vapor lock

[Don Jordan]

I think I'm familiar with the concept but then what? I was just out for a drive (about 90° +/-). My car runs about 180°. Thought I'd stop for a beer. When I was done I went out and the car would not start. Would not pop or sputter. I pushed it out of my parking spot and tried to bump start it in reverse going down the drive way. Nothing. It's a long and unbelievable story how I got home but I did. It's getting spark and fuel. I waited over night and today it still won't start. It was running fine when I shut it off. (that's actually a funny line).

I've heard old wives' tales about clothes pins on the fuel line. Any merit to that? I had a new garage built and I can't get my cars in it.

[TodFitch]

If you waited overnight and it still won't start, then it is something other than vapor lock. . .

[Don Coatney]

Remove your spark plugs and report what they look like.

[Young Ed]

If you are getting spark and fuel that rules out any sort of vapor issue. As Tod said vapor lock wouldn't last overnight. Typically vapor lock is actually the carb flooding over and flooding the engine. You'd have to have some pretty serious flooding for it to not have evaporated overnight.

[De Soto Frank]

Tod and Don have good suggestions.

 

Another couple things to remember:

 

1) True "Vapor lock" occurs when the engine is running.

 

 

2) "Percolation" is what happens when you park the vehicle "hot", the fuel in the carb bowl boils, and gets forced through the jets into the manifold, OR, the carb-bowl simply boils dry.

 

Modern, ethanol-blended fuel is especially susceptible to percolation.  It doesn't do this in a fuel-injection system, because those are a "closed loop", under high pressure, which prevents the fuel from boiling and flashing into vapor.

 

Try a shot of starting fluid on it;  if it still doesn't start or even try, that suggests spark issues.

I have found that carbureted vehicles with down-draft carbs tend to start hard when they are hot, due to percolation.  I usually depress the accelerator slowly to the floor while cranking, and hold it there until the engine starts.  This helps clear-out the excess fuel.  When the engine starts, it usually runs rough and belches black smoke for a few seconds until the engine clears-out the percolated fuel.
 

Happens with my '41 De Soto, '61 Rambler, '60 Chrysler,  anything with a down-draft carb.  

The Model A doesn't do this, because it has a gravity-fed updraft; (and if the fuel in the carb does boil, it just drips out the air-horn onto the ground)  but it HAS actually vapor-locked while waiting in line at a Turnpike toll-both on a very hot day.

Good luck with your P-15 !
 

 

Frank

 

[desoto1939]

This sounds more like electrical than fuel issue.  I would suggest that you might want to chnage the condensor.  This might have gone bad on you. Try than and also check the points gapping. 

 

I do not think its the coil since if the coil got real hot and an internal wire in the winding broke then the car when hot sometimes will not start but then when they cool down the wire then are cooled and they then make contact and the car would fire up.

 

Check the battery cabales to make sure they are not loose onthe posts and also where they attach to the motor or other point on the car. Check the rotor and cap.

 

Just points to look at first.

 

Rich HArtung

desoto1939@aol.com

[54Illinois]

Gas can sit in the manifold overnight and prevent the car from starting.  Just turn over the engine and work out the fuel through the motor, do not pump the gas. 

[Don Jordan]

Is there some sort of test for the condenser? This car is just not going to start for me. Now I know why people always refer to them as girls - they are so temperamental. I've got in on the charger right now - it's much too hot to stand outside. I think I'll wait till it cools off and then check the points.

[ptwothree]

" I had a new garage built and I can't get my cars in it. "   That's a funny line too!

[Don Coatney]

Check the spark plugs and report the results.

[Don Jordan]

I bought a new condenser and tomorrow I will pull a plug or two. I'm grasping at anything now...

[De Soto Frank]

While you're in the distributor,  check the insulated jumper-wire between the insulated terminal on the side of the distributor body and the points.

 

 

This little guy is famous for chafing and shorting against the breaker-plate, and/or the wire strands fatiguing and breaking inside what appears to be a perfectly good wire.   

