Thermoquad Tuning & Troubleshooting

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LJS30

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My rebuilt Thermoquad was working well for awhile now suddenly I am having a few issues with it. First off upon really hammering the accelerator to the floor one of two things occur. Either my engine suddenly runs super rich and stumbles or my accelerator gets stuck in the down position. Mind you, there are no obstructions on my linkage near the transmission nor does my pedal inside the vehicle actually appear jammed. This problem only occurs when I really hammer it to the floor board. Second upon hard breaking my engine stalls. What is going on guys?
 
check float level. if its stickin', check the action of the carb then check the action of the cable to eliminate how it is getting stuck or acting like it is.
 
Go over to Moparts.com and find Demon Sizzler. He's supposedly an ace with the TQ's. He even sells jet kits and such.

don
 
OK, as you may know...the step up metering rod piston is operated by a cam and lever under the plastic bowl in the base plate. This cam/lever cannot be seen unless you take the carb to pieces.

The "cam" is part of the primary butterfly shaft

The step up "piston" adjuster screw rides on this cam/lever, and as the shaft rotates, the cam lever raises the step up rod "piston". Therefore, the piston is operated mechanically as well as Vacuum released.

Now..

.as you also know, the "piston" is spring loaded and held in the top plate by a small retaing plate.

OK - Heres the important bit......This means that the adjuster rod and piston can only travel so far "up" , b4 contacting the retaining plate.

Unfortunately....IF the adjuster screw is adjusted clockwise too far (raising the rods)...it lengthens the adjuster screw to a point where the piston cannot travel up, and the adjuster screw interferes with the cam lever a sit rides up.

Basically you can make the step up adjuster 1" long, but theres only
3/4" travel available!!

To check this, you need to remove the phenolic bowl and check the "cam" and make sure the shaft is not riding the "cam" up against the adjuster and forcing the piston hard up against the retaining plate.

Heres a test:

If you plant your foot, making the carb "stick"
Then, undo the piston retainer top plate

If the piston "jumps" out of the sleeve, AND THE BUTTERFLIES RELEASE, then the cam at the bottom has been "cramming" the adjuster screw against the top retaining plate.

The fix?

I would then:

Remove the bowl and check to make sure the cam is not broken, the piston adjuster is not snapped, or the butterfly shaft is not bent.

Good luck!!
 
dusterdon said:
Go over to Moparts.com and find Demon Sizzler. He's supposedly an ace with the TQ's. He even sells jet kits and such.

don
Click to expand...

Hes a member here as well.
 
Moparmal has some good info there. Also check your cable, they can start to fray internally and cause it to stick.

As for the stalling and stumbling you may have sunk float(s). Those phenolic floats are known to take on fuel. If just one is sunk you can tell the difference in weight, otherwise compare it against a new one.
 
Guitar Jones said:
Moparmal has some good info there. Also check your cable, they can start to fray internally and cause it to stick.

As for the stalling and stumbling you may have sunk float(s). Those phenolic floats are known to take on fuel. If just one is sunk you can tell the difference in weight, otherwise compare it against a new one.
Click to expand...

Or, you can submerge the float in hot water and see if any bubbles come from it...
 
The floats are either nitrophyl or brass........the centre section is phenolic.

The hot water expands the air inside the float, and if theres a hole it escapes and causes bubbles...

Similar to testing for a leak in a tyre.

Im not sure whats so hard to understand about the concept Ramcharger? [-X
 
Moparmal said:
The floats are either nitrophyl or brass........the centre section is phenolic.

The hot water expands the air inside the float, and if theres a hole it escapes and causes bubbles...

Similar to testing for a leak in a tyre.

Im not sure whats so hard to understand about the concept Ramcharger? [-X
Click to expand...

Of course this would work on brass float. But why bother if all you have to do is shake it and listen for trapped fuel?

The nitrophyl floats work with "closed cell" construction, similiar to a foam cup. They go bad when some of the cells start to absorb fuel. There is no inner sealed "area" where air is trapped for flotation, hence dropping them in hot water will show nothing. Drop them in a container full of solvent and see if they float. Simple. No need to boil water. :)
 
RC - Thats interesting about the Nitro..floats..I had assumed the test was valid for both - I guess thats "15 all" in tennis speak!!....
 
The accelorator pump on my thermoquad is bairly spraying out. The carb has been sitting for some time. At first it didnt spray at all. I removed what I think to be the needle valve under the nozzel where the fuel comes.It was stuck in there. I cleaned it up and now I get a LITTLE fuel.the car Idles ok but when you hat the accelorator it just hesitates.Any suggestions would be great.
 
Your going to have to make sure the path ways are clean and clear with a good plunger. OE plungers are leather and can dry out and curl up.
 
I agree with the "Feisty Fish"....sounds alot like a dried up accelerator pump piston,

(Assuming you've blown the shooter out with compressed air?)

A worn Accelerator pump shaft (yes they do wear over time...) can allow the fuel to bypass the piston as well - so can a leaking pump plate at the base of the Acc pump shaft.
 
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