1989 5.7 350 chevy van won't start - 1990 Chevrolet K2500

Has the electronic engine control system (OBD2) been scanned for fault codes? That is the very 1st thing you must do.

Make sure battery has a full charge. Have a helper crank it while you check for spark at the plugs. If spark everywhere, use a gage and check proper fuel pressure and fuel injector pulse. How long since a tune-up? Any applicable trouble codes?
Chevy doesn't have a fuel cut-off switch. As far as ford--chevy--Chrysler, ford is the only one I know of that has a fuel cut-off switch.

Fixed Problem (it was my van) no power to ignition wire at starter. Replaced Ignition lock cylinder. just worn down. (Delivery van 50-60 starts a day). 160k miles.

what you have coil or cap and rotor.

the high humidity (water) is attacking your electrical starting system, whens the last time you changed your spark plug wires , distributor cap & rotor ? how about your fuel & air filters ? cleaned your battery terminals ? try it , it will help !!!!!!!!!

Had the same issue with our 1999 chevy astro van, would crank but would not start. It had been raining and windshield had a leak, after 2 days of no rain it started. Pulled codes and was the Security system in the ignition switch. Hope this helps.

One thing to check into would be the antitheft system. Not knowing what year or type of vehicle makes it hard to help. But like i said, engine shut down in 5 seconds or less is a symptom of a bad antitheft security system. This link explains.
http://vatspasslockpasskeysecurityhelp.yolasite.com/

To sell junker the website is very helpful for who are selling junker.i suggest all my friends that this website was very usefull.some kind of key word was given below......................................................... junk my van, junk my truck, scrap my car, scrap my vehicle, scrap my truck, scrap my van, remove my van, remove my van, remove my vehicle, scrap truck, scrap vehicle removal, scrap car removal, vehicle, disposal, tow my scrap car, tow my scrap vehicle,

http://cashcashcars.com/

I would be looking for fuel first a faulty fuel pump. second seeing if you have spark, bad wires or plugs or even distributor, timing could be out

i had the same problem and this sounds funny but on the top front of your motor theres the big hose that comes from the rad. theres a sending unit for the temp. it got 2 wires on it, will try changing that. that what tells your computor whether its cold or warm, if that goes bad you could be trying to start your van and the computor could be saying that the motor is hot. i hope you know what i mean if not get a hold of me.