroud around the fuel pump to capture and direct the fan blast around the pump. The 41 and up senior models used a heat shield at the base of the carburetor. 33-39 Eights (most models) also had an upper heat shield around the carburetor fuel bowl where it was in close proximity to the exhaust manifold. Many older models wrapped the exhaust header with asbestor wrap. Lower engine compartment splash pans pretty much insured that much of the air blast under the hood remained at engine level and exited at the rear. Those Packards remain, for the most part, pretty immune to vapor lock so perhaps you're onto something important with underhood air flow and temperatures. Perhaps a couple of air deflectors would help, though there is the authenticity issue if that's important to you. Looking forward to more data.

Was told the same thing, about the orange, by a man who used to drive a VW bus in Arizona in the sixties. In hot weather it would vapor lock. His VW mechanic told him to stick half a grapefruit on the fuel pump. Here is how you do it. Any brand of orange or grapefruit will work so long as it is juicy. Buy a sack of grapefruit or oranges from a roadside stand or grocery. Cut one in half with your jack knife. Smush one half on the fuel pump. Eat the other half. Drive around until your car vapor locks again, should be several days or a week. When the orange or grapefruit dries out you will get another vapor lock. Just throw away the old one and put on a new one. Hope this is clear.

[critterpainter]

Also adding to the problem of heat is the fact that the base of the intake man has a heatsink to help the 1930's fuel vaporize. The heat shield idea suggested above might be a good one. Often on 39 buicks the lower panel between the grill and the radiator that forces air to pass through the radiator is missing causing the car to run a bit warmer. If the heat riser butterfly is not opening fully that can help heat the base of intake too.

Bill

[rons49]

Rusty, too sticky. To bad BP did not give a solution... Like kerosene etc. Need to increase the boiling point, since engine temp is probably as good as it can get.

[DavidMc]

BP's solution is to run our cars on BP Racing Fuel which they say best approximates the fuels these cars were designed for. That would be fine if we only drove our cars near race tracks or where ever you can buy the stuff!

We used to be able to fill up with fuel at a local service station where they had a kerosene bowser so it was a simple matter of adding a few gallons each time. Then they removed the kerosene bowser so I switched to diesel for convenience but it was not as effective. Now we have to buy the kerosene in plastic bottles from the hardware store. The cost and expense makes it difficult to get the concentration needed for very hot weather . I have used up to 15% when it was available at the service station.

My cars (1920's Packard's) have vacuum tanks which make the problem worse than the '39 Buick with its mechanical pump. The vacuum tanks sits over the exhaust manifold and on a hot day you can hold your ear to the tank and hear the fuel boiling. Heat shields, insulating the exhaust, re-routing the fuel lines etc all help buy lots of kerosene works best.

Given the practical problems of getting the kerosene ( or racing fuel!) I think it time for an electric pump bypassing the vacuum tank in my case.

I like to keep them original but without the original fuel the electric pump seems to be the only solution. I would think the same applies to the Buick.

[alfourfire]

I too have a vacuum tank on my '29 Whippet. I was going to add an electric fuel pump just to fill the vac. tank when needed, not to by-pass it. I'm told any more than 1/2-1/4 psi will overpower the carb. float and flood the motor. No one seems to know where a low pressure reducing valve can be found to prevent this. Any thoughts?

[DavidMc]

Rick, I learnt to drive on a 1929 Whippet.

Using an electric pump feeding into the vacuum tank wont solve vapor lock problems. Assuming the vac tank is working it will draw ample fuel from the tank under the hottest conditions, the problem is in getting it from there to the engine. There are a few 6v pumps with regulators on line but they don't go down to 1/2 - 1/4 psi. I too would like to know where they can be obtained or whether they need to regulate to such a low pressure.

[Dynaflash8]

It's ETHANOL my man. Any fool (National lawmakers) knows or should know that alcohol boils at a temperature lower than water.

I've had the pictured 1939 Buick since 1963 and it never ever vapor locked in all these years until 2010 when we were stuck with Ethanol by the Governor of Florida. Suddenly niether of my 1939 Buicks would go without vapor locking, so I had to install an electric fuel pump in line, connected through a toggle switch. Whevever I felt a vapor lock coming on while driving down the road at 55 mph on a hot day, I'd just flip the switch and straighten it right out. Yet, that is a nuisance. Then I found one gas station over in the middle of town who was a holdout from Ethanol. I started getting gas there and solved the problem as far as limited testing seemed to show, but it was 30 cents a gallon higher and hard to get to and not available on a trip. A friend recommended this sponge rubber-like tubing that you put onto hot water heater pipes to reduce heat loss. We wrapped the fuel lines from the fuel pump to the carburetor in that and I haven't had a vapor lock since, but I haven't had the '39s out on a 85 degree day since then either. I removed the wrapping for the Louisville 75th Anniversary show and went on one of the tours and did need the electric fuel pump once or twice. Unfortunately the generator went out while in Louisville and I was only able to do one of the tours.

