Vapor Lock

[Tiny]

I know some don't believe in it but I'm looking for some input on an issue I'm having.
My coupe has an OLD rebuilt motor there is a date of 060945 stamped on the block. I have rebuilt the water pump, distributor, and rewired the car. I used "modern" points and a B profile distributor cam because the price was right(free). Both Snyders parts.
It has a stock Tilotson X model that was also refurbished by yours truly. I say refurbished because I didn't drill out the plugs and replace them. I did however thoroughly and cautiously clean all the jets and passages as well as check the float level and mating surfaces. I have the yellow Tillotson book as my guide.
OK now that the back story is done
The car starts and runs great. The Temp comes up to about 145 and stays right there. I can let the car sit and idle for extended periods without issue. The problem comes when I shut it down, say at the gas station like yesterday. Fill her up and get ready to leave, she barely runs. Coughing and choking I'm barely able to get her going. As I try to drive away its as if I'm on a bucking Bronco not in a 31 Ford. After about 10 minutes of driving all is well again.
Anyone have any insight?
I'm thinking vapor lock but isn't that not a problem with Tillotsons?

Is it time for clothes pins on the fuel line?

As always thanks in adavance

[heneste]

Do you know if your tank is very clean inside? It may be that adding fuel to the tank stirred up any deposits you have at the bottom of the tank which could interrupt the fuel flow when you go to take off.

[Tiny]

The tank is not perfect but not a rusty mess. I forgot to ad that I have also just replaced the tank shut off and fuel line as well as put a pencil filter in the tank. This was a problem before I did these things though

[BRENT in 10-uh-C]

What is the exterior temperature this time of year??

[Tiny]

62-72 but it did it on a 38 degree day a couple weeks ago

[Tom Wesenberg]

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Forget the clothespins, you need to tape magnets to the fuel line to set up correct fuel molecular polarity.

Seriously, it sounds just like my car when I used the crap gas.
What kind of fuel are you using?
I had problems in the upper 70's and above, but below that I never had a problem, so you mentioned a problem in the 38* range and that's hard to explain.

[Tiny]

Tom
All we get is crap gas in California 10% Ethonal. It's driving me nuts. If I had hair I'd be pulling it out by now.

[Hicktick]

I think it would be impossible to get vapor lock at 38 degrees .

Normally vapor lock starts with cutting off at low idle .

[Tiny]

Maybe vapor lock is the wrong term. It only happens after it is shut down for a short period of time. Less than say 15 minutes. Would heat sinking be a better description maybe?

[whirnot]

It isn't the gas, there are thousands of A's running it in CO without issues.

[Tiny]

What the heck?
No thoughts or opinions fellas?
No talking dogs offering advice?
You guys are slipping.
No one has even derailed the thread saying Vapor Lock doesn't exist!!!

[Ron/IA]

Tiny - I have never experienced vapor lock. If I did, I didn't know it; I always looked for another solution to the problem. I might add that as long as I have been a member of our local Model A Club, I have never know or heard of anyone experiencing vapor lock. Thus, I won't have a solution for it.

However, I can offer one solution that worked after experiencing the same problem as you (engine not running right after short shutdown). After running the car long enough to thoroughly warm up the engine; when I stopped for a short time then restarted, it did not run well. I originally thought it was the carburetor. I completely cleaned and rebuilt it; all new parts, confirmed all passageways were open, repaired loose throttle shaft, etc. The engine continued to do the same thing.

Then I changed the distributor (using the club's spare we take along on tours), and all was well. I rebuilt mine from the ground up, and the engine has continued to run fine ever sense.

I am not sure which component of the distributor was causing the problem; as I didn't take the time to replace one part at a time. But I thought I would pass along my experience.

As they state: if you think it is an electrical problem, work on the carburetor; if you think if is a fuel problem, work on the electrical system.

Good luck.

[Hicktick]

Ok , it barely runs after shutdown ,

Will it rev up ???

Check to see if its firing all four plugs ,

When it does this do you move the spark ???

When you stopped for gas , do you close the fuel shut off ???

You must test to determine if its fuel or spark .

[Tiny]

OK now were getting somewhere
yes it revs up, in fact I set the idle higher with the hand throttle to help it stay alive, but its still runs rough.
Advancing the spark changes the conditions very little.
Yes if the motor isn't running the fuel is shut off.

[rons49]

I know I am bucking a lot of smarter fellows here, but 1. you restored the Tilly. Tillotsons have a nasty reputation of warpage of the white metal body that will cause issues of fuel mixture. 2. re check the float level. You may have a leak down of fuel into the carb while sitting. That will cause a rich mix upon restart( short time). It might be possible to crank the engine with the throttle wide open to restart. But, I would swap another carb that is known to run well. See what happens.

[QGolden]

Is it predictable enough so you can "make it happen" ? Will it happen in your own dooryard, or do you have to drive a distance first ? What happens if you drive to the Gas station, but do not stop and drive back home? Will it do it then? Sometimes you have to rule out Enviromental issues, which you have started to do by acknowledging that it happens over a range of temps. Might not be fuel, Could be a hot condenser. If you can make it happen in your shop you could do some electrical checks.

[Hicktick]

So when it runs rough , it will still rev up .

Next time it does this put you hand on the coil and see how hot it is .

I would change the condenser if the coil is ok .

[Tiny]

Ron I'm doubting its a warped carb but that cannot be ruled out yet maybe this weekend. I have a new gasket set on my bench.
QGolden Your line of thinking is a road I have been thinking about also. The plates, points, and condenser as I said were freebies but I believe were purchased from Snyders. They were new in the package, given to me by a hot rodder friend who said "your gonna need these, they came with a car I bought and sold a few years ago".
The other factor is:
Last spring I rebuilt the water pump. I left the hood off for most of the summer, as its a pain to put back on by oneself and it just seemed to never happen. I don't remember this being an issue before when it was off.