 

 

 

(And before folks  start recommending electronic ignition conversion,  I'll just state for the good of the order, that in nearly 30 years of driving old six-volt iron, both as daily-drivers and privileged garage-queens,  I've never "had to" convert from six-volts or from breaker-points.  Have found both to be quite reliable.  The '41 De Soto in my avatar is still running on stock ignition system, with its original spark plug wires (!), distributor cap, and "Solar-Spark" coil, at 72 years and 105,000+ miles. )

Edited August 8, 2013 by De Soto Frank

[John Reddie]

Ah yes DeSoto Frank, that pesky little pigtail wire. I had that happen to me once and it drove me almost insane until an old time Plymouth mechanic told about that wire. The wire flexes as the breaker plate moves when you accelerate and the vacuum advance is working. Over time, the wire can break down and fail. It could very well be Don's problem.

John R

[austinsailor]

I find it interesting that we have all these suggestions of fixes for spark problems, and nowhere has it been determined that spark is the problem.

It's just too simple to either stick an extra plug on a wire, or pull the coil wire, crank and watch.

Am I missing something?

And I agree with Desoto Frank. Points systems work fine. An added advantage is, if you have a problem you can usually get it going again with a screwdriver and maybe a bit of sandpaper. If those fancy systems quit, what the heck can you do??

[Alshere59]

Reading the posts I see two from Don to pull the plugs. Those are looking for fouled plugs due to "flooding/percolation"? If it is percolation then you may need to lower the float. A search will get you that info. True vapor lock. Maybe but on the long list of things to check IMHO. (After looking at fouled plugs from flooding.) Then carbs as mentionted.

The as mentioned above electrical.

[Tom Skinner]

Put wooden clothes pins on the gas line.

Problem solved.

 

It cools the gas lines somehow?

The car starts right up - no problem.

Its the magic of the wooden clothes pins.

[Tusler 49 New Yorker]

Tod and Don have good suggestions.

 

Another couple things to remember:

 

1) True "Vapor lock" occurs when the engine is running.

 

 

2) "Percolation" is what happens when you park the vehicle "hot", the fuel in the carb bowl boils, and gets forced through the jets into the manifold, OR, the carb-bowl simply boils dry.

 

Modern, ethanol-blended fuel is especially susceptible to percolation.  It doesn't do this in a fuel-injection system, because those are a "closed loop", under high pressure, which prevents the fuel from boiling and flashing into vapor.

 

Try a shot of starting fluid on it;  if it still doesn't start or even try, that suggests spark issues.

I have found that carbureted vehicles with down-draft carbs tend to start hard when they are hot, due to percolation.  I usually depress the accelerator slowly to the floor while cranking, and hold it there until the engine starts.  This helps clear-out the excess fuel.  When the engine starts, it usually runs rough and belches black smoke for a few seconds until the engine clears-out the percolated fuel.

 

Happens with my '41 De Soto, '61 Rambler, '60 Chrysler,  anything with a down-draft carb.  

The Model A doesn't do this, because it has a gravity-fed updraft; (and if the fuel in the carb does boil, it just drips out the air-horn onto the ground)  but it HAS actually vapor-locked while waiting in line at a Turnpike toll-both on a very hot day.

Good luck with your P-15 !

 

 

Frank

I have a 49 New Yorker with the L8 and it is doing the exact same thing. Cold it starts great everytime but after driving a while and turning it off, go into the store and when I come back out to start it, it is flooded everytime. The only way I have found to get it started is hold the pedal to the floor so a bunch of air can get in while cranking on it and so far it starts before the battery quits. When I shut the eng off it gets so hot I can not touch anything around the carb. The carb has been rebuilt and a full tune up done. The old motor runs great otherwise.

[55 Fargo]

hello, this topic has been discussed many times over the years, and almost deserves a section or sub-section of it's own. I have had the percolation difficulty starting too over the years. The 47 Chrysler would do it on hot days, and with 6 volt systems, a little more challenging. The 55 Fargo truck does it to, but with a 12 volt system, not very difficult to restart no matter what. 