That was another interesting thing. The armature had thrown the solder out of about half of the contacts and the generator would charge a little bit, but not enough to charge the battery. That, in turn, resulted in a miss, like bad points. Once the generator was repaired, the miss went away. In my past experience a generator was either all good, or all bad, not somewhere in between.

Edited April 2, 2011 by Dynaflash8 (see edit history)

[DavidAU]

I know this does not help Bill with his 39 Buick (although thinking about it, it may) and I dont want to detract from his post however the Prewar Rolls Royces suffer from the same problem as they have a vacum tank high up on the firewall over top of the exhaust manifold (great when its snowing, lousy in summer).

For many years owners have fitted an aluminium cover around the tank to shield it from the direct heat however one of the large restoration companies in England recently did a lot of testing on a 6 cylinder Phantom 2 to try to find a solution to the problem and intalled clear fuel lines so they could watch what happened to the fuel when the car vapour locked.

What they eventually discovered was that when the fuel in the Vacum tank started to boil it built up pressure and actually pushed all the fuel in the line back to the tank.

Their solution to this was to install a one way valve in the line on the tank side of the vacum tank to maintain the volume in the tank and they say that this helps to alleviate the problem. This idea could well work on other vehicles.

The vacum tank in the photo is the round nickel plated tank and as you can see it is mounted in the hottest place under the hood. I might add that is not my car and I dont think they came from the factory with a nickel finish to the tank. I believe they were always black paint.

[alfourfire]

Dave, the 6v fuel pump would only be used if the vac. tank empties due to long storage etc. Then it would be operated only until the tank level comes up to the operating range, then shut off. That way you don't have to remove the top and prime the tank. No one to date on the WORK forum has found a pressure regulator in the 1/4-1/2 psi range, so by-passing the vac. tank with the fuel pump is not an option. My question is would it be possible to develop vapor-lock in the fuel line between the outlet at the bottom of the vac. tank and the inlet to the carb. Still a fun car to drive.

[WHSEWARD]

Hi, everyone, I'm back with some new data, from two drives today (2 April):

Drive #1 - 30 minutes, top speed 30-35 mph, ambient temperature 75ºF; final dash temperature 165-170ºF, temperature at carb 155ºF, temperature at fuel pump 110ºF.

Drive #2 - 20 minutes, top speed 50-55 mph, ambient temperature around 85ºF, dash temperature 190ºF, temperature at carb 188ºF (Yes!), temperature at fuel pump 135ºF

This says to me that after a long drive at sustained speeds, once I slow down or stop, fuel could be vaporizing all the way from the fuel pump to the carb. On this second drive I was getting some engine misfires at low speeds and had to switch on the aux electric fuel pump to keep going. The temporary fix for the effect (vapor lock) looks like wrapping the fuel pump and lines and kero in the gasoline (Jim, I found the TSC store in Katy). I'll have to wait until later in the year (summer) to dig into the cause (hot engine/lack of cooling).

Dynaflash8, do you have more info on the sponge rubber tubing

? How high a temperature is it good for?

Thanks, everyone.

[DavidMc]

Rick,

We are getting away from the topic of the 39 Buick , maybe we need a new topic for cars with vacuum tanks.

However in answer to your question about whether vapor lock can occur between the vaccum tank and the carb, I been stopped on the side of the road with vapor lock and have removed the top of the vac tank to find it full of fuel and boiling like a pot on the stove. Under these conditions the car will not run either because the fuel is vapor locked in the pipe to the carb or in the carb. Either way the quick fix is to cool the vac tank with a damp rag and pour a little water on the cab. This gives an instant fix and if you can catch it while the the vapor lock is starting and the engine just starting to run roughly it will immediatly settle and run smoothly , until it happens again shortly after.

Based on these observations I can't see a non return valve in the supply line to the vac tank helping on my car because there is plenty of fuel in the vac tank and carb, it just wont flow because its boiling and cooling it fixes it immediately. If there was reverse flow happening then I would expect the vac tank to be low on fuel when the engine stops however Iwould welcome DavidAU's thoughts on this.

Ethanol has made it worse but I have been having these problems long before ethanol was thought of.

[Joseph P. Indusi]

The temperature at the carburetor seems high. Also, the voltage regulator should limit the generator current output to minimize the solder slinging from the armature. I would check the insulator on the base of the carburetor and be sure the regulator is limiting the current to the generator current rating.

Joe, BCA 33493

[Owen_Dyneto]

Geez, that temperature at the carburetor is beyond belief - small wonder you have vapor lock issues. I'd say forget fuel line wrap and the like, and find out why your underhood temperatures are so high. Don't know about Buick, but an insulating block between the manifold and carburetor and the fuel pump and block was common on cars like Packards and others; did not Buick use something similar? Packard even went to far as to use phenolic insulating sleeves between the fuel pump attaching bolts and the fuel pump. Nothing like that on a Buick?

