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Is Modern Gasoline Incompatible With Carburetors? Please Help!


carbdoc
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Because if it is not, then I must have taken a big ol' handful of stupid pills and completely forgotten that I did so. Jeff Dreibus here, owner of The Old Carb Doctor. And now the Doctor needs some "medical advice".

The following complaint seems to have been "phasing itself in" over the past few months until now it has reached a full-blown epidemic. I send a restored carburetor out -- and it comes back because it is leaking from, well, everywhere. Upon testing and subsequent disassembly, the carburetor is found either to have no defects whatsoever, or found to have the moisture-cured urethane float coating (applied to keep the oxygenates in the 1996-up era gasoline from attacking the soldered seams in the brass floats) peeling off.

This is occurring over a wide geographical spectrum here in the U.S. and seems to affect all designs of carburetors regardless of needle-and-seat or float design. I have stopped coating the brass floats altogether (and crossed my fingers and prayed a lot) but it would certainly help to find a new fuel-impervious coating.

But it is the apparent effect upon the needle-and-seat assemblies which has me really mystified! In carbs which indicate no float failure whatsoever, the unit invariably passes all bench tests and engine tests (at least, those which I can install upon an engine). Yet it leaked like crazy on the customer’s vehicle. Why?

I have not changed a thing about the way in which I restore carburetors whatsoever. I use the same exact materials and techniques which I have used for the past 13+ years to accommodate the previously-reformulated gasoline. So: what is going on? I must conclude that it has to do with the current gasoline quality and the ongoing vapor-lock and electric fuel pump failure epidemics, but what have the government/oil companies actually done to cause this? Something surely happened! And what can WE, the old car enthusiasts, do to mitigate it?

I hope that this doesn’t sound like a rant, but I’m running out of ideas. And I not only depend upon this business for my livelihood, but I really dislike disappointing my fellow hobbyists (customers) as well. Are there any SAE guys out there who would like to comment? Anyone who can offer any insights or solutions whatsoever? I’m going to contact SAE on Monday, but I imagine that getting in touch with the right individual will be akin to navigating a mine field. Any suggestions regarding to whom else I can turn would be appreciated.

Jeff Dreibus

Edited by carbdoc (see edit history)
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Jeff, I have had a world of problems with my 2-stroke engines (string-trimmers, chain saws) since ethanol was mandated here in Texas a couple years back. I don't know if there is a connection here or not. Are your customers in areas where this is the "New Law"?

STA-BIL seems to have helped somewhat, but alcohol and aluminum do not like each other and it seems that the alcohol wins. It really seems to draw water out of the air and contaminate everthing. I have a neighbor that rigged a contraption to attempt to let the ethanol rise up and siphon the gasoline off the bottom, but that is not really feasable for a large amount of fuel. If you figger it out, please post your theory.... Good Luck!

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I recently spilled a small amount gas on my leg. Took the skin off just like hot pizza off the roof of your mouth. Changeing a deisel filter the other week I had some fuel run down my arm. It took almost two weeks to get rid of the rash and itch. There's SOMETHING in fuel in the past year that wasn't there before. I also spilled a little gas on a fender that was brush painted some time before 1948 and it took the paint right off.

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Jeff - we have never had a problem with brass floats, and have never coated them.

As to the leaking, it is important to find out from the customer WHEN the carburetor is leaking.

The volatility of modern fuel is ridiculous. Ask the customer to remove the air cleaner and run his/her vehicle in the driveway, where they can observe the engine while running. If you can get the customer to do this test; virtually ALL leakage will occur once the engine has been turned off! When the engine is turned off, the inlet check valve in the fuel pump closes, preventing fuel from running back to the tank. The heat in the engine compartment causes the pressure in the fuel line from the fuel pump to the carburetor to increase (volatility) to the point where the float and fuel valve CANNOT close off the pressure. This causes from a teaspoon to two or three tablespoons (depends on diameter and length of fuel line) of fuel to be dumped into the carburetor. This raises the fuel level in the bowl above the main discharge jet(s). The fuel runs through the main discharge jets down onto the throttle valve(s) which is closed; and then runs out the throttle body by the throttle shaft and drips down onto the manifold.

