I believe that my 1976 stingray is experiencing vapor lock. I did notice that the fuel line seems to be touching the water pump. Could this contact be the source if my problems?

 

Heat in the fuel lines can cause vapor lock and cause the car to stall and not run until the car has cooled down again. The water pump can get very hot and it is a potential problem and I would pull gently on the metal fuel line to bend it away so you have about 1 to 1.5 inches of clearance from the water pump to remove it from a suspect list and see if it fixes the problem. I would check the fitting on the fuel pump to see if you loosen the fitting after moving the fuel line.

 

More information needed. It is unlikely that it is the only source of your problem. Can be a part of it...but it would only be valid when the engine is hot. If the condition(s) that make you think it is vapor locking occur when it is cold and the engine warming up...then the fuel line ( hopefully steel line) on the water pump is not the problem.

Describe your problem that makes you believe that it is vapor locking???

If you have a functional fuel return coming off of your fuel pump. The chance that fuel will vapor lock is unlikely due to the fuel return. Like I mentioned...when does the problem happen.

DUB

 

I inspected my 1977 and the metal fuel line on my car is about 1.5 inches away from the water pump and if it is touching the water pump could be suspect. The 1976 is an odd year this is also the first year they started to put a canister for a closed fuel system under the hood for air return to the fuel tank for emission control systems so the fuel vapors did not get out into the atmosphere and pollute the air. I had 2 1976 Malibu Classics with the L48 engines.

 

I went to a cruise night at a local mall. The car ran fine. When I was there I didn't lift the hood. I stayed about 30 minutes then I decided to leave (actually my 7 year old daughter decided that she wanted us to leave) I started the car and it was stumbling a bit. I coasted out slowly behind another car. Just at the exit the car stalled. I tried to start it and it wouldn't start. I check the carb and there was no fuel coming out of the jets. I left the hood up for about 15 minutes then the car started. I let it idle for a while then it stalled again after about 2-3 minutes. I waited another 15 minutes and then it was able to start again. I put it in drive then drove through the mall parking lot then it stalled again.
I had it flat bedded home. At home it started so I backed it into the garage.

 

Have you replaced the Fuel Filter Lately? Just a thought also. On my early model 1972 to 1976 Chevy's I put an in line filter on all of them all and removed the original fuel filters at the carb. I like the glass ones best so I could see when they were dirty.

http://www.ecklerscorvette.com/corve...1976-1981.html this is a stock fuel filter on 1976 thru 1981 corvettes I have not look at mine yet on my 1977 since I have only owned it for 6 weeks but I will put an in line filter into it soon.

 

I don't recommend a glass filter, they're usually cheap, restrictive, made in china garbage.
I do recommend an inline filter though.

 

Remove the fuel line at the pump coming from the tank to look for full gravity flow, plugged sock on pickup or tank vent.
Change the filter in the carb.
If it still acts the same, your pump is probably just getting weak, doubt it's vapor lock.

 

Vapour lock occurs at the inlet of the fuel pump only, not downstream. If the fuel is too hot and vaporizes, nothing gets pumped. That's why GM put a three outlet pump on Corvettes with the third line acting as a bypass. Many people downgrade their cars with a shiny two outlet pump and inadvertently induce the problem.

 

That line near the water pump isn't going to cause vapor lock. The fuel being pumped by the fuel pump would quickly push the vapor out of the system.

I had similar syptoms and a new fuel pump cured mine. I could actually get going again by pouring water on the fuel pump to cool it down.

 

Vapor lock seldomly occurs in the pressurized line to the carb as the fuel is under pressure. I would suspect the fuel in the carb boiling.

 

New replacement fuel pump put on last year. New fuel filter.

I wondered about sock on the inlet but the car starts again when it cools.

I have been told to check the carb. The float may be sticking when hot.

 

If the sock is partially blocked it may cause the vapor lock only when the car is hot.

 

Is there any fuel coming from the accelerator pump jets when you pump the gas?

 

Has the car started since it has cooled?

If this only occurs when hot you can see if it's vapor lock by pouring water (about a gallon) on the fuel pump. This will cool it and cause the vapor to condense back into a liquid. It will take a little cranking to get the fuel to the carb and fill the float bowl but it will start and run good if vapor lock is the problem. Then you will need to figure out why it is happening.

It could be that your fuel pump is bad.

 

Mike is correct: Vapor lock does not occur between the pump and the carb. The fuel in that line is under 4-6 pounds of pressure, and this will prevent fuel vaporization issues, even if the line is hot.

"Vapor lock" occurs on the suction side of the pump in the line between the tank and the pump. This line is under suction, so it promotoes vaporization of the fuel in the line. If the weather is hot, and especially if you're going up-hill, the diaphragm fuel pump can start ingesting vaporized fuel on its suction side. When a diaphragm pump sucks on vapor, fuel pressure at the outlet goes to zero. This problem is solved, as noted above, by running a return fuel line to keep fuel circulating through the suction line at all times. This rapid circulation eliminates the vapor lock issue. Be sure to always use the return line system on any street car - we even build return systems for all older cars that are used on the street, even if they never had a return system originally installed.

The other common issue is fuel percolation in the carb after shutdown. This is usually caused by radiant heating (not conduction - the heat won't conduct through the insulation created with the stock type base gaskets) of the fuel in the bowl from the hot engine. The boiling fuel can bubble out through the accel pump circuit and the main discharge nozzles after shutdown, giving a "flooded" symptom upon hot-start. As Mike indicates above, if the fuel has bubbled and percolated out, you will often not have an accel pump shot, so you can check to see if you have a steady, strong pump shot as an indication of the problem. The fix for this issue is the installation of a reflective heat shield to keep engine radiant heating out of the carb. GM used these on some applications, and they're highly recommended for street cars used in hot climates. I have a BG Carb Installation paper that shows how to build and install one of these shields - contact me via e-mail if you'd like a copy.

Lars
V8FastCars@msn.com

 

The OP mentioned in post#5 that the carb was empty and he also lives north in the Buffalo area, not real hot this time of year.

Try and simulate the condition and remove the tank line at the front fuel rail to see if you have gas there. It should free flow a full stream. First with the cap on, then off. If it changes it could be a vent problem.
You can also remove the line at the carb inlet, put a long 3/8" hose over the pipe and crank for gas flow.
A partially clogged sock can refill the lines after sitting a bit and then run for a few minutes as you mentioned.
A crudded up system can plug a new filter in a matter of less than a hour.
Many new parts including pumps can be defective.
Rubber tank to steel line at rear may be aged and sucking air.

And of course check to see if you are running the return line, but I've had no problems without it on different cars here in hot S Florida, so it's not always the answer, but good prevention.

Do the simple tests first, don't just assume it's vapor lock because you get no pump shots.

 

I am dropping the tank to have a look. The fuel line isn't putting out any fuel now so I am going to check the condition of the rubber line on the tank. It can't hurt and so far I have used lots of penetrating oil to get the bolts loose to remove the tank. I will keep everyone posted.

 

BTW, yes, Buffalo, NY area. The weather has been nice the past couple of days.