Calling all Thermoquad Experts! again...

Okay been having problems with my 73 440 thermoquad in cold weather not wanting to stay running until warmed up and today after the truck was warmed up and been driven around a little bit acted like it was going to stall so I tapped on the pedal to give it a shot of gojuice and it stalled anyways and then sounded like it ran backwards. Then it wouldn't start. I finally got it to start and run but now if I let off the gas it just stalls. No idle!

I know I have to disassemble and inspect but what should I be looking for that might have went bad?

First question, are 100% certain it's the carb?

Demon sizzler will build you a great carb, but I would read and do this first.
http://www.thermoquads.com/page204.html

Well pretty sure. Everythings new I suppose it could be the new petronix plug-n-play distributor but I highly doubt it. I checked to see if each cyl was recieving spark when it wouldn't start and they all were. so it's got to be fuel related...

If you are certain it's fuel related dont be so quick to dig into the carb itself. The first thing I'd do is check for a clogged fuel filter, trace everything up to the carb intself first, if it's good then search for a vacuum leak, (a dry rotted rubber vacuum hose is a common problem and can cause intermitant issues like that) have you had a vacuum gauge on it while it's running?

You said it has issues when both hot & cold, is your choke opperating properly? Maybe hanging up or sticking?

First thing I checked was for a vacuum leak. New hoses but I'll recheck in the morn. Never checked the fuel filter as it's fairly new (about 1500 miles on it). It's getting fuel via the accelerator pump so I'm assuming that it's not running dry. not vacuum gauged it. Just acting like it was running out of fuel at idle. Just noticed lately when it was cold started I had to pump it about 3-5 times to get it to fire up then it would start and run good for about 5-10 seconds then stall at any RPM until it got hot. Then it was usualy fine. Now all of a sudden when it's hot it will start and run as long as the RPM's are up but once you let off the gas it stalls. I think my choke (mechanical heat type)is not working properly which would explain the cold start problems but not the hot idle problem?

Hmmm, well be sure the choke is functioning properly then trying a vacuum gauge would be the next move, see if it holds steady or fluxuates. Try spraying some starting fluid around the base of the carb and the intake and see if it picks up any rpms, sometimes leaks come and go with hot/cold situations.

I'll check that out in the morning!

Thanks!

No problem, if you ever get up to Spokane I'll be happy to have a look at it for you "on the house".

Good luck!

Bought my 67 D100 stepside there about a month ago.

From Ralph?

don't remember his name. White with blue racing stripes

I emailed you some pics.

if you do rebuild it, remember to check the jet wells for fuel leakage. This would cause a over rich condition.

I saw that truck but I don't think Ralph had it (hes a local friend of mine who buys about every old Dodge truck he sees).

*I gave your carb problem some further thought. Try unhooking the fuel line at the inlet and turn the engine over until you are sure the carb is out of fuel, this will drop the floats down lifting the needle all the way from the seat, then hook it back up and start it up. Sometimes if there is some crud clogging the seat the incomming fuel will wash it out when it's opened up like that. Also, once you eliminate all external possibilities, you would want to be sure you don't have a leaking/sunk float. The internal "O" rings ademon mentioned can certainly cause issues but it's not that common for them to just suddenly fail, it's usually something that surfaces immediately after a rebuild due to an impropper installation.

Sounds like a lean condition. Generally speaking, a lean T.Q. will have a poor or no idle circuit until the engine and intake are warm enough for the fuel and air mix to atomize. At this point, the engine will gain most of the idle circuit but will likely still be lacking, David.

Fuel pump maybe? How much pressure do you have at idle & at higher rpm?

I was thinking along those lines as well David, but when it does it after warming up I started thinking otherwise (like it may not be the carb at all).

Either way, long distance diagnoses of a carb issue isn't much more than a guessing game/process of elimination IMO, which is why I usually stay off these types of threads. Hopefully he'll get to the bottom of it and we'll all know for sure.

Another vote here for a LEAN condition...... and could the OP have NO CHOKE and a blocked intake heat cross-over also ?

That makes cold-starts even worse.

I've been suspecting my valley pan isn't sealing right since I reused the old one when I did a cam change. Think I'll pull it off and install a new one just to be sure.

UPDATE: Well pulled the intake off and sure enough, as suspected, it was sucking oil and air from under the valley pan. Now I remember why I always say NEVER try to reuse gaskets... That must have been why the truck was running hot all the time! Also I have a new problem! Seems the reason why it's not been running right is because I have no spark sometimes!!! ARGH!

There you have it! None carb related.

I apologize for blaming the thermoquad! Will you all forgive me?

Quote:

---

UPDATE: Well pulled the intake off and sure enough, as suspected, it was sucking oil and air from under the valley pan. Now I remember why I always say NEVER try to reuse gaskets... That must have been why the truck was running hot all the time! Also I have a new problem! Seems the reason why it's not been running right is because I have no spark sometimes!!! ARGH! [/quote

Curious about this... How can you tell it been doing that after pulling the intake?? What do you look for?

Assuming you are talking about sucking air from under valley pan? There will be oil all over your intake runners of the heads and valley pan.

On your spark issues........I once installed a Pertronix conversion on a 1966 440 (which was otherwise 100% bone stock original) and I had an intermitant miss immediately upon start up. The supplied rotor did not fit well and was wobbling causing it to slam into the contacts in the dist cap. My distributor was an original single point chrysler piece, it seemed that Pertronix had a design flaw in the 440 application? I don't know, all I know is that it fit like crap on mine and I shelved it and went back to points.

I have there distributor system. Which has been working flawlessly for the last 1500 miles but I think my Flamethrower II coil just took a crap because I get a constant flash (when cranking)when hooking the test light to the coil neg. but I get no spark out of the secondary coil wire going to the distributor cap. Sucks when new stuff doesn't last!

Quote:

---

Assuming you are talking about sucking air from under valley pan? There will be oil all over your intake runners of the heads and valley pan.

---

thanks