The ONLY feasable solution to this issue is to install a return line all the way back to dump into the top of the tank thereby relieving the pressure.

Another possible issue is the fuel tank vent. Many older vehicles were vented through the fuel cap. The repro "one size fits all" fuel caps are not vented. If the tank is not vented, heat from the exhaust will cause pressure inside the fuel tank (volatility) which can overdrive the carburetor float and cause the carburetor to flood, even leak profusely, while the engine is running.

The test, simply remove the fuel cap and observe. The solution, fix the tank vent.

A third possibility is the fuel pump. Lots of enthusiasts are installing electric pumps and regulators. The $19.95 inline dial-type regulator that one buys at the local auto parts house is really useful if one has a rabbit problem in the garden and a strong right arm (or left arm); but they do NOT adequately regulate fuel pressure! Nothing wrong with installing the electric pump (most of my collector vehicles have been so-modified) but VERY IMPORTANT to spend enough to get the RIGHT electric pump and do the job right.

And one other issue which I am hesitant to mention, but will with no names. There is one company in the fuel pump business that seems to have the philosophy that if a part fits, it is the right part! Since fuel pump pressure on mechanical pumps is controlled by the tension of the diaphragm return spring, too stiff a spring can cause LOTS of pressure. We have tested some of these pumps to 18 psi. No carburetor float and fuel valve will shut this off.

The test: an inline pressure gauge at the carburetor.

And finally, since we have had a very hot summer, remember to inform the customer about how much the ambient temperature effects the pressure (again, fuel volatility).

The absolute key is being able to calm the irate customer sufficiently such that they can inform you went the leakage occurs and thus you can help them minimize the problem. Until the government comes to its collective senses (never???) there is NO solution.

10 years ago our most pressing carburetor issue was dealing with ever-changing government regulations. Now by far the most pressing carburetor issue is deathanol.

Jon.

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Thanks for the input, everyone.

I am told that, on certain computers, "smilies" were visible throughout my original post. This, of course, was not intentional but rather the result of some "code error" whch my computer semi-literate mind cannot grasp. Hopefully, they are now gone for good. Please let me know if they are not as I can't see them on my 'puter.

Any additional commentary/solutions regarding the gasoline issue is welcomed. Thanks again.

Jeff

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Too much fuel pressure,I had a mechanical fuel pump put out way too much pressure before. The only problem I am having so far with the modern fuels is heat soak after the motor is shut,I am going to put plastic carb spacers on the two I am having this issue with to see if it helps

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Jon's reponse is right on. I just want to add my view on the matter. I send carburetors all over the world and I'm not having problems like Jeff is. I also don't coat the floats. As Jon says customers all over the country are complaining about gas boiling over when the hot vehicle is stopped.

When I send out a carburetor, I add a pre printed letter that explains some of the problems with todays gasoline and with ethanol. From that the customer just wants to know what they can do about it. It reminds me of the vapor locking problems we had in the good ol days.

Oh yes, the pumps and regulators are a big problem. I tell every customer that is having a problem to test the pressure, especially on new pumps. It's all about how cheap they can make things these days, which is how Americans have been conditioned to shop. Quality is of no concern.

Isn't is amazing that the government has forced environmental changes on our vehicles for the last 40 some years and big money came along and did more environmental damage than we ever saved over the the 40 years.

Jeff, call me anytime you want to compare notes. 360 347-1077

Mike's Carburetor Parts

Edited by mmikemitchell
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Fuel formulations are a result of the "enviormental friendly" government agencies that rule our lives. Refiners would love to go back to the old formulations as they were a lot easier and cheaper to produce and didn't require different formulas for different geograpical areas or different seasons. As the government orders less and less emissions from internal combustion engines we'll have more and more problems with new fuels vs. old cars.

