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1957 Roadmaster - Altitude+Hot Days+Ethanol= Vapor Lock


High Desert

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Living at 6,000' elevation (lower boiling point), using modern premium fuel, and driving in 90+ degree heat is the perfect combo for vapor lock. I first noticed the potential for vapor lock after installing the glass bowl fuel filter and watching it seemingly half-filled while the engine was idling on a warm day. 

It didn't take long for vapor lock to show itself during my test drives. I'm sure it exhibits itself in different ways for different cars. For me it looks like this:

1. The car runs well when moving 30+ mph in general and temp gauge always stays in happy place. 

2. Short stops, like stop signs, also don't affect the car. 

3. Idle is never affected. Sitting at a stoplight for 3 minutes or more isn't an issue. 

4. Pulling away from the stoplight in #3 is where the problem shows itself. The Buick will get through the intersection and up to 30 mph before stalling out. The severity of the stalling is directly related to the length of time the car sat idling before moving. 

5. The stalling eventually subsides after 15-20 seconds and the engine pulls hard again. 

 

Realistically, vapor lock just turns me into the jerk who doesn't know how to get up to speed and holds up the line of cars behind me. Emotionally, it adds anxiety and reduces driving enjoyment. 

 

Addressing vapor lock while trying to maintain originality is a challenge. Most solutions seem to involve installing electric fuel pumps near the fuel tank. 

 

I added 3' of heat-reflecting sleeve to the engine fuel supply line. This helped greatly but not completely. The fuel filter area was still directly exposed to engine compartment heat. 

 

Last night I made a fuel filter wrap using layers of aluminum foil and some greenish bamboo fabric I had laying around. 

 

Test drives today have been promising! It isn't hot enough for a real test yet. I'm just trying to delay the heat getting to the cool fuel from the tank with these shielding options. Not sure what can be done about the fuel once it is in the carburetor though. 

 

I'll update this thread with more results as I drive it more. 

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Install an electric pump at the tank.

Vapor lock occurs on the suction side of any fuel pump...any fuel pump will push fuel and any vapor in the line, so all those wraps between the fuel pump and carburetor are useless.  Vapor lock is worse this year since (my research shows) the EPA is allowing the highly volatile winter blend fuel because of covid.  And that winter blend boils at 100*F.

Install an electric pump at the tank.  You can turn it on 'as needed' or full time like I have to do this year.

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57 minutes ago, Ben Bruce aka First Born said:

Or, do as I did.   EFI!  Holley makes one that when installed would take a sharp eye to tell the difference.  Even allows the original air cleaner to be used. NO fuel today is carburator friendly, at any altitude.

 

  Ben

 

 

:DThat way you will be forced to have a fuel pump back at or inside the tank.;)

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6 hours ago, old-tank said:

:DThat way you will be forced to have a fuel pump back at or inside the tank.;)

 

I decided to put heat shielding on the 40" of fuel line prior to the fuel pump too based on your comments. 

I drove it today and the vapor lock is almost completely gone. It is still a problem after the engine is off for a while and the heat gets to "soak" into everything, like when it is off to refuel and started again. 

When the engine is idling, pulling fresh fuel, and the fan is pulling air, it is so much better than before. 

Today was pretty hot too, so I hope I tested the upper extremes. 

I have thought wistfully about an electric pump at the tank but am concerned that it is a slippery slope. First the fuel pump, then I might as well do a Holley efi, then upgrade to a direct injection megasquirt system. Next thing I know I'm doing a full Tesla battery and drive train conversion in the Roadmaster and using the turbo-efi nailhead for my Cub Cadet.  All the time getting upset that people keep telling me to post updates only in the "modified" section of the forum. 

Think of the children. 

 

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NO slippery slope unless you desire to slide down it!  The booster pump which Old-Tank added to his car is NOT the same pump that any EFI system would tolerate.  As the EFI systems usually need about 54psi in order for the injectors to fire.  NOR as expensive as the normal "electric fuel pumps" which used to be used to feed 780cfm Holleys on Big Block Chevies.

