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Old 06-24-2020, 09:38 PM   #1
zoegrant
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Default Vapor lock or not ?

The flathead in my 36 Ford runs with the following temperatures after a good 10 mile run at 50 mph and an even 5 minute shutdown. ambient TEMP OUTSIDE 80.. Temps are then taken with lazer temp gage...Car is very difficult to start. Radiator is aluminum.

CYL HEADS...201---203
INTAKE...200
CARB...124
FUEL PUMP...140
WATER PIMP...145
GEN...197
GEN CUTOUT...165
RADIATOR...140
COIL...119
STARTER...122

I am presuming vapor lock is my hot start problem...there is a phenolic block under the carb. There is room to install another phenolic spacer on top of the old spacer....WOULD THAT HELP ?
ANY SUGGESTIONS ?
Thanks ...
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Old 06-24-2020, 10:03 PM   #2
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Default Re: Vapor lock or not ?

Check/clean your battery connections and all ground connections....
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Old 06-25-2020, 02:50 AM   #3
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Default Re: Vapor lock or not ?

It was running when you shut it down. So there must have been fuel in the carb float chamber.
Unless it leaked out there must be still fuel in the carb. So why won’t it start?
I would guess there is a tiny crack in the carb base allowing the fuel to drop down into the manifold and flooding the engine. I had that happen on a Pinto. It took a few months to figure it out but I took the top off the carb after it sat five minutes and the carb was dry.
A junk yard carb cured the problem.
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Old 06-25-2020, 06:56 AM   #4
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Default Re: Vapor lock or not ?

Leaking power valve ? Even with a spacer the carb. or fuel pump may be hot enough to percolate our crap fuel........ .02 cents or nonsense ?
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Old 06-25-2020, 08:29 AM   #5
Seth Swoboda
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Default Re: Vapor lock or not ?

Make sure your ignition system is operating at 100% efficiency. A weak coil, bad wires, a distributor that needs rebuilt or timed can cause you a lot of starting problems.

Do you have an electric back up fuel pump mounted inline near the fuel tank? When I experience vapor lock I flip my under dash electric fuel pump switch to clear out the fuel vapor.

Normally when I restart and the engine is hot, I don't have a problem with starting. After I drive a short distance and the fuel in the float bowl is used up, the vapor lock becomes evident. Therefore, I think some of what you are experiencing could be ignition system problems.
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Old 06-25-2020, 09:16 AM   #6
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Default Re: Vapor lock or not ?

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Or maybe it needs a little more gas to start hot? I know it goes against logic but that is what it takes to start my Merc. Always give one pump on the gas pedal on a warm/hot start or else it will crank without firing up. Probably just unique to the condition of my carburetor but it wouldn't cost much to try on yours.
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Old 06-25-2020, 09:36 AM   #7
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Default Re: Vapor lock or not ?

Zoegrant


A lot of good info here, so far. Were it me....I'd follow "Petehoovie's" advice first and easiest to do, GOOD grounds are OH SO important. Then I'd follow SethSwaboda's advice and "make 100%" sure your coil is good (Has Skip put his magic wand on it?), points and timing are good (have you had Mike at Third Gen work his magic on your distributor?) and your condenser is solid. NEXT, just for extra insurance.....I'd check all my fuel line connections and make triple sure ALL the fuel line connections are GOOD and tight!!! THEN IF the problem persist we can work from there!!!! Just my $ .02 worth
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Old 06-25-2020, 10:16 AM   #8
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Default Re: Vapor lock or not ?

If your issue is vapor lock, it isn't really a carburetor condition. It's from heat in the fuel supply lines or fuel pump that boils the fuel and the fuel pump can't push it anymore.

Sal
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Old 06-25-2020, 10:26 AM   #9
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Default Re: Vapor lock or not ?

What is vapor lock?
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Old 06-25-2020, 11:04 AM   #10
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Default Re: Vapor lock or not ?

You need to check your fuel pump pressure . I had similar issues with my 41 Ford pick up with a worked over flathead. I installed a electric fuel pump before the old mechanical pump and the problem went away.
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Old 06-25-2020, 05:57 PM   #11
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Default Re: Vapor lock or not ?

Quote:
Originally Posted by Kube View Post
What is vapor lock?
Here is Wikepedia's definition.