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My car has 35 year old lacquer and never had problems with a little gas spilling on the paint until this year. Paint has never discolored on the fender before. Filled up in Ohio and must have spilled a little on. Picture tells the story of the new gas on lacquer paint. Maybe with the new clear coats there is no problem. I guess all of us with old restorations can get the cars repainted. Glad to help the environment out at any cost.

post-31856-143138285147_thumb.jpg

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Spot on about pressure regulators. Had a dial in on mine Was running a 12v Carter gerator pump on my 6volt system (5.5 v at the pump) OK, until the car sits for a few days & the weak start up torque held back the 12 v motor from starting, due to gas evaporation. When it ran it put out 7psi, too much, I felt so I put on a dial in pressure reg. Fine until I switched to a 6v solenoid pump from AC Delco( Airtex makes em also) engine fuel starved under load. Pulled the Reg, tested pressure, got only 4.5 - 5 psi removed any regulator and no problems. At the dial setting of 5, I could not even blow through the inlet port better at 3 and blocked at 1/2. Moral, use only good pressure regs with screw and locknut adjuster. See Summit racing. Most of our cars have only one carb and a single outlet port is necessary. Also maybe a check valve would be of value1/3 psi cracking pressure is available at McMaster-Carr.

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just throwing out a couple of ideas here, if it was the gas, wouldn't it cause all gaskets in all carbs to leak, new and old? assuming you are getting all your gaskets from one manufacturer, have you contacted them as to why their gaskets are all leaking? Why are they not holding up to moderrn gasoline? we have yet to have a problem on any carbs at our restoration shop but maybe the canaidian gasoline is different. i have noticed gasoline turns bad alot quicker than it used to.

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Before gasoline went to $5 a gallon in Southern California my 91 Mercury had no detonation problems. The first brand that lowered their price was Arco, which I had already been using, and I got severe detonation on the first and every tank after that. I switched brands, to Chevron, and got rid of most of the detonation except under very light throttle application. Shell with nitrogen added got rid of all detonation but dropped my mpg by 2. This tells me that something in the gasoline formulation was changed at that point in time and would be a good place to look for the problem. The Arco still causes detonation, even premium grade.

I had a 68 Chrysler Town and Country wagon which had an orange sealer in the fuel tank, this sealer was rapidly deteriorating when ethanol was added in larger amounts to the fuel in SoCal. I got the newer tank sealer (from por15) that was supposed to hold up to ethanol but sold the car before trying it.

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just throwing out a couple of ideas here, if it was the gas, wouldn't it cause all gaskets in all carbs to leak, new and old? assuming you are getting all your gaskets from one manufacturer, have you contacted them as to why their gaskets are all leaking? Why are they not holding up to moderrn gasoline? we have yet to have a problem on any carbs at our restoration shop but maybe the canaidian gasoline is different. i have noticed gasoline turns bad alot quicker than it used to.

Modern fuel is not even consistant from station to station, let along what you may get in Canada.

As to gasket material:

There are MANY different gasket materials available. And at many different costs. Unfortunately, many consumers look at bottom line only. This forces many companies (not just carburetor kit companies) to cut quality in order to reduce prices for the "low-price shoppers" JUST TO STAY IN BUSINESS!

The preceding paragraph explains why neopreme accelerator pumps are sold in the parts store kits. In manufactures quantities, neopreme accelerator pumps are 25~40 cents each. The leather pumps we make cost us from 9~30 DOLLARS each!

And, according to our government whom is knowledgeable in such things, neopreme is an "approved" material for use with ethanol.

Take a look at all of the different gasket materials next time you do a carb. Some (like the Armstrong N-8090 we use) are impervious to ethanol. Velumoid (common use by many manufacturers) is not.

And here in the US, it seems some states are worse than others. Leading the list (the wrong way) are Colorado, followed fairly closely by California and Florida. The fewest issues we see come from western New York, and eastern Pennsylvania. My own native Missouri comes in not far from California and Florida.

And you are certainly correct about the age of the carburetor and leaking. However, modern carburetors are much more tunable, thus more adaptable than many of the older (pre-1935) carburetors in areas of driveability.

My opinion only, others will differ.

Jon.

Edited by carbking (see edit history)
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Before gasoline went to $5 a gallon in Southern California my 91 Mercury had no detonation problems. The first brand that lowered their price was Arco, which I had already been using, and I got severe detonation on the first and every tank after that. I switched brands, to Chevron, and got rid of most of the detonation except under very light throttle application. Shell with nitrogen added got rid of all detonation but dropped my mpg by 2. This tells me that something in the gasoline formulation was changed at that point in time and would be a good place to look for the problem. The Arco still causes detonation, even premium grade.

