Was this a vapor lock?

[harmony]

I've never had a vapor lock happen but I have read the threads here about it. One thing though that I don't recall reading is a starving for fuel from the fuel pump.  Does that happen?

 

I filled up about 40 miles ago.  I drove the car to the painters which was about a 40 minute drive a few days ago.  I just picked the car up and did the same return trip.  It ran smooth as usual coming home.  Thankfully I got right to the entrance of my shop.  I shut the car off and took some pictures.  About 15 minutes later I tried to start the old girl and drive it into the shop and it wouldn't start, it tried once with a little sputter, but that was it.  I tried pumping the gas ( which I never have to do) and still nothing.  I popped the hood and there was lots of gas around the base of the carb and even on the inner fender.  I thought at this point maybe it was a stuck float bowl.  But then I noticed that the clear see through fuel filter just prior to the carb was empty.  I thought maybe with fuel all over the place I went through a tank of gas somehow.  Not likely but I was just speculating so I jumped in my daily driver with a 5 gallon can of gas and filled it up at the gas station.  I was back at the car in maybe 15 to 20 min.  I started to fill the tank and I could hear the gas coming up so I watched for it and sure enough it came up the filler neck after I put in about maybe 3 gallons.  I then tried to start it and after a few tries it fired up.   I got her back in my shop and after I shut her down I popped the hood again and now the fuel filter was full.

It was a long day so I decided to investigate further tomorrow by pulling the carb and seeing if anything looks weird.

The temperature as around maybe 18 C or 68 F.  

Was it a vapor lock?

[Sniper]

No, it's Carburetor Percolation

 

https://www.carburetor-blog.com/knowledge-base/what-is-carburetor-percolation/

 

Vapor lock happens when the engine is running.  Carburetor Percolation happened after you shut it down. 

[harmony]

Thanks for the link and explanation sniper.  I've always used 94 octane and I have the fuel pump shield installed.  It wasn't even a hot day or a long trip,  so it looks like the fix would be to install an electric fuel pump.  I was following along with a recent thread.  Some guys even suggested blocking off the manual fuel pump hole and just running the electric fuel pump only.

Well I guess this will be my next project.  My memory is sooooo bad.  I can't remember tooo much about that thread but will I have to run a return line back to the fuel tank if I run only the electric pump?  

[harmony]

I just found that thread I was referring to, and Sam Buckanan set me straight about not needing an extra return line and I believe I'll be looking for a Carter 4259 pump

Edited April 8, 2022 by harmony

[Young Ed]

Before you do all that check your float setting. Also are you sure you didn't pump it before you tried to start? It's a habit for many myself included but my plymouth starts much better when hot if I can remember to just hit the key.

[harmony]

3 minutes ago, Young Ed said:

Before you do all that check your float setting. Also are you sure you didn't pump it before you tried to start? It's a habit for many myself included but my plymouth starts much better when hot if I can remember to just hit the key.

Pretty sure Ed.  The only time I ever give it one pump is when it's dead cold first thing in the morning.  But what threw me off was the empty fuel filter.

[harmony]

I'm wondering if the gas cap failed to vent?  Obviously the fuel tank wasn't empty, but maybe taking the cap off, allowed the tank to vent and then when I hit the ignition after adding gas, that's when the fuel filter refilled.  Maybe?????

[Bryan G]

13 minutes ago, harmony said:

I'm wondering if the gas cap failed to vent?  Obviously the fuel tank wasn't empty, but maybe taking the cap off, allowed the tank to vent and then when I hit the ignition after adding gas, that's when the fuel filter refilled.  Maybe?????

I could see that happening. I think some more testing is in order; hopefully it won't happen again but if it does you can approach it scientifically, trying one thing at a time. 

 

I had one old car that had terrible problems with gas boiling out of the carb in the summer. I found that adding a gallon of kerosene or diesel (to a full tank of gas) helped the situation, and I saw no unwanted side effects.

[harmony]

4 minutes ago, Bryan G said:

I could see that happening. I think some more testing is in order; hopefully it won't happen again but if it does you can approach it scientifically, trying one thing at a time. 

 

I had one old car that had terrible problems with gas boiling out of the carb in the summer. I found that adding a gallon of kerosene or diesel (to a full tank of gas) helped the situation, and I saw no unwanted side effects.

interesting

[Sniper]

An electric pump won't fix the issue of percolation.  It might make it easier to restart though.

 

Might be a case of winter gas, which evaporates easier in cold weather but can lead to this issue when it heats up.

[harmony]

3 minutes ago, Sniper said:

An electric pump won't fix the issue of percolation.  It might make it easier to restart though.

 

Might be a case of winter gas, which evaporates easier in cold weather but can lead to this issue when it heats up.

