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Charger is hard to start after sitting 5 minutes

moopa

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Hello there.
I have an annoying problem with my 69 383 Charger in my signature. It has the following problems starting( cranks alot, then finally starts): After sitting more than a week, after hot when driving and shut off for more than 5 minutes.
However,the car will start right up when, hot right away,if shut off onlyfor a minute or two. It will also start fine after sitting a few hours.The car runs beautifully, after starting. I'm running the original points ignition distributer.( points gapped correctly and in new cond) but I now have a brand new edelbrock 750 performer carb(that does not have elec. choke) on top of a factory 69 road runner/magnum 4bbl intake .The only setting I've played with are the idle mixture screws on the front.
I was leaning toward thinking it was fuel related, but after sittng more than a few hours after being hot, it's fine. By hot, I mean car does not get over 180 according to temp gauge.
I'm probably over-carbbed with a stock 2 bbl engine, but that shouldn't cause these symptoms, should it?

Thank you for your time, Mark
 
You didn't say if the heat crossover in the intake was blocked off or not, but I'm guessing it's not.

Probably what is happening is the fuel (if you can call what we have to run on these days "fuel") is boiling out of the carb. If your crossover isn't blocked, I'd recommend blocking it off.
 
I had the exact same problem with my 383 when I had that same carb and an Edelbrock performer intake, I tried everything to fix the problem by adjusting the carb. It did run better after putting a 1" plenum spacer between carb and manifold (you'll probably have to jet up a bit, I found the spacer leaned it out too much). Then I put a 750 speed demon on and the car start perfectly every time and the power improved 10 fold. I agree it must be heat related as the edelbrock's float bowls are tucked in quite close to the carb itself.
 
You didn't say if the heat crossover in the intake was blocked off or not, but I'm guessing it's not.

Probably what is happening is the fuel (if you can call what we have to run on these days "fuel") is boiling out of the carb. If your crossover isn't blocked, I'd recommend blocking it off.

You're right, it's not blocked off, and I was thinking the same thing, fuel is boiling out, and there's nothing left in the carb. But what puzzels me, is after a few hours or days of sitting it fires right up.So where is that fuel coming from? But if it sits a week or,so...crank,crank,crank....
I wonder if it could be a weak diaphram in the fuel pump( brand new stock-style), not keeping it's pressure when hot? Or some kind of an air or vapor lock? The car sat for the better part of early 1980's until about 2007 with very few miles put on it,so it wouldn't surprize me if something funky might be going on in the fuel system somewhere....
Mark
 
I should at least be able to put your mind to rest about the fuel pump.

My 68 383 Runner/Carter carb acts exactly like yours.
But... I have an electric fuel pump... and the crossover is blocked off in the alum intake...Electronic dist and MSD.

I turn the key on to "RUN" and let the pump build up pressure (It's loud enough that you can hear it slow down when the pressure comes up) and then "Start".

I've tried to start it every way possible but always the same.
Fires right up when cold or immediatly after shutting it off.
When hot, 15-20 seconds of cranking then it kind of labors to life.
I expect an insulated spacer of some sort will help but I haven't tried one yet.

Oh, and the electric pump stopped the long cranking after a week of sitting cause it fills the carb.
 
I should at least be able to put your mind to rest about the fuel pump.

My 68 383 Runner/Carter carb acts exactly like yours.
But... I have an electric fuel pump... and the crossover is blocked off in the alum intake...Electronic dist and MSD.

I turn the key on to "RUN" and let the pump build up pressure (It's loud enough that you can hear it slow down when the pressure comes up) and then "Start".

I've tried to start it every way possible but always the same.
Fires right up when cold or immediatly after shutting it off.
When hot, 15-20 seconds of cranking then it kind of labors to life.
I expect an insulated spacer of some sort will help but I haven't tried one yet.

Oh, and the electric pump stopped the long cranking after a week of sitting cause it fills the carb.



