Won't rev

[DonaldSmith]

Today I took the 47 DeSoto for a neighborhood drive.  Seemed OK under 25 mph.  Took it on the main road, and it upshifted but bogged down.   Back in the garage, could not get it to rev.  Bogs down, tries to rev but slows down,  lup lup lup.   

 

DeSoto Convention 4 weeks away!   Carburetor suspected.   I'll remove the top and check the step-up piston and look for anything out of place.   The shop manual says, if there are any problems, rebuild the carburetor.  Wah.   I got a Carburetor Exchange in 2015, 8 years ago.  Maybe better than trying to rebuild it myself.  Thoughts?   Sympathies?  

[Plymouthy Adams]

does it bog out of gear and setting still?  if not and only under load....would think you may have condenser issue 

[uncleaud]

I rebuilt the carb in mine and was pleasantly surprised at the ease of it. Except for the accelerator pump there doesn't appear to be any moving parts to wear out. Everything else can be corrected with a can of carb cleaner and some compressed air. Sounds like crude in the bottom of the float bowl that got into the main jet. If you are mechanically inclined at all I wouldn't be afraid of tearing into the carb. Think it took as long to get the air cleaner off a redo the carb.?

[DonaldSmith]

P Adams, it bogs out of gear, sitting still.  Related to engine speed, not road speed or load. 

 

Uncle aud - trying to encourage me?   What's a good source for carb rebuild?  (Mike's Carbs comes to mind.) 

[Plymouthy Adams]

thanks for the feedback.....before you dig into the carb.....may be worth a glance at condition of the ignition system.....if you enrichen the mixture with the choke does it seem to do better?

[DonaldSmith]

Automatic choke.  I've got the air horn off already.  But after checking internals, I can put the carb back together, and manually close the choke valve,  

The symptoms occur with the car standing still, which is good.  I'll know when I can get it to rev again, without venturing out of the garage. 

[kencombs]

Remember the first rule of troubleshooting performance issues:   Most carb problems are ignition related.   I'd  first rule out points, cap and condenser.  

 

Then fuel pressure and flow to the carb.

 

Lastly deal with the carb if still needed.

[DonaldSmith]

Too late to rule out ignition.  I put the top back on carb, started the engine.  Revved up, sputtering badly.  Fuel running out of carb.   Float valve?  Took top off, put hose to fuel intake, float valve working.   Something wrong. 

Carb Exchange out of my model.  I'll go for the DIY rebuild.  Mike's Carbs wants 70.95 tor the kit, plus recommended add-ons.    I won't know if I need any add-ons. 

I might look around for other sources for the rebuilding kits.  Wish me luck. 

[plymouthcranbrook]

I had so much trouble with my B&B on my 52 that I finally converted to Langdons 2 Bb conversion. Best running step I ever took

[DonaldSmith]

Langdon 2 bb conversion?  Tell me more, tell me more!

[Sniper]

21 minutes ago, DonaldSmith said:

Langdon 2 bb conversion?  Tell me more, tell me more!

 

Not available anymore, he's shutting down.

 

If it's a BB carb Rockauto has the kit for half the price you mentioned and I don;t know what add ons he's trying to sell you but I didn't need any.  If it

s a Stromberg, to quote Feldlwebel Schultz, I know nothing.

[andyd]

Langdons carby was a Weber 2 barrel that I think was used on the 2ltr Ford Pinto type 4 cylinder plus possibly a few others........here in Oz it was used on the 1980's Ford 250 cube 6 cylinder so may have been on similar size engines in the USA........think it was listed or known as a 32/36 Weber or some such designation........andyd

[Doug&Deb]

Donald changing the carb may not be an option for you. I’m assuming you have the semi auto trans and that limits your carb choices. Rebuilding your carb is never a bad idea especially since most of the new kits have ethanol resistant parts. If that doesn’t fix the problem then I recommend basic ignition diagnosis. Start with a compression test and go from there. Good luck.

[rallyace]

Is your vacuum advance working properly? Is the vacuum line connected to the carb and not to the manifold?

[DonaldSmith]

The vacuum advance was connected to the carb, and has been.  This symptom came upon me suddenly.  The carb is off, waiting for the rebuild parts.   (The battery is disconnected, lest some absent-minded fellow (me) turns the key and turs on the electric fuel pump.)

While the line is disconnected from the carb, can I check the vacuum advance with some sort of pump? .  

[Sniper]

Vacuum advance doesn't apply at WOT.

 

Yes you can use a vacuum pump to at least test the vacuum, advance diaphragm for leaks.

 

Once the engine is running you can use the pump to test max advance, the FSM ought to have the numbers you need to test.

[D35 Torpedo]

What I have discovered, is that the step-up circuit can mess with things big time. The needle and jet do wear out, by the way. When vacuum takes over and slams the needle shut, I get sputtering and a lack of power. Perhaps the piston and bore are worn to the point of having an internal vacuum leak. Not sure. Pop the top and inspect the condition of the needle and spring. Make sure the o-ring that the piston seats against is intact. 

