Vaper lock

[Standing Elk]

On hot days my 48 will sometims want to vaper lock. Is there a trick that will help this problem? Thanks S.E.

[54Illinois]

I put a heat shield between my carb and manifold?

[HanksB3B]

A mechanic I know swears by clipping a "Wood Clothespin" (must be wood) to his fuel line.

Who Knows?

Hank

On a more practical note based on actual experience: If your engine is full hot after a long drive, it's a better idea to walk away, go have a cold one, let your engine cool down before attempting to start your vehicle running your battery out of juice and REALLY be stuck.

Edited June 22, 2012 by HanksB3B

[Dave72dt]

I've heard of the clothepin trick before and some swear by it. i've also heard of taping a cow magnet to the fuel line, wrapping the line with aluminum foil. Any scientific basis to any? Who kows. Giving the engine a few minutes of cool down time with the engine running and circulating coolant helps dissipate some of the heat buildup in the engine compartment and engine components so the fuel is less likely to vaporize.

[TodFitch]

On hot days my 48 will sometimes want to vapor lock. Is there a trick that will help this problem? Thanks S.E.

In recent years I've experienced this and think that it has a bit to do with a change in the volatility of modern gas: Since nearly all cars on the road have high pressure (relative to carburetor based systems) fuel injection systems they don't need to worry as much about higher volatility fuel components vaporizing before they get into the manifold. So I think the gas nowadays is more volatile and more susceptible to heat issues.

On my car, and I suspect many others, there seems to be several things happening:

1) On a hot day the gas in the tank is already 90 or 100 degrees, you don't have to add much heat to it to get it to vaporize.

2) The fuel pump, located under the exhaust manifold, can get pretty hot. If fuel vaporized in it, and on the suction side the temperature for vaporization is lower, then it won't pump well if it pumps at all.

3) If the fuel in the carburetor "heat soaks" on parking then you can get gas into the manifold making a rich mixture that is hard to start.

Anyway, on my car the problem seems to be with the fuel pump. The car will run strong until you either come to an idle and let it idle for a while (several minutes) or if you park it but then restart before it is fully cool. In both cases it will run, or in the case of starting, start and run for a few minutes and then die. The cure on my car is to cool down the pump. I generally carry drinking water and splashing some on the fuel pump quickly cures the problem. Once you are under way the air flow in the engine compartment keeps things cool enough that there is no problem. Being mindful of the conditions can help too: If I've been pushing it hard, then doing a mile or two at 45 MPH or lower will get things cooled down enough that I don't have a problem. Or if I've parked it after driving hard, then getting the car up to speed without a lot of idling will get the air flow up and everything is fine.

My car was built before they added the heat shield. I strongly suspect that if I retrofitted one my problems would go away.

So my first question: Do you have the fuel pump heat shield installed? If not, that would be the first thing to fix.

The next thing would be to keep heat from getting to the fuel pump from other sources. If the metal line between the pump and the carburetor runs close to the manifold then it will conduct heat to the pump.

I don't see how clothes pins on the gas line will help at all. But I do see how insulating the fuel lines can help. And I can really see how an electric pump back near the tank where it is relatively cool will fix the problem. Even if gas vaporizes in the line after the pump the vapor will simply be pushed out into the carburetor and then vented to the atmosphere.

Second question: Is this a hot start issue? That is will the car not start at all when hot? Starting and then dying a little later is a different issue. If so, then you might have the float level set a little high. During heat soak on stopping the gas will expand some and if it ends up in the manifold you'll have a rich mixture that could keep it from starting.

Finally some old sage, source I no longer remember, claimed that 90% of all carburetor problems were electrical. Smart alec way of saying lots of issues suspected of the fuel system weren't actually fuel system related. I had a VW bug many decades ago that had a bad coil that would quit when hot and start working again when cool. Took me a long time to figure out that problem as I kept looking for problems with the carburetor, fuel pump, choke, etc.

