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Curios, vapor lock or ?
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udoittwo
Posted 2020-04-07 8:10 AM (#596538)
Subject: Curios, vapor lock or ?


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Location: Valley Forge, Pa.
I've had this problem for 15 years but never really bothered with it, just curios if it is vapor lock or ?

I have a 1960 318 stock motor with stock 2 bbl car. If she's only been sitting a couple days, she'll fire up before half a rotation.
If its set for more than a few days, it take several cranks until it fires. Guessing the fuel leaks out. Not external.

When I go some where, if it is only a short trip, it will fire right up. If it get hot, it takes 10 seconds of cranking to start and I sometimes smell fuel but no external leaks.
I've rebuilt the carb a couple times. I've put 4 different correct stock carbs, including an NOS and a factory rebuilt on it with the exact same conditions. Set float levels, ect.

Again, I've had this issue from day 1 so I don't too often even think about it but now I have more time than I care to have sitting at home,
I'm wondering if they all do this, is it common, is there a fix? The bowl seems to be empty after sitting but there's no sign of gas in the oil. Does it bleed back into the tank?


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wizard
Posted 2020-04-07 10:15 AM (#596545 - in reply to #596538)
Subject: Re: Curios, vapor lock or ?



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The modern fuel has a lower steam point than the old "true gasoline". Also the modern fuel tends to have a blend of 5% ethanol.

What will happen is that when you stop the engine with normal operating temperature (hot), the fuel in the carburetor bowl will boil and leak down into the intake manifold. As the valves in the fuel pump has become weak with age and/or ethanol, the fuel leaks down to the same level as you have in the tank.
Hence the carburetor is next to empty and the fuel line from the pump up to the carburetor is also empty.

With cold engine, the fuel has evaporated, due to the above and the longer time without starting. Worst case, the pump has to start suck from the tank instead from the fuel line.

Actually, there's nothing you can do about this, strange thing is that two identical cars, with the same carburetor and engine could show very different results.

The only thing to do is to mount an electrical fuel pump, either as a prime pump, or to replace the mechanical pump.

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58coupe
Posted 2020-04-07 1:22 PM (#596547 - in reply to #596538)
Subject: Re: Curios, vapor lock or ?



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Wizard is correct, the technical term is "vapor pressure" If you want to confirm this, wait until your gas tank is close to empty and add about 10 gallons of aviation gas to see if the problem goes away. It has a much higher vapor pressure so it will not cause this problem at high altitude. (this is not technically legal for on-highway use, you didn't hear this from me)
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60 dart
Posted 2020-04-07 4:25 PM (#596557 - in reply to #596538)
Subject: Re: Curios, vapor lock or ?



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use an inline one way fuel valve after the fuel filter before the carb and your problem will most likely go away but you have to make
sure the valve stays clean----------------------------------------------later
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ronbo97
Posted 2020-04-07 11:49 PM (#596565 - in reply to #596557)
Subject: Re: Curios, vapor lock or ?


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Wizard, I tend to disagree. My 58 Plymouth 318 2bbl will sit at a car show for hours. When I turn the key, it starts right up after one crank. I'm wondering if udoittoo has the glass bowl filter attached to the carb. My glass bowl is always filled to the top with fuel. So the pressure from the pump will push that fuel past the needle into the carb and start the car. It might take a week for the fuel in the bowl to fully evaporate. It doesn't happen in a couple hours.

Ron

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wizard
Posted 2020-04-08 2:38 AM (#596574 - in reply to #596538)
Subject: Re: Curios, vapor lock or ?



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As I wrote Ron, "strange thing is that two identical cars, with the same carburetor and engine could show very different results".

A friend with a 61 New Yorker 413 engine has big problems, my 60 Saratoga with a 383 engine has minor problems.
Practically the 413 and the 383 is the same engines, with the same type of carburetor, fuel pump, fuel lines and tank.

For this, I have no explanation as I have adjusted the ignition timing and carburetor on both cars……...
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udoittwo
Posted 2020-04-08 8:03 AM (#596579 - in reply to #596538)
Subject: RE: Curios, vapor lock or ?