In this case I'd check for a bad coil.....especially if it's of "stock configuration" and still mounted on the intake
 
In this case I'd check for a bad coil.....especially if it's of "stock configuration" and still mounted on the intake

Could be a defective coil...It's a brand new one, Installed when I bought the car and converted to 4 bbl.( approx 3000 miles ago). Are you thinking coil could be failing when hot from intake? It is mounted on the intake like the old one.
 
Yup. Had that very issue with my Duster. Changed the coil, no more problem.
 
Is it an accel canister coil? I had a horrible experience with more than a few of those leaking the oil and shorting out to their case causing them to overheat with my barracuda (and a friend of mines duster)years ago, similar cranking,starting problem to yours,have you tried spraying starting fluid down the carb while it's having trouble starting? I think this way you can narrow it down to a fuel issue for sure if it catches on right away.
 
I haven't tried the starting fluid trick, yet, but sounds interesting....I haven't tried taking off the air breather, and looking inside while pumping it to see if it's squirting fuel,either. Could be good ideas to eliminate possible lack of fuel causes.
Mark
 
Any solutions to your issue, moopa? Got similar prob here...

Edelbrock 750 on the 440 Magnum with mild cam...not great when starting cold, but downright terrible if warm or hot. Installed 1" phenolic spacer...not sure if it helped much.

For cold, this is what I have been shown and is the closest to being predictable. I know it sounds hokey:

- Pump gas pedal 3 times
- Pull choke all the way and then ease up on it just a tad
- Keep foot pressed on gas pedal 3/4 way and crank...if it fires, gotta keep 'er running and ease up on the choke as it warms. If it stalls, could be in for a long wait.

For hot, like going to a grocery store etc., experiencing the same symptoms as the original poster/moopa above. Pretty sad when an old lady drives by you in the parking lot and says: Oh sonny, those old Dodges...they were terrrible for flooding and once they stalled took quite a bit to get 'em runnin', eh.

I'm kinda choked (pardon the pun) that the shop that installed the carb didn't give me an option for the electic choke version...would that help?
 
I should at least be able to put your mind to rest about the fuel pump.

My 68 383 Runner/Carter carb acts exactly like yours.
But... I have an electric fuel pump... and the crossover is blocked off in the alum intake...Electronic dist and MSD.

I turn the key on to "RUN" and let the pump build up pressure (It's loud enough that you can hear it slow down when the pressure comes up) and then "Start".

I've tried to start it every way possible but always the same.
Fires right up when cold or immediatly after shutting it off.
When hot, 15-20 seconds of cranking then it kind of labors to life.
I expect an insulated spacer of some sort will help but I haven't tried one yet.

Oh, and the electric pump stopped the long cranking after a week of sitting cause it fills the carb.

Are you talking about Julies Duster :rolling:
 
A WWII vet that has a 62 Plymouth Belvedere Sedan has the same problem. Never met him but it sound the same.

I'm just a kid but I'll let you know what I think.

- You might be running too lean.
- Flush your fuel lines and check the quality of your fuel.

If it's your coil replace it.

I think you should go back to a stock indcution set up, and see how it performs, to set a baseline.
 
well next time you go to start it take the air cleaner off and see if it is pumping fuel. if it is pumping fuel there is still fuel in the bowl. next check your spark. spark fuel compression is all you need to run one of these old babys
 
if you had the money it will make a world of difference if you would throw a msd ignition on her too eliminate the points
 
I have similar problems with some of my cars. My 66 Bel II is horrible after sitting from a warmed up state and if it sits for a few days it's also not too good. 20 yrs ago I ran a Torker with a Holley with the heat cross over open and never a problem. Recently my old 66 F250 was having similar issues until I blocked the heat cross over, then it didn't run as good cold.

