I finally got my carb installed and tuned, everything works fine accept its leaking bad onto the exhaust manifold. The car is a '53 Desoto. The engine is a 251 L-head with the M6 semi-auto tranny. Its leaking out of the plunger in the first picture. There is no gasket of any sort going to this. It seems like it is acting as a drain, perhaps the float isn't set right? I'v got to get this fixed before the car bursts into flames.
Fuel leaking from the plunger would indicate the fuel level in the bowl is too high. Possible causes: (A) Defective fuel valve (B) Defective float (C) Improper float setting (D) Too much fuel pressure coming into the carburetor Jon.
Thanks Carbking. I just installed a new stock fuel pump, I hope its not that. The float seems to be good. I will pull it all back apart and check the fuel valve and float setting. Whats this plunger do anyway?
You can check the float level just by pulling the top off the carb. No need to remove the whole thing. That lever should be the arm that actuates the accelerator pump. It goes up and over, so it sees 'dry'. When you have the top of the carb off - still with fuel in there - see where it is coming from (how the fuel is getting to the vertical channel the linkage goes through). If you remove your accelerator pump. there is a check ball under it - don't lose it. If your accelerator pump circuit is plugged, then when you depress the accelerator the fuel is escaping out the top and flowing out. You can tell if the acc pump circuit is working - just look down the carb as you open the throttle butterfly. These are simple carbs. Don't be afraid of it. It is just a regular B&B with a couple of electrical switches thrown in - a full throttle switch for kickdown and an open throttle switch for the ignition interrupter. And you can reuse the old gaskets, no problem.
I had the top off today while the carb was still on the engine. I also had the accelerator pump out, but i never thought to look underneath it. It was still full of fuel. The carb is doing its job, the engine idles fine and is pretty responsive for a 1bbl. Thats why I am not thinking float adjustment. By the way, I am still having issues with my M-6. That, or I really don't fully understand it. From what i've read, you only need the clutch to put the tranny in gear then let it out and it should go like a modern automatic. Heres my issue, after i press the clutch and put it in gear, as i let off the pedal the car creaps and stalls if I don't give it some throttle. Its acting just like a normal manual tranny. Is this normal??
Bill, I will take you up on that when I decide to run a multi-carb intake. OR if my carb turns out to be junk. Thanks.
The M-6 is 'like' an automatic, but it is not an automatic. It is a semi-automatic. It is a standard transmission behind a fluid coupling. The transmission is dual range, with 'automatic' shifting between gears within a range, and manual shifting to select a range (or reverse). You engage the clutch to shift between ranges: low, high and reverse. In low range, the car starts in first gear and when you lift off the throttle, after a pause, the solenoid shifts into second with a clunk. You do not need low range for normal driving. In high range, normal driving, you engage the clutch and shift into high range. You release the clutch without giving any gas. The motor slows down a little and you hear the fluid coupling whirring. You press the gas and motor away in third. You lift, and the solenoid shifts you into fourth. When slowing down, the tranny will shift back into third by itself at a few mph. To accelerate smartly, you floor the accelrator and it downshifts - into third, if you are in high range. With this tranny it is hard to go through all four gears. You would have to start in low (first), let it shift into second, then use the clutch to shift into high range, but by then the governor will put you right into fourth gear, so then you have to kick down into third, and then release to shift into fourth. This is not a tranny for the drag strip!! Your car should want to creep a little but the motor should not be stalling. That is not right. Maybe a vacuum leak or something. The nice thing about these transmissions is that the motor would NEVER stall. Even if you locked the brakes, the fluid coupling would slip. You also do not have to give any gas when releasing the clutch pedal. Just lift your foot right off. So, if your motor is stalling, something is wrong. BTW you have a fluid coupling, not a torque converter. There is no torque multiplication. It is just a torus with the same straight fins on both impellers. The fluid coupling is very efficient as it locks up completely at higher rpms as the fluid is slung to the outside and everything locks up. The idea behind this rtranny was pretty neat, but the implementation was hobbled by the poor control mechanisms (switches, solenoids and so on) married to pretty much a standard standard transmission. The interuptor momentarily breaks current to the coil when the tranny shifts up or down. That smooths things out. MoPar even put hemis in front of those trannys. Amazing.
With the top off, and you work the linkage, the accelerator pump well should empty via the nozzles in the venturi. See if that causes the leak you see. Easy to check, just stop the motor and pump the linkage and see if the leak appears.
Thats what I'm saying! It does creep a little before the engine stalls out. You have to feather the pedal to keep it alive, but naturally by doing that the car moves when you don't necessarily want it to.
