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

[Pclancy]

Hi Guys:

It's Peter and his Canadian Newport once again. More questions:

My lean burn system was acting up. So I had my expert mechanic delete the lean burn. See earlier threads where you guys suggested how to do that.

In making the conversion we elected to keep the original TQ carb. The engine is a 400.

After a few adjustments to the carb, we got the engine running well at all speeds.

Now after use in hot weather, the engine won't start if you let it sit for a bit. It starts if you start it again after use right away, but if you wait more than a few moments, it won't start for many hours. Then it starts right away.

Note that the engine runs well in city/highway conditions. Has never stalled. The problem is only after you shut it down after use.

So I suspect this issue is vapor lock, or boiling fuel in the carb, or both.

I guess my question is this: Should I attempt to fix the carb (it's the original lean burn carb) (possible issues include the float level, exhaust heat riser valve, gaskets, flanges etc) or should I find a pre-lean burn TQ (72-74?) and install that? Or an E-brock carb?

What's the best solution here? I attempt to use the Newport as a DD and don't want to get stranded.

Thanks,

Peter

 

[65sporty]

Most of the guys here will tell you go with the Edelbrock. Did you look down the throat of the carb to see if it's out of fuel? Did you try to hold the throttle to the floor because if the carb is leaking it will be flooded.

 

[1978 NYB]

Eddie 1406. It has an electric choke and it will start every time out of the box. There is numerous threads on the conversion here on FCBO that will tell you what adapter s you will need.

 

[detmatt]

Make sure it's not a combination of things including boiling ethanol. If you're having fuel delivery issues that aren't quite bad enough to show themselves under normal conditions but you add elevated temps and start boiling away an already depleted fuel supply. You should check things like the length of your fuel pump pushrod.

 

[WorkerBee]

The T-Q carb was designed to be cooler than an all aluminum carb, so I doubt that it's the problem. On top of what was already recommended, I would check to see if your fuel return line is restricted and check if any fuel lines are touching the engine. You could try insulating all the fuel lines in the engine compartment with insulation like this Taylor 2590 | Buy Taylor Heat Shields, Wraps & Sleeving at JEGS

 

[commando1]

Please describe exactly what is happening on these "won't starts".
You turn the key and...

 

[Ripinator]

Hi Guys:

It's Peter and his Canadian Newport once again. More questions:

My lean burn system was acting up. So I had my expert mechanic delete the lean burn. See earlier threads where you guys suggested how to do that.

In making the conversion we elected to keep the original TQ carb. The engine is a 400.

After a few adjustments to the carb, we got the engine running well at all speeds.

Now after use in hot weather, the engine won't start if you let it sit for a bit. It starts if you start it again after use right away, but if you wait more than a few moments, it won't start for many hours. Then it starts right away.

Note that the engine runs well in city/highway conditions. Has never stalled. The problem is only after you shut it down after use.

So I suspect this issue is vapor lock, or boiling fuel in the carb, or both.

I guess my question is this: Should I attempt to fix the carb (it's the original lean burn carb) (possible issues include the float level, exhaust heat riser valve, gaskets, flanges etc) or should I find a pre-lean burn TQ (72-74?) and install that? Or an E-brock carb?

What's the best solution here? I attempt to use the Newport as a DD and don't want to get stranded.

Thanks,

Peter

I installed an Edelbrock half inch phenolic / wood spacer between the carb and the intake. All my problems with boiling ethanol fuel and associated hard starting and sudden engine shut off went away. . .

 

[WorkerBee]

After thinking about it, I find it odd that the OP states "it won't start for many hours". It should start within an hour cool down time.

 

[commando1]

After thinking about it, I find it odd that the OP states "it won't start for many hours". It should start within an hour cool down time.

That's why I asked..

Please describe exactly what is happening on these "won't starts".
You turn the key and.

I think he needs a new starter. Older ones on their last legs wont crank when hot.

 

[Pclancy]

Please describe exactly what is happening on these "won't starts".
You turn the key and...

It cranks and cranks but does not start. The battery is strong and the starter sounds good. You get the feeling that there is no fuel at all. Depressing the accelerator 1/3 or 1/2 way down does nothing. Pumping the accelerator does nothing. Leaving the accelerator alone does nothing. You can smell fuel vapor if you try it too long......

You wait--sometimes this can take hours---and then it fires right up. And then drives very smoothly. No missing, great acceleration, no strange noises.

Before this problem started, at least in late spring weather, it fired up right away with no need to press the accelerator. Turn the key and it started almost immediately.

Yet now after a ride, turn it off, and it just cranks. Let it cool, and then it starts up.

 

[Pclancy]

After thinking about it, I find it odd that the OP states "it won't start for many hours". It should start within an hour cool down time.

It's funny but it won't. Takes more time than that by far.

 

[commando1]

Heat soaked coil.

 

[Pclancy]

Make sure it's not a combination of things including boiling ethanol. If you're having fuel delivery issues that aren't quite bad enough to show themselves under normal conditions but you add elevated temps and start boiling away an already depleted fuel supply. You should check things like the length of your fuel pump pushrod.

Thanks.

 

[Pclancy]

Heat soaked coil.

I'll check that.....

 

[commando1]

I'll check that.....

When heat soaked, it will still produce a spark, albeit a very weak one. Best to buy a new one altogether.

 

[Pclancy]

Most of the guys here will tell you go with the Edelbrock. Did you look down the throat of the carb to see if it's out of fuel? Did you try to hold the throttle to the floor because if the carb is leaking it will be flooded.[

Will check next try, thanks.

 

[Polara_500]

Heat soaked coil.

I've also had the pickup in the distributor give the same indications.

 

[Pclancy]

Eddie 1406. It has an electric choke and it will start every time out of the box. There is numerous threads on the conversion here on FCBO that will tell you what adapter s you will need.

Would you be kind enough to tell me where to find the thread or what adaptor to use?

 

[Carmine]

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.

 

[Dobalovr]

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?