I had a 68 Chrysler Town and Country wagon which had an orange sealer in the fuel tank, this sealer was rapidly deteriorating when ethanol was added in larger amounts to the fuel in SoCal. I got the newer tank sealer (from por15) that was supposed to hold up to ethanol but sold the car before trying it.

Sometime in early part of the year Ca. fuel was required to have at least 5% ethanol and Arco was using 10%. Now the state requires 10% ethanol and Arco is at 15%. On one of my vehicles that I really keep tabs on was at 42MPG at 5% and has dropped to 40MPG on 10% and 37-38 MPG on 15%. In response to the original question about carburetors and fuel compatibility.... It's not just carburetors, Fuel injection has had it's problems too. The automotive manufacturer I worked for had various voluntary recalls well out of warranty by years and mileage on vehicles built in the 80's and 90's for fear of fires because fuel hoses were turning into ABBA ZABBA. Before I retired I left one of my restored at my retirement house with a full tank of gas and had replaced all the hoses because of the above concern. When I got back to my place ( a month later) I opend the garage door the smell of fuel almost knocked me down all the fuel had leaked out. When I would go up to my place I usually would arrive at night and for some reason I left at a different time and came up in the daytime. All I would have needed was a tiny spark from the light switch going into the garage and I would have been toast.

Don

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I am surprised nobody has asked about hard hot and cold start problems or running and idle problems with modern fuel. All the old cars are running lean today. They also run much hotter with the 10 percent blends. Rumor is 20 percent alcohol will soon be upon us :-(

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  • 2 weeks later...

As one if Jeff's customer's, whose Detroit Lubricator 51 is somewhere on his bench, let me clear up some mis-conceptions. The carb that Jeff built was a piece of art when it arrived. I installed it, and the car fired immediately. No adjustment was even needed. It idled beautifuly. It ran and drove like like a dream. For five months it was fine. I put less than 20 miles on it in five months. I use no electric fuel pump, instead a fully functional Stewart gravity flow tank. I used Chevron Techron 87 octane with that bloody cornyhol. 10%. I started her every week, and often went around the neighborhood. I would cut the fuel line and let her gasp for fuel, then say goodnight. One weekend, about to go for a spin, I turned the fuel line on, walked in the house to get the key and returned to garage only to smell the strong odor of gas. I opened the hood and gas was running through it like a sieve. Cut the gas line tap gently and rock the accelerator in case the needle isn't seated. Gas on, same thing. It was flowing in so many places, I could not tell from where. I sent it to Jeff. So some of the good points made here are out the window with regard to pressure and or heat issues. I live in Houston where the gas is refinery fresh. I also used Sta-bil. One suggestion that someone made is that if the carb was built with neoprene tips, today's gas breaks it down. It may be true with Viton. Jeff, the only thing I can think of as to why they may test fine is maybe by the time it reaches you, some of the the swelling goes down. Possible?

Edited by 1Packard
Typo (see edit history)
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Just remember Clint, there is a federal law prohibiting the use of lead in any car to be driven on a public road. it's OK for aeroplanes though.

FYI it's also illegal to use it even in your lawn mower!

Edited by helfen (see edit history)
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Just remember Clint, there is a federal law prohibiting the use of lead in any car to be driven on a public road. it's OK for aeroplanes though.

FYI it's also illegal to use it even in your lawn mower!

I suspect that your state will more upset about using fuel that doesn't have a road tax collected on it than the feds will be about the lead.

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I suspect that your state will more upset about using fuel that doesn't have a road tax collected on it than the feds will be about the lead.

I live in your state.

Don

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  • 2 weeks later...

OK Kingoftheroad, where are you and what kind (brand) of gas are you using in your vintage cars? I am curious to know. Maybe we should try to get some thoughts from many different members about what gas brand they use and where they are located. This MAY form some interesting data! :(

I am currently having problems with my carb doing exactly what Jon described in his first post (#6) - after shutdown, fuel pouring into the throttle body causing extensive fuming. (I am running a Carter BBR-1 and original style AC mechanical fuel pump - no electric pump). My car has had the same setup for almost 15 years and only started this issue this summer! I also have starting and running problems related to the carb this season (idle mix screw apparently ineffective).