There should be a dashpot on the carb that boosts the idle a bit when the trans in engaged. If its missing, you can probably do a work around and just give it a bit more initial idle speed. I have found that you need to set the float lever lower with todays fuels. Especially when it gets warmer. the factory setting was for a lot less volatile than the stuff they are feeding us today. this crap expands more at lower temps than the old stuff. So when it gets warm it perculates out of the folat bowl as it expands and leads to flooded engine hot start problems. Also if you put a rebuild kit in, some folks have been reporting a discrepency with some of the kits, in that the new needle and seat assembly is not the same length as the old ones so what you thing is the correct float level will not shut off the flow of fuel. Sometimes the small clip the holds the float pivot pin will also not be set in all the way also keeping it from closing the needle. In any case check the float level, the float pin retaining clip and the needle and seat.
I am also having some issues with the choke on this carb. I took the heat riser out of the exhaust manifold, now I am worried that there will not be enough "heat" going up the tube to get the choke to open on its own. Is there a way to convert this carb over to a manual choke?
One more thing I forgot to ask about this carb. Does this have a manual primer? I ask this because there is a button about midway down on the right side of the carb. I really wish I could find a good exploded view of this particular carburetor.
the fitting you are noticing is likely the item that is activated by the dashpot to regulate the idle withthe transmission engaged. Not your carb but you can see the dashpot on this on acting on a lever connected to the throttle likage. The heat riser should not have to much effect on the heat of the manifold as far as the choke is concerned. There should be plenty of exhaust heat to pull the choke open. the should be s sheet metal "stove" o top of the manifold. there is usually agasket to keep the heat i but these deteriorate over the years.
I hate to disagree, because plym_46 knows his stuff, but I do not recall a dashpot on the single-barrel flat six versions of these carbs. But I do agree with him that your idle might be a little too low. Set the e-brake, chock the wheels, start the motor, put her in gear and set the idle such that the motor just keeps running. If you absolutely need a manual choke just hook the cable to the arm at the end of the choke shaft. These motors usually run without a choke - just pump the crap out of them on a cold cold start, and let the motor warm up a bit. There is no primer on these carbs. That button is probably a plug sealing a drilled passage.
Upon some further reading you car does have a dashpot, it the item nnear the float bowl where the two wires connect. According to the site below this was the carb equipped on ealier cars withthe M4 edition of the semi auto. but it shold work as detailed on the data sheet illustrated http://old-carburetors.com/Chrysler/pages/014-Chrysler.htm I am trying to get some one to post a picture from a later application, but from what I remember these came with stromberg carbs. maybe somebody swapped this on over time. This from a discussion a few years back on the p15 d 24 board "The other thing to consider in Fluid Drive vehicles that won't act like they're supposed to, i.e., keep running at a stop with the clutch out, is the carburetor. Fluid Drive vehicles had a carb with a dash pot. The purpose of the dash pot was to keep the vehicle from decelerating too quickly and stalling the engine. If a non-dash pot carb were installed I'm not sure you'd get the full advantage of the Fluid Drive. "
I can't view the pictures or post on p15d24, my account has not been activated yet. I noticed you posted it as a '51/'52 desoto. Mine is actually a '53, dunno if it makes a difference. Also, mine has the Canadian engine.
Here are a few photos of a carb I pulled off the shelf. It clearly is a Carter carb. I was under the impression that this carb came from a MoPar with a Gyromatic transmission. It does not have a dashpot. It does have two electrical switches. One is a full throttle switch and the other is a idle switch. Is what we are calling the dashpot the idle switch? Or, maybe this is a carb from a vehicle with an OD transmission. I once had a 50 Dodge with the M6 and it did not have a dashpot as best as I can recall. Maybe the earlier cars did not? In any event, here are also some photos of the underneath and side so that the OP can see where the accelerator pump flat linkage goes up inside. Also, a close-up of where you would attach your manual choke cable.
Very similar, perhaps just older. For example the cover on the top of the switch on mine is aluminum. That is definitely the same "button" that I have on mine, but mine does not have that linkage. I can't tell if yours had it or not, but if you look at my pictures with the wiring shown you'll notice a third wire going to the middle of the carb. Pretty much directly across from the "button", so that could very well be the electric dashpot.
the web page of the carb calls the item on the carb that the wire connect to a dashpot. seems to be internal rather than external. it purpose it to keep the idle a bit high at slow speeds so the trans doesn;t drag down the engine.
The Jalopy Journal