[Todd B]

I have to wonder if the gas has changed. I have driven my semi on many hot days and the first time I ever had a vapor lock was a few weeks ago on a very hot Sunday afternoon. What I did was open my gas cap to check if I had fuel and I heard and felt the presure behind the cap. I realized it was a vapor lock and hit the starter and it immeditaly started. I have electric fuel pumps on all my trucks so the heat shield theory don't make sense with me.

Very Interesting, Todd B

[pflaming]

What kind of electric pumps are you using and where have you located them, Tom? I

[Todd B]

I bought mine @ NAPA and mounted them on the frame in front of the fuel tank. When I turn the key I can hear the pump turn until the line is full, then hit the floor starter. I was sick of changing the normal fuel pumps, I had lots of problems with them.

[TodFitch]

I have to wonder if the gas has changed. I have driven my semi on many hot days and the first time I ever had a vapor lock was a few weeks ago on a very hot Sunday afternoon. What I did was open my gas cap to check if I had fuel and I heard and felt the presure behind the cap. I realized it was a vapor lock and hit the starter and it immeditaly started. I have electric fuel pumps on all my trucks so the heat shield theory don't make sense with me.

Very Interesting' date=' Todd B[/quote']

Sounds more like an obstructed vent hole in the filler cap to me.

I bought mine @ NAPA and mounted them on the frame in front of the fuel tank. When I turn the key I can hear the pump turn until the line is full' date=' then hit the floor starter. I was sick of changing the normal fuel pumps, I had lots of problems with them.[/quote']

I rebuilt the fuel pump on my old Plymouth as a matter of course when newer fuels came out that would attack old materials. But I don't recall the pump ever failing in all the years I've had the car. The only old style fuel pump I recall replacing was on my '82 TC3 which failed at about 120,000 miles. For my old Plymouth I have a spare pump on the shelf, but my impression is that "normal fuel pumps" are very reliable. Except, perhaps, nowadays with the latest gas when the ambient temperature is in the high 90s to low 100s and the car has been driven long and hard enough to get everything very hot.

[Plymouthy Adams]

how did you confirm it is vapor lock????

[HanksB3B]

More likely the high float gas boilover senario. After I measured and set my carburator float I never had the hot-start (that we all seem to assume is vapor-lock) again. I don't have a heat shield but would like to someday just because it is a good idea.

Hank

[54Illinois]

So far the heat shield appears to be keeping the gas at bay...

[48Dodger]

I have to wonder if the gas has changed. I have driven my semi on many hot days and the first time I ever had a vapor lock was a few weeks ago on a very hot Sunday afternoon. What I did was open my gas cap to check if I had fuel and I heard and felt the presure behind the cap. I realized it was a vapor lock and hit the starter and it immeditaly started. I have electric fuel pumps on all my trucks so the heat shield theory don't make sense with me.

Very Interesting' date=' Todd B[/quote']

What you described Todd is Vacum Lock (occurs in the tank), it can have the same affect as vapor lock (occurs in the carb). If you have both happen...well...lol.

StandingElk, The RVP (Reid Vapor Pressure) is higher in winter grade gas...so if you haven't filled up with summer fuel, you may have to high a RVP. Winter gas needs help vaporizing.

RVP is under strict control of reformulated gas.

48D

[Tom Skinner]

If one go's to Google and types in Ethyl Free Gasoline Stations for NC (choose your own state) then one can find a list of these stations nearest to your house. Go then and buy a full tank of this "real" gas again and see for yourselves that there is a difference. Your vehicle will start and run right again. It costs a tad more (25cents/gal) more, however, you will also notice a better mpg average along with the responsive acceleration and smoother motoring.

I know some of you will nay say this but until you try it you can't believe it.

I don't know what kind of corn filler they are dumping in our fuel but it is just junk filler to make a fast buck - make no mistake about that.

Go then try this out and come back with a response/result.

One thing I noticed is I went farther on a tank of gas somewhere around 15-20% farther along with just wanting to gun it sometimes along the way and the egine responded to my pedal when I leaned on it. Its like the days of old

again. Roll down your windows and listen to the engine purr. There really is a difference.

[Young Ed]

Toms right. Only sucky part around here is to get no ethanol we have to buy 91 octane so its about .75 a gallon more.

