1977 Newport with a vapor lock and/or boiling fuel in carb problem

Dobalovr said:
Exactly Carmine. When I converted my Doba from LB to Electronic the TQ would do this exact thing. Going to non LB TQ may solve it or given my dislike of TQ's an Eddy. Is there a way to "hotwire" that LB TQ to work? Or is a carb replacement happening anyway?
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If you remove the rubber seal from the bowl vent, it will vent all the time without actuation. However, you created a fuel leak path in a rollover accident.

It would be good to know what problem was being "solved" by removing the LB.

I like eddy carbs and have a few vehicles with them. I've also had well-tuned TQs which were very good, but require more patience and knowledge.
 
WorkerBee said:
Couldn't you put 12V to this bowl vent solenoid when the ignition is on the start and on position to vent the carb?
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I don't have a FSM that describes the operation in front of me, but I'm guessing the solenoid was active after shutdown by a timer within the LB. If you open it only during start/run, what good is that? The fuel boils out during the "off" time.
 
WorkerBee said:
Oh.....I didn't know about this timer with the Lean Burn thing.
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I didn't say that was the logic... I don't have a FSM in front of me, so I can't say it does or not.

However it just makes sense that it would need to be opened when ign is "off". Opening a small vent over the carb bowl at startup won't dry the wet intake. The best way to prevent the problem would to open the vent for let's say 10 mins after shutdwn. Eventually the solenoid has to go off, or it kills the battery. The best way to control this is with a computer.
 
Carmine said:
One reason I don't get involved in these "tech threads" is because everyone is so anxious to pound a finish nail with a sledge hammer.

Slow down. There are diagnostics involved. Crazy as it may sound, the best time to swap a carb/ign is when it runs well. We cannot easily return to a baseline condition because in the quest to "solve" a problem, you can introduce a new one.

Some later Thermoquads used a bowl vent that is actuated with a solenoid. Guess what actuates the solenoid? The Lean Burn computer.

The first thing I'd do is determine if the issue IS the carb flooding the engine after shutdown. (vs. A weak coil, also a valid concern) Do that by holding the throttle wide open (floored) during hot crank. If it cranks longer, but then fires, flooding is your issue. If it makes no difference, then you (might) have an ign issue.

BTW to give credit where it's due, that was the second suggestion in this thead. Have tried that? You mentioned every throttle position but WOT. And within a few hours we're already talking new carbs, dist pickups, spacers, etc. and it could just be a matter of a now inactive bowl vent solenoid. I would also take advantage of the Google machine and look at aphoto of a TQ with a solenoid. If you have one, it's now not being activated and would almost surely cause your issue.
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Thanks Sir. The car has been sitting in 95 F weather for about 3 hours since it last started. I just attempted to start it. Accelerator all the way to the floor while I cranked. No hint of wanting to start. As I walked away from the car, you could smell just a hint of fuel vapor.

As to a bowl vent solenoid, I am not sure I am capable of determining for sure whether it has one or not. But I have a very good mechanic. I am waiting for him to have enough free space in his garage to diagnose the issue. Like you, he counsels more diagnosis.
 
Pclancy said:
Thanks Sir. The car has been sitting in 95 F weather for about 3 hours since it last started. I just attempted to start it. Accelerator all the way to the floor while I cranked. No hint of wanting to start. As I walked away from the car, you could smell just a hint of fuel vapor.

As to a bowl vent solenoid, I am not sure I am capable of determining for sure whether it has one or not. But I have a very good mechanic. I am waiting for him to have enough free space in his garage to diagnose the issue. Like you, he counsels more diagnosis.
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How long did you allow it to crank? (these should be 10 second bursts with 10 seconds of cooling between so as not to overheat the starter motor). I would go for 3-4 of these. Do not release the pedal in between cranks.

Removing the air cleaner lid (hood open) will allow more air into the engine. What happens (if the issue pertains to the bowl vent) is that hot, expanding liquid fuel pushes into the throat of the carb, just as if you had madly pumped the accelerator.

With the accel pedal held down at Wide Open Throttle (WOT) you use the engine as an air pump to dry out the intake path (manifold and combustion chamber). The ignition system cannot create a spark because the current passes through the path-of-least resistance (wet fuel) rather than a higher resistance air gap (spark plug). If you dry it by pumping air, eventually a few cylinders will spark and it will run roughly for a few seconds until the excess fuel is burned off.

That is the idea behind cranking at WOT. Don't move your foot off the gas until you've given up cranking. Any throttle movement will introduce more fuel.
 
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Or if you're lazy and don't feel like sitting there with the car floored while you wait between cranks, take off the air cleaner lid and prop the carb blades open with a screw driver and then crank and touch nothing.
 
Mr C said:
Or if you're lazy and don't feel like sitting there with the car floored while you wait between cranks, take off the air cleaner lid and prop the carb blades open with a screw driver and then crank and touch nothing.
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That was SOP when I was a teen in the 60's and to this day I always have a rusty screwdriver in the glove compartment of my cars exactly for that reason.
 
commando1 said:
That was SOP when I was a teen in the 60's and to this day I always have a rusty screwdriver in the glove compartment of my cars exactly for that reason.
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Let's try not to scare the f*** out of a new mechanic.

...and be sure to use a LARGE screwdriver. This is not the place to use your eyeglass or "computer precision" screwdriver!
 
Mr C said:
Or if you're lazy and don't feel like sitting there with the car floored while you wait between cranks, take off the air cleaner lid and prop the carb blades open with a screw driver and then crank and touch nothing.
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Years ago, I had a '66 Beleveder II with the 426 hemi. In the morning, I always had to start the car this way - only I did it with a pencil.
 
Ripinator said:
Years ago, I had a '66 Beleveder II with the 426 hemi. In the morning, I always had to start the car this way - only I did it with a pencil.
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You probably had a lot of lead in that pencil back then also....

Ok that was just weird :realcrazy:
 
1.jpg
 
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