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Thermoquad idling extremely rich **UPDATE**

Posted By: DUFFMAN

Thermoquad idling extremely rich **UPDATE** - 06/17/09 01:17 AM

A week ago I swapped an Edlebrock 1406 for a factor 340 TQ (6139 I think) that I had just rebuilt. It was running great all weekend, then tonight the car started hard and when I did finally get it started it was running so rich it's puffing out black smoke.

I took the top of the carb off, check the float height (brass floats), took the needles out inspected them and blew out the seats. I couldn't find anything wrong with it. I put it back together and it's still running rich like before.

I'm not sure what to do next.
Posted By: DUFFMAN

Re: Thermoquad running rich - 06/17/09 01:46 AM

I'll also mention that I did swap a 14" Edlebrock air cleaner for a factory drop door air cleaner last night. (I noticed it menation as a problem on Demonsizzler's site) but the rich condition continues even with the air cleaner removed.
Posted By: RapidRobert

Re: Thermoquad running rich - 06/17/09 01:56 AM

Is the metering rod tree being pulled down at idle
Posted By: DUFFMAN

Re: Thermoquad running rich - 06/17/09 02:15 AM

Quote:

Is the metering rod tree being pulled down at idle



I don't know, but it is moving freely. My kids are in bed now so I can't start it to check if it's being pulled down by vacuum.
Posted By: DUFFMAN

Re: Thermoquad running rich - 06/17/09 11:00 AM

For the day crowd.
Posted By: DUFFMAN

Re: Thermoquad running rich - 06/17/09 06:45 PM

Here's what I'm thinking; the problem didn't start until I swapped air cleaners, so I must have bumped something in the process. The only 3 external things I can think of that would affect fuel metering are;

1. The metering rod tree. Which seems to be moving freely, but I will watch it with the engine running to make sure it pulls down.

2. Divorced choke. I can take measurements to make sure it is still adjusted properly.

3. Choke pull off. I'll hook a vacuum pump to it and make sure it's still working.

Anything else I should check?
Posted By: boydsdodge

Re: Thermoquad running rich - 06/17/09 06:53 PM

Did you check the needle movement yet?
Have you adjusted the needle height?
Do you know who rebuilt your carb and what size needles used?
Not answers but some thoughts.
Posted By: DUFFMAN

Re: Thermoquad running rich - 06/17/09 07:33 PM

Quote:

Did you check the needle movement yet?



They move up and down freely, I just don't know if they are being drawn down by vacuum or not. I will check that tonight.

Quote:

Have you adjusted the needle height?



No, but it was running fine before, so the height should be okay.

Quote:

Do you know who rebuilt your carb and what size needles used?



I rebuilt it myself. The needles had "2127" on them. It was running fine before with them so I can rule out the needles themselfs. Also it still drives fine, the problem is only at idle.
Posted By: boydsdodge

Re: Thermoquad running rich - 06/17/09 07:35 PM

Any leaking around the shafts?
Thats a good carb to build 72 is a good year.
Posted By: DUFFMAN

Re: Thermoquad running rich - 06/17/09 07:41 PM

Quote:

Any leaking around the shafts?



If it was leaking around the throttle shafts I should have a lean condition.

Quote:

Thats a good carb to build 72 is a good year.



I bought it to make my 1972 318 into a 340 clone.
Posted By: DUFFMAN

Re: Thermoquad running rich - 06/17/09 11:15 PM

Okay, the metering rods are dropping, the choke pull-off is holding vacuum and the divorced choke is working fine, but it's still running extremely rich. I'm afraid I'll have to go back to the Eddy.
Posted By: 1_WILD_RT

Re: Thermoquad running rich - 06/17/09 11:44 PM

What style "O" rings did you install in the wells? If they leak/seep your carb is gonna dump fuel & it's fat city...
Posted By: DUFFMAN

Re: Thermoquad running rich - 06/17/09 11:46 PM

I originally used the square o-rings, when I took the top off I replaced them with the "X" style o-rings that Demonsizzler recommends using. No change with either style o-ring.
Posted By: RapidRobert

Re: Thermoquad running rich - 06/18/09 12:55 AM

Dont give up on it yet it's gotta be something simple(it will be when you find it )especially since it happened suddenly. More thoughts: put the old aircleaner assy back on & see what happens. maybe the underside of the lid on the new one is too close to the vents but I wouldn't think it'd cause that kind of richness. I'm wondering if one of the wells in the phenolic body sprang a(slight) leak and when you had the top off neither of the floats were waterlogged? I would take the whole carb off & go over it w a fine tooth comb. You'll have a good laugh when you spot it.
Posted By: Michael Ecks

Re: Thermoquad idling extremely rich - 06/18/09 12:59 AM

It's been a long time since I have had my hands in one. IIRC on the bottom of the bowl there are two smaller bakelite pieces glued to it to form a kind of V shape in one of the fuel passages. Those are bad to leak over time. When I was working on them we put something like JB Weld around those seams and also put a foam part from a Q-Jet in between the bottom of those V's and the base casting to keep upward pressure on the seam.