I think that today's gas is not carb friendly because the vapor pressure is higher, and with the modern FI cars it's not an issue. What seems to be happening is the fuel expands from heat and floods the engine through the main discharge or just good 'ol vapor lock. On the F250 the air cleaner breather hose would condense the vapor so I always had a little puddle of gas in there, but that went away when I blocked the heat riser. To prove this gas theory I ran a high concentration of race gas in the Bel just to see the results and it was happy. Next I might try adding some percentage of diesel to hopefully change the RVP (reid vapor pressure). I found the article below to be most informative. Get comfy cuz it's a long read.

Part 1:

Racing Fuel Basics
by David Poffenbarger

Racers all know that high performance engines require special fuel. High compression ratios, combined with lean air/fuel mixtures and advanced ignition timing, all create circumstances in which detonation can occur. For many applications, high octane racing fuel is required to provide maximum horsepower and to avoid potentially engine damaging detonation. But will a bracket racer benefit from the same high octane racing fuel? Just how high an octane rating does a bracket racing engine require?

Most racing fuel manufacturers try to provide as much usable information about their products and their applications as possible. However, what do all these numbers mean and how does a racer use them? In this article, we will try to provide a working knowledge of what racing fuel really does for an engine and, at the same time, dispel as many of the myths as possible.

How Racing Fuel is Made

At the refinery, crude oil, taken from deep under ground, is distilled into a wide range of petroleum products. On one end of the spectrum are the very light, high quality petroleum products like natural gas and butane. On the other end of the scale are heavy products such as asphalt. From this range of crude oil products, race fuel is blended using only the best ingredients possible for racing. However, like chefs following a recipe, there are as many ways for the product to turn out as there are refineries blending racing gas.

A particular race fuel may contain anywhere from 50 to well over 100 individual ingredients in a particular blend. However, for discussion purposes, the ingredients can be broken down into three families of hydrocarbons: aromatics, olefins and saturates. Olefins, while commonly used in pump gas, are only present in trace amounts in racing fuels. Saturates constitute the primary family of ingredients in modern leaded racing fuel, usually accounting for 75% or more. Aromatics are also used, but usually only consist of 25% or less of the total make up of a particular fuel.

A more useful way of looking at the ingredients that make-up a racing fuel is by weight and the temperature at which the ingredients vaporize. The lightest ingredients, based on molecular weight, are the most volatile and are called front ends or light ends. The front ends vaporize at the lowest temperatures, usually under about 130 degrees. As the ingredients become heavier and vaporize at a somewhat higher temperature, between about 130 and 250 degrees, they are called medium fractions. Heavy fractions vaporize above 250 degrees and, obviously are the heaviest. Most manufactures provide this information for their fuels in the form of a distillation curve. More on distillation curves later.

The medium and heavy fractions contain most of the thermal content of racing fuel. This thermal content, measured in British Thermal Units (BTU’s) per pound of fuel, is what’s released as heat when the fuel is reacted (burned) in the combustion chamber. As the fuel is reacted, it expands rapidly, pushing the piston down and creating the work that ends up being horsepower.

The medium-to-heavy fractions also have the highest octane values. Considering this, it may seem that the fuel that would make the most power would be that with the most heavy fractions. The drawback to that idea is that, since heavy fractions vaporize at the highest temperatures, they are the hardest to react. This is where the light ends come into play.

The light ends in racing fuels are the most volatile and vaporize at very low temperatures. They are necessary to begin the reaction that burns the heavy fractions and releases the energy in the combustion chamber. They are also necessary for starting a dead cold engine. Think of front ends as the lighter fluid that starts the charcoal briquettes in a barbecue. However, light ends contain little thermal content and, by themselves have relatively low octane value.

Octane

When bench racing gets around to fuels, discussions about what octane is and how much an engine needs top the list. However, most racing fuel vendors will tell you that octane is one of the most misunderstood concepts in racing. Octane is not a fuel additive or even a substance. Octane is strictly a scalar that indicates a fuel’s resistance to detonation. Octane is to fuel as pounds are to weight and feet are to distance.

