Thermoquad dry fuel bowl at cold start and restart

[Geoff 2]

When you remove all the screws, enough gap is there at the lower gasket for fuel in the bowl to run over the edge into the base cavities....before you have time to lift off the bowl.

 

[Charlied]

When you remove all the screws, enough gap is there at the lower gasket for fuel in the bowl to run over the edge into the base cavities....before you have time to lift off the bowl.

Hi Geoff,
OK,will re-assemble using new gaskets, new O rings and hope for the best!
FYI attached photos of O rings, pair on left is what I pulled out (look fine, pliable, no distortion) Second photo shows top pair what I removed and brand new ones on bottom, look and feel identical.
So still have no explanation why fuel bowls run dry. Options are add an electric fuel pump, or a brand new carb.
Have you any recommendations on new carb, leaning towards Edelbrock (what model), what do you think?
Thanks again for your time and guidance, much appreciated.
Just want to drive the car with confidence it will re-start !

 

[Jonas Nordstrom]

Strange that the fuel bowls still runs dry...
The TQ is awesome but patience is needed and parts are hard to find.
Changing carb I would go with the TQ light: the Holley Street Demon 625cfm.

 

[Charlied]

Strange that the fuel bowls still runs dry...
The TQ is awesome but patience is needed and parts are hard to find.
Changing carb I would go with the TQ light: the Holley Street Demon 625cfm.

Jonas,
Thanks for your recommendation.
Not ready just yet to give up on the TQ, but my patience running short. Disappointing that I can’t explain why with no leaks bowls run dry. Don’t know what I can do to test.

BTW TQ kits readily available here and I some other parts ,if you need something let me know.Do have fairly good extra fuel bowl ( no leaks).

Be well.
Thanks

 

[LB0442]

I rebuilt quite a few of the thermoquads but there are a few people that do them professionally, I'll just add 1 trick I have learned. I was rebuilding a head on a GM 2.5 and had to buy fuel line O rings, noticed the small return line. Next thermoquad I did I used that small O ring inside the quad ring and it fits perfect. It is not too fat so it will still go to it's correct crush and it adds a little bit more of a sealing area. It is # 22514722. Kinda hard to see in the picture but I have 1 inside of the factory Quad ring. Since it is a fuel line ring the ethanol doesn't bother it. I have done about 5 carbs with this and so far no problems.

ACDelco GM Pipe O Ring Seal Escalade Cavalier Hummer H2 217-452 22514722 Qty10 | eBay

Probably get them cheaper from your local dealer the way shipping is now.

 

[Charlied]

I rebuilt quite a few of the thermoquads but there are a few people that do them professionally, I'll just add 1 trick I have learned. I was rebuilding a head on a GM 2.5 and had to buy fuel line O rings, noticed the small return line. Next thermoquad I did I used that small O ring inside the quad ring and it fits perfect. It is not too fat so it will still go to it's correct crush and it adds a little bit more of a sealing area. It is # 22514722. Kinda hard to see in the picture but I have 1 inside of the factory Quad ring. Since it is a fuel line ring the ethanol doesn't bother it. I have done about 5 carbs with this and so far no problems.

ACDelco GM Pipe O Ring Seal Escalade Cavalier Hummer H2 217-452 22514722 Qty10 | eBay

Probably get them cheaper from your local dealer the way shipping is now.

View attachment 1517454

This is a great tip,off to my local Chevy dealer tomorrow. Sounds like what the doctor ordered.

Thanks
Charlie

 

[Geoff 2]

Charlied,
The o rings in post #42 look to be the correct type. They are an X in cross section. I have been using standard o rings now for many years, fuel resistant, 1/16" thick about 3/8" OD.

Even if the main jet pods on the black body were still leaking, they would only fill the cavity in the base; provided the gasket was sealing, no fuel could leak out. So I do not see how this could be draining the bowls.
I would try this bench test: fill the carb by pouring fuel into the bowls through the front tube. Stop when fuel dribbles out of the pri boosters. Leave as reqd. Look for leakage under carb. Next day, turn carb over & see how much fuel comes out.

Stick with it.

Edel carbs: an 800 AVS for a big block, 650 AVS for a small block.

The Demon carb is made by Holley, so best left in the box. One fitted to a 400 engine bogged, no amount of tuning helped & neither did a ph call to Holley from Oz. Refitting the QJ fixed the problem...

I would install a Carter 4594 elec fuel pump. They last forever & easy starting.

 

[Jonas Nordstrom]

The Demon carb is made by Holley, so best left in the box. One fitted to a 400 engine bogged, no amount of tuning helped & neither did a ph call to Holley from Oz. Refitting the QJ fixed the problem...

I would install a Carter 4594 elec fuel pump. They last forever & easy starting.

We all have different experiences, Ive fitted and tuned the Street Demon on four cars. Runs perfect with no bogs.
Though if it was me I would stay with the TQ.

 

[Charlied]

Charlied,
The o rings in post #42 look to be the correct type. They are an X in cross section. I have been using standard o rings now for many years, fuel resistant, 1/16" thick about 3/8" OD.

Even if the main jet pods on the black body were still leaking, they would only fill the cavity in the base; provided the gasket was sealing, no fuel could leak out. So I do not see how this could be draining the bowls.
I would try this bench test: fill the carb by pouring fuel into the bowls through the front tube. Stop when fuel dribbles out of the pri boosters. Leave as reqd. Look for leakage under carb. Next day, turn carb over & see how much fuel comes out.