See also: http://forums.aaca.org/f219/modern-fuel-volatility-issues-carter-bbr-289770.html

And also: http://forums.aaca.org/f219/modern-fuel-volatility-issues-carter-bbr-289771.html

Edited by 1936 D2 (see edit history)
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Jeff,

This is a little unrelated, but I had inadvertantly put a few gallons of ethanol blended gas in my 62 vette and all the rubber hoses and fuel pump rubber parts were totally eaten up. The carb looked like it had coffee in it and the whole system from the tank to the carb was replaced. Has anyone had a similar experience?

Thanks in MN

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One important thing to keep in mind when you buy ethanol, other than the stuff at the liquor store with a tax stamp, is that it's denatured, that is, other chemical solvents are added to make it unfit for internal consumption. There are literally hundreds of these SDA or specially denatured" ethanols and many contain solvents that are far harsher on rubber than pure ethanol, and that's no doubt what happened to you.

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The E 10 fuel does not seem to matter in Model T's, but I suspect that is due to the very low (3.5 to 1?) compression ratio. It may be carb design too. I run an NH Holley carb, and always fill up with the 87 octane Mobil gas. The E 10 will cause problems in an old fuel system by dissolving varnish clinging to the inside of an old tank. Had an old tank cleaned out at a radiator shop, and it still clogged the carb up. Marine Clean took the old varnish off real nice.

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The E 10 fuel problems are related mostly to cars of late 1920's to 1980's with diaphram fuel pumps, low pressure fuel lines, OEM/NOS rubber components, and carburators. The problems are not showing as apparently in the Model T and A community. Model T and A's have a gravity feed supply and short line to the tank. They were also designed to run on a variety of fuel grades.

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I am on east coast 36 plymouth can't remember if I every had the carb open the only problem is when it sits a few Wks the gas ether disapates or runs back to tank have to run the starter a while but no carb leaking also 31 Plymouth,,,,, updraft running a BB1 rebuilt it this summer and adjusted the flot changed diafram on pump no problems BR

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I am on east coast 36 plymouth can't remember if I every had the carb open the only problem is when it sits a few Wks the gas ether disapates or runs back to tank have to run the starter a while but no carb leaking also 31 Plymouth,,,,, updraft running a BB1 rebuilt it this summer and adjusted the flot changed diafram on pump no problems BR

LOL, I have the same problem when my old cars sit a couple weeks, it takes a couple tries hitting the starter & pumping the gas pedal...

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OK Kingoftheroad, where are you and what kind (brand) of gas are you using in your vintage cars? I am curious to know. Maybe we should try to get some thoughts from many different members about what gas brand they use and where they are located. This MAY form some interesting data! :(

I am currently having problems with my carb doing exactly what Jon described in his first post (#6) - after shutdown, fuel pouring into the throttle body causing extensive fuming. (I am running a Carter BBR-1 and original style AC mechanical fuel pump - no electric pump). My car has had the same setup for almost 15 years and only started this issue this summer! I also have starting and running problems related to the carb this season (idle mix screw apparently ineffective).

See also: http://forums.aaca.org/f219/modern-fuel-volatility-issues-carter-bbr-289770.html

And also: http://forums.aaca.org/f219/modern-fuel-volatility-issues-carter-bbr-289771.html

I'm not using anything special, I run generic 89 octane unleaded, a little Sta-bil, a little lead additive. I buy at the same places I go for my newer cars..

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As stated in earlier post am in NJ run a 31 plymouth with carter BB1 seems to run fine and even if it sits a while starts right up my 36 plymouth has to be cranked a while if it sits even during winter doint always use stable buy gas from any station that seems to be busy and looks like they change thier filter ofter-------------BR

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As stated in earlier post am in NJ run a 31 plymouth with carter BB1 seems to run fine and even if it sits a while starts right up my 36 plymouth has to be cranked a while if it sits even during winter doint always use stable buy gas from any station that seems to be busy and looks like they change thier filter ofter-------------BR

Sorry, think I miss read your post.

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