The Stovebolt Site Forums The Shop Area Engine Shop Vapor Lock, is it possible with a 216 at only 90°?

I’d like to here from some of yous guy livin’ in the tropics or other wise known as the Sun Belt. Just how typical is vapor lock in your 216 with the stock single action fuel pump and fuel line routing?
The temps are just now getting into the 90’s around here, I know, I know, that’s sweater weather for you guys out there in Phoenix, but twice now I have experienced the truck feeling like it is running out of gas. It wants to go on its nose when I step on the accelerator and I have to nurse it up to speed and it seems better once I’m up to cruising speed and she will run right along at 50-55 mph but still acts like it’s running lean. When I stand on the pedal. A little choke helps it accelerate better. I prayed to make it home before she shut down, just can’t afford those charges for the car hauler.
When I got back in the garage yesterday, I checked and cleaned both the fuel filters, the glass one on the pump, which had a little sediment, but nothing on the filter screen and the AC sediment filter just before the carburetor, which had no sediment in it at all. I checked all the vacuum lines, cap, rotor, points (right at .018” dead nuts) they are all new parts with in the past 2k or so, I checked all the primary and secondary wiring, it’s new also and intact, nothing is broken, corroded or loose.
My fuel is standard 87octain 10% alcohol which probably will vapor lock quicker than a straight non-alcoholic fuel or a higher-octane fuel with a higher vapor pressure.
When I first pulled into the garage I popped the hood and noticed that there was a steady trail of small bubbles rising up the side of the glass bowl on the fuel pump. It looked like from under the gasket on the passenger side of the bowl, i.e., directly opposite the block. This continued for quite a while after the engine was shut down.
So, have any of you warm weather pilots experienced vapor lock problems?
Denny Graham
Sandwich, IL

Denny, No 216 experience but I ran my 235 as a yr. round daily driver for 14 yr.@ approx. 12K mi/month, no problem. Doing the same with a 292 now. Been probably 20 days over 115 deg. this season already. Look at some old pics of building Boulder Dam in Vegas, for example, if you need some inspiration how good these old motors are.
As a side note, I've never used lead substitute in the gas, either.
Doug

Denny,
Another 216 in the frying pan of the USA. Never has vapor locked on me. Should be 108 degrees today.

Where is your fuel tank located? If it's still inside the cab, a true vapor lock situation would be nearly impossible, because there's a gravity flow from the tank to the pump. The old flathead Fords and some of the early Cadillac OHV V-8's had chronic vapor lock problems because of the distance the vacuum side of the pump had to lift the gas, over 13" in some cases. Gasoline under high vacuum conditions and high temperatures will vaporize in the fuel lines, and the pump doesn't like to move vapors, only liquid. If the pump is at or below the outlet of the tank, vapor lock is highly unlikely.

What can, and does happen is a vacuum leak that develops at the inlet check valve of the pump. Remove the inlet line and adapt a vacuum gauge to the pump. Run the engine at idle for a few seconds on the fuel left in the carbutetor float chamber, then shut it off. The gauge should show 10 inches of vacuum or more and hold the reading for several seconds after the engine stops. Not enough vacuum, or an immediate loss of vacuum is good reason to replace the pump.

A similar check should be done at the outlet. First, pump gasoline into a container with the engine idling. A good pump should produce at least a pint of volume in 30 seconds at idle speed. Pressure on a gauge should be 3 to 5 pounds with the pump deadheaded against the gauge, and should stay put for several seconds after shutdown.

I used to run the pump test in this sequence- - - -volume, then pressure, then vacuum. Failing either the pressure or vacuum test was cause to replace the pump. Low volume, but good vacuum made me check for tank pickup restrictions, and/or a kinked or clogged line from tank to pump. 13 years of driving a high-performance flathead Ford V-8 gave me lots of practice at fuel pump testing. Most of my fuel supply problems were solved by using a Carter fuel pump!
Jerry

What you describe is textbook for what I've always called vapor lock. Right, wrong or in between, the way vapor lock was explained to me by a 40 year master mechanic was that the problem is on the push side of the pump. Any engine at normal operating temp will give off enough heat to vaporize some of the fuel in the line between the pump and carb. The greater the heat the more fuel is vaporized. If the pump is too weak to overcome the vapor and pump enough gas to the carb you experience vapor lock. You are basically running out of gas. Eventually the fuel pump will fail completely. If you are seeing a line of bubbles rising from the diaphragm (the diaphragm is also the gasket between the pump halves) in the glass bowl you possibly have a failing pump. The best way I know of to check it is to rebuild or replace the pump.

Just for giggles, Have you checked the fuel filter. a dirty filter will cause the symptoms you describe.

denny,

have never experienced vapor lock here in the lovely southwest, but my 216 does tend to want to run a little "funny" when it gets hotter. actually what i notice the most is after repeated stops in 100 plus, i actually have to choke it a bit when starting and upon initial driving in order for it to run decent. have always wanted to investigate this condition more but since it hasn't stranded me just yet, it has not been a priority.

i haven't checked compression or valve clearance or had any major part of the original engine apart at all (unlike the work you've done) so i have no idea if that would cause this problem, but it seems like yours should be running like a top.

will be curious to see what you find out.

