Thermoquad Question.................

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Eat My Dust-er

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I have a 440 with a 4 bbl. thermoquad I'm having trouble with. When I drive it to town and shut it off for a while, then start it to go again it kills. The fuel filter is full but the carb is empty, when I pump the throttle by hand there is nothing. I have to dribble gas into the carb from a bottle to get it to go again. Then it runs for a few miles around town and kills again. When I am driving on the highway and keep the rpm's up it seems to be fine. What could be causing this? It's seems to have some obstruction in the carb. I can unscrew the steel line from the carb and suck gas up through the filter with no problem so it isn't the filter. Bad needle/seat, sticky float??
 
Common problems are:
you need to block the exhaust cross over to stop the intake from heating up and causing the heat to evaporate the gas in the bowls.
You could have a internal leak in a gasket or the bowl its self
Floats are to low or jammed in a way to restrick fuel flow.
has the carb ever been opened up and clean or rebuilt
Are you having any trouble with over heating and running the temp very high
Are the fuel lines running near the exhaust system at all,this will causing the vapor lock and push fuel back into the tank.
Looki into these items and post back,mrmopartech
 
I'd say you would need to tear into this carb and find out where everything is sitting and clear all passages and reset the parts to proper measurements.

Floats and such are out there new. NAPA and other AP stores should have them.

OH, and what he said............
 
It isn't pushing it back to the tank, the filter is usually full. The car was setting for a couple of months so it could have crap or varnish making something stick in the carb. The carb hasn't ever been rebuilt that I know of. The car isn't overheating. The motor and carb were taken out of another car and installed right into mine so the crossover "shouldn't" be a problem. It only happens periodically. It went 2-3 weeks the last time before it happened again. So far it seems like it does it when I shut the car off for a 1/2 hour or so and start it to go again. When I get out on the open road it runs fine again.
 
The BBD on my 318 does that all the time now that the weather's warmed up. Just crank it for a couple seconds and it should fill the carb back up. Definitely rebuild it though, it might help a bit.
 
MOPEkidD-3 said:
The BBD on my 318 does that all the time now that the weather's warmed up. Just crank it for a couple seconds and it should fill the carb back up. Definitely rebuild it though, it might help a bit.
Click to expand...

I can crank the engine and pump the throttle until my face turns purple and the battery go's dead and it doesn't pump gas up to the carb. I might just try another carb and see if that helps, if it does I'll rebuild this one.
 
Well then that's either a fuel line/filter/pump problem or your floats are messed up. With the top of the carb off you should see fuel spurting into the bowls as you crank the engine.
 
it doesn't pump gas up to the carb.
Click to expand...


MopeKid is on it ------ Fuel pump failure.

Heres the cause and effect -


Fuel pump fails...

- Fuel Bowls then empty,

- Fuel remains in the line (theres no pressure to force it into the carb - and the carb works on fuel pump pressure to feed the bowls, NOT vacuum effect)

- No fuel in bowls means no pump shooter and no throttle.

Sounds like the diaghram (or if electrical an electrical contact) is failing when the engine gets hot - engine cools down and you have a working pump again

IF - the carb is a new addition - then it may well be a vacuuum lock - but if its been on the car a while Id suggest its unlikely.

A crucial question - Has this just started happening - or is the carb a new swap in?
 
It was doing it earlier (approx. 1 month ago) so I replaced the mechanical fuel pump but with a used pump and it has run fine for a month or so but now it's acting up again. Theres some crap in the filter but I think it would take a lot to plug it. But anythings possible. Maybe I'll start with a filter and see what it does.
 
Allso you may want to make shur there is a filter befor the fule pump. There should be a filter sock in the fulr tank. With out a filter of some kind befor the pump you will be sucking all that junk through the pump. Allso I change my fule filter every oil change.

It sounds like a bad fule pump to me though.
 
Just my 2 cents, having been down the thermoquad rebuild road with no success (more than once ) I wouldnt waste the time or money rebuilding
the thermoquad. The plstic bodies are so old, and they warp etc. that you just cant fix them. Mine leaked raw fuel into my engine to the point of hydrolocking the cylinders. Had to remove the plugs in order to drain the fuel'
Not to mention that when i took the low mileage engine apart to "Check things out" after it had been sitting a few years, the bearings were wiped due to gas in the oil, No, I'd invest the money in a new carb,Based on my TQ experience
 
Poor fitting O rings cause flooding - not starvation.

Id also agree on the sock - except he's getting fuel up to the filter.....
 
Exactly. When it's running it has fuel. When he turns it off and tries to restart, the carb is empty. The fuel drains and then evaporates out of the hot motor.

Just a possibility
 
Since there might be some things going on you haven't mentioned I'd do these things.

1) Put a fresh rebuild kit in the carb making sure your jetwells aren't leaking and O-rings are in place. Install new floats and set them correctly
2) Install fuel pressure guage and make sure you are getting a steady 5.5-6.5psi
3) If fuel pressure is inconsistent or low check for obstructions, bad hoses/sucking air, cracked lines or bad fuel pump.
4) If fuel pressure is good and carb rebuild is good look elsewhere for your problem.
 
I'd check out the cheaper stuff first like filter, hoses, and fuel pump.
Then if those aren't the problem then move to the more major stuff.
You might save yourself some cash. I know from experience.
Good luck
 
Rebuild the carb. This (? gas ? ) they are selling us has so many chemicals in it that it kills the o rings in the bowls therefore draining the carb. I love these carbs are great. I ran super stock in the 70s and have one on my 410 braket motor. All you guys that hate them send them to me and they will get a good home.
 
I'm wondering if the fuel tank is vented properly? Maybe someone capped the vapor line, thinking it would be a good thing to do. Check it out?
 
Since nobody mentioned it yet. Do you have the thick insulator base gasket on it?
 
The car was setting for a couple of months so it could have crap or varnish making something stick in the carb. The carb hasn't ever been rebuilt that I know of.
i think it's the accelerator pump leather that has gotten hard over the years.
these carbs are easy to rebuild....if you've never done one, i'll talk you thru it over the phone with you while you do it on the car...or send the carb and kit to me and i'll do it, road test it for free...i hate to see people get rid of these, they work soooo good..
 
Todays ? gas is very hard on termoquads .I love them and our 410 " Valiant is running 11 with one. Usually the orings in the phenolick block go bad and leak all the gass out. Buy a kit and replace those orings . You can go to DEMON SIZZLERS web site for trick parts. These are great carbs on are very simple to work on.
 
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