Vapor lock beats the straight eight.

[Rosiesdad]

Sadly, it appears that I cannot solve the constant vapor lock problem with my '50 Buick Super.

The final attempt used a 9psi fuel pump to the fuel filter followed by a "Tee" and a 1/8" gas return line to the tank. See PIC.

I have tried everything. As you can see from this photo the fuel level has fallen to the bottom of the stone filter. The electric pump is running and some fuel is returning to the tank but the vapor bubble remains. After it sits for 1/2 hour the throttle can be pumped, fuel level quickly restores to top of filter and engine fires.

I seriously think I am dumping the straight eight. I hate to but have no choice.

[Guest shadetree77]

Phil, have you tried the electric pump setup WITHOUT the return line? That's what I use on my straight eight and it works perfectly.

Also, I don't understand how you could be running out of fuel at the filter if the electric pump is hooked up right and functioning correctly. It should be pushing liquid fuel from the tank through the lines vapor lock or no. Could you give us a quick run-down of how you have everything hooked up and routed from fuel tank to carb?

Something else you might try would be to get rid of the glass bowl filter and try an inline filter under the car away from heat sources. Just to see if the glass bowl filter might, itself, be the problem.

Wish I was nearby so I could take a look. Don't give up on the old straight eight yet! Opening the hood and seeing that big old inline eight is half the charm of owning an old Buick.

[Ben Bruce aka First Born]

Phil, please remember, it is not the Straight Eight. It is the gas/carb combination. When you say get rid of the Straight Eight, are you talking engine or car? If engine, you are modifying it. If you go with an engine using a carb, same problem can[will] pop its ugly head up.Try a throttle body fuel injection. Pricey, but MUCH less than an engine swap. I have been thrilled with mine.

Ben

[1937-44]

I agree with Shadetree77, lower the electric fuel pump pressure and eliminate the return line and see what happens. I tried a setup like that on my car and the electric fuel pump couldn't keep up at speed. I eliminated the return line and just use the electric for starting and on the occasional times it starts to stutter due to lack of fuel. The other possibility might be to raise the pressure higher on the electric fuel pump and experiment.

Carl

Edited May 1, 2014 by 1937-44 (see edit history)

[60FlatTop]

I scrolled back up to see how far away from me you are located. I also looked through your previous posts and saw the December 2012 discussion on the same problem.

I think I was about 14 the first time I saw a '49 or '50 Ford with an array of clothes pins across the fuel line. At the time the term "urban myth" had not been used, but I knew those clothes pins were a crock. A few years later I made it my profession to turn liquids into vapor, first with water and then a whole range of volatile liquids. I, personally, don't think any flow of fuel has been "locked" from flow under typical driving conditions at any time during the last two thirds of the last century. Maybe in the late 1800's and very early 1900's when gasoline was purchased in drug stores it could have happened and the myth perpetuated for good story telling.

I used to service a friend's car and he was hovering around telling me all kinds of cracker barrel stuff. If he left the car and went on vacation he was generally amazed at how well his cars performed when he returned and would not believe the simplicity of what I did.

If your car was his I would first bring if into the garage and disconnect the vacuum advance. I have some short sections of tubing with fittings to adapt my vacuum tester. Putting vacuum on the advance and releasing it should show nice crisp action of the breaker plate. If it drags slowly ( maybe even half an hour) it is going to give hot start symptoms that feel like flooding or a fuel problem. A second try pumps more gas in.

After that is checked, the float level, vents, and general carb stuff, then I would cap and pressurize the fuel line to be sure no air is being sucked in, then I would take a close look at the check valves in the original fuel pump, working my way through each component, and then take all that added stuff off and return the line, sending unit, pump and carb to the condition of all the ones that traveled out of the showroom to happy customers.

And watch out for those repeated stories from the Dust Bowl days. Those guys would pull your leg.

Bernie

Edited May 1, 2014 by 60FlatTop (see edit history)

[old-tank]

Either the electric fuel pump is defective or it is still suckin' air between the electric fuel pump and the gasoline.

[Rosiesdad]

Phil, have you tried the electric pump setup WITHOUT the return line? That's what I use on my straight eight and it works perfectly.

Also, I don't understand how you could be running out of fuel at the filter if the electric pump is hooked up right and functioning correctly. It should be pushing liquid fuel from the tank through the lines vapor lock or no. Could you give us a quick run-down of how you have everything hooked up and routed from fuel tank to carb?