Stick with it.

Edel carbs: an 800 AVS for a big block, 650 AVS for a small block.

The Demon carb is made by Holley, so best left in the box. One fitted to a 400 engine bogged, no amount of tuning helped & neither did a ph call to Holley from Oz. Refitting the QJ fixed the problem...

I would install a Carter 4594 elec fuel pump. They last forever & easy starting.

Geoff,

Thanks for your continued guidance, not ready just yet to quit on it. Frankly speaking this isn’t rocket science, so should be able find and fix issue (famous last words!)

Will try bench test , but don’t understand putting fuel in through front tube, got a picture? I‘m lost here.

Thought you might like to see the car. My first new car, purchased 74 Satellite Sebring Plus, big block, 4spd car, quite unusual, frankly never seen another one like it. Yeah, I’m that old !
Thanks again for your patience and guidance.

Charlie

 

[Sixpactogo]

I had the same issue with my TQ years ago. I too thought it was the carb leaking but it ended up being the fuel pump leaking back after shut down. I don't know how it siphoned fuel from the bowls but after I replace the fuel pump, my issue disappeared. Might try that.

 

[sam dupont]

Geoff,

Thanks for your continued guidance, not ready just yet to quit on it. Frankly speaking this isn’t rocket science, so should be able find and fix issue (famous last words!)

Will try bench test , but don’t understand putting fuel in through front tube, got a picture? I‘m lost here.

Thought you might like to see the car. My first new car, purchased 74 Satellite Sebring Plus, big block, 4spd car, quite unusual, frankly never seen another one like it. Yeah, I’m that old !
Thanks again for your patience and guidance.

Charlie

View attachment 1517713

SLEEPER!

 

[MoparLeo]

I recommend Harm's.

Services

 

[Geoff 2]

Charlie,
Nice car & nice colour.

Reasons for topping up carb through front vent tube is twofold:
- convenient way of getting fuel into the bowls of a carb that is sealed up
- fuel dribbling out of the boosters tells you the bowls are full. Now ready to test for fuel loss.

 

[Charlied]

Charlie,
Nice car & nice colour.

Reasons for topping up carb through front vent tube is twofold:
- convenient way of getting fuel into the bowls of a carb that is sealed up
- fuel dribbling out of the boosters tells you the bowls are full. Now ready to test for fuel loss.

D

 

[Charlied]

Eureka, I retested fuel bowl and found a leak. Put gas in both sides and within 2-3 minutes level dropped on one side ( other side stable) and saw stain on cardboard. I have two other fuel bowls that I’m testing Question the leaker has casting number 2409-A , the other two which look identical have casting number 2383-A, any difference ? Any concern in using them ? Thanks

 

[Geoff 2]

Charlie,
The pri venturi size is smaller for the 800 v the 850 carb. So you need to check that.

The wall that separates the pri & the sec bores; some later carbs were thicker here.
Not sure about other differences. Maybe the original bowl can be repaired with epoxy? I have had success doing this, but would also depend on where the crack is.

 

[Charlied]

Charlie,
The pri venturi size is smaller for the 800 v the 850 carb. So you need to check that.

The wall that separates the pri & the sec bores; some later carbs were thicker here.
Not sure about other differences. Maybe the original bowl can be repaired with epoxy? I have had success doing this, but would also depend on where the crack is.

Trying epoxy repair today, prefer to use it if it works. Let you know. Thanks for the great support.

 

[Charlied]

Hi Geoff,
OK,will re-assemble using new gaskets, new O rings and hope for the best!
FYI attached photos of O rings, pair on left is what I pulled out (look fine, pliable, no distortion) Second photo shows top pair what I removed and brand new ones on bottom, look and feel identical.
So still have no explanation why fuel bowls run dry. Options are add an electric fuel pump, or a brand new carb.
Have you any recommendations on new carb, leaning towards Edelbrock (what model), what do you think?
Thanks again for your time and guidance, much appreciated.
Just want to drive the car with confidence it will re-start !

View attachment 1517254

View attachment 1517255

 

[Charlied]

Hi Geoff,
Wanted to bring you up to date on the continuing saga with my TQ, I thought I had it licked, not so.
In reassembly used a new (used) fuel bowl that I had, tested for leaks all good, when I dropped the air horn on top it would not drop in and air horn would rock slightly so fuel bowl top is somehow not square (flat) what? The bottom sits perfectly on the throttle body. Put the air horn on the origin fuel bowl it drops right in.
At the end of the line, feeling defeated. Meanwhile my car sits idle in the garage. Thanks for listening.

 

[Jonas Nordstrom]

Hi Geoff,
Wanted to bring you up to date on the continuing saga with my TQ, I thought I had it licked, not so.
In reassembly used a new (used) fuel bowl that I had, tested for leaks all good, when I dropped the air horn on top it would not drop in and air horn would rock slightly so fuel bowl top is somehow not square (flat) what? The bottom sits perfectly on the throttle body. Put the air horn on the origin fuel bowl it drops right in.
At the end of the line, feeling defeated. Meanwhile my car sits idle in the garage. Thanks for listening.

But the top part does rock a little before it is tightened down.
...it rides on the x-seals. Tightening it down compresses the seals and make them seal.

If it dropped right in before then the x-seals wouldnt seal properly.