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No glass bowl and I've had a few fuel pumps over the years.

Actually, the last one I replaced a few years ago failed out in the sticks when I was taking my Dad fishing. It was sort of funny. I was going up this dirt road with a farm house every 1/2 mile or so and just passed this young couple walking.
A 100 years passed them and it died. Sat for a moment as the couple got closer and it started up. Drove for a few seconds and it died again.

The young couple got a little closer this time and it started. Same thing but this time the couple passed by. Always wondered what they were thinking about these 2 old guys in their old car stalking them or something?
The pin that the fuel pump push rod pivots on fell out. Pulled out one of my arm rest screws. Had a small nut and cross threaded it on and off we went.

That's what I like about older vehicles. Carry some assorted tools, some odds & ends hardware, duct tape, a length of wire, possibly rope and you can temporarily fix 90% of the problems at least enough to get you home.

Thanks for the impute. Again, really not too concerned just wondering if it was a common thing or what might be the cause and I agree, every car has it's own quirks and personalities.
Shes starts if it's ZERO or 95 degrees, never overheats on the hottest days towing my boat yet I've had cars that overheated at 85 on a flat road. Replaced water pumps, thermostats, radiator, rebuilt motor, gauge, ect.
Why don't my brakes work after $1000s spent and more than 6 "EXPERT" mechanics working on them yet your car stops on a dime?
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ronbo97
Posted 2020-04-08 8:23 PM (#596600 - in reply to #596579)
Subject: RE: Curios, vapor lock or ?


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OK. 1960 parts book says that the glass bowl was replaced with a sealed filter between pump and carb. Glass bowl would show you if pump is working or not. And you could watch the bowl fill as engine was cranked.

Pin falling out of fuel pump ? You must've bought a piece of junk, since I've never seen or had that happen. Also, never seen a fuel pump fail suddenly. If they go bad, you can see them leaking. But they will still work, more or less.

Ron

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udoittwo
Posted 2020-04-09 10:15 AM (#596624 - in reply to #596538)
Subject: RE: Curios, vapor lock or ?


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The pin fell out and at that point, it wouldn't pump. I have no idea what make the pump was. I'm fairly sure it would have been an Ebay item.
If your interested, I'll look for it. If I still have it, I'll show you a picture.
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wizard
Posted 2020-04-09 3:57 PM (#596632 - in reply to #596538)
Subject: Re: Curios, vapor lock or ?



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Just started up my car today after two weeks in the garage, ambient temperature 64º F.
Continuos cranking for 7-8 seconds before start.

Normally I don't crank more than 4 seconds, but I wanted to know.

Hypothetically, that means that the carburetor bowl was empty or next to empty and the fuel line down to the pump empty as well.


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ronbo97
Posted 2020-04-09 9:08 PM (#596636 - in reply to #596632)
Subject: Re: Curios, vapor lock or ?


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wizard - 2020-04-09 3:57 PM Just started up my car today after two weeks in the garage, ambient temperature 64º F. Continuos cranking for 7-8 seconds before start. Normally I don't crank more than 4 seconds, but I wanted to know. Hypothetically, that means that the carburetor bowl was empty or next to empty and the fuel line down to the pump empty as well.

Wiz - Does your car have a 2bbl or 4bbl carburetor ? My Plymouth has a 2bbl, where my Desoto has a 4bbl. While the Plymouth bowl will fill and start up fairly quickly, it takes significant time to fill the 4bbl bowl after sitting for a month or more. Which makes sense since the bowl is larger on the 4bbl WCFB than on the Stromberg.

What car/engine do you have ?

Ron

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wizard
Posted 2020-04-10 1:39 AM (#596640 - in reply to #596538)
Subject: Re: Curios, vapor lock or ?



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The engine is a 383 cui with 4bbl carburetor Ron.
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wizard
Posted 2020-04-10 1:18 PM (#596655 - in reply to #596538)
Subject: Re: Curios, vapor lock or ?



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The day after the first test, the car started next to immedeately, perhaps half a revulotion on the crankshaft. Not over one second.