Something else you might try would be to get rid of the glass bowl filter and try an inline filter under the car away from heat sources. Just to see if the glass bowl filter might, itself, be the problem.

Wish I was nearby so I could take a look. Don't give up on the old straight eight yet! Opening the hood and seeing that big old inline eight is half the charm of owning an old Buick.

Yep. I don't know why the vapor wont go back to the tank unless it just stuck at the high spot in the system. on cold days it get a nice stream of fuel back to the tank. Yesterday it was 90 degrees but this thing vapor locks at in 75 degree temps. too. I think it must be the crappy gasahol.

Engine runs great but I an tired of being stranded.

[60FlatTop]

The car looks nice, but it can't be worth much if it doesn't run. I would be willing to risk a little money on it if you are tired enough to think of selling.

My '60 Electra had not run in about three years when I bought it. The owner had been trying to figure out how to repair it and finally gave up; total time to repair: three years and 6 hours.

Bernie

[Rosiesdad]

I don't think it's a vacuum advance hot start problem because I can SEE the issue in the fuel filter. I pulled the tank and inspected the line from the pickup to the new 9psi Airtex pump mounted next to the tank. The line is original to the rebuilt mechanical pump. Then up and over the engine though an insulated line to the glass bowl filter and a gas return tee.

I tried a different inline filter. I tried bypassing the mech. pump. I tried regulating down to 5psi with a step down regulator under the car which I removed when I put the Tee in. I made sure the exhaust manifold heat riser is stuck open. Engine vapor locks even when it is at normal temp after restarted for a 5 minute drive.

[avgwarhawk]

I can understand you frustration. We are going through similar with a 1960 Imperial that evaporates the fuel in the bowls in about a day. Need to prime by pouring gas down the throat. We have tried the one way valve to assure gas is still in the line. Next is a electric fuel pump at the tank. Knock on wood I do not experience sever vapor lock like you are but when I do I put the pedal to the floor and crank until started.

Your gas cap is vented?

Edited May 1, 2014 by avgwarhawk (see edit history)

[TexasJohn55]

Phil, You need a pressure guage hooked up at the glass filter to see the pressure when the fuel level drops. You have a delivery problem whether it is a plugged line or sucking air I don't know but you must monitor pressure. You can put any engine you like in there and it will have the same problem.

Chris, Remove your carb, fill with gas and see where it leaks out the bottom. Fuel CANNOT run back to the tank through the needle and seat.

[avgwarhawk]

Chris, Remove your carb, fill with gas and see where it leaks out the bottom. Fuel CANNOT run back to the tank through the needle and seat.

This we understand. However, the fuel level gets below the accelerator pump after a week(many threads about Carter 4brrl and Holley as well) Takes 20-30 seconds of cranking to start the car. However, I will take the carb off and watch for leaks from the seats.

Returning this thread to Rosiesdad.

[60FlatTop]

Remove the carb carefully, keeping it level, and set it in some heavy paper or cardboard. The leaks will be at the lead or aluminum plugs that seal off drilled passages.

Quadrajets have two in the center that get bad enough to cause a rough idle. I used to start those cars cold and then pop the carb off quickly. You could see the raw gas in the intake manifold. New plugs are available.

On the old straight 8 remember what Ron said:

Bernie

[old-tank]

Where is the electric fuel pump mounted? It should be as close to the tank as possible and at or below the the fuel outlet on the tank. Fill the tank and see if that improves it.

[buick5563]

I, personally, don't think any flow of fuel has been "locked" from flow under typical driving conditions at any time during the last two thirds of the last century.

Bernie,

I'll pay your plane ticket and your fee if you can combat my perceived vapor lock on any 55 I own when driven in a Texas summer.

I'm not sure what Phil's pic shows. Is the filter before the mechanical pump? If yes I would eliminate that. If after the mechanical pump, I would eliminate the "T".

There should be a filter before the electric, then the original filter right before the carb.

My opinion, only.

[60FlatTop]

Sure, Texas in the summer. If you can hold out until the fall of '17 I will stop by on my way to the Cayman's. I have confidence that each of these instances did not show the symptoms when new and anecdotal assumptions are causing the source of the problem to be overlooked. (Sorry about the vocabulary, an engineering proposal I am writing is minimized while I take this break).