If you search this topic, you will find a lot of threads with a lot of good advice and info...happy motoring

 

Tod and Don have good suggestions.

 

Another couple things to remember:

 

1) True "Vapor lock" occurs when the engine is running.

 

 

2) "Percolation" is what happens when you park the vehicle "hot", the fuel in the carb bowl boils, and gets forced through the jets into the manifold, OR, the carb-bowl simply boils dry.

 

Modern, ethanol-blended fuel is especially susceptible to percolation.  It doesn't do this in a fuel-injection system, because those are a "closed loop", under high pressure, which prevents the fuel from boiling and flashing into vapor.

 

Try a shot of starting fluid on it;  if it still doesn't start or even try, that suggests spark issues.

I have found that carbureted vehicles with down-draft carbs tend to start hard when they are hot, due to percolation.  I usually depress the accelerator slowly to the floor while cranking, and hold it there until the engine starts.  This helps clear-out the excess fuel.  When the engine starts, it usually runs rough and belches black smoke for a few seconds until the engine clears-out the percolated fuel.
 

Happens with my '41 De Soto, '61 Rambler, '60 Chrysler,  anything with a down-draft carb.  

The Model A doesn't do this, because it has a gravity-fed updraft; (and if the fuel in the carb does boil, it just drips out the air-horn onto the ground)  but it HAS actually vapor-locked while waiting in line at a Turnpike toll-both on a very hot day.

Good luck with your P-15 !
 

 

Frank

I have a 49 New Yorker with the L8 and it is doing the exact same thing. Cold it starts great everytime but after driving a while and turning it off, go into the store and when I come back out to start it, it is flooded everytime. The only way I have found to get it started is hold the pedal to the floor so a bunch of air can get in while cranking on it and so far it starts before the battery quits. When I shut the eng off it gets so hot I can not touch anything around the carb. The carb has been rebuilt and a full tune up done. The old motor runs great otherwise.

 

 

[Don Jordan]

It's getting to be that time in the desert. I am familiar with the concept of vapor lock but I don't exactly know what it feels like. I was driving down the road and the car just quit running - stopped. I thought it was out of gas so I went and got 5 gallons ($20.00) and it started right up an went for about 5 miles and stopped. Not knowing what else to do I put in another 5 gallons. (my gas gauge has been a bit inaccurate). Today when I picked the car up (interior work) drove it home and it purred. All I could think about was it was over 100° on the way in and in the 80°s on the way back.

a conundrum at best.

[_shel_ny]

Sounds like it could be a problem in the tank.

[Don Jordan]

I just got a used tank and had it boiled out - I sure hope that's not the problem - again.

[John Reddie]

Don,

  It could have been vapor lock at the high temperature that you mentioned but possibly a weak fuel pump as well. One of the P15's that I had was doing that. It would die out and not restart. A short time later it would be fine again until it had run for a while. Check your fuel line from the pump to the carb and be sure it isn't close to the exhaust manifold and be sure the fuel pump heat shield is in place. If it occurrs again, remove the air cleaner and work the throttle while looking into the carb throat. If it is fuel related, you won't see any gasoline squirting out. Good luck to you.

John R

[Jeff Balazs]

This sure doesn't sound like the classic case of vapor lock to me. It seems to me that if you were rolling down the road at speed and it just cut out......it is either a fuel supply issue or an ignition problem. I would start by testing the fuel pump against a pressure gauge. If that reads say 3# to 5# then I would pull the distributor and check the leads inside for fraying etc.....and replace the condenser while I had it out.

 

Most vapor lock or heat related fuel issues tend to show up when at idle or more often while attempting a hot restart.

 

Hth.

Jeff

[Don Coatney]

Actually vapor lock is explained very well in posting #5 of this link.

 

http://p15-d24.com/topic/33817-vapor-lock/

 

Why a second thread was started on this topic by the original poster is a mystery to me. Very little if any of the advice given in this first thread was followed.

[Plymouthy Adams]

it has only been 10 months Don C.  this stuff takes time ya know...