The test procedures used to calculate octane were developed in the 1920’s and are same ones still used today. For street use, the octane rating gives the average consumer the information necessary to choose the correct fuel for the family sedan. Even for racing, octane rating is one of the important numbers used in choosing a racing fuel. However, a high octane rating isn’t all there is to selecting the correct race fuel for a particular application.

Octane rating is usually expressed in one of three different ways. Research Octane Number (RON) is calculated using a single cylinder engine run at 600 RPM and will generally provide a more generous octane value than does the test that calculates the Motor Octane Number (MON). MON is tested similarly to RON with the exception of being at 900 RPM. MON is generally regarded as the preferred measure of octane rating for use in racing engines since it more closely simulates the types of conditions found in racing. The third value is R+M/2 value, which is the average of RON and MON. This value is what is seen on the yellow stickers attached to fuel pumps in service stations.

By itself, a high octane rating doesn’t add any horsepower to an engine. What high octane ratings do is allow the engine builder to use higher compression ratios with advanced ignition timing that would detonate using lower octane values. However, using a higher octane value than an engine requires, while doesn’t hurt performance, it also doesn’t help it either. If an engine only needs a fuel with an octane rating of 110, spending the additional money to purchase 118 octane racing fuel is a waste of money. Consider that 118 octane racing fuel can cost upwards of 3 dollars a gallon more than 110 octane, and it becomes obvious that the difference could be a significant amount of money over the course of a racing season.

Another common misconception is that higher octane ratings react (burn) at a slower rate. This is incorrect. A fuel’s octane rating has nothing to do with how quickly it will react in the combustion chamber. It should be noted however, that different fuels can have different rates of reaction (flame speed) within the cylinder. The distillation curve will provide hints as to how a fuel will react in use. More on that soon.

When a racer requests information on a particular fuel, the vendor will usually supply a data sheet that contains its octane rating(s) plus a lot of additional information. Understanding this information is an important step towards making informed choices on a fuel and even more important if a racer gets caught short of fuel and must use another vendors wares. Lets look at some of these numbers and what they mean.

Distillation Curve

The previously discussed fuel distillation curve is an important piece of information provided by most racing fuel manufactures. This curve is derived by heating a sample of a fuel and measuring the temperature at which it initially boils and at each point where the volume is decreased by a 10% increment until the sample is gone. Finally, the solid residue is weighed to determine its percentage of the initial sample, which are usually negligible in racing fuels. Figure 1 contains a few of the distillation curve points for three different fuels.

The distillation curve provides an approximation of the fuel’s distribution of front ends to medium and heavy fractions and the temperatures at which they vaporize. Knowing this is important because a fuel must be vaporized before it can be reacted. One of the things to look for in the distillation curve is for the fuel to vaporize relatively evenly over the temperature span. This will contribute to a more complete reaction of the fuel in the combustion chamber.
 
Part 2

Most racing fuels have an initial boiling point of around 100 degrees and a final point of approximately 250-300 degrees. If a fuel’s maximum vaporization temperature is to high for a particular application, all of the fuel may not be vaporized in the combustion chamber leading to an incomplete reaction. If the initial temperature is to low, the engine may be prone to vapor lock. If the initial temperature is to high, the engine will be hard to start, although, this varies somewhat with application. A nitrous application for example, may not need a low initial boiling point because of the additional cooling from the nitrous. Turbo-charged or supercharged applications may require a higher vaporization temperature because of the additional heat in the intake tract. What’s important is that the distillation curve provides a lot of information that can be used to help determine the correct fuel for a given combination.