If the situation can be predicted and duplicated, after doing my standard compression, vacuum, ignition, and visual tests, I would put an oscilloscope on the ignition system during the failure to start event. The secondary voltage should be around 2500 to 3500 volts. If cylinders are starved for fuel the lean air gap at the plug will raise the secondary circuit resistance and you will see spikes into the 5000 to 6500 volt range. This will tell you for sure if a lack of fuel is caused to no start condition. Although I also have an inductive high voltage meter for spot checking this oscilloscopes are easier to find these days.

If there is fuel be sure the timing is actually retarded the correct amount. The odds are still with me on that.

If fuel is lacking, cap off the last connection of the fuel line and pull a vacuum on it from the connection at the carb and maintain it. 25" should be maintained. That is the equivalent of about 10 PISG of pressure externally. If it doesn't hold you are leaking air.

Just these tests will pinpoint the problem quite well. Especially if you test during the problem event. Running through them before hot weather is certainly a good idea and may avoid a walk home.

When I licensed my first Jaguar I increased the range on my AAA towing service. The Jags always got home. My wife teases me because the Buick ended up being the one that failed to proceed.

Bernie

[bhambulldog]

Mix 4 ounces of Marvel Mystery oil in every tankful of fuel.

Mine has not vapor locked in 42 years, Dad and then I have been using Marvel Mystery oil since then.

[Rosiesdad]

Bernie,

I'll pay your plane ticket and your fee if you can combat my perceived vapor lock on any 55 I own when driven in a Texas summer.

I'm not sure what Phil's pic shows. Is the filter before the mechanical pump? If yes I would eliminate that. If after the mechanical pump, I would eliminate the "T".

There should be a filter before the electric, then the original filter right before the carb.

My opinion, only.

The stock filter is directly before the Tee which is attached to the carb. there is a built in filter on the new Airtex 9psi pump mounted low next to the (Clean) tank. It appears the fuel may be boiling in the float bowl. Before adding the Tee I would purge the vapor bubble by opening the gas line at the filter or removing the sight plug from the side of the float bowl and pushing down on the floats. This was tricky and often resulting in a flooded engine that even starting fluid would not fire! That was the only way to get the vapor out. I REALLY thought the Tee setup would cure the issue once and for all. Guess not but I can't fathom why.

Thx,

Phil

[TexasJohn55]

Hmm, maybe your float is sticking sometime? Boiling should automaticly lower the float level and open the needle valve. I will have to think on that one awhile....

[TexasJohn55]

Maybe the vapor in the filter remains because it is being replaced with air at little to no pressure.

You still need a pressure guage tee'd in where your return line is now. You also need to disconnect fuel line at the fillter, run an extension into a bucket and submerge it, watch for bubbles and monitor fuel stream to see if it diminishes after awhile. It should fill the bucket quickly with no bubbles. Do this with engine off and electric pump running. If this test is ok, rely on the pressure guage to show you something.

If you have a restriction anywhere in the system it will starve the carburetor. If you have an air leak anywhere behind the electric pump it will suck air and starve the system. If you have a combination of both........Oh me!!

The electric fuel pump has a flow rating in GPM OR GPH, that can be tested.

Edited May 3, 2014 by TexasJohn55 (see edit history)

[JohnD1956]

Is the vent on the carb bowl blocked? I know my Rochester 4 gc is vented externally. Maybe yours is too? I have heard of incorrect installation of the internal carb gaskets blocking the vent.

[Guest shadetree77]

Your gas cap is vented?

This would be an easy place to start Phil. An excellent suggestion by Chris. Check that your tank is venting like it should. My 1952 manual says there is an internal vent going from the baffle inside the tank up to the gas cap. Not sure if it's the same on your '50. Maybe if there's something wrong with your gas cap it might not be letting the vent work correctly. If your vent isn't working right, would this not cause a vacuum in the tank which would stop fuel from reaching the engine? Someone correct me if I'm wrong on that.

[TexasJohn55]

Eventually yes but that is a relatively long term effect, short term it may even pressurize as the fuel is warmed and returned to the tank, more so if it is sucking air and returning it to the tank. The bowl vent is a good idea, I didn't know if it was possible to block the vent with the wrong gasket. Now we know.

Edited May 3, 2014 by TexasJohn55 (see edit history)

[Rosiesdad]

Hmmmmm. I did replace the gaskets in the (Carter) carb. last year. I don't know if it has a vented bowl. That is a interesting thought though. Yesterday I put a small plastic gas filter in line replacing the vintage glass bowl. It ran great but the weather is cool now. I am running a gas return line to the tank filler so there is no venting issue there.

