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?

You can have fuel after the pump in the line if the pump stops pumping, the carb will not suck up the fuel in the line, it has to be presureized. You should put an inline fuel presure gauge or just change out the fuel pump from a local parts store. Cost is about 18-20. You should have about 4lbs of presure runing. Do you know if you have a three or two line pump? 

I have a 3 line fuel pump and this one was put on a month ago. Do not know what pressure I havem need to get a gauge.

If it only does it when its hot, vapor lock may be the problem.

I have run the vette when hotter, even with AC on and not have it to lose fuel to carb. This really is getting me since it does not seem to be a definite cycle, timing or use that will create the problem. When we did the other work to address possible vapor lock on the fuel line from pump to carb we installed the 500 degree heat sleeve over it since before just a naked steel line running up the front of the block.

  What else do you propose could be vapor locking? The fuel pump? I had fuel from the outlet of the pump when I tested it about 10 minutes after loss fuel to carb's throat.

? I don't know for sure but do you have a vented gas cap??  I am not extremely familiar with the 81 set up but I know that may cause no fuel to the carb when running for a while if you don't..if the evap system is that tight and not allowing air to got back to the tank..try to run it with the gas cap loose..simple but may work..get the clear filter or pressure gauge on it too..that will help if it happens again..

That is strange. Just guessing but maybe vapor locking right in the carb....if gas is everywhere but the carb it may be boiling fuel out of bowl. Does it start and run ok after sitting and cooling down?

Yes it has run fine once cooled. In Corvette Forum one guys mentioned carb vapor locking and mentioned adding another spacer under the carb. When I changed the carb it did have 2 spacers under it but I only added one back so thoughts on that? I can add the other spacer back, still have both I took off old carb.

I'm gonna take this post to my Corvette Mechanic.  I got an idea why its doing that but not sure.  I will have an answer for you in a couple of days.

[QUOTE=Almond81Vette]

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.[/QUOTE]

If you're moving the throttle by hand, a Quadrajet requires a pretty quick movement to actually push much fuel thru the squirters. If you were just slowly working the throttle, it may not have pumped any fuel like that.

"The engine just stopped"....as in just shut off like you turned the key off? If it just shut down like that, then chances are the ignition module in the distributor is about to take a doo-doo. That is one of the most common failure modes for them....they'll just shut off. It may start right back up after a few minutes of cooling off, or it may take an hour or so to cool enough to start back up. You've done a ton of work on the fuel system....I kinda think the problem is somewhere else. The fuels today will RARELY create a vapor lock....the stuff is just not volatile enough. Of course, if you get any metal carb or fuel line hot enough, it will certainly boil the fuel, which is what a vapor lock is. You'd prolly have other problems too if it was running that hot, imho.

I'd be checking the ignition system.

The electronics on your car(ECM) really only controls the idle fuel mixture, and the timing.

hth