[Tiny]

Hick
Yes still revs up
I check the coil temp next time I start it. Hopefully in the morning
I may just change the condenser to eliminate it

[1937pickup]

I bet it is ignition-either coil or condenser.

[Tiny]

Originally Posted by 1937pickup

I bet it is ignition-either coil or condenser.

I'm starting to think you guys are on to something here.

[Duffy1]

Sounds like the gas cap is not venting . Had the same problem as you and turned out to the gas cap was not venting .

[Tiny]

New gas cap from Bert's. So I doubt it

[Jim/GA]

Originally Posted by Tiny

New gas cap from Bert's. So I doubt it

New repro 30-31 gas caps are notorious for not venting properly. Do not assume that new means good. Run a test with the gas cap loose to rule out a problem with the cap vent.

[bikejunk]

do you see gas dripping or smell gas when this happens ? next time you stop shut off the gas and see if their is any change, rule out one thing before going to the next
me thinks a new A&l condenser is in your future

[jrp]

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this happened to me. I found that opening the carb rich a 3/4 turn gave greater gas flow for a short time solved the problem soon you can return to usual adjustment

[t farr]

I also have a continuing problem with what I believe is vapour lock. When the fuel level reaches 40mm and Ive run the car hot, m/way or hill climb, then just after ive dropped the speed she stops dead. Put a gallon of fuel in it and away she goes. Its happened 4 times, twice in exactly the same circumstances. Has to be vapour lock, tank is perfect. Maybe not enough head of pressure to push the air through???

[Ron Lachniet]

I know most people say model a's don't get vapor lock but when I stop for gas on a hot day it is not unusual to be hard to start and runs rough for the first minute or so. I think todays gas has a lot to do with it.

[Tiny]

Update time!!!
I spent the day in the workshop. I'm almost embarrassed to report my findings.
I started with the ignition system.
The points were a little tight.
The timing had moved just a hair.
I checked the clearances in the body at the 4 lugs. They were at .004, .006, .014 and .016. They are all now .025.
I also replaced the condenser for good measure

I took it for a test spin at this point and it was better but not right.

Upon returning home it was peeing fuel out of the carb.
I took the carb off and apart thinking stuck float. When i disconnected the fuel line nothing drained out. The tank valve was shut after the motor had been shut down. I cleaned and blew out all the passages. Then regasketed the carb with new and reinstalled it.

It started right up and ran great. I let it warm up and went for a test spin. After about a 5 mile drive I stopped at a buddies to shoot the breeze. After 10 minutes it was test time. She fired right up and drove home without any issues.

My final diagnosis
I don't believe it was a true vapor lock.
What I had was " the Death of a Thousand Cuts" or a lot of little issues becoming a big problem.

Thank you everyone who offered advice.
I love this place

[QGolden]

Glad you figured it out!

[Tiny]

Thank you I am too.
Thanks for your solid advice also

[tbirdtbird]

I am glad it is fixed but I have no idea what the problem was.

Vapor lock is a very real issue but prolly not what you were experiencing, esp at cooler temps.
Wonder if your gas line was too far into the carb, touching the back wall and cutting off fuel flow. This could have been corrected when you removed the carb.

I have experienced vapor lock on cars since the '60s, many diff. kinds of cars, incl. Model As. Once you have had it happen it is unmistakeable. It is the only self-correcting problem I am aware of.

I was also gonna suggest changing the condenser/ or coil; they can be sensitive to heat

[dixieroadster]

i had this same problem if you are sure all your electrics are good what finaly fixed mine was marvyl mystory oil a gas aditive

[Tiny]

I run MMO in every tank of fuel and in every oil change. Love that stuff!!
Went for a spin today. Issues still appear to be solved. I'm trying to make it on my first club tour in about a week so I want it running tops. Nothing like the new punk kid showing up for his first tour and breaking down. I don't wish to be that guy

[Patrick L.]

Just got to read this post.
Does the fuel line have correct pitch ?
Some fellas have brought up the theory of an improper ground and that the fuel line may be acting as a ground causing the line to get hot/warm.

[Ron/IA]

Tiny - In your post #29, you mention the clearances between the distributor body contacts and the rotor contact was from .004" - .016". This discrepancy just might have been your main problem. (Speculation on my part only.)

This item is very often over looked, but is just as important as the gap at the sparkplugs.

Glad you got it running.

[Tacoma Bob]

Quit screwin around and remove the gas cap. It sounds like the vent is full of rust. Just enough venting to let it idle until the second coming of you know who but when under load it runs out of venting air. Try blowing the rust out of the caps...it may help. Been there and it drove me nuts. Next time it happens, immediately and SLOWLY remove the gas cap. If you hear a swwoosh of rushing air that's it.

[Tiny]

Bob
Its not the gas cap. Never has been. That's an easy fix. Read response #29. It was much more than a simple clogged vent

[Tacoma Bob]

LOL Glad the problem is solved. I was speaking from personal experience and it was trial and error for me. Part of the problem in my case was two fold as I was running a micro filter and a pencil filter. The micro filter collapsed after being freshly installed and the I discovered my gas cap full of rust and swoooosh when I unscrewed it. New gas cap and no micro filter.....life has been good for 10 years. Whiskey for me and fresh horses for my men!

[jm29henry]

I am on the same band wagon try and chance your condenser it cheep fix and easy to do!!!!!!!!

[Tiny]

Problem still solved. Ran some errands last night after work with the boy. Got the approval of all the hobos that hang out around the post office.
I'm very familar with the gas cap issue as my car had a quail and a radiator cap when i bought it!!