Any help will be great for I am at wits end now on this fuel or lack of fuel problem. Sorry for long post but want to give as much info as can.
1981 Corvette – stock 350 engine, auto trans, Q-jet carb, ECM and all parts in place and working.
Problem: Sunday drove home 15 miles in about 90 degree temps, got to garage, stopped engine while got out to open garage, cranked engine drove in and stopped engine again. Open hood and waited a few minutes and then proceeded to crank engine again and made a slight idle adjustment, to increase RPM just a tab. While doing this the engine just stopped. I checked the fuel flow into the carb thru the jets as I moved the throttle level and no fuel.
With assistance from the wife I unconnected the fuel line to the carb and had her spin the engine, no fuel came out (but as later discovered may not have spun the engine long enough).
With no fuel from line I jacked up the vette and went underneath. I first unplugged line from fuel tank to fuel pump and had fuel. I then disconnected the outlet fuel line from the fuel pump and she spun the engine and I had fuel there. I then blew out the fuel line from the pump to the carb, good air flow, no restrictions.
I connected everything back underneath and went back engine side. Before reconnecting line to carb I had her to spin the engine again. Still no fuel but then I told her to spin engine until I told her to stop, she was only doing it maybe 2 seconds at a time and even this short of time initially.
The last time I had her spin the engine I got fuel out in about 3 to 4 seconds so I had fuel to carb now. One of my thoughts is now I may have had fuel initially just didn’t spin it long enough, don’t know for sure.
Reconnected line to carb, spun engine, checked fuel thru jets, no fuel. Re-spun engine and pump gas pedal a few times and re-checked the gas thru jets, had fuel now. Started engine up, she ran fine.
Past work that has been done:
New rebuilt Q-jet carb from Ecklers; new manual fuel pump; gas tank cleaned out and new sock on fuel pick up line; lines from tank to fuel pump blown out; fuel line from fuel pump to carb replaced with new line and line wrapped with 500 degree heat cover. New ECM box installed, new power chip prom in ECM. New ERG valve installed; New fuel filter (goes inside carb, replaced 1 month ago).
Again I wanted to give as much info as possible to seek the best advice on where to go next. Could it be the plunger inside the fuel filter sticking? If so can I remove that and still operate normally?
Could it be the fuel inlet needle sticking? If so what would make it just do it every now and then?
I had this problem twice before hence all the other work done on the engine (once before carb swapped). Luckily yesterday it happened once in my garage where I could check items, before both times while on the road and had to get hauled back home, and once back she cranked up but had to pump gas pedal several times so was hard to ID where the problem was then.

 

Maybe double check the in-carb fuel filtrer and the can fuel filter. You could be picking up s some crud on the bottom of your tank. Can you drop a known, good carb on it???

 

I replaced the in-carb filter a month ago, waited some time after the fuel tank was drained and cleaned, work was done a local Chevy dealer on cleaning tank so feel they knew what they were doing better then I.
If fuel filter again, then something need to change, take it out and put an inline filter in somehow?

 

if you need an inline fuel filter then you have a problem. The tank may have been cleaned, but I am still guessing crud. I would guess it needs to be replaced like mine about 7 years ago. Look at the filter and what is plugging it, if it is rust, then you probably have to replace.

 

Sounds to me like it's vapor locking. It happens when you shut of the motor and let the carb get heat soaked with no fuel running through it. When you go to start it soon after shutting it off, all the fuel in the carb has turned to vapor. You can try some sort of spacer between the intake and carb. You either have to let the engine cool or pour some cool gas down the butterflies. I have a 1" thick plastic spacer on mine.

 

You may be on something there. When I changed out the old carb there were 2 spacers plates and I only installed 1 back (didn't see where 2 was needed) so I may need to re-install the 2nd one to create a bit more clearance.

 

Vapor lock doesn't happen at the carb. It happens in the fuel lines between the pump and the tank. The gas in the line boils and the pump is suddenly trying to suck vapor, not good.

to fix it you need to protect the fuel lines to the pump, insulate, re-route and protect.

Also check the lines for pinholes and collapsed liners. pinholes will slowly seep gas but allow air in the fuel. air + hot fuel == vapor lock.

Original rubber lines should be replace automatically on any C3 as even the youngest ones are now what 32 years old?
And the alcohol in the gas is REALLY hard on the vintage or even 10 year old rubber.