Reid Vapor Pressure

Another value usually included in fuel manufacturer’s literature is Reid Vapor Pressure (RVP). RVP is a measure of how much pressure will result from heating a sample of race gas inside of a confined space. This information is another way of determining the amount front ends are in a particular blend of race fuel. Pump gas typically has RVP’s in the 7-13 PSI range, depending on season. The RVP will be higher in the winter and lower in the summer. Racing fuels typically have RVP’s in the 5-8 PSI range and don’t change with the seasons like pump gas does. High RVP values suggest the fuels use many volatiles in the blend, which can cause an engine to be prone to vapor lock. Low RVP’s can make the engine hard to start in cold weather.

Specific Gravity

A fuel’s specific gravity is a measure of how much a volume of fuel weighs when compared with the same volume of a standard liquid. Water is the standard liquid for comparison to fuels. Therefore, if a fuel has a specific gravity of 0.750 it weighs ¾ as much as an identical quantity of water. Racing fuels can have a specific gravity from a low of about 0.660 through a high of about 0.780, which is a significant difference.

The tool used to measure specific gravity looks like a thermometer that partially floats when dropped into a volume of fuel. The specific gravity is read off graduations on the outside of the bulb. These tools are relatively inexpensive and can usually be purchased from well-stocked fuel suppliers or chemistry supply houses like Cole-Parmer.

Knowing the specific gravity of the fuel a racer is using can be important to help determine how to re-jet the carb when a fuel change is made. Since jets meter by volume, if a lighter fuel is used, it will usually require a larger jet to maintain the correct air/fuel ratio. This phenomenon can also be seen by measuring the effects of heat on the specific gravity of a fuel. As fuel becomes warmer the specific gravity decreases. Most racers understand the effects of hotter weather on jetting and a fuel’s specific gravity is another indicator of this relationship.

Another use for measuring specific gravity is to check for stale fuel. If race fuel is stored improperly it can become stale. Racing fuel should be stored in sealed metal containers in a cool location out of direct sunlight. If race fuel is stored properly, it can last indefinitely. However, if fuel is left in fuel jugs inside a racer’s trailer, where temperatures can reach in excess of 100 degrees, the front ends of the fuel can begin to vaporize. When the jug is opened, this vaporized fuel will vent to atmosphere and is lost. As the front ends go away, so does the fuels ability to react the heavy fractions and power will suffer. This loss of front ends will show up as a slight decrease in the fuels specific gravity and is another reason to test this aspect periodically.

Heat Content

A fuel’s heat content, measured in British Thermal Units (BTU) is another number sometimes thrown around in bench racing sessions. However, the reality is that there isn’t a significant difference in BTU content between various racing fuels. Most racing fuels have a BTU content of around 19,000 BTU per pound (surprisingly, this is about the same as pump gas as well). Since race fuels weigh approximately 6 pounds per gallon, this equates to around 114,000 BTU per gallon. Based on percentages, even an increase of 1000 BTU per pound is a relatively small increase in thermal content at the carb jet.

Another common misconception is that heavier fuels, those with a high specific gravity, have a higher BTU content. Again, this is not necessarily true. The chemists that brew racing fuel have ways of juggling a fuel’s specific gravity and BTU content to accomplish whatever goal they are after. Consider the BTU content of the fuels in Figure 1. C-14 is the lightest fuel, based on specific gravity, however it has the largest BTU content.

What is more important than BTU content in making horsepower, is the ability to release as much of the thermal energy as possible. This gets back to knowing how and when the fuel vaporizes relative to ignition and reaction.

Race Fuel Myths

A couple of the myths surrounding race fuel have already been discussed concerning what octane is and isn’t and its relationship to fuel burn rate. However, a couple more myths are worth discussing. Racing fuels are often compared by how they will affect an engine’s exhaust gas temperatures (EGT), suggesting that raising or lowering EGT’s is a good thing. Given that the BTU content of most racing fuels is not significantly different and that when reacted, they will burn at approximately the same temperature, it is very unlikely that a fuel by itself will have significant effect on EGT’s. An engine’s EGT is a function of many different factors; it’s basic design, ability to breath, ignition timing, and valve timing. Additionally, it takes a significant amount of dyno testing to determine what a particular engine’s ideal EGT should be. So to suggest one fuel is better because of its effect on EGT is gross oversimplification.