THX!

Phil

[rick60]

Has the heat riser been checked to see if it is working correctly?

[Pete O]

I don't think it's a vacuum advance hot start problem because I can SEE the issue in the fuel filter. I pulled the tank and inspected the line from the pickup to the new 9psi Airtex pump mounted next to the tank. The line is original to the rebuilt mechanical pump. Then up and over the engine though an insulated line to the glass bowl filter and a gas return tee.

I tried a different inline filter. I tried bypassing the mech. pump. I tried regulating down to 5psi with a step down regulator under the car which I removed when I put the Tee in. I made sure the exhaust manifold heat riser is stuck open. Engine vapor locks even when it is at normal temp after restarted for a 5 minute drive.

The original routing of the fuel line does not have it going up and over the engine. It comes up from the fuel pump around the front of the engine at the level of the valve cover back to behind the carb where it does a 180 into the filter. At no point is the fuel line higher than the float bowl on the carb. With the original routing, it is also in the airstream coming off the fan where it is subject to cooling. I'm guessing here, but I think that if at some point the fuel line is higher than the float bowl, you might end up with a syphoning effect which causes a lower pressure on the down-hill side compared to the uphill side. The drop in pressure might cause the bubbling. Only a theory....

[avgwarhawk]

You are not alone. Check out the insulation on this fuel line.

[avgwarhawk]

I was reading at another forum that a participant had a similar problem. He found that rubber hose(original to the car) that feeds through the frame somewhere between the tank and carb creates issues. He finally replaced his fuel pump and this rubber hose. Problem went away. Possible your original rubber hose, if original, is collapsing from suction/heat.

Edited May 5, 2014 by avgwarhawk (see edit history)

[60FlatTop]

A friend stopped by tonight and told me his car with an AFB won't start hot and he has vapor lock. I'll probably get it out here and fix it for him.

I WILL use test equipment on the car when I recreate the problem. The first check is compression, like the training video says and like I learned in 1959. You just don't waltz up to an engine and start monkeying around without and compression check and an ignition system inspection. When I get a no start condition I will check the secondary voltage to see if the cylinders are starved for fuel or rich.

Although this is a Mopar video, they do a good job overall. Pay attention to the antiperculation comments.

Bernie

[FLYER15015]

Phil,

Up here at 8500' where the air is thin, and we are forced to buy 10% corn gas, vaporlock is a way of life......

My solution was an electric pump and a BIG clear filter back at the tank on a toggle switch. Helps with priming too.

Lock the heat riser wide open.

Wrap the exhaust pipe with fiberglass tape from the heat riser all the way back past the M/C and to the muffler.

Reroute the gas line along the passenger side fender, across the firewall and to the carb, and enclose it in 1/2" heater hose. My line is 3/8" copper.

The pusher fan in front of the radiator is also on a switch.

Out here we pull some long grades in thin air and on a hot day, she still bucks a bit, but just cruzin round town she does fine.

Mike in Colorado

[carbking]

There may be multiple issues here.

As far as the carburetor venting and replacing the gaskets is concerned: I didn't see a picture of your carburetor, but you stated 1950 Buick and Carter carburetor. The 1950 Buick would have used a Carter type WCD 2-barrel number 725s on the 40 or 50 series and number 726s on the 70 series. Often the tag is missing and people guess. Carter produced a total of 112 DIFFERENT type WCD carburetors and they do get changed. Generally if the tag is missing, the carburetor is NOT original. For the record, we offer 37 different rebuilding kits for the various type WCD carbs. Using incorrect parts can create issues.

Carburetor tags. Carburetor tag numbers are REQUIRED to determine the EXACT REBUILDING KIT for a carburetor. Tags are often missing and GENERALLY because the carburetor is NOT the ORIGINAL carburetor to the vehicle. Commercial carburetor rebuilders (selling their product through auto parts stores) GROUP many different but similar carburetors together under their OWN identification number, and throw away the tag so an informed customer does not know what he/she is receiving. Generally (NOT always) these grouped units will fit the manifold and function (although NEVER as well as the original), but internal parts may be different.

As far as the hard starting hot issue, please read this link: http://www.thecarburetorshop.com/Troubleshooting.htm#Hardstarthot

As far as the vapor bubble and carb running out of gas when running: As others have mentioned, an electric pump is a "pusher" type pump. It would push a liquid around the world, but it will not pull a liquid uphill more than maybe 2 or 3 inches! For proper results, the electric pump should be mounted as close to (and preferably below) the fuel tank as possible.