In operating temperature, parked for 2 hours, I had to crank for 3-4 seconds.

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udoittwo
Posted 2020-04-19 3:50 PM (#597086 - in reply to #596655)
Subject: Re: Curios, vapor lock or ?


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That's exactly what mine does so it is probably not a problem, just the way it is. I have been dealing with it like that for years.
The only time that it would be a problem is if the battery were weak but if I pay attention, that should never be a problem.

Not that this is related but yesterday my boss called me up to go with him to look at a car in a garage that he said has been sitting for a few years. To my total surprise, it was a totally complete 1969 Corvette Coupe and it has been sitting since 1986. A true barn/garage find. The #s match and it has 95,000 with a 4 spd. 350/350 hp. My boss was looking for something cheap that he could drive around and wanted no parts of it. The owner inherited the house and he wanted the car out so he could put a gym in the garage.

I offered $1500 and he was happy. I am ecstatic. In 1973 I had a 69 Vette with same body and color except it was a 427/435 HP. This picture is what happened to it. I am hoping for better luck with this one although I'll probably just sell it.
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udoittwo
Posted 2020-04-19 3:51 PM (#597087 - in reply to #597086)
Subject: Re: Curios, vapor lock or ?


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dpolara
Posted 2020-04-20 11:46 PM (#597164 - in reply to #596655)
Subject: Re: Curios, vapor lock or ?



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Wizard and Ron, thanks so much for the feedback. I've had the same problem with mine as well. 383 4bbl. I've started carrying a portable battery charger because sometimes I have to crank it quite a while to get it started when the engine is hot. And yes, 100LL AvGas does help...I won't tell you how I know :).

Thanks again!
Dpolara
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udoittwo
Posted 2020-04-22 6:31 AM (#597211 - in reply to #597164)
Subject: Re: Curios, vapor lock or ?


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My friend has a 79 Triumph motorcycle. All he ever runs is av gas. Can steady use of it do any damage. Does it burn hotter? Since I've know him, he's had trouble with the motor.
I think he had it rebuilt twice and has had valve issues or what ever it uses. Honestly, he gets talking and there's no stopping him so I sort of turn off when he talks about his bike which is all the time.
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58coupe
Posted 2020-04-22 8:16 PM (#597236 - in reply to #596538)
Subject: Re: Curios, vapor lock or ?



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The lead additive in avgas produces a coating on the exhaust valves that actually helps protect them from burning. That is why when the auto industry switched to unleaded, they had to start using hardened exh. valves and seats. It also is 100 octane which works good in high compression engines. The only downside to using avgas is it will foul sparkplugs sooner. Of course, I wouldn't advertise I was using it in a motor vehicle.
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Woodruff
Posted 2020-04-23 10:55 PM (#597277 - in reply to #596538)
Subject: Re: Curios, vapor lock or ?


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Pump regular fuel today is 50% vapor @ 170* F. So say you are running a 195* T-stat. You shut the car off and walk into the store, your engine temp spikes to 210-215*. Consider an older model Rochester Quadra-jet, which already suffered from not enough bowl capacity, then put on top of a big block in a vette, which gets hardly any fresh air by comparison. All the fuel was gone before you even ordered your whopper! As far as the continuous cranking after a couple days of sitting, this past Tuesday I drained a Holley bowl full of pump regular into an open container, and left it out on the bench in the shop. About 30 hrs later it was completely evaporated. I like the later model a Thermo-quads with an electric bowl vent that sealed off the fuel to the atmosphere, when the vehicle wasn’t running.
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51coronet
Posted 2020-04-24 9:32 PM (#597311 - in reply to #596538)
Subject: Re: Curios, vapor lock or ?


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Electric fuel pump and a check valve near the carb will help this. I am pretty sure your fuel bowls are empty or near empty when this problem occurs. Wizard is correct. If you want easier starts use an electric pump let it prime up for a few seconds then crank the engine, also use a magnetic pickup distributor or pertronix. These will make hard starts really easy provided everything else is good to go. Small investment for easy starts.
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