Sal

https://en.wikipedia.org/wiki/Vapor_lock
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Old 06-25-2020, 07:06 PM   #12
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Default Re: Vapor lock or not ?

I never had a vapor lock until I put dual exhausts on my ‘46 Ford.
Every time I was in a lineup on a hot day that turkey would vapor lock.
This week I am changing the engine on a ‘46 Mercury coupe with dual exhausts.
Today I noticed the entire left exhaust pipe n muffler is within 4 inches of the fuel line, except right where the clutch pedal pivots. There it is two inches away.
The owner said on warm days it was so bad the couldn’t drive it so the put an electric fuel pump on it.
the GD fuel line is too close to the exhaust system!!
When I get done with the engine isolation I’m gonna reroute the fuel line just to prove to him what is causing the vapor lock.
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Old 06-25-2020, 10:36 PM   #13
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Default Re: Vapor lock or not ?

5 minutes is not enough time to percolate fuel out of the float bowl, especially with a phenolic block; or leak down from some little flaw in the carb. Even if the fuel pump is vapor locked, it should re-start and run for a while on the gas in the carb.

Have you tested the spark. It is very common for the ignition coil to weaken as it gets hot. Enough spark to keep it running, but not enough to start it after sitting.
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Old 06-26-2020, 12:16 AM   #14
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Default Re: Vapor lock or not ?

Quote:
Originally Posted by Kube View Post
What is vapor lock?

Ha....! You got 'em AGAIN! DD


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Old 06-26-2020, 11:18 AM   #15
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Default Re: Vapor lock or not ?

Yah, that's a real rip snorter.

Sal
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Old 06-26-2020, 09:41 PM   #16
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Default Re: Vapor lock or not ?

Maybe, there is an issue with the coolant system. Hot temp of 200-210 is not usual. I have to work the motor a lot to get there. Grounds have nothing to do with engine temp... but an electrical issue. Look at how it cools. Exhaust manifolds is not a horrible idea, but how did people get around back in the day.

Last edited by Tinker; 06-26-2020 at 09:47 PM.
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Old 06-26-2020, 09:51 PM   #17
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Default Re: Vapor lock or not ?

Too throw another monkey wrench in the gears. Octane was half of what it is today... block the heat risers, take the temp stats out, and have a good coolant system. But i'd guess you need another condenser or coil on hard starts. or you need a good rebuild stromberg.

Last edited by Tinker; 06-26-2020 at 10:43 PM.
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Old 06-27-2020, 08:31 AM   #18
zoegrant
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Default Re: Vapor lock or not ?

There are a lot of good ideas here. the first thing I will check will be the spark from the coil after car is run enough to get it hot then wait a few minutes before testing the spark at the coil.
If it test OK then I will move in to all electrical grounds to make sure they are clean and tight.
From there I will change the condenser.

I am thinking that it is electrical as I do have an electric fuel pump that is inline before the mechanical pump and it does not seem to help start the car when hot.
The carb was rebuilt by professionals on this site a couple of years back.
No gas lines are near the engine except that the fuel pump sits on its stand on the block.
I WILL POST WHEN PROBLEM IS LOCATED AND CORRECTED.
Thank you to all with your possible solutions.
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Old 06-27-2020, 11:19 AM   #19
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Default Re: Vapor lock or not ?

If you can see two fine streams of fuel squirting when you look down the throat of the carb when you open the throttle, and you pump the throttle a couple times, the engine should start, unless there is another issue like the ignition.

Sal

Last edited by scicala; 06-27-2020 at 06:25 PM.
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Old 06-27-2020, 12:29 PM   #20
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Default Re: Vapor lock or not ?

Ive had in the past on my car, stromberg 97, float set perfectly to spec..
Lean of the engine in the car about 3 if I remember correctly. Gas will flow out the body of the carb where the emulsion tube enters the venturi. Trickles down into the intake manifold. Makes it tougher to start in a short time later.
If your parked on a slant with the front of the car higher than the rear it's worse yet.
I solved it setting the float level lower. In theory the spec. shows the gas in the carb. to be level. With the 3 slant its NOT.
So, I set the float lower, took it for a drive under different loads to see if it starved for gas. It never did.

Something to consider once you know all your electrical, fuel pump and lines, carb. are "known" good working order.
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