1988 GMC V1500 Suburban Sierra Classic 8 Cyl 5.7L
Possible trouble with carb.
It will start and run for about 20 minutes.It will then kick into high idle ,and if the accelerater is pressed it will die and will not restart.It will fire while the starter is engaged ,When starter is release it will sputter for a second and die.
In order to determine if the cause is carburetor (loss of fuel) or something else, when the engine stalls and will not restart or restarts and dies, what us mechanics would do is to spray (very carefully - don't get nuts) an alternative fuel source like 2+2 CARB CLEANER in the throat of the carburetor intermittantly while starting it. If you are able to keep it running with timed sprays of 2+2, then you know there is a fuel starvation problem. If you stop the spray it stalls again. This could be a bad fuel pump as well as a bad carb. But if after it stalls and you try to restart it, it does not react to the sprays of 2+2, then you know it is not a fuel problem and you need to focus on the ignition as a cause.