I'm guessing your vapor lock problem is the consequence of some other problem, not a stand-alone problem.

[rons49]

Hudson also uses phenolic sleeves on the pump bolts and washers. I get temps like that as well. Especially in Az summers of 105+.You can't get rid of most of the heat, and what problem is there, if the radiator temp is good & is not boiling over? Wrapping lines only postpones the problem. Then the insulation holds the heat in once the lines get to the "danger zone". Electric pumps are the only (IMO) solution and what are the rules in judging standards re. post WWII . Time for a change? Pressure regulator are sold at Summit that drop to 1-4 PSI. I can go to a little less by opening the valve to max. Our gas is cooking in the fuel pump or 6 inches before or after it. Long shot: carbs ,but the damage has been done before that point.I like the kerosene idea. Still waiting for answer on adverse effects using it, however. Has anybody pulled the head and viewed the valves etc.? BP will never advise using stuff like kero. Hydro carbon emissions will skyrocket.

[DavidMc]

I called BP some time ago and spoke to one of their technical people about this problem and he recommended the use of kerosene. He said it would not have any detrimental effects. I guess its like most things if you speak to enough experts you will get a range of opinions.

Is 1 psi low enough to prevent flooding on a carb without a viton seat?

I wonder if the 1939 Buick is more prone to overheating in the engine bay because of the small open area at the front compared to say the '38 and '40 models with their larger grille area.

[rons49]

Dave, I just thought of something. Let say you place a elec fuel pump in the rear near the tank. Then, put a pressure regulator in line near( or inside) the vacuum tank. then place a restrictor threaded into the carb or in the line to the carb. The regulator will cut pressure to 1 psi, then the restrictor, if a small enough orifice is drilled, can drop pressure to < 1psi. Many of the Hudson members set up a fuel feedback system using a 1/8npt fitting female on each end for 1/4 hose barbs with solid brass tapped as such and a .030 hole drilled to maintain fuel pump pressure. The question is, if 030 is too narrow to supply enough fuel? That is where you woud need to experiment.

[rons49]

Are we talking about your 39 buick or a vacuum tank gravity system. 39 Buick just needs a pressure set at 2 - 3.5 PSI. (set at 3psi) Summit sells these regs for @$30.

[Guest De Soto Frank]

Dave, I just thought of something. Let say you place a elec fuel pump in the rear near the tank. Then, put a pressure regulator in line near( or inside) the vacuum tank. then place a restrictor threaded into the carb or in the line to the carb. The regulator will cut pressure to 1 psi, then the restrictor, if a small enough orifice is drilled, can drop pressure to < 1psi. Many of the Hudson members set up a fuel feedback system using a 1/8npt fitting female on each end for 1/4 hose barbs with solid brass tapped as such and a .030 hole drilled to maintain fuel pump pressure. The question is, if 030 is too narrow to supply enough fuel? That is where you would need to experiment.

That might create a starvation issue on long pulls / sustained high-speed running.

It's kind of like just cracking the shut-off spigot on a garden-hose... as long as the hose nozzle is shut-off, it will eventually build-up pressure to the level of the supply source. Open the hose nozzle, and the pressure quickly dissipates, but the continuous flow is also reduced, possibly beyond a useful level.

The vacuum tank usually has a float-valve in it - does this shut-off the fuel from the tank, or the vacuum supply ? Perhaps a standard regulator bewteen the electric pump and the vacuum tank would be sufficent? ( This would maintain the gravity feed from the Vacuum tank to the carb)

Edited April 6, 2011 by De Soto Frank (see edit history)

[rons49]

OK! I put in a quart of kerosene in a tank of 10gal 87 octane of my 308 Hornet. So far no problems starting or at idle. Will drive it next week. What are you guys paying for kero? I paid 10.49/ gal at Lowes. At that rate that turns a 3.60 into a 4.12/gal . MARTY, do you notice a drivability change with diesel? Heck of a lot cheaper, and easy to find. But, man, do you still add 10% diesel.... yipes, that's 2 gallons in 20? And, does is mix well with gas? Since it is so heavy, will it lay a the bottom in a more concentrated mixture?

[Owen_Dyneto]

Kerosene and gasoline are mutally soluble, and easily so, so there should be no problems with strata of differing concentrations as long as they have a little time to mix. Hitting a few pot holes should help, and not hard to do in some areas. But 10% seems like a very high concentration to use, at least based on my own experience from years ago. i tried 1 gallon added to 24 gallons of gasoline. Car ran OK, a bit of black soot and smoke from the tail pipe. No comment on vapor lock, I've never expeienced it and just tried the kerosene out of curiousity.

[rons49]

That is what I thought, so I added 2.5% kero( 1qt in 10gal of gas). But what about diesel?