I had an interesting morning today. Here's the chronological order of what happened. Any ideas/suggestions would be greatly appreciated.

*Started up the car from home; no problem.
*I have about 2 miles before I get on the freeway. Car ran fine for the most part. There were a couple of tight turns that I took where I 'sensed' some hesitation in acceleration, but figured the car just wasn't fully warmed up.
*On the highway about 2 miles. Again, felt a tiny bit of hesitation, but got up to 80 at one point with little effort.
*Chugga Chug Chug... Car dies like it ran out of fuel. I was able to pull it to the side of the road.
*Tried to restart, no go. Waited a couple minutes and tried again and it fired with a couple pumps of the pedal. Thought I may be low on gas (gauge red 1/3 tank, but I don't trust it), so I decided to head toward a gas station.
*Car died again after about 100 yards. Waited the 2 minutes and it started again with a couple pumps on pedal.
*Car died again, this time after about 200 yards. Waited the 2 minutes and it started again with a couple pumps on pedal. At this point I'm just trying to scope a good place to park it and get a couple gallons of gas by foot.
*Just had a couple hundred more yards to go, so I gunned it. The car took off as if nothing was wrong. I took the chance of going all the way to the gas station approximately 2 miles away and made it. No more hesitation that I could feel.
*At the gas station now, looked in the tank and although the fuel appeared to be near the bottom, it definitely wasn't empty.
*Filled the tank to the rim and it took 11.8 gallons. That's 44.655 liters to our metric friends.
*Cranked the car and it started in a millisecond with no need to pump the pedal.

Here's my car and its fuel system related parts:
*1971 Corvette 350 270hp rebuilt ever so mildly
*Fuel tank and lines up to fuel pump are all stock.
*Return line is still connected.
*Fuel pump may or may not be stock, but not upgraded, so stock configuration.
*If you click on my pics, you should be able to see that I have a 3/8" steel braided line from the pump to a distribution box on the wheel well which then separates into two lines to the primary/secondary of the carb.
*Carb is a Holley Street Avenger 670cfm. Approximately 5 years old
*Air Cleaner is chrome. (Come on, I'm trying to stay in good spirits.)
*This has happened just once before (a couple years ago), but died only 1 time when I was going uphill with about the same reading on the gauge. I guess this is why I don't trust the gauge and fill up just under a half tank reading or around 120 miles.

Questions:
1. I've heard Vapor Lock has similar symptoms to running out of gas. Can someone please explain what the heck is vapor lock and if this could be the issue?
2. Is it true that all of these vettes have 24 gallon tanks? That's all I'm finding for replacement tanks. If so, I was definitely not low on gas.
3. If not vapor lock (whatever that is), then is the fuel pickup not adjusted properly?
4. Maybe something is in the tank blocking the outlet?

Thank you!

 

I had a similar thing happen to me a few years ago and it turned out to be a bad sock in the fuel tank. It became plugged with rust and when the car sat for a while (after dying) the suction let all the debris fall to the bottom of the tank again...and then the car would restart. But I would start by looking at your fuel filter in your carb (or on the way to the carb). Not sure what kind you have. If its paper cut it open and look inside for any tales of debris from the tank. If its metal, you may also want to cut it open for clues.

As far as vapor lock, back in the 60's my dad's 53 Merc used to have that. On hot days the fuel would turn to vapor and the car wouldn't run. He used to keep a gallon of water in the car and pour it on the fuel pump to cool it off. One cool it would start right up again. Oh the good old days!

 

Although I just installed headers 2 months ago, they nor the weather was warm enough to create fuel vapor so scratch that idea I guess...

I really wouldn't be surprised there is something in the tank. Kind of hard for something not to be in there considering the massive nozzle hole standing straight up. Not the best design I've seen GM ever do.

Any other ideas before I pull my entire fuel system out???

 

Check your fuel filter(s): condition of sock in tank, any filter in the line between pump and carb, any filter internal to the carb. If you find a significant amount of 'junk' anywhere, that could be your problem. Also, you might want to use the fuel in the tank down to the level where you had your problem...then run it some more to see if the same thing occurs. You could have a pickup tube problem or a fuel pump problem where fuel is not being delivered properly once the tank is depleted so far.

 

Just drove her home and had no problems. Even survived a good half throttle stoplight launch, so apparently it just doesn't like the low fuel level. But is it really low? If tanks are 24 gallons and I put in 11.8, the math is pretty easy that I wasn't even at a half tank. Can someone confirm the size of the fuel tanks?

 

Vapor lock is simply a state the turns the gasoline into vapor usually causing your fuel pump not to pump. Once cooled a bit, it becomes a liquid again and your good to go. A plugged or partially plugged fuel sock in the tank can increase the risk of vapor lock.

The vapor pressure of gasoline is regulated by law and if purchased after Sept 15th you will have a gasoline that is more prone to vapor lock in summer weather. It could just be that your tank fill cured this.

Even here in S Florida, it was unbearably hot today, and I have never had vapor lock.

 

is there someway you can see what exactly is in the bottom of your tank? ya never know what may have been put in there over the years but kids, unhappy husbands etc.

 

This is a great question. I would prefer to not pull the tank if I don't have to do so.

 

Does it cut out suddenly like somone turned off the ignition? I'd start looking at a bad coil, points, condenser etc.

This whole scenario also sounds exactly like the failure I had on a Pertronics unit years ago.

 

Like others have stated, start with the easiest like your fuel filter/carb and work backwards to narrow the problem down.

Sean

 

Pretty much the same thing happened to me this ,past sunday. However, I had a full tank of gas. I went for a 15 minute ride. stopped at a buddies house. Drove halfway home and the exact symptoms you descibed happened to me. After it cooled it cranked righty up. Are you running the fuel return line? I am not and many have suggested that that is my problem. Planning on installing one this week.

Wade

 

Mike_Ward - I'm pretty confident it is not electrical. Doesn't die immediately, but more of a struggle to keep running like it is choking from not enough air or fuel.

75vettehelp - I think it is time for the filters any ways, but considering it was fine after filling the tank, I'm more inclined it's towards the back. I'm not sure how to check this "sock in the tank". No idea what it is or how to access it. Anyone?

BlackRat - I am running a return line and the engine wasn't fully warmed up yet. I hope your return line fixes your issue!


Just want to send a quick thanks to all of the ideas!

 

You didn't hear a "woosh" when you opened the tank at the gas station did you? If so, you are creating a vacuum in the tank and this will restrict flow.

Just for kicks, if it does it again, try removing the gas cap.

 

I hear the "woosh" on fuel injected cars that I've had. I always thought it was normal but those cars have higher psi fuel pumps. Can't say that I remember ever hearing the vacuum release, but I'll pay attention next. If it has vacuum, how is that fixed?

 

In my 71 you can look down and see the sock through the gas filler. In my case you could see crud at the bottom my tank, but I could also see the same crud in my fuel filter in the carb. Thats why its suggested that you start with the fuel filter in the carb and work back. If your carb filter is clean and looking down the fuel filler the bottom of the tank looks clean I would not suspect the sock.

Should you decide the chance the sock, you will need to drop the tank and pull out the sending unit to replace it. Socks can be purchased separately or they come with new sending units.