Another myth is that race gas can be doctored by home “chemists” to make significantly more power. Most racers have heard the old wives tale that a handful of mothballs thrown into the fuel will really wake up an engine. Unfortunately, it usually doesn’t work quite like that. While there are a few commercially available additives that do add horsepower, most come with either significant risks to a racer’s engine or personal health, or are expensive, or both. It’s important to remember that there are a whole bunch of well educated and talented people working for racing fuel manufacturers who are constantly looking for ways to improve their fuels. If there were a safe and reasonably priced additive that would create more power in a racing engine, they would be using it. Trying to doctor fuels at home is taking unnecessary risks. Leave this to the chemists and engineers working for the manufacturers.

How to Choose a Racing Fuel

So far, we covered the science side of racing fuels, but how does a racer choose a fuel for their car? Is racing fuel even required for all applications?

To answer the second question first, serious bracket racers concerned with every thousandth of a second in consistency should consider using race fuel. Even if a particular engine application could run on pump gas, the regional and seasonal variances in the blending of pump gas can lead to inconsistencies in engine performance. Pump gas purchased in a metropolitan area of California in the winter can be significantly different than the same brand purchased in the Midwest during the summer. One of the benefits of race gas is the consistency in the blends and that alone is a good enough reason to use it.

OK, we know we need to use race gas, so which one is best. There are several factors in deciding on a race fuel. First, if you don’t build your own engines, talk to your engine builder and get their recommendation. But don’t stop there. Also talk to the manufacturers of the fuels that are readily available in your area. Fuel manufacturers have tech-support people who know racing and can advise racers on which of their fuels will best meet their needs. They will want to know some things about your engine including compression ratio, whether it’s naturally aspirated or blown/turbo-charged and the type of racing you do (in case some non-drag racers are reading this article). Also be certain that the fuel is readily accessible in your area. Finding the perfect fuel and not being able to purchase it readily can be a significant problem.

Once a racer has decided on a fuel that works for their application, stick with it. Keep adequate reserves of the fuel (stored safely, of course) so that you don’t get caught short. Be careful about depending on trackside suppliers. Most that I have worked with are dependable, but being a trackside supplier is difficult and thankless work with little financial reward, so it’s not surprising when one quits. Additionally, the track owner may change suppliers of the track’s “official fuel” on relatively short notice. Be aware of these things so that you don’t get caught short of fuel on race day.
 
Hopefully, this article has provided the racer with enough background to make use of the information contained in a racing fuel data sheet. If a racer learns as much about fuel as they usually know about engines, the correct fuel can be chosen to make maximum horsepower without the risk of detonation. Discuss any remaining questions you have with your engine builder and fuel manufacturer concerning your application. Once the correct fuel is found, stick with it and take advantage of the consistency that racing fuel manufacturers go to great lengths to maintain. Accomplish this and you will have one less thing to be concerned with on race day and you will be the racer in the know during those all-important bench racing sessions.

The writer would like to express his gratitude to the fine people at VP Racing Fuels, San Antonio, TX (210-635-7744) for their patient assistance in researching this article.






Figure 1

Here are most of the properties that are typically provided on a racing fuel data sheet for 3 different fuels. Data courtesy of VP Racing Fuels:

Property VP Red C-12 C-14

Specific Gravity .742 .709 .694
Reid Vapor Pressure, 7 PSI 7.75 PSI 5.5 PSI
BTU’s, per pound 18,800 18,834 19684
Distillation Curve (in degrees)
Initial Boiling Point 127 98 130
10% 170 129 170
30% 202 165 NA
50% 218 196 200
90% 288 228 212
End Point 348 240 232
Motor Octane Number 105 108 114
Research Octane Number 110 110 114
R+M/2 107.5 109 114
Color Red Green Yellow
 
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