 

Don;t forget the clothes pins!

 

NTX5467

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All of my cars now have an accessory electric fuel pump

(except for the 1915 Hudson which is gravity feed).

That is how we solve the vapor Lock issue,

and we live in an area where heat is an issue most of the year.

I had exactly the same issues with my 1954 Cadillac and 1937 Roadmaster before adding the pump.

This addition will make a huge difference in being able to depend on your car.

You won't regret it.

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I had a 1941 Packard that had to relied on electric pump often due to heat lock ,not original of course but kept car drivable..Current car 49 Buick doesn’t seem to have problems with fuel but always use non ethanol, and live in lower altitude 850 above sea level.Glad you found a solution for your car I know how frustrating it can be.

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I agree with old-tank, Marty Roth and the rest of the electric fuel pump proponents.

 

I put my Buick together with only the mechanical pump and the first time it was driven in ambient temperature above the mid-80s, it started exhibiting vapor lock symptoms.

Adding a low pressure electric pump at the tank totally eliminated the problem.

 

Based on my experience and the advice of others I respect, I am adding an electric "pusher" pump to all of my other cars (except the '23 Cadillac; it has a pressurized fuel system).

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I can now buy at a reasonable price 87 Octane, ethanol free gasoline and mine runs well even in 95 degree days.

Ask your legislators to get the ethanol out of our gasoline.  Honest testing shows that emissions in total do not reduce emissions and may even increase overall auto emissions.

Edited by Caballero2 (see edit history)
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Another way of doing the same thing is to get the fuel filter that is used on 59 and up air conditioned cars.

It has a return line going back to the tank and it keeps the gas flowing.

I have had 2 cars (60 Electra and 64 Riviera) that had that feature and both with AC and not had an issue even with the temps we get in Texas.

 

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7 hours ago, Bill Stoneberg said:

Another way of doing the same thing is to get the fuel filter that is used on 59 and up air conditioned cars.

It has a return line going back to the tank and it keeps the gas flowing.

I have had 2 cars (60 Electra and 64 Riviera) that had that feature and both with AC and not had an issue even with the temps we get in Texas.

 

The car had a return fuel line running back to the tank along the driver side frame rail. It wasn't connected at the engine and terminated at a t-connection just ahead of the tank. The return leg of the t had been soldered shut. I don't believe it was factory, just really old. 

 

I'll probably put an electric booster pump on once I reinstall the air conditioner. That extra heat will likely be just too much, even for my added heat shielding. 

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  • 2 weeks later...

I believe that ThermoTec has some tubular heat insulation products that do more than "shield" a particular section of the tubing.  But you also have to consider the "heat gain" from other sources the tube/fuel pump/carb are attached to . . . on the engien and all the way BACK to the fuel tank.

 

Consider, too, that liquids under pressure have a higher boiling point than liquids under a partial vacuum.  The volatility of the fluid can accentuate the latter.  In earlier designs, putting the pressure toward where the fluid will end up made sense and could lessen possible fire damage.  Putting pressure throughout the system could worsen it, should some part of the fuel line be compromised and leak.  Which means that using steel fuel line is much better than using rubber fuel line, in these cases.

 

Just some thoughts,

NTX5467

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The first issue is understanding the issue!

 

The symptoms mentioned by the OP in post 1 are NOT a result of vapor lock, rather exactly the opposite (too much pressure)!

 

http://www.thecarburetorshop.com/Troubleshooting.htm#Hardstarthot

 

The above link describes what happens when the engine is turned off. The same thing happens when the engine sits for a period of time idling, except that fuel both "puddles" in the intake manifold, and also vapors fill the air cleaner.

 

The insulation provided by the OP proves the issue, as the insulation made the effect significantly better.

 

Under these conditions, if an automatic transmission, place the transmission in park toward the end of the light, and rev the engine to 1500~1800 RPM for maybe 5 seconds. This will clear the puddling and air cleaner vapor issue, and the car will run normally.