I got my first 216 when I was 14 in 1951 (1937 Coupe) I have had 216's and 235's off and on ever since and never had vapor lock problems. I have had to install electric back up pumps on some other vehicles to push the gas past the vapor lock. Cadillac Feerd, Dodge come to mind. But again the fuels we get now, that they call gasoline are far different then what we used to get.
Cleon

Ya got a point there Jerry, she’s all stock 1950, and I got’um full fuel tank also, which puts tops out about level with the air cleaner. Back to the drawing board. I’ll give the pump a test and see if the check valve is solid. Not sure if the symptom fits though, she runs right along at highway speed.
Then again, it might just be time to put that new double action pump on that I’ve been saving for a rainy day. Just didn’t want to get into the vacuum plumbing quite yet.

Jerry is right as far as Vapor Lock taking place on the vacuum side. In an airplane this becomes a real problem the higher you go when using standard auto fuels. Avgas is formulated with a higher vapor pressure because of the decrease in pressure at altitude. As the pressure on a liquid decreases it wants to convert to a gas. Just the opposite is true, that’s why liquids with a very low vapor pressure like liquid Nitrogen or Oxygen are stored under pressure, at standard pressure they are a gas.
Thanks guys for your thoughts.
I’m swinging more along the lines of there maybe is something has gone wrong in the good old Rochester ‘B’ or else as Jerry suggests, the pump is going getting ready to go south.
Then again maybe the check valve had some crud wedged under it. Now that I think about it, when I cleaned the fuel pump sediment bowl out there was this one strange piece of thin silver plastic or paint flake about 1/4"x 3/8" all by itself in with the rust powder. I didn't think much about it because I was thinking, that's what the screen is in there for. But if that got stuck in the check valve that could cause the problem that Jerry described. An inline filter before the pump might also be on the addenda for this weekend.
Denny Graham
Sandwich, IL

Vapor locking is more common in older vehicles now than 40 years ago because unleaded is more prone to vapor lock than the old leaded gas. I have a couple of c stores that have been in the family 45 years. We had to get rid of the suction dispensers and put in submerged pumps when unleaded came out in 1975. I would not put a filter between the pump and the tank. A restriction would cause the pump to break vacuum like holding your hand over a vacuum cleaner. It was very common in the 50's to wrap insulation on the fuel line between the pump and the carb. It was also common to put a bunch of wooden clothes pins on the line to dissipate heat. When 10% alcohol was tried in Texas in the 70's, one of the downsides was vapor locking. There is no problem because EFI requires an electric pump. I would stay away from the alcohol blends and probably rebuild the fuel pump.

My favorite cure for vapor lock is wooden clothes pins on the fuel line between the pump and carb dropping the temp somewhat. Of course a quick fix is to remove the gas cap and blow real hard which will break up the vapor.

That clothespin thing is Voodoo... but I know guys who swear it works.

Back in the 60s we used to wrap our fuel lines with aluminum foil clamped on with clothespins (spring type) to prevent vapor lock. The foil acts as an insulator and cooling fins. If I were doing this today I'd use wire ties instead of the clothespins.

But- - - -but- - -those clothespins look so cool! It doesn't really matter that it would take a dufus with the IQ of a rutabaga to believe something that hokey would really work!
Jerry

Can't get away from alcohol blends here, all gas sold in Illinois is 10% Ethanol.

Taint vapor, I'm convinced now it's internal to the Rochester.
Got the carb off but I'm finishing up putting a couple of HO52 carriers back together so I haven't had time to autopsy the carb.
Denny Graham
Sandwich, IL

An old timer once told me 90-percent of fuel problems are electrical.
Electrical issues will often act like fuel starvation.

I just went on Power Tour, and for one day rode with a guy in a 383-powered Road Runner that was having vapor lock issues. While honkin' down the highway, no problem. When stuck in slow-moving traffic, it'd vapor lock. The night before, during a parade, the fix was to let it cool down, then the problem went away. I wasn't there, but I think they also soaked a shop rag in water and put it on the fuel pump. When I was there, they tried the same thing.

Finally, after the fuel pump was cold to the touch, and the fuel filter up by the carb was, we jumped back in. And under any load, it would cut out again.

That's when I told them what the old man told me.

The coil was horrendously hot. We soaked the rag and laid it on the coil, until the coil was cool. Fired up like a champ and we were on our way.

When you're driving down the road, the air flow through the engine is also hitting the coil, and cooling it enough to keep things running. When you get stuck in traffic, it's a hot day, and the coil is questionable, you end up with "vapor lock" issues.

Try replacing the coil.

-Brad

Pull the choke out a little, runs fine, not electrical, something not right in the carb, must have picked up something through the filters, no time now to autopsy!
Denny G