[Tom Vaught]

I had a similar issue years ago when I got some gas that had additives in it.
IT MELTED THE FUEL SOCK IN THE TANK. I WAS ON A TRIP.

I posted about this years ago but will say on inspection of the pick-up /sock, it was melted.
I threw the sealed sock 30 feet. Ran great the rest of the 3000 mile trip.

Tom V.

[Formulajones]

I've used that insulation in some situations when making fuel lines, and slide it on before I make the flare. Good stuff

[Formulajones]

Originally Posted by Tom Vaught

I had a similar issue years ago when I got some gas that had additives in it.
IT MELTED THE FUEL SOCK IN THE TANK. I WAS ON A TRIP.

I posted about this years ago but will say on inspection of the pick-up /sock, it was melted.
I threw the sealed sock 30 feet. Ran great the rest of the 3000 mile trip.

Tom V.

I've seen some socks in pretty bad shape. It's a forgotten item, out of sight out of mind.

I'm not sure what they are made of today but I wonder about the quality.

[Brentco]

Loads of great advice here, but we may be getting ahead of ourselves with extensive modifications before diagnosing the problem. First steps:

1) Put a fresh tank of gas in and see if it still stalls. Given the year-old gas, the fuel could have gone bad, or it could have been a bad tank to begin with.

2) If that doesn’t fix it, next time it stalls hold the pedal down while you try to restart the engine. If it starts, the problem is vapor lock. The fact that it’s stalling in 90 degree weather and then not restarting until it cools off sounds like classic vapor lock. But old/bad gas could mirror the symptoms, so try a fresh tank first.

[zippy]

Todays fuel also vapor locks so much easier than fuel or even 10 years ago. Also evaporates out of carbs quick too

[STEELCITYFIREBIRD]

From experience, a quick sniff of the exhaust when the no start occurs….

>If the exhaust while cranking smells of raw fuel it’s it’s an ignition problem

>If it doesn’t smell of raw fuel it’s fuel delivery problem.

��SPARK
I would check for spark quality ….AT the spark plugs!….engine cold. Compare that to the spark quality when the no start condition is active.
All good…same spark quality. Move on.
Weak spark work back upstream. Or go to the coil and check spark quality there. Good at coil look to cap , rotor, coil wire…then ignition wires to plugs.

⛽️FUEL compare the accelerator pump discharge cold engine to no start condition.
If it’s weak or absent with a FEW full pulls on the throttle during no start condition. Remove fuel line at carb and crank engine, discharge ~ a pint into a glass jar. If no discharge work back from there to the tank. Let jar sit and see if it separates…water at the bottom….fuel quantity, quality and contamination check, sniff it smells “stale”. An Aquired smell to recognize, but “not normal “ .

Meanwhile if Fuel to the carb, but accelerator pump discharge runs out after a few full pulls on the throttle or weak and runs out of shot after a pull or two ….Fuel inlet needle and seat problem.



A logical check of fuel and ignition systems will yield a first time, viable repair. The repair is the easy part, a proper diagnosis makes that possible.
������

[78w72]

regarding the "gas gone bad" suggestions, IMO that is most likely not the issue. not sure what problems those in warmer climates experience with gas storage, but for us in the colder climates that have long cold winters, we have to store our cars & other equipment for a long time, sometimes 6 month or more. i have been storing my cars for 30+ years & do the same thing each year, have never had "bad gas" from storage. if the OP used stabil & its only been 4 months, the gas is not bad, or at least not bad in the sense it would make the car just die after only 5 minutes of running... & the temp of the gas is nowhere near 190° anywhere in the system after 5 minutes of running so probably not vapor lock related.

each year i put 5-10 gallons of gas in the tank, used stabil for ~10 years with excellent results but now i use seafoam as its a fuel stabilizer too. then i let them sit unstarted for 5-6 months before spring, i may start them 1 time in early spring for ~1 minute just to get some oil circulated, but i don't start them in the middle of the winter like some do thinking that helps anything, it just adds moisture to the oil. when i do actually get them out they start & run like the day i put them away, no signs of bad gas, no hesitations or dying etc, they run perfectly just like a mid summer day. i do run them down to almost empty & add new gas but there is never any sign of the gas being bad after 4-6 months. my dad does this same thing for 50+ years with his motorcycle, never any issues.