If those seams are leaky they would allow fuel to pour into the throttle bores between the bowl and the base casting.
Posted By: 1_WILD_RT

Re: Thermoquad running rich - 06/18/09 01:09 AM

I too prefer the X rings (proper term is quad ring) I'd also suggest looking at the bottom side of the wells as a possible leakage point, remove the carb, lift it straight uo, don't tilt is si the fuel stays in the bowl... remove the screws & lift the body off the baseplate, if theres fuel in the base plate where the well extensions sit you've found your problem... Typically a good cleaning with a dremel & a coat of JB Weld will cure that issue... It may have been an old leak or when you rebuilt the carb the cleaner you used may have attacked the old sealer...

Edit, I see while I was on the phone MM covered the wells pretty well... Well Well
Posted By: DUFFMAN

Re: Thermoquad running rich - 06/18/09 01:12 AM

Quote:

More thoughts: put the old aircleaner assy back on & see what happens.



I've been running it without an air cleaner and it doesn't affect it

Quote:

I'm wondering if one of the wells in the phenolic body sprang a(slight) leak and when you had the top off neither of the floats were waterlogged?



Float bowl levels looked normal.

Quote:

take the whole carb off & go over it w a fine tooth comb. You'll have a good laugh when you spot it.



I'll probably still go back to the Eddy to make sure the TQ is the problem. If it is I might just end up sending it to Demonsizzler to get rebuilt
Posted By: 1_WILD_RT

Re: Thermoquad running rich - 06/18/09 01:19 AM

Quote:


Quote:

I'm wondering if one of the wells in the phenolic body sprang a(slight) leak and when you had the top off neither of the floats were waterlogged?



Float bowl levels looked normal.



You'd never see a visable flaw in the wells, seperating the body while it still has fuel in it you should see a wet area.. Most experianced TQ guys just epoxy them as SOP...
Posted By: astrobuf

Re: Thermoquad idling extremely rich - 06/18/09 02:34 AM

Quote:

A week ago I swapped an Edlebrock 1406 for a factor 340 TQ (6139 I think) that I had just rebuilt. It was running great all weekend, then tonight the car started hard and when I did finally get it started it was running so rich it's puffing out black smoke.

I took the top of the carb off, check the float height (brass floats), took the needles out inspected them and blew out the seats. I couldn't find anything wrong with it. I put it back together and it's still running rich like before.

I'm not sure what to do next.




I'm afraid I've seen this problem with my TQ. The problem turned out to be high fuel pump pressure. I was running at 5-6 psi and this was enough to push the needles off the seats. The problem only occurs when the engines running and the high bowl level ends up spilling fuel from the bleeds into the throttle bores. It makes the car run really rich and unresponsive to idel screw adjustments.

To fix this, I ended up plumbing in a fuel pressure regulator and dropping pressure to 3.5 psi. Problem solved!

Astrobuf
Posted By: DUFFMAN

Re: Thermoquad idling extremely rich - 06/18/09 02:47 AM

Well I got the Eddy bolted back up, but I didn't get it back on until after the kids went to bed so I'll have to wait until I get home from work tomorrow to fire it up.
Posted By: 68Bullit

Re: Thermoquad idling extremely rich - 06/18/09 03:02 AM

Quote:

I'm afraid I've seen this problem with my TQ. The problem turned out to be high fuel pump pressure. I was running at 5-6 psi and this was enough to push the needles off the seats. The problem only occurs when the engines running and the high bowl level ends up spilling fuel from the bleeds into the throttle bores. It makes the car run really rich and unresponsive to idel screw adjustments.

To fix this, I ended up plumbing in a fuel pressure regulator and dropping pressure to 3.5 psi. Problem solved!



I think this would be VERY worth checking out. I talked with DemonSizzler about this very thing and we agreed that it couldn't hurt to add a regulator just to be sure.

My TQ is doing the exact same thing BTW, and I haven't taken anything apart yet. DemonSizzler just sent me this carb and it looks great, and I'm also confident that it has been prepped sufficiently.

