1991 safari starts ok, but dies out if accelerator is not pumped continuously, cause?

when is the last time you had your ignition system cheked for spark plug gap or rotor wear or roto cap cracked

Check the fuel pressure

limited backfeed but id try a vacume leak

Sounds like the engine is starving for fuel - plugged fuel filter, failing fuel pump, malfunctioning fuel regulator, etc. Have the fuel pressure checked.

my van starts for 2 seconds and dies.i changed fuel pump,filter,distributor,module,cam and crank sensors and still does samething

Mine is same year with 5.7 . 110,000 miles did exact same thing . Replaced fuel pump & fuel filter . all went back to normal. (feul pump collector filter was falling apart) Try just putting a new fuel filter first . Driver side under cab , on the frame. Hope it helps.

Other problem areas to check are a clogged catalytic converter and rear axle gear oil level (Astro/Safari axle seals leak causing shuddering under load and eventually seizing).Also GM's have had strange intermitent engine and trans problems that dissapear after replacing the main fuses. Check with a GM dealer for TSB's for your truck.

if it will run with you manually putting fuel to it . then check the pump relay. if the relay is ok check the fuel filter. if thats ok then its either the pump or a bad connection at the pump.

If it has a regular carburator, replace the acceleration pump. It's a small diaphram on the side, near the fuel inlet.

What shape is the catalytic converter in? If it plugs up you have back pressure that causes issues.