this year due to fuel prices being so high & other issues taking much of my time i have only got one car out of storage, the other 2 have been sitting in the same place since nov of 2021, 10 months! i just started those 2 for the 1st time a couple weeks ago... started exactly as they always have, couple cranks to get fuel to the carb, pump the pedal a couple times to set the choke & they start within 5 seconds of cranking & run perfectly, no misfires, no stinky varnish smell. one is a mild built 78 400 ta with stock pickup & fuel pump, one is a 500+hp E-head stroker with a dead head robbmc pump, both have cliff built q-jets. i will get them out to drive for the next 3 months or so before going back into storage. my 81 turbo has been out since may & after 6-7 months it started & ran fine on the winter storage gas... this is also winter blend gas since they go into storage in mid to late november so its not as good as the summer blends.

with 30 some years of doing this, & at least for myself i have never had any issues with gas going bad. stabilizers work very good, & will easily keep fuel good for 4-6 months. shoot, i have pulled cars out of fields or barns that have sat for 5-8 years that still started & idled ok, granted the gas smelled bad but the engine still ran. sorry for the long post, just wanted to state my experience with storing vehicles since others were sharing theirs.

but based on the symptoms described, i still dont think the issue here is fuel related, or at least not "bad gas" related, it may be a fuel system issue like bad fuel pump or acc pump/carb, but its not because it was stored with stabil for 4 months & its likely not hot fuel related because it only ran for 5 minutes. as i said early on & a few others mentioned, check all the basic systems & even get a meter on the coil/module/power wire to test per the service manual for proper ohms & volts. finicky issues like this are hard to diagnose on a forum without being there, can end up chasing your tail or throwing parts at it which is never a good thing.

[mchell]

Originally Posted by 69f bird

Thank you for all of the responses. A few answers:
All new wiring, distributor, cap, etc. Under cap Electronics. When it runs, it generally runs at a reasonable temperature. The engine was built, and all the new electronics, lines, wiring (all harnesses), etc. were installed 2-3 years ago. Paul Spotts built the engine, new water pump, clearanced the water pump plate, has a stock fan shroud, new clutch fan, upper and lower baffles, new radiator, the thermostat is 180 I believe. Last year, even in 90+ degree temperatures, it ran around 190 all the time. The crossovers in the heads were aluminum filled.

When it dies, it is a hiccup and stall. When I pump the accelerator when the car is stalled, and then try to start, it wants to start, and then hiccups again. It definitely feels fuel related and not spark. It is the in-carb fuel filter, and it was clean. I have to figure out how to add a temporary fuel pressure gauge. The entire fuel setup is all new stainless lines that I do not want to damage.

Sounds like it’s flooding or vapor locking……I would double check your float height and make certain your float and needle/seat are in good condition. Set your float height a smidge lower than the specs for your carb…. Run it, and see how it responds

[Schurkey]

Originally Posted by 69f bird

All new...Under cap Electronics.

WHAT "under-cap electronics"? Is this genuine-GM HEI, knockoff HEI, or some other aftermarket electronic ignition?

Originally Posted by 69f bird

It definitely feels fuel related and not spark.

That's a guess. It might be an accurate guess. Spark testers calibrated for HEI, or for ballast-resistor ignition, or even adjustable, are readily available.

Originally Posted by 69f bird

I have to figure out how to add a temporary fuel pressure gauge. The entire fuel setup is all new stainless lines that I do not want to damage.

Remove stainless tube from pump to carb. Install temporary hose using adapters and barbed fittings as required, cut hose to install pressure gauge adapters.

Yeah, you end up buying a bunch of adapter fittings, three feet of fuel hose, and some clamps. But you NEED to know the fuel pressure when it runs, and when it stalls.

