230 I6 and HEAT Questions

[meadowbrook]

Hi folks. I really enjoy this forum, it's a big part of the joy of owning an old Mopar (even if it's a D34 )

I wonder what your thoughts are concerning my experience below.

I drove the Dodge all day Sunday and it ran pretty well in the hot weather (around 85F) around town. It started to vapor lock whenever I would run at higher speeds in the highway (at the lofty 2500 RPM range at 75-80 MPH…love the overdrive) and then stop at a light. So I would keep revving the engine to keep the fan blowing at higher speeds. The car would then buck as I accelerated for the 1st ¼ mile or so and clear up… until I stopped at the next light (no longer going up to 75 now, just around 45). I developed quite a technique to keep from stalling .

When I got home, I tweaked the idle speed a little higher to around 600 RPM(I have to tweak carburetors for no reason:D) and I can see why the vapor lock occurs, I burned my hands just from the radiated heat from the manifold as I tweaked the idle speed screw and the fuel line is very close to that area before it goes in the carb. I wonder also if the fuel in the fuel bowl was what was boiling and starving then engine of fuel, but I heard no boiling sould when I shut the engine off. This is not surprising as the intake manifold is bolted to the exhaust manifold and the exhaust gases actually are routed under the carb area of the intake to reduce icing in cold weather, I suppose that is no help in really hot weather. There is a thermostatically controlled flap to divert the exhaust from that area as the engine warms up, and I replaced that with a new one and the weight looks to be in the right (closed) position when the car is running, so I am sure that’s not the problem

The engine itself never overheated, though, the temp gauge stayed at the normal position. I did hear these cars had a very good cooling system for the time…not bad for a 62 year old radiator and engine (never rebuilt).

I want to try the old vapor lock ‘fix’ I heard of putting clothes pins on the fuel line to see if it works or if it’s bunk. It should not work according to physics and I can see the wooden pins catching fire, but hey, you only live once.

BTW, I do have the heat shield in place by the fuel pump.

[Plymouthy Adams]

first question of the day back to you is this..is your heat riser stuck?

[Young Ed]

You can also remake that fuel line a little longer and have it as far out from the manifolds as possible.

[1941Rick]

Is the heat shield in place around the fuel pump?

[JBNeal]

I had stalling issues on my '48, so I installed a heat shield sleeve on the fuel line from the fuel pump to the carburetor after routing a new fuel line, keeping as much distance from the manifold as the line is at the carburetor. To keep the sleeve in place, I used a long piece of aluminum electric fence wire I had laying around to tie it off at the carburetor, then coil it around the sleeve to make it look like a compression spring. The truck ran much better in the 90+ heat.

[meadowbrook]

Thanks for the responses, as clarification, yes, the shield is in place and the minifold 'flapper valve' does move freely.

Sounds like I should insulate the fuel line by the carb.

Curious, has anyone heard of the clothes pin 'fix' for vapor lock (I hear some folks swear by adding clothespins to the fuel line and it 'fixed their vapor lock. I have a hard time believing this works unless they added so many to the line near the manifold they effectively insulated the line.

[Don Coatney]

What is vapor lock and why do you think that is your problem?

Do a forum search for "vapor lock".

[55 Fargo]

Sounds like my issues once in a while in the 85-90 degree heat, while not sure you have what is referred to as "vapor lock", or modern gasoline getting good an hot and reeking havoc.

I have employed the methods you have described, at stop lights, rev up engine, gets the fuel flowing, less problems when cruising at speed.

Under hood temps get quite high, the nature of the mechanical fuel pump, the pathway of the fuel lines, and the carb, get good and hot. I knwo this does not happen in my case, at cooler temps, say 70-75 and under, it is when it starts to get good and hot outside.

Like you, my engine temp stays very stable, maybe climbing an extra 5-10 degrees on hot days, this can climb even higher, when pushing engine at higher rpm too.

The mentioing of "Vapor Lock", gets some peoples temp rising, not sure if it really exists, or if the gasoline, with the now ethanol blend gets good and hot.

Last week on an 85 degree day, after a good ride, did notice the very warm gaoline, do some funny things in the see through filter, looled like it was expanding, bubbling a little too.

Man, maybe this is "vapor lock", or percolating or who the heck knows, but the symptoms still exist.....

[meadowbrook]

Vapor lock is very simple, it is fuel starvation due fuel boiling somewhere in the fuel line, causing the fuel bowl to run dry and stalling the engine. Engine off, no more fuel (assuming machanical pump).

Being that my 230's fuel pump is quite a bit below the manifold, i am beginning to think the issue may actually be the fuel boiling at the fuel line between the pump and the carb. Maybe even some at the fuel bowl, considering the heat i felt on when i tried to tweak the idle speed later at home (for unrelated reasons).

