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Stalling Vapor Lock?


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I've had some issues trying to work the bugs out of this car so hopefully someone can help. A while back I had problems with the vacumm tank. We thought it was the carburetor so we put a rebuilt one on and had the same problem with sputtering and stalling. Once a new vacumm tank went on that problem went away. Also had/have problems with my radiator being clogged. After rust from the engine getting into the radiator I had some over heating problems. After many flushes I finally got it to stop over heating in cooler weather. (I am currently having a radiator recored)

So today just for giggles I thought I'd run the car in this 90 degree heat to see if it would over heat. After a couple of minutes with the car just sitting and idling it would stall out.I thought great! I have vacumm canister problems again. I took the canister out and filled the outer tank with fuel and ran the car. Same thing. It would stall. I removed the glaas bowl to see if any setiment was obstructing the passage to the carb. I didn't see any. The one thing I thought was strange was that when I replaced the glass bowl and opened the valve to let the fuel drop down from the canister, it only came down in tiny dribbles. Only when I loosened the glass bowl holder to let air in did it come gushing down like it normally would??? Is this normal?

I drove this car the other day in cooler weather and it ran perfect for hours. The only thing I can think of is vapor lock??? The fuel line from the canister to the carb is about 1 1/4" from the manifold. Too close? Suggestions??

Incidentally, when the car would stall, I would add a little extra fuel to the canister and after a few minutes it would fire right back up and run great for a few more minutes and then stall out again. Am I barking up the right tree or should I consider looking at other things??

Thanks in advance!

Dan

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Thanks Big Mark but my fuel lines are all copper so that wouldn't help. Nearchocolatetown.. Can you explain to me what it would tell me if there was fuel in the bowl of the carburetor or not? I have heard of vapor lock occuring within the carburator but I can't imagine that happening here because it is an updraft carb and it it is below the manifold and as we know heat rises. The line from the vacumm canister that supplies the carb is right next to the manifold. That is were I suspect the vapor lock is occuring.

If vapor lock were occuring in that line wouldn't it be disrupting the feed to the carburator and thus there would be a lack of fuel in the bowl? At the same token, if there was an obstruction some where in the line wouldn't there also be a lack of fuel in the bowl?

I'm just trying to undersatnd what it would tell me if there was or wasn't fuel in the carb.

Thank you for the reply

Dan

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Nearchoclatetown.. If you'll notice in my other threads I'm asking for clarification because I DON'T have the answer!It doesn't make sense to me. And some opinions I get from other people in other places on the forum are beneficial because some body very knowlegeable will only read certain posts.

As far as you not being able to see the car and know the history. No kidding?! That's why some body invented the forum!

If you don't know the answer to my question I understand. But don't try to turn this on me as if I'M being out of line here because I am not. I am just trying to learn.

Dan

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  • 3 weeks later...

Sounds more like your vacuum tank is not dumping the load of gas once its float triggers it. Check to see if manifold vacuum is reaching the vacuum tank. Then check to see if the gasket between tank and top casting is not blocking the hole for the atmospheric bleed tube (the little bent copper tube coming out of top) There is one "odd" hole in the gasket and it must be aligned with the bleed tube hole. Also make sure you dont have all sorts of loops in the gas line to the carburetor. I have seen some of those loops so severe that they prevent gravity feed down to the carburetor. They also trap gasoline making a perfect place for so called vapor lock.

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Dan-

One way to solve it, is an electric fuel pump- I've been thru this many times- I know not original, but neither is the 2008 gas we get. You can hide it under the frame & install a switch behind the dash.

Have to watch pressure at the carb, but that can be solved.

Yea, the old 30s cloths pin trick, rag of water around the line, thing like they did in the old days-

It's up to you- It's just good fun anyway ( keep your cell phone handy !!!)

S Jones

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May be I can help. I have spent the last four weeks fighting the rising waters which has flooded my barn and caused me to lose a lot of parts. Lets see if we can solve your problem. Lets think about how an old car with a vac system works and where the problems occur. Starting at the back of the car you have a fuel tank. The first problem you can have is rust and gunk coming out of the tank. You mentioned a fuel filter which should be installed between the tank and the vac tank not between the vac. tank and the carb. The second problem can be a perforated line in the tank due to water rusting through the fuel line. The next potential problem is the vac tank which can have a plugged vent hole, a leaking vac. fitting a bad float or a leaking gasket. The next potential problem would be the carb which could have a bad float, a float set wrong or a bad needle valve. When I try and solve this type problem I start at the carb. and work backwards. Crack the inlet line to the carb and see if you have fuel. If you do then you have a carb problem. If you do not have gas then the delivery system has a problem. The next problem is vapor lock which occurs when gas vaporizes in the line and creates an gas vapor embolizim blocking gas from coming down the line. Putting a electric fuel pump will not solve the problem only create additional problems. Cars with mechanical or electric fuel pumps can still have vapor lock and we didn't solve the problem until we put return lines in but what a fuel pumps causes with old carb is flooding due to over powering the needle valve. If you have no gas at the carb disconnect the line from the vac. tank and see if you have fuel coming out. If you have fuel coming from the tank and none at the carb you probably have a vapor lock. Some mechanics put a loop in the line between the carb and tank, some put insulation on the line and cover it with aluminum foil and I have seen the cloth pin method tried. If you do not have gas then check the vac. line and make sure it is not plugged on leaking. If you have a fuel filter remove it and see if it helps. The reason you do not put a filter between the tank and carb is that gravity is the only pressure you have and you will compromise it with a filter. A filter between the vac. tank and the fuel tank works better because it is on the suction side. smile.gif

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Sorry some of the 'posters' appear difficult.