[Blued and Painted]

Vapor lock is a myth. Check and adjust the float level to a factory speck. Them make idle and mixture adjustments with a complete engine compartment heat soak. At least 15 minutes of driving.

[25stevem]

I don't see a need for a fuel pressure gauge if the stalling situation takes place repeatedly.

Once the fuel level in the Carb gets low enough for the motor to not idle or even idle bad then the accelerator pump will not work properly, or not at all, and that's easy as hell to check for.

No fuel pump shot= no fuel.

Also the simple act of spraying some starting ether in to the Carb at that point would the motor to kick strongly or run for 2 to 3 seconds which would also prove out ingnition function.

[Gator67]

A friend here had similar symptoms with his car. Would just sputter and die after driving a few miles, wouldn't restart, then after 30 min or so would start up fine. Spent a ton of time trying to figure it out considered. Turned out there was debris in the tank. Enough to clog the sock and after sitting for a while it would unclog just enough to start again.

[zippy]

Originally Posted by Blued and Painted

Vapor lock is a myth. Check and adjust the float level to a factory speck. Them make idle and mixture adjustments with a complete engine compartment heat soak. At least 15 minutes of driving.

HAHAHA OK Sure. Had it many time, many vehicles. AND Cured it every time. Vapor lock in a suction line of a mechanical pump is for sure a thing. Had it many times with my 455 until I switched to a Elec tank pump. Not stalling, but not starting after 3 min to 40 min off time when hot. Mech pumps hate sucking air and boiled fuel makes nothing BUT air

[Formulajones]

Originally Posted by Gator67

A friend here had similar symptoms with his car. Would just sputter and die after driving a few miles, wouldn't restart, then after 30 min or so would start up fine. Spent a ton of time trying to figure it out considered. Turned out there was debris in the tank. Enough to clog the sock and after sitting for a while it would unclog just enough to start again.

I had a 71 Corvette like that. Big flakes would attach themselves to the sock while running (sucking fuel) and would fall off after I shut it down.

Easy to see that scenario on a C3 vette as you can remove the filler cap and look straight down into the tank and see the sock.

There are more of these cars every day that have nasty tanks in them after 50-60 years and owners aren't even aware or don't think about that scenario.

Tanks are so easy to change and cheap to buy I've gotten to the point every classic car should just have it replaced by now.

[Lemans64]

LOL, had a beetle bug stuck in a tank suction line that caused this issue. Truck had been sitting for quite some time, tank was from another truck so was exposed
to the elements. Drove for a while then had systems like described, finally got truck home after a few hours of waiting, pulled the tank and found a beetle bug stuck in the suction line.
so ya weird things can happen. Cleaned him out and was good after that.

[78w72]

Originally Posted by zippy

HAHAHA OK Sure. Had it many time, many vehicles. AND Cured it every time. Vapor lock in a suction line of a mechanical pump is for sure a thing. Had it many times with my 455 until I switched to a Elec tank pump. Not stalling, but not starting after 3 min to 40 min off time when hot. Mech pumps hate sucking air and boiled fuel makes nothing BUT air

i dont doubt vapor lock is a real thing & can happen in certain situations... but in my experience, living in a hotter climate than canada & owning & driving these 2nd gen firebirds for 30+ years i can say i have never had it or anything close to it. have used all kinds of stock or performance mechanical pumps on builds from stock to mild 375-425hp to current ~525hp E-head stroker engine, daily drivers to street racers & drag strips, to driving half way across the country to/from AZ, TX, OK, no heat wraps or phenolic spacers or crazy mods etc etc.

worst thing i have had related to heat is on a 455 in a 78 ta that had a slow turning stock worn out starter with headers, but the timing was probably advanced too far on that car when i would push it too far "power tuning" it, always started within a few tries when it acted up. that car would also get to 200 on super hot days & long drives but it had a stock 195 T stat, never boiled the fuel or died while running.