[Todd B]

we have had this discusion several times before. I completely believe that my truck runs extremely well when I burn Shell Premium. I know several of you claim the engine was designed for a lower octane fuel, but I have tried several different fuels and it was clear that Shell premium fuel was a very noticable difference. I noticed it more when I am pulling my trailer.

Todd B

PS. Thanks for clearing up the difference between vapor lock and vacuum lock. I had no idea there was difference. Thanks again.

[knighthawk]

clothes pins DO work ! even had to use them on my motorhome once, helps dissapate the heat.put them on the fuel line before the pump. Also what helps is to use a fuel filter with a 1/4 return ine and return some excess fuel back to the tank, by either adding a return line at the tank , or a sender with 2 fittings

[48Dodger]

Simply put....Octane keeps gas from preigniting. If you have a high compression engine, you need a high Octane. Why? The compression alone will cause the low octane fuel to ignite. Not good, you want the spark to initiate "the push". 8.5:1, 9:1 compression engines don't benifit from higher Octanes, they use 85 or 87. if you put 100 Octane into a "normal" engine that calls for 85/87.....you notice a smooth idle but the power is flat. When you tow...or race...you increase the dynamic compression or air ramming into the cylinders...upping the compression. So you need a higher Octane. In my race car, a 72 Charger Street Stock, I ran a 2.76 gear with a 408 ci engine with a 11:1 compression @ 6500 rpms.....I used a 110 octane. I use this same motor at Bonneville and use 93 Octane , since I don't run higher than 5500 rpms. The technology of Octane during WW2 wasn't what it is today...so to help keep the fuel in figther planes from preigniting, they used water injection during the exhaust stroke to cool the cylinders.....this tech is still used on race cars today.

http://www.ftc.gov/bcp/edu/pubs/consumer/autos/aut12.shtm

http://en.wikipedia.org/wiki/Water_injection_(engines)

48D

[ggdad1951]

Toms right. Only sucky part around here is to get no ethanol we have to buy 91 octane so its about .75 a gallon more.

place about 2 miles from my house that has the good gas at the same price as at the other gas stations....

[Young Ed]

Wow wish we had one of those!

[ggdad1951]

house for sale across the street, 3 stall garage!

[55 Fargo]

Here is the kind of weather that makes a carb boil, or may cause the Phantom Vapor Lock.

Tonight was 90 in the shade at 8:00PM, was 102 in this ame spot in the sun at 5:00PM.

I am not sure what the official temp for the area was today, but it is good and hot and muggy.

I had my 47 Chrysler out for a nice drive this morning, was much cooler at 72, car ran and drove flawlessly cruisn at 60 mph and nice around town too.

I hope everyone is havin a nice summer night....ps sorry to Southern Alberta, will try and send some of the heat to you, as it was only 57 their today

[55 Fargo]

After I picked up and today with my 55 fargo, the see-throughy fuel filter between fuel pump and carb, was bubbling. The filter was hot, so was the carb, the carb base weeping some fuel. The glass bowl on the fuel pump, and the see-through filter between the gas tank and fuel pump were just fine.

So this carb was percolating, and the gas boiling or severly expanding, so what is the answer to this?

I have lowered floats, moved fuel lines, gonna try close pins next......LOL

[HanksB3B]

Rockwood,

Interesting I realize it's hot (90deg in the shade) but also wonder if your engine is not running extremely hot. Assuming you run the 180deg thermostat. I know I'll get a load of sludge poured on top of me (like those commercials) but what happens if you use a 160 deg thermostat?

Just a Thought,

Hank

Also sounds like you NEED a heat shield. Here down by the beach I seem to get away without one.

[Young Ed]

I run 160° thermostats in both my vehicles. Typically they run right at 160°. Last sunday it was in the 80s and I was idling around the MN state fair grounds during back to the 50s for a good 45min-60min. Maybe even longer. By the time we left I was up to maybe 185. My theory is that if I started at 180° because of the thermostat it would just put me that much closer to boiling over. If I went up the same amount from 180° that would put me at 205°. Now there's no proof that I would go up the same amount but it works for me.