 I filled up the tank on Sunday.  The previous gas in it was only a week old as well.  

I've driven in much much hotter weather and even at parade speeds.  Shut her down and restarted with no issues at all.  Not to mention each time I stop to refuel each time.  The engine is off for maybe 5 minutes for that refill and she always starts the instant I bit the button, no pedal.

[harmony]

Maybe the old girl isn't happy with the paint job I gave her, and she's letting me know. ?

[Sniper]

30 minutes ago, harmony said:

 I filled up the tank on Sunday.  The previous gas in it was only a week old as well.  

I've driven in much much hotter weather and even at parade speeds.  Shut her down and restarted with no issues at all.  Not to mention each time I stop to refuel each time.  The engine is off for maybe 5 minutes for that refill and she always starts the instant I bit the button, no pedal.

 

Something changed.  You didn't do anything to the car, who knows what gas was at the station.  I don't know when you change over where you live, but it is a possibility that you bought winter gas.  Your gas essentially boiled out of the carb.  An electric pump won't stop that all it will do is refill the bowl.  Did you happen to touch the carb or fuel line to see if it was excessively hot? 

 

https://www.gasbuddy.com/go/summer-blend-and-winter-blend-gasoline

[Sam Buchanan]

My P15 starts nearly instantly five minutes after a hot shut down. But wait 20 minutes and it struggles a bit.

 

Yes, fuel percolation as the gas boils in the hot carb, overflows the bowl and dumps raw gas down the intake manifold. Now we have a “flooded” carb. Some cranking is needed to clear the puddle in the manifold and regain proper fuel/air mixture. Pumping the gas pedal is the kiss of death…

 

Winter gas really makes this situation worse because the higher vapor pressure makes the gas boil at a lower temp.

Edited April 8, 2022 by Sam Buchanan

[keithb7]

I’d be inclined to monitor it more before throwing a pump at it. 
 

We know your engine was at full operating temp. This actually takes a while. 180 on the temp  gauge does not mean its warmed up. It means the hottest part of the engine, the cylinder head is warmed up. The other 700 pounds of steel and oil takes a wile to heat up fully. 
 

Meaning short trips 15 mins or so and less, then shutting it off for for fuel at the gas station the engine is not quite a big heat sink yet. 
 

After your longer drive it was indeed a massive hot, heavy, chunk of steel. You shut the engine off for 15 mins. Is it possible the carb bowl percolated? Yes. What about the fuel in the filter. Where did it go? Drain back thru the fuel pump to tank? Doubtful. The fuel pump 1 way flow valves prevent that. 
 

Edited April 8, 2022 by keithb7

[harmony]

17 minutes ago, Sniper said:

 

Something changed.  You didn't do anything to the car, who knows what gas was at the station.  I don't know when you change over where you live, but it is a possibility that you bought winter gas.  Your gas essentially boiled out of the carb.  An electric pump won't stop that all it will do is refill the bowl.  Did you happen to touch the carb or fuel line to see if it was excessively hot? 

 

https://www.gasbuddy.com/go/summer-blend-and-winter-blend-gasoline

No, I didn't think to see if the carb or fuel line was hot.  But I did hit the throttle linkage while under the hood at one point and I removed the air cleaner and I touched the choke plate.  Nothing felt abnormally hot.  Mind you I did have some gas in a jar in my shop.  ( not old gas)  So at one point I poured a bit down the carb to see if that would get it to start.  While pouring the gas in the carb, I noticed some steam/vapors rising, so maybe that indicated that the carb was indeed hot.

[harmony]

14 minutes ago, keithb7 said:

I’d be inclined to monitor it more before throwing a pump at it. 
 

We know your engine was at full operating temp. This actually takes a while. 180 on the temp  gauge does not mean its warmed up. It means the hottest part of the engine, the cylinder head is warmed up. The other 700 pounds of steel and oil takes a wile to heat up fully. 
 

Meaning short trips 15 mins or so and less, then shutting it off for for fuel at the gas station the engine is not quite a big heat sink yet. 
 

After your longer drive it was indeed a massive hot, heavy, chunk of steel. You shut the engine off for 15 mins. Is it possible the carb bowl percolated? Yes. What about the fuel in the filter. Where did it go? Drain back thru the fuel pump to tank? Doubtful. The fuel pump 1 way flow valves prevent that. 
 

Yes the empty fuel filter is a head scratcher.  What about my theory of by removing the gas cap, it allowed the tank to vent, and that allowed the fuel pump to draw fuel again? 

So while I was trying to start the car, cranking maybe a total of 2 minutes, 15 seconds each time (guesstimate), than that might have drained the gas out of the filter.  If the carb was flooded at this point then that might explain gas on the carb body.  Beats me how it got as far as the inner fender. 