[PunchT37]

One wonders why Pontiac put that black foam insulation on the fuel line from the pump to the carb.

[Sirrotica]

Originally Posted by PunchT37

One wonders why Pontiac put that black foam insulation on the fuel line from the pump to the carb.

Because it works..........

[Schurkey]

Originally Posted by Sirrotica

In 1977-79 Pontiac had factory fuel lines from the fuel pump to the carb that were foam insulated for preventing vapor lock.

Originally Posted by PunchT37

One wonders why Pontiac put that black foam insulation on the fuel line from the pump to the carb.

Originally Posted by Sirrotica

Because it works..........

It wouldn't work to prevent vapor lock, because vapor lock happens in the pump and on the suction-side of the fuel plumbing. There wouldn't be vapor lock in the pressurized part of the fuel system.

It likely worked to reduce fuel boiling in the carburetor, AFTER it's sprayed out of the needle 'n' seat assembly. Suddenly at atmospheric pressure instead of 4--5--6 psi, the fuel or some volatile fraction of the fuel could boil-off. The boiled-off fuel would drive the mixture rich, causing driveability issues.

Point being, it could be a valid solution to driveability problems, but not for the problem of vapor lock specifically.

[Sirrotica]

A few years ago I had replaced a fuel hose on my pit cart with nicopp metal line where neoprene had previously been used. At Norwalk during the Pontiac Nationals I'm experiencing fuel starvation. This is during a very hot ambient temperature, plus I'm on asphalt which is as hot as 165 degrees during the daytime.

All I have to do to get it running again is let the engine sit for 10 minutes, and it restarts, runs well, but drive is less than a mile and it shuts down again. This is with an air cooled engine, and gravity feed fuel. So the next year I reroute the fuel line, use neoprene line, and for years, I have zero problems ever since.

The question I pose. since there is no fuel pump, and the fuel is gravity fed, did it vapor lock? The fuel did boil in the lines and gravity was feeding it. I guess I need the correct term here so I can describe what phenomenon happened.

The pressure of atmospheric pressure wasn't enough to keep the fuel from evaporating when it reached the carburetor bowl, because the metal line absorbed so much heat. So how is this atmospheric pressure fed gravity system heating the fuel to such a temperature that the needle and seat can't handle the vaporized fuel in a normal manner? My inquiring mind needs the answer.........

Is it fuel boiling, or does vapor lock exist without a fuel pump?

Here's what I came up with for a definition of vapor lock, and gasoline boiling from the net:

What happens when you have vapor lock?

Vapor lock happens when your fuel boils in your carburetor or your fuel line. Vaporized fuel creates back pressure in your fuel system and prevents gas from getting to your engine. It commonly occurs when a car has been idling or has been turned off and then back on. Mar 1, 2019

What happens when gas boils?

Image result for gasoline boiling definition
Bubbles of vaporized liquid (i.e., gas) form within the bulk liquid and then rise to the surface where they burst and release the gas. (At the boiling temperature the vapor inside a bubble has enough pressure to keep the bubble from collapsing.)

So, did my fuel boil, causing vapor lock without a fuel pump?

Seems maybe this discussion is becoming absurd, in dissection of terminology, but maybe I'm wrong. It wouldn't be the first time.

I do know that changing that neoprene line to metal was detrimental. Changing it back, and rerouting it cured the problem.

Vapor lock is real, fuel boiling is real. If you don't think so ask someone who has raced an oval track Pontiac, I have, and it happens. I've taken second place while leading a race, because under a yellow flag while you sit idling on the track while they realign the field, then run a lap before they throw the green, you punch it. and the car falls flat, and you get passed by a ford. Second place sucks........

The night that it happened, in 1982, I didn't give careful consideration to which phenomenon I had experienced, because I really didn't care at the time. Maybe 40 years later, I should reflect upon what happened, or not......

Once the car was back up to speed, the engine, and fuel cooled off enough that it never ran out of fuel for the final 2 laps, but when it mattered, it cost me first place.