 

This is NOT a function of old cars only. Daily drivers from the 1970's and 1980's which I have had exhibited exactly the same symptoms, although most of mine were standard transmission, so easy just to rev the engine in neutral. Personal experience is how I learned the issue, and how to bypass the issue. Also, it happens with non-ethanol fuel.

 

The electric pump will help a cold start, but not the hot start, or the stalling from a light.

 

Jon

Edited by carbking (see edit history)
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On 8/25/2020 at 10:14 AM, old-tank said:

An electric fuel pump is not just a convenience issue it is a safety issue!

 

How does that safety pump shut off in the unfortunate event of an accident?

 

Weather. I still have to adjust my mower deck for this weeks glacial rebound. The last two nights have been in the low 50's. It's going to take some of that global warning to see vapor lock around here.

 

Bernie

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30 minutes ago, 60FlatTop said:

 

How does that safety pump shut off in the unfortunate event of an accident?

 

Weather. I still have to adjust my mower deck for this weeks glacial rebound. The last two nights have been in the low 50's. It's going to take some of that global warning to see vapor lock around here.

 

Bernie

Something like THIS.

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4 hours ago, carbking said:

The first issue is understanding the issue!

 

The symptoms mentioned by the OP in post 1 are NOT a result of vapor lock, rather exactly the opposite (too much pressure)!

 

http://www.thecarburetorshop.com/Troubleshooting.htm#Hardstarthot

 

The above link describes what happens when the engine is turned off. The same thing happens when the engine sits for a period of time idling, except that fuel both "puddles" in the intake manifold, and also vapors fill the air cleaner.

 

The insulation provided by the OP proves the issue, as the insulation made the effect significantly better.

 

Under these conditions, if an automatic transmission, place the transmission in park toward the end of the light, and rev the engine to 1500~1800 RPM for maybe 5 seconds. This will clear the puddling and air cleaner vapor issue, and the car will run normally.

 

This is NOT a function of old cars only. Daily drivers from the 1970's and 1980's which I have had exhibited exactly the same symptoms, although most of mine were standard transmission, so easy just to rev the engine in neutral. Personal experience is how I learned the issue, and how to bypass the issue. Also, it happens with non-ethanol fuel.

 

The electric pump will help a cold start, but not the hot start, or the stalling from a light.

 

Jon

To me this describes percolation or fuel boiling out of the carburetor bowls.  ONE of the problems with volatile fuel.

I solved this problem by blocking all exhaust crossing over in the intake manifold.

 

On 8/23/2020 at 11:08 AM, High Desert said:

3. Idle is never affected. Sitting at a stoplight for 3 minutes or more isn't an issue. 

4. Pulling away from the stoplight in #3 is where the problem shows itself. The Buick will get through the intersection and up to 30 mph before stalling out. The severity of the stalling is directly related to the length of time the car sat idling before moving.

This is a lean condition (that will not occur with an electric fuel pump) where no fuel is delivered due to vapor lock on the suction side of the mechanical fuel pump.  Problem TWO of volatile fuel.

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High Desert,

Look at your pictures closely and just think about it.

Your fuel line comes up from the pump, turns 90 degrees to the filter, which is held in place with a steel bracket, which is hooked directly to the thermostat bolt.

THINK HEAT TRANSFER !

Then it wanders over to the other bank, does a "U" turn back over the galley, then another 90 into the carb,

Only area under the hood that gets hotter is the exhaust manifold !

 

 Your set up is exactly the opposite of winding a copper coil in a can with dry ice !

 

Get some fuel line and re-plumb this, to come up from the pump turn 45 degrees with a clear plastic filter, and head straight for the carb !

 

Oh, and put an electric pump back at the tank, with a BIG clear filter, and wire it to a toggle switch under the dash, with a fuse to something that is always hot, like the cig lighter.