That may explain why i only experience this after a highway run in really hot weather, never while on the highway or while moving, only after stopping. I suppose the combination of a hot exhaust manifold, a hot intake manifold and radiant heat surrounding the fuel line approaching the carb with the now slow moving cooling fan and slow engine speed at idle would accumulate more heat to the now slow flowing fuel in the line.

I guess i answered my own question. Thanks for the Intellectual stimulation, though. Sounds like i need to insulate the line between the carb and pump. Maybe a switched inline 6v fuel pump by the gas tank would also help.

[greg g]

i only experience this after a highway run in really hot weather, never while on the highway or while moving

Sounds like perculation to me, to much fuel rather than alack of it. Set your float level a bit lower leaving a bit more room in the float bowl for the more volitile (ease of evaporation, not likelyness to ignite) If you float is set to high, as the fuel expands with heat it overflows the bowl flodding the intake with fluid gas rather than atomized fule it needs. This sounds counter intuitive but I'm placing my money here as opposed to not getting enough fuel.

Check the base of the carburetor after a long run with high under hood temps, and see if it gets wet around the throttle plate pivot either at idle or shortly after shut down. If it does with fuel this would support the perculation excess expansion of the fuel in the carb.

[Don Coatney]

Vapor lock is very simple, it is fuel starvation due fuel boiling somewhere in the fuel line, causing the fuel bowl to run dry and stalling the engine. Engine off, no more fuel (assuming machanical pump).

As I suggested, do a forum search for "vapor lock". I am in agreement with Greg. Your issue sounds more like too much fuel. If the fuel in the line from the pump to the carburetor were to boil (doughtful because this line is under pressure when the carburetor float is closed and the boiling point of pressurized liquid is higher than non pressurized liquid) once the float valve opened there would be movement of fuel to the carburetor. As the carburetor is vented any boiling vapor would be expelled and liquid will flow. But as Greg said if the float bowl is too full there is no room for heat expansion and the expanded fuel will flood the engine. I do not believe your engine problem is vapor lock.

[meadowbrook]

I will certainly look at that possibility.

If it happens again, i will pull the air cleaner with the engine stalled and look down the carb throat to see if there is any fuel being squirted if it actuate the throttle. If there is not, then it should indicate a dry fuel bowl from vapor lock

[55 Fargo]

i only experience this after a highway run in really hot weather, never while on the highway or while moving

Sounds like perculation to me, to much fuel rather than alack of it. Set your float level a bit lower leaving a bit more room in the float bowl for the more volitile (ease of evaporation, not likelyness to ignite) If you float is set to high, as the fuel expands with heat it overflows the bowl flodding the intake with fluid gas rather than atomized fule it needs. This sounds counter intuitive but I'm placing my money here as opposed to not getting enough fuel.

Check the base of the carburetor after a long run with high under hood temps, and see if it gets wet around the throttle plate pivot either at idle or shortly after shut down. If it does with fuel this would support the perculation excess expansion of the fuel in the carb.

Hi Greg, this sure sounds like a problem, many of us encounter, when operating in hot weather.

Is this a by-product of alcohol induced gasoline?

I have set, my float down, twice, but still encounter, this type of symptom, and yes it is fluid fuel flooding the intake.

Today I drove the 47 for the first time to town, stopped for gas, outside temp cool and cloudy, get in to start engine, and it is mildly flooded, but she does start, and away she goes.

I would like to try and find a better solution to this problem.

Is it possible, if my throttle return spring, is not tight enough, flooding could be a result.

I did find this with my 55 Fargo, tighter spring, and it did not happen again, but it is 12 volt, and spins way faster, so clears faster and easier, when mildly flooded.

I enjoy driving the 47, but get annoyed when I have to drive in warm weather, and this problem persists intermittently, almost makes a guy want to convert to 12 volts, for the faster spin. My battery is 6 years old, it could be getting weaker....

[greg g]

when your cup runeth over the only thing that a tighter throttle plate will do is puddle the gas in the carb rather tha in the manifold. The later cars with the shorter casting under the carb, had a sheet metal heat shield mounted between the carb and the manifold that extended forward under the float bowl. Plus some also had a phenolic spacer between the carb and manifold.

This one look home made and larger than stock but you get the idea.

[Rusty O'Toole]

Some have found relief from vapor lock by adding 10% diesel or kerosene to the gas. Not recommended if your compression ratio is 8:1 or higher.

[55 Fargo]

Okay, so how many have problems with "vapor lock", "percolation", hot fuel issues, that caus flooding or create hard starts????

I have owned many carburated autos/trucks, in my 35 year driving career, and do not recall too many issues with hot starts, flooding,percolating or the vapor lock voodoo.

But I do have issues with both my flatheads, being finicky, and many times down right hard to start after a drive on wram to hot days, when underhood temps can get good and hot. I have tried all the suggestions, move fuel line far away as possible from the exhaust manifold, lower float, so what is the problem, is it something I am doing, or not doing?

Is it the modern alcohol impaired fuel, is my engine drunk, and confused with this new "governmant green peace cocktail", or what?