 

Mind you, the cap looked fine.  I can look closer tomorrow.  But it's the same cap as always and it worked fine all the way home.  A few stop lights and it idled fine and accelerated fine.  

[harmony]

If it starts up normal tomorrow morning, I'll perhaps try to recreate the event.  Drive 40 minutes or so.  Come back to my shop, shut it off for about the same time frame and then pop the hood and restart it from under the hood and watch the fuel filter.  I have one of those hand held remote push button stater gizmos with the alligator clips.

 

Nope that's a lie.  Were supposed to get a few days of rain, so after the rain I'll try that.

 

So Sniper, why would the carb be hot after 40 min with outside temp being around 65 F ?

I'm not educated enough to make a valid comment on winter blend vs summer blend.  However I drive the car each month of the year and almost at least 50 weeks of the year when it's not raining or snowing, and I've been doing it for 3 years and this is the first time this has happened.

Edited April 8, 2022 by harmony

[Sniper]

7 hours ago, harmony said:

So Sniper, why would the carb be hot after 40 min with outside temp being around 65 F ?

 

Stuck heat riser valve is the first thing that comes to mind.  I usually give mine a wiggle whenever I am under the hood and the engine isn't hot.  If I remember, lol.

[Merle Coggins]

For Hot restarts I find that holding the throttle open (about 1/4 - 1/2 throttle) will allow a quicker start. The fuel percolation issue pushes fuel into the intake manifold and the engine is flooded. Holding the throttle open gives it more air to counter the flooded condition and allow the engine to start.  

[Sam Buchanan]

7 minutes ago, Merle Coggins said:

For Hot restarts I find that holding the throttle open (about 1/4 - 1/2 throttle) will allow a quicker start. The fuel percolation issue pushes fuel into the intake manifold and the engine is flooded. Holding the throttle open gives it more air to counter the flooded condition and allow the engine to start.  

 

That's the technique I find most useful as well if the car has sat for 15 minutes. Holding the throttle open reduces intake vacuum so more fuel isn't drawn into the carb which would make the problem worse. Once the engine has cranked enough to clear the puddle of fuel it starts.

 

I don't think ambient temp has much to do with this. The carb is bolted to a chunk of iron that is in turn bolted to an even bigger chunk of iron that gets pretty hot regardless of air temp. 

Edited April 8, 2022 by Sam Buchanan

[keithb7]

One little intricacy I have noticed with my recently rebuilt flathead.  When the engine is stone cold, I flip on my electric pump for a few seconds to build pressure and ensure the carb bowl is full. I then turn the pump off again. I give the throttle 1 pump to stroke the accelerator pump once. Injecting shot of raw gas into the intake. It does not atomize at this point as everything is cold. I hit the foot starter and she rolls over super clean and quick. Fires up in less than the blink of an eye.

 

A hot engine, this spring, that very well likely has winter gas in the tank; after sitting for 15 mins or so, it is a little stubborn to start. I do not give it any throttle at all. I hear the starter straining more. Definitely laboring more to crank the engine over. The battery is certainly not weak and the generator is working very well. It was just rebuilt too. I too believe this is from percolation. The fuel boiling out of the carb. Flooding it while sitting.

 

I know my exhaust manifold diverter valve is working. I just rebuilt it and tested it. I run the fuel pump heat sink plate. I run a heat sink plate at the bottom of the carb.

I have a rebuilt mechanical fuel pump and carb. Electric pump for back up and priming.

 

Seems to me it's likely a winter fuel problem in my example. We'll see. My laboring starter to me is an indication the engine is flooded. The tonal difference in the starter turning over is a clue to me.

 

[1949 Wraith]

1 hour ago, Sam Buchanan said:

 

That's the technique I find most useful as well if the car has sat for 15 minutes. Holding the throttle open reduces intake vacuum so more fuel isn't drawn into the carb which would make the problem worse. Once the engine has cranked enough to clear the puddle of fuel it starts.

 

I don't think ambient temp has much to do with this. The carb is bolted to a chunk of iron that is in turn bolted to an even bigger chunk of iron that gets pretty hot regardless of air temp. 

I also give about 1/4 throttle on restart after 15-20 minutes (coffee stops). Vehicles will start right up cold or after 1 hour, but shutdown for around 15 minutes the flooding of perculation can be an issue.

[harmony]

1 hour ago, Sniper said:

 

Stuck heat riser valve is the first thing that comes to mind.  I usually give mine a wiggle whenever I am under the hood and the engine isn't hot.  If I remember, lol.

I have mine sprung open all the time.

[harmony]

Thanks guys but at times I'm a little thick headed.  I'm not understanding why if the carb percolated this one time.  Why only this time?  Why not every time I stop to get gas or stop to buy a poverty pack of beer after a nice long drive?