Think about this. If you go back to your Eddy carb, and it runs fine, I still wouldn't discount that if your fuel pressure is high, that one carb may do fine (though probably temporarily), while the other one runs overly rich (This case being the TQ)
Posted By: RapidRobert

Re: Thermoquad idling extremely rich - 06/18/09 03:11 AM

It happened all of a sudden which makes me think leaking wells rather than the psi suddenly going higher, if it's not regulated now there is no regulator to fail to let the psi go higher, that & when it happened it also would not start so I dont think excessive psi would come from a fuel pump at cranking speed. . If the wells spring a minute leak it would flood it & make it hard to start & when it does start it'd be way rich as described.
Posted By: DUFFMAN

Re: Thermoquad idling extremely rich - 06/18/09 12:45 PM

I'm not giving up on the TQ just swapping for the Eddy for right now. First, to make sure that the problem is with the carb and not something else. Second, since the car is my weekend cruiser, and the weekend is almost here, so I want it drivable again.
Posted By: Rug_Trucker

Re: Thermoquad idling extremely rich - 06/18/09 06:11 PM

Quote:

It happened all of a sudden which makes me think leaking wells rather than the psi suddenly going higher, if it's not regulated now there is no regulator to fail to let the psi go higher, that & when it happened it also would not start so I dont think excessive psi would come from a fuel pump at cranking speed. . If the wells spring a minute leak it would flood it & make it hard to start & when it does start it'd be way rich as described.



Another symptom of leaky jet wells is you have to prime it after it sits overnight. The carb goes dry.
Posted By: DUFFMAN

Re: Thermoquad idling extremely rich - 06/18/09 08:00 PM

Quote:

Another symptom of leaky jet wells is you have to prime it after it sits overnight. The carb goes dry.



That wasn't a problem. In fact it popped right off after sitting overnight without even stabbing the gas to give it a pump shot and close the choke.
Posted By: boydsdodge

Re: Thermoquad idling extremely rich - 06/18/09 09:23 PM

Posted By: DUFFMAN

Re: Thermoquad idling extremely rich - 06/18/09 11:05 PM

It's running great with the Eddy, so there is definetely something wrong with the TQ.
Posted By: DUFFMAN

Re: Thermoquad idling extremely rich - 06/19/09 11:02 AM

Whatever the problem is it requires vacuum. The carb has been sitting on my work bench now for 1.5 days full of gas and hasen't leaked anything.

I still want to find the problem and fix it because I would like the stock appearence and it has better throttle response than the Eddy.
Posted By: DEMONSIZZLER

Re: Thermoquad idling extremely rich - 06/19/09 11:16 AM

More than likely, either the needle seat(s) is/are not tight enough in the top and the float bowls are over-filling or a float is defective and taking in gas(only if it feels heavier than it should and you probably already know it is not)or you are missing one or both of the seat gaskets. Float level too high is the last possibility, David.
Posted By: DUFFMAN

Re: Thermoquad idling extremely rich - 06/19/09 12:50 PM

This happened suddenly. So is it possible that that one of the seats loosened up?

When this all first started I took the top off, checked the float level and inspected the needles and seats (which are new). I noticed some brass shavings in the bottom of the passenger's side bowl so I cleaned them out. Maybe I have a defective seat?
Posted By: DUFFMAN

Re: Thermoquad idling extremely rich - 06/24/09 12:56 AM

Quote:

More than likely, either the needle seat(s) is/are not tight enough in the top and the float bowls are over-filling or a float is defective and taking in gas(only if it feels heavier than it should and you probably already know it is not)or you are missing one or both of the seat gaskets. Float level too high is the last possibility, David.



Over the weekend I openned the TQ up and noticed brass shavings in the bowl again. So I swapped the needle seats with the old ones and reset the float height.

Tonight I put the TQ back on and it's not running rich anymore, but I still have a problem, I still can't get it to idle below 850 rpm without it dying and after I peg the throttle it settles back down to around 1000 rpm even if I push the throttle closed. I also noticed the choke plate isn't openning fully.
Posted By: patrick

Re: Thermoquad idling extremely rich - 06/24/09 02:01 AM

Quote:

Quote:

More than likely, either the needle seat(s) is/are not tight enough in the top and the float bowls are over-filling or a float is defective and taking in gas(only if it feels heavier than it should and you probably already know it is not)or you are missing one or both of the seat gaskets. Float level too high is the last possibility, David.



Over the weekend I openned the TQ up and noticed brass shavings in the bowl again. So I swapped the needle seats with the old ones and reset the float height.

Tonight I put the TQ back on and it's not running rich anymore, but I still have a problem, I still can't get it to idle below 850 rpm without it dying and after I peg the throttle it settles back down to around 1000 rpm even if I push the throttle closed. I also noticed the choke plate isn't openning fully.



sounds like a vaccuum leak
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