Does anyone want to take a run at Me, or suggest I do some searching on this, or should I be happy that the engine still starts and gets me back home.

The 47, with a 6 volt system, is a real beach to start, once heated up, but does usually catch. The 55Fargo, will restart much easier, with 12 volts, and then needs to clear, and then runs smooth again.

I do expect this sort of thing in 90 degree weather, but not ona 70 degree day.

Well thats my story, and I am sticking to it, happy motoring.....

[meadowbrook]

I do believe my issue is vapor lock, not flooding, as i dont smell any fuel when the car stalls.

My dad (74 years old) tells me he ran into vapor lock issues all the time in his youth while living in Brazil, in 100 degree weather. The common fix was to drape a wet rag on the fuel line, which would stop the fuel from boiling and the car would then start, this seems to reinforce the vapor lock theory.

Maybe we are used to our modern cars that rarely stall and rev low at highway speeds, so we get surprised by these issues and try to fix them with electric fuel pumps and overdrives.

[55 Fargo]

I do believe my issue is vapor lock, not flooding, as i dont smell any fuel when the car stalls.

My dad (74 years old) tells me he ran into vapor lock issues all the time in his youth while living in Brazil, in 100 degree weather. The common fix was to drape a wet rag on the fuel line, which would stop the fuel from boiling and the car would then start, this seems to reinforce the vapor lock theory.

Maybe we are used to our modern cars that rarely stall and rev low at highway speeds, so we get surprised by these issues and try to fix them with electric fuel pumps and overdrives.

Yup, summer fuel/winter fuels, and the Reid vapor pressure may cause this problem. Whn it gets hot in srping, and the gasoline is still wintr blend, that may be a problem.

Thes carbs also do not have anti-percolation mechanisms/features.

What do the experts say??????

[meadowbrook]

Another detail is that at least according to wikipedia, todays fuels are less volatile than those in the past, so they would be less likely to vaporize. The alcohol that is added for emission reduction makes it less volatile also.

I experienced this while living in Brazil and driving a 100% alcohol fueled carburated car. In cold weather, like 50 degrees C, the thing was a bear to start and you had to warm it up thoroughly before driving or it would stall.

[54Illinois]

I can see the fuel boiling in the fuel filter on mine. Then the gas slowly drips into the manifold from the carb...my worry is the gas smell in the oil. Would the gas be getting into the oil via the valves, or pistons?

The Plymouth book I have says the oil filler cap ventilates for this reason, but it states for "unusual driving conditions" is the reason for gas in the oil.

[TodFitch]

I can see the fuel boiling in the fuel filter on mine. Then the gas slowly drips into the manifold from the carb...my worry is the gas smell in the oil. Would the gas be getting into the oil via the valves, or pistons?

The Plymouth book I have says the oil filler cap ventilates for this reason, but it states for "unusual driving conditions" is the reason for gas in the oil.

Another reason for gas in the oil is a bad diaphragm in the fuel pump...

[54Illinois]

Another reason for gas in the oil is a bad diaphragm in the fuel pump...

I was told that as well. This is the 2nd new fuel pump.

[Dan Hiebert]

I'd hang my hat on it being vapor lock. We had problems with that ALL the time when I was in high school in Presidio, TX ("Sunspot of the Southwest"). It'd get so hot that I once saw a coyote chasing a jackrabbit, and they were both walking. Nyuk, nyuk.

Anyway, vapor lock is not the fuel "boiling" in the line, its when it gets hot enough to vaporize the fuel (but I guess that's technically boiling), and a vacuum based pump (its how mechanical pumps work) can't pull or push the liquid fuel through the gas - viola - "vapor" lock. That's why electric fuel pumps solve vapor lock problems, they use an impeller to physically move the fuel.

Always happened with older cars and trucks with engine compartments that got really hot, regardless of whether or not the engine ran hot or not. Our fix while stranded on the side of the road in the middle of nowhere, and still miles from anywhere was to either let the engine compartment cool (which took an awful long time when it was 100 degrees out), soak a rag in the ice chest and cool the fuel line, or in a pinch, pee on a rag and cool the fuel line.

Knock on wood, I haven't had that problem with the D24, but my daughter's Falcon would act up occasionally in New Mexico. We put insulation on the fuel lines through the engine compartment and solved the problem.

[ptwothree]

Try this as a diagnostic measure ..... replace the metal fuel line from the pump to carb with a non metallic one and route it away from heat sources .....see if this helps or hurts.

I agree with Don C. that pressurized fuel won't create vapor lock, but, it is still absorbing heat that gets released in the fuel bowl, which could cause problems, especially if the float level is set on the high side.

Now, with the engine shut down, heat can boil in the feed line to the carb, over power the needle and seat and cause starting problems. I remember drag racers running stock pumps soaking the fuel lines with cold rags, ice, alcohol or whatever was available so they could restart their engines between runs...

[54Illinois]

I did find a heat shield from the parts car. It sets between the carb and manifold.