Vapor lock

[rgshafto]

It's summer again and for the 1st time in years I'm having a vapor lock problem with my coupe (in the fuel line between fuel pump & carb). I know the best solution is a bypass line or electric fuel pump, but don't want to go this route if I can avoid it.

I wonder if anyone knows of a source of a simple metal heat shield that might clip on to the fuel line, shielding it from the exhaust manifold? I believe that will do the trick.

Thanks,

[joe_padavano]

I wonder if anyone knows of a source of a simple metal heat shield that might clip on to the fuel line, shielding it from the exhaust manifold? I believe that will do the trick.

Thanks,

The source is your kitchen. Grab the box labeled "Reynolds"...

Seriously, wrap the line loosely with aluminum foil, shiny side out. Leave an air gap between the foil and the line. It's easily removed for shows.

[Friartuck]

Bob Shafto,

You don't mention which vehicle but nonetheless, may I suggest a simple remedy: Fresh Fuel. Fuel refined today seems to have a life of about 60-90 days. I too had a vapor lock incident using 5 month old fuel and when replaced with fresh gas, ran fine.

[joe_padavano]

Bob Shafto,

You don't mention which vehicle but nonetheless, may I suggest a simple remedy: Fresh Fuel. Fuel refined today seems to have a life of about 60-90 days. I too had a vapor lock incident using 5 month old fuel and when replaced with fresh gas, ran fine.

That's an excellent point, but there's more to it than just old fuel. Refineries have different blends of gasoline for specific predicted ambient temperatures. Fuel blended for winter has a lower vapor pressure that fuel blended for summer. If you have six month old fuel in your tank, you will definitely have the wrong vapor pressure (well, unless you live in southern California... ). Winter gas will vapor lock much more readily in the summer than summer-specific blends.

[ply33]

Bob Shafto,

You don't mention which vehicle but nonetheless, may I suggest a simple remedy: Fresh Fuel. Fuel refined today seems to have a life of about 60-90 days. I too had a vapor lock incident using 5 month old fuel and when replaced with fresh gas, ran fine.

Not always old fuel. Just finished a 1600 mile trip in my 1933. On the last day, the second tank of gas for the day, I stopped after running 60 MPH for about an hour in 90+F temperatures. Car did not restart until I cooled the fuel pump down with a little water from my drinking water supply. Best explanation I can come up with is the pump (not the line from the pump to the carburetor) was hot enough to vaporize the gas.

Simple cure for me: Don't stop in the Central Valley the Bay Area is cool enough that I don't have that problem here.

[ARUCKEY]

My suggestion is to purchase the cloth type (weave) used to wrap exhaust systems. It is available from a number of hot rod type suppliers. It is approx. 2-3 inches wide and comes in various lengths. Wrap it around fuel lines and get it as thick as you can. It is an excellent insulator to keep exhaust manifold heat away.

The mechanical fuel pump is another issue. In the past in hot weather I fashioned a temporary wire mesh basket around the pump. When I get vapor lock I simply drop in some Ice cubes from my cooler. The basket holds the ice against the fuel pump and cools it as it melts.

Too much variation in gasoline these days. Lots on alochol being added which boils off too fast and creates vapor inside the fuel lines. Not a problem in car has fuel injection.

[joe_padavano]

I'm going to disagree a little bit here. The problem with insulation is that eventually the part inside the insulation also gets hot. The insulation is not perfect, it just slows the rate of heat transfer. That works in both directions, of course. Once the part inside the insulation gets hot, the insulation keeps it hot longer. If you are talking mainly about short trips, the insulation will likely work fine. Longer trips may be a problem. The nice thing about a reflective surface is that it will deflect the radiant heat.

[ARUCKEY]

Hello again

Going back to the original question, "how do I shield or insulate the fuel linn from the exhaust manifold heat. My insulation suggestion would be material equivalent to a welders glove. I would suggest an experiment. Put a welders glove on one hand and wrap the other hand in Reynolds aluminum wrap. Hold both hands 1 inch from a hot exhaust manifold. Which hand would you have to remove first?

You have to remember that the underhood area gets to about 150 F on hot days. The fuel in the tank maybe 90 or 100F. this cooler fuel in moving thru the line and tries to cool the fuel line. If the car is shut off and soaking, thats a different story. However, with the weave type wrap, it delays the heating up of the fuel line.

Al Ruckey

Detroit

[rick60]

When I worked as a mechanic I replaced a lot of air conditioning hose assemblies. GM had a reflective insulation material that was installed over the AC hoses to protect them when routed near exhaust manifolds. I would cut the old hoses and remove the insulation. It cleans up easily. You can disconnect the fuel line and slip the insulation over the line. It is not original, but it looks nice. It worked well for me. Maybe you can talk to your local mechanic or AC shop and ask them to save you some of this material. You may be able to scrounge some at your local salvage yard as well. Good luck.

[Larry Schramm]

For the wiring harnesses, Packard Electric/ now Delphi calls it Moon Tape. It does a good job of reflecting the heat.

[rgshafto]

Thanks everyone. Surely it is a gas reformulation problem – it has fresh gas – so some kind of insulation is probably the best solution since it only happens after I park the car and leave it for several minutes.