 

I did this to my '40 Buick LTD and it solved my vapor lock several years ago, and I live at 8500 ft.

 

Mike in Colorado

 

PS; The black hose running across the rocker box is my fuel line, covered in heater hose, which was re-routed away from the thermostat, to the back of the engine along the firewall.

final dump 044.JPG

Edited by FLYER15015 (see edit history)
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Heat transfer from the engine itself can be an issue, as can air flow OVER the engine from the radiator fan.  With the size of the carb float bowl having a secondary influence.

 

An example would be that in the middle 1980s, when the OEMs knew that some sort of fuel injection was coming in 1987 (as with GM in particular), there had been "hot fuel handling" problems with many Camaro/Firebird V-8s which had not really had any problems before that.  Chevrolet put out several TSBs to address this issue.  Magazine letters in Chevy enthusiast magazines noted marginal improvements afterward, but no full "fix".

 

Then one day, I was walking across our service drive and an "affected" Camaro was sitting there with the hood open.  Suddenly, lots of red flags appeared.  First one was that there was very little air flow that could get to the carb, with all of the a/c and vacuum lines between the radiator and the carb, which blocked MOST Of the air flow to the carb, whcih might then get UNDER the bottom of the low-profile air cleaner/snorkle assy.  Second red flag was the realization of just how small the original float bowl was in the Rochest QJet 4bbl (and 2bbl variation of) carb.  Which was then further reduced with the phenolic needle/seat area deflector of gasoline coming into the bowl.  End result, not much "reservoir" at all, compared to earlier years!  End result, basic underhood ambient heat which was probably multiplied by slow-moving traffic, made even worse by ambient air flow coming from the rear of the vehicle, rather than the front.  So many design "fails", some worse than others.

 

As GM knew that FI was coming, no real desire to spend money on anything other than what might be termed "Band Aid fixesw".  But they should have known about the RFG (with ethanol as an "extender") that was coming, too.  Which probably generated the TSBs a bit earlier-on.

 

But also understand that the OEMs had to design fuel systems to work in varied climates.  In the summer, heat underhood could be an enemy, but in winter, it could be an asset for good cold-weather drivability.  Which could explain the way many of the '50s cars fuel systems were plumbed.  Can't forget how it all worked at the engine and vehicle assembly plants, either!  OR consider the cost/assembly line complexity of different fuel lines for various optioin pairings!  End result, some things were not as WE might have designed them, but they looked good under the hood at first glance.

 

Which can bring up the issue of vehicle authenticity for higher-level show judging situations.  Where well-executed incognito upgrades would receive fewer point deducts than something more "in your face" and obviously not correct for the vehicle.  Various levels of sensitivity there!  A variable situation, at best.

 

I remeember reading questions in various car magazines (back in the '50s!) of how to deal with "vapor lock" in hot weather AND in the hotter states of the USA.  So this is NOT a new situation to deal with on MANY now-vintage vehicldes.  Just made a bit worse with the more modern, alcohol'd fuels.  Clothes pins on the fuel line for heat dissipation between the tank and fuel pump was a common trick.  Putting cool water on the fuel pump was nother, but not as relaxing as "going for ice cream", gettng an extra cone to apply the cool treat to the body of the fuel pump itself (as one writer claimed worked once for him).

 

Possibly, using some red ScoltchBrite to polish the existing metal fuel lines for greater heat reflectivity might be an incognito upgrade that would not hurt authenticity too much and help hot weather driving?

 

Enjoy!

NTX5467

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Rod,

That I don't have right now, but I can tell you that I used 3/8" copper tubing.

Came straight up from the pump and then under the air vent hose, back to the firewall.

Under the coil and as you can see up and over the valve cover, with a home made bracket to stabilize the line.

Then just turn 90 into the back of the carb.

The whole line is sleeved over with 3/4" heater hose from the pump to the carb.

The filter is rubber hosed to the carb fitting to isolate the line from the carb body heat.

 

Mike in Colorado

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