Again as others have mentioned, the fuel tank MUST have an operable vent to allow pressure inside the tank to equalize. Otherwise very little fluid could be added to the tank, and very little fluid could be removed from the tank.

If the electric pump is correctly mounted, AND there is so air leak between the fuel source and the electric pump, AND the fuel tank is correctly vented; then the electric pump would blow the vapor bubble out of the filter, and the carburetor would not run out of fuel.

DON'T GIVE UP! It will turn out to be something simple that has been overlooked, and a few years from now you will be able to tell the story and laugh about it.

Jon.

Edited May 7, 2014 by carbking (see edit history)

[carbking]

Mike - at 8500' you need MAJOR recalibration of the carburetor. Are you certain you have vapor lock, or is there a possibility that some recalibration might be needed.

In round numbers, at 8500' compared to standard carburetor calibration from the factory:

Idle fuel reduced by 15~18 percent

Cruise fuel reduced by 18~22 percent

W.O.T. fuel reduced by 22~28 percent

Jon.

Edited May 7, 2014 by carbking (see edit history)

[60FlatTop]

Jon,

Too bad you don't live in the frozen wilds of western New York. You could have joined three of my friends and I for coffee last Saturday morning.

I started the conversation off by saying "You know that forum I tell you about? They have had a topic going on vapor lock." We are old and the waitress thought we were all suffering from strokes! Spent about ten minutes laughing with tears in our eyes and telling stories about tin foil and clothespins.

You offer hope, anyway "few years from now you will be able to tell the story and laugh about it."

I was taught to be cynical, but i learned how by paying more attention than the teacher.

Bernie

[Aaron65]

A friend stopped by tonight and told me his car with an AFB won't start hot and he has vapor lock. I'll probably get it out here and fix it for him.

I WILL use test equipment on the car when I recreate the problem. The first check is compression, like the training video says and like I learned in 1959. You just don't waltz up to an engine and start monkeying around without and compression check and an ignition system inspection. When I get a no start condition I will check the secondary voltage to see if the cylinders are starved for fuel or rich.

Although this is a Mopar video, they do a good job overall. Pay attention to the antiperculation comments.

Bernie

I've got a cold and I couldn't sleep this morning...Watching "Tech" the carburetor guy didn't make me feel any better, but it did make me think I took too much Sudafed!

[60FlatTop]

It was a Mopar presentation so I think I'll Dodge any incriminating comments.

B

[Rosiesdad]

Uggg. Pretty bad u guys....

The air bleeds could be suspect. I had found a restricted primary tube when I bought it. I never boiled out the carb but it runs great and idles at 450RPM so it been good except for the starving / flooding scenario when hot. I read in the carb manual that a bowl vent problem would restrict high speed operation and I don't see that.

Gas line from pump is in the stock location gradually up to filter. I doubt I have 9psi out of this pump especially at idle as my voltage drops to 5 pretty quick. I think this battery is junk already! I am anxious to get some heat around here. Maybe this weekend try the new filter again.

Cheers,

Phil

[Rosiesdad]

Thanks Jon, but I would have to get rid of the pedal starter to use the hot start advice. I agree with the idea though.

p

[Rosiesdad]

You are not alone. Check out the insulation on this fuel line.

[ATTACH=CONFIG]246361[/ATTACH]

Problem with insulation is that it eventually gets up to temp and doesn't really do anything at that point. I do use insulated reflective panels to shield my Freon lines from the tube headers in the BMW though.

[Rosiesdad]

I may look into the heat riser again but it appears to be frozen where I left it. Considering welding it up!

[JohnD1956]

After looking over this thread again I think we glossed over the problem that was mentioned back at post 19. That being a sticky float. Reading the description at post 18 you said you sometimes released the vapor bubble by removing the sight plug and pushing down on the float. Bob pointed out that if there was a flow blockage before the carb, the float would have already been at the bottom of the bowl. Further you indicated doing this resulted in a flooded engine, which makes me wonder because pushing down on the float would open the needle valve to fill the carb's bowl, not operate the throttle to open the butterfly valves or activate the fuel pump. Therefore the carb should fill with gas only.

Maybe we could get a better description of what you did to the carb when experiencing this situation?

Also I keep seeing the picture from the other thread where the fuel line on the straight eight is directly attached to the down draft pipe. If your line is also attached there I would try to do something about insulating the line at that location.