[Guest De Soto Frank]

Thanks everyone. Surely it is a gas reformulation problem – it has fresh gas – so some kind of insulation is probably the best solution since it only happens after I park the car and leave it for several minutes.

It's the fuel. :mad:

Classic "heat-soak" problem; hot vehicle gets parked, fuel in the carb / pump / lines vaporizes, car is hard to start until it cools.

Make sure the bowl vent on your carb is not blocked, and if equipped with an "anti-percolation valve", make sure that is operating correctly too.

Not sure how your Pontiac is set-up with respect to the location of the fuel-pump to the exhaust manifold / exhaust system, but my flathead MoPars have the fuel pump mounted low the side of the block, under the front of the exhuats manifold. There is a long 3/16" rod with a nut at the top that mounts to the fuel-pump body, and at the top end of the rod, is secured a sheet-metal heat-shield, to deflect some of the heat from the exhaust manifold away from the fuel pump. If this shield is missing, the MoPar can have all sorts of hot-weather issues...

Such a shield may help your Pontiac ?

This question has been getting kicked-around a lot at the Model-A dept of Fordbarn, and some guys are having good results from using foam pipe insulation around the fuel line to keep things cool... just need to make sure you're not in danger of melting any foam / soft insulation... if there's that much heat near the fuel line, I would be looking for cooler routing, even if it deviated from stock.

I'm kind of surprised you're having this sort of issue, way up in Maine... has it been getting really hot up there ?

[Guest danielhenry31]

That's right!The refineries have different blends of gasoline for ambient temperatures predicted. The mixed fuel in winter has a low vapor pressure, the fuel mixture for the summer. If you have six months old fuel in your tank, you will probably pressure steam bad

[mastertech]

I also have the same problem, driving along just shut off as running out of fuel ,checked and no fuel in carb thought to myself self fuel pump bad. I let the car sit and got a ride home to get my jeep and some tools by the time i got back it started ok vapor lock. it was about 90+ out and i had just filled the tank, drove the car home replaces the pump anyway because didnt know how old pump was, ( this is a 1965 chrysler 300 with a 383 4bbl carb) . after pump was on car ran fine for about a week then did the same thing ok so i replace points plugs dis cap rotor added a clear fuel filter to see what was going on if happen agin. Went to show in the next town over on july 3 temp in am 70-80 no problems ran 55-60mph ran like a champ, come home after show temp 88-90 no problems, but sunday did same thing shut off waited them started up. Now tonight it did the same thing noticed lots of bubbles in filter ran hose on pump started, dont know how to cure this I even tried an old trick by putting close pins on the fuel lines,that didnt work. all lines are away from heat sourse i have replaced all rubber lines with new, only thing left is to install an small electric pump. Napa has one that has 1.5-4.5 psi will that work (going to leave the mech pump on also) ? i want to use this car and cant have it shutting off as most shows around here are a distance away. thanks for any help. Also a buddy of mine has a 70 dart 340 that is doing the same thing , and comming back from show on the 3rd another friend of mine 54 chevy did the same thing so its just not my car doing it, we dont h ave much choice as to gas station as all are the same in at least a 50 mile raduis a convience store chain we dont have any gas stations here any more

[Guest 34ACD]

If you have a heat riser valve in or below your exhaust manifold you might want to check if it is stuck closed. Common and often overlooked if vapor lock is sudden problem and nothing has changed otherwise.

[Guest De Soto Frank]

If you have a heat riser valve in or below your exhaust manifold you might want to check if it is stuck closed. Common and often overlooked if vapor lock is sudden problem and nothing has changed otherwise.

Excellent suggestion...

[19tom40]

Bubbles in the filter indicate an air leak between the tank and the filter. Check all fuel lines for tightness and replace any flex lines as they can develop small air leaks.

[Seldenguy]

There has been several opinion's on fuel pumps and gas lines in conjunction with the dreaded "vapor lock" (and a little dancing around the subject also), but so far I haven't seen any thing about gravity feed systems. Are they immune? This system was in use from the early 1900's up to and including the '31 model A Ford. But so far no one has reported any problems with vapor lock and the gravity system.Does the tank head pressure solve the problem or is there no problem?---Bob

[rons49]

From the vapor lock capitol of the world, Arizona.For years I have struggled with this on my 6 volt 308 Hornet.unreliable over 90F especially after standing at a light.Instant fuel starvation. Winter gas flashes off at @105F, summer,145F.Neat ha? AS Joe P said wrap the line with insulation and you will gain some time, but eventually the line will heat up and stay hot longer, same for the mech fuel pump. Tried 3/8 line for more volume.Nyet. Diesel fuel added; more time, again NG. Neither did a fuel feedback line to the fuel filler neck. An elec pump in line works(solenoid style) but once the starvation occures it must remain on. And these pumps, IMO, are unreliable as the new gas causes the lining seals to swell and although the motor turns, they fail to pump and the mech pump can't draw enough fuel to maintain flow to the carbs. Only answer is to add one of two style pumps,a. rotory vein or a carator(gear driven) pump, and these are only 12 volt, but work well on 6v albeit half the PSI. Be advised these can not be added in line, as they will restrict the fuel to the mech pump. Therefore, adios to the mech pump. I prefer safety to originality,but, whatever.