my truck wont stay running and now it wont strart at all

Hows your choke/heat riser? in the olden days we used to have a lever that you'd have to pull out for the choke, then the bi-metallic spring what loosened with temperature connected to a butterfly at the entrance of the carb. Now with fuel injection there is still a throttle, but this problem could be caused by any number of things. Foul plugs, choked air filter, vacuum leak, old cap and wires...the list goes on and on...

I