Check some other things which can be made more pronounced with higher outside temps:

1. remove # 1 spark plug and look for soot; carbon. Means too rich a carb mix. NAPA and the DB Club vendors sell new plugs. NAPA required a purchase of a box of 12 when I bought because special order. That way you have 6 in block and 6 ready to go. Check the garage section on this site for plug number and torque values. Turn down carb idle as soon as engine runs. Look as tail pipe: is it sooty carbon? Too rich

2. Replace spark plug cables between spark and distributor. Many purists insist on the old time color braided cables with the push in connectors. Skip those and buy the new molded modern cables. Measure them but roughly: 2 @ 15 inches; 2 @ 12 inches and 2 at 9 inches.

3. Consider the after market electronic ignition distributor from Romar or Myers or other reliable DB vendors. You do need a compatible coil. It makes a big improvement.

None of these directly address your vapor lock concern but in my experience the above issues can amplify out of tune conditions with hot weather or run temperatures.

Paul

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  • 2 years later...

have you tried using alot of choice words throwing your keys down wondering if God hates me wile sitting on the running board and crying , I currently have the same problem on a beautiful 1936 dodge d2. That's what i do but im thinking Jan Anett seem to make the most sense

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  • 1 month later...
  • 8 months later...
Amigo, Did you ever get your problem resovled? I have a 1936 D2 as well that doesn't start when it is warm. You too?

amigo seems to have figured it out on this post...

http://forums.aaca.org/f143/1936-dodge-doesnt-start-when-hot-174348.html ;)

(Sorry for the "rediscovery" of an old post. Just making sure some followup questions get covered.)

Edited by 1936 D2
added info (see edit history)
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1936 D2,

Thank you for following up! I no longer have the problem of my Dodge not starting when it is hot. I think the main culprit of my problem was my fuel pump, because shortly after my post, the car would stop running after about 10 minutes of driving. I decided to replace the fuel pump and things are fine now. In addition, I have also replaced the battery, plugs, plug wires, points, condensor and distributor cap just to be safe. So I think it is the combination of all of the above that have helped me, but my guess is that the fuel pump was the main driver since once it got hot, it didn't perform well and just got worse and worse. It worked fine when it was cold.

Slow progress, the deck lid is done and the passenger rear fender is done and now we are just driving it around until the weather warms back up and my father in law can move to the passenger front fender. We are keeping it drivable during the "restoration". Next on the list is a new wiring harness for the entire car. Any suggestions on where to look? Rhode Island Wiring was mentioned.

I'm sure I'll be back in touch once we run into some challenges.

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Pretty sure Rhode Island is where I got my replacement. (I also had them put wires in the loom for directional signals and fog lights so those wires don't show as loose wires. They did a very nice job with that!) I think there was a post here for discussion on wiring looms earlier. Try a search in the "Dodge & Dodge Brothers" forum and see what comes up.

Sorry for stepping on your post "29Chrysler".

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Hi. Brian here. There is a great joy that overcomes oneself when one troubleshoots a problem yourself, and succeeds in finding the problem........ So lets start at the beginning...........You have an engine that gets starved for gas,and then quits, this is something you KNOW to be true. Start with the tank where the fuel begins......first open the fuel cap partially so you are SURE its vented. you may have to temporarily secure it so it doesn't completely fall off. And you don't want to leave it off completely and have gas sloshing out of it. Try to run it untill warm(or as long as you ran it to see the problem arise). If it runs good and doesn't die, then you HAD a venting problem. If it dies, we go to the next step. We want to see if there is an obstruction in the tank or fuel tank line to fuel pump. Disconnect the fuel line where it connects to the fuel pump. attach a plastic or rubber hose to the end and BLOW air into it to see if you can blow air into the tank. Take the gas cap off to ensure you are able to easily overcome the atmosphere that resides on the tank. If you blow through bubbles relatively easily, you KNOW the fuel is able to pass through the line from the tank to the fuel pump. If in blowing into it you meet resistance to getting air through, you may have an obstruction in the fuel line (gummy gas?) or sediment/etc. in the tank, obstructing fuel flow. Once you have ruled out venting, and obstructions, you then check out the fuel pump, the next item in line.......The fuel is SUPPOSED to go to the upper chamber of the vacuum tank via the simplest of pumps.....ATMOSPHERIC PRESSURE.... pushing on the fuel UNOBSTRUCTED from the PROPERLY VENTED fuel tank. (which you've of course allready checked out, and found to not be an issue). The atmospheric pressure gets a little boost to push fuel by the SUCTION that comes from turning the engine over, and letting the pistons do a little sucking via a line connected to the fuel pump from the INTAKE MANIFOLD with the throttle closed(so it can't draw air through the carburetor air inlet) Once inside the upper chamber the fuel then flows by gravity into the lower chamber, and flows from there via fuel line into the carburetor float chamber carburetor (also via gravity) So............what you'll be looking for is.......Is your vacuum line from the intake to the fuel pump clear and SECURE? Is there any loss of suction through the intake via a leak somewhere in the intake to carb side? (so it can help suck fuel out of the tank). Is the passage from the upper chamber to lower chamber (fuel pump) able to flow? Blocked? (where the fuel drops by gravity to the lower chamber) Is the line obstructed from the fuel pump to the carb float? Having systematically checked all these things in order, and ensuring fuel flow right up to the carb float. About the only thing left, assuming the carburetor is functioning properly, and there is no major overheating condition, that would leave the carb float sticking as a possibilty, also there is a screen that could be plugged in the inlet to the float, where the fuel line comes into the float. I hope this stuff makes sense to you. If not, just ask and i'll see if i can walk you through this thing. Hope this helps. Regards.

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