[DonaldSmith]

I've started the carburetor disassembly -keeping the small parts in zip bags.  Mike's carbs included detailed instructions, which I'm following religiously.  I won't be able to  clean the carburetor until I remove the vent tube, and the tool won't get here for another week.  I did stick a screwdriver down the shaft and engaged the vent tube slot.  It took little turning to see that the screwdriver wanted to slip out of the slot.  OK, I see. 

 

I've looked into the Simple Green Pro Heavy Duty instructions for the day I can dip the parts.  I've been keeping the various related parts together in the bags.  Maybe I'll soak them together in separate containers. I don't want to get the balls mixed up.

 

(You sophomores in the back of the class can do something with that, such as, "I told the parts guy that I had all the carburetor parts; I have two balls, and one is smaller than the other.  He looked at me funny."  This also works in a discussion of parts for a trailer hitch.  I'll go back to my Andy Dodge corner now.)  

[desoto1939]

I like to place the small parts in a numbered egg cartoon to eliminate any issue of which part is the next one to go back into the carb especially those tinny tiny ball bearings.

 

Rich Hartung

 

 

[DonaldSmith]

I'm getting the Simple Green tomorrow, and through this week I can clean everything except the main body, which will still have the vent tube installed. I may use separate jelly jars for the related parts which I am keeping in separate bags, to keep each group together.   I can begin to reassemble things that don't go in the main body, until I get that special tool for the vent tube.  (An egg carton would work to keep the parts separate, but I can imagine myself bumping it and scattering the contents.)

 

[DonaldSmith]

Class today on "Vent Tubes". 

Mike's Carbs' diagrams and instructions cover a thin tube that goes up at an angle from under the main body, No. 36, the "Tube -Main Vent".   "Do not remove it unless you have a special tool."   OK, I won't.

Then there's that slotted brass thing at the lower left, for which I am awaiting the special tool, known only as a "Vent Tube"? 

This is the Fluid Drive, automatic choke carb, so it must have a special function, something to do with the large chamber beside it?  Dashpot?  Yes! My Shop Manual shows all sorts of dashpot parts.  I should be working off the diagram in the Shop Manual, to supplement the instructions that came with the repair kit.   Happy days. 

   

 

 

[DonaldSmith]

The Simple Green has been mixed, and the major carb parts are soaking in it.  (2-hr max or the metal will discolor.)  Then rinse, dry, blow out passages, ,etc. 

Been waiting for days for a special tool.  Comedy of errors.  The seller mistakenly cranked out a rebate for me.   Then I received the tool and found that the tool is nowhere close to being right.  Wrong info on the forum?  I'll pay the postage to return the tool, and leave the rebate as it stands. 

 

I thought the tool came from Mike's carbs.  No, they cobble their own tools if they need them.  But soaking the parts should work.  Maybe clear the passages with a wire.  Don't remove the main vent tube - blow it out.   I removed the throttle valve, for cleaning off gas residue, but they recommended leaving the choke valve alone.  I'll clean the small parts as needed.  Assemble per the book, per the book.  Take my time.   

 

My Shop Manual illustration shows me that  carburetors for use with the semi-automatic transmission have additional features:

Kick-down switch built into the carb body. 

Dashpot system, with:  Anti-Stall Magnetic lockout and Screw;  Dash Pot Lifter Link and Pin;  Dash Pot Rod and Plunger;  Dash Pot Valve Cage, with Valve Cage Plunger and Rod and Operating Spring.  I'll know these by heart by the time I'm through. 

 

Mike's Carburetors kit seems to have all the special parts, and then some.  Two versions of needle valve seat, for different connections to the fuel line.  Scads of gaskets, for  every conceivable variant.  Good instructions, but light on dash pot info. 

 

Wish me luck. 

[Kilgore47]

I have rebuilt hundreds of carbs.  Never used a special tool to remove a jet.  I just modify an old screw driver to fit the slot on the jet.  Minor grinding or filing is required to fit the hole and slot.  You want the blade to be as wide as possible so that it catches both sides of the jet and it should be thick enough to fill the slot on the jet.  Never damaged one using this method.  I have had to remove many jets that other people have ruined and that usually requires drilling.  And after you are done you can still use the screw driver as a regular screw driver.  A pawn shop is a good source for old screw drivers if you don't want to modify the tools you have.

[DonaldSmith]

Shazam!  My big old screwdriver fit perfectly!  All that angst over a special tool to remove the "Dash Pot Valve Cage".  I blasted it with carb cleaner and compressed gas and now I can screw it back in. 

On to the next minutia.  Step by step, check my work.  When I got this rebuilt carb several years ago, I took photos of it from six views.  Those photos are invaluable to check if I got the parts back together right.    

[DonaldSmith]

C-clip conundrum - Carb going together, step-by step.  Pump Discharge Pump Ball (the smaller ball) in place in a recess in the bottom of the pump shaft.  To be secured with a wire C-clip that engages four lugs.  The C-clamp keeps the ball in place.  The ends of the C-clip should be opposite the ball. 

The C-clip came out easily enough, but I have trouble getting it back in place.  Too deep and dark for needle nose plyers.  "Special tool"?  Another way to secure the ball?  Artistic bend of a paper clip?

 

Here's the carb body, with a view down the pump shaft, with the wire C-clip beside the carb.   The ball is out of view, but two of the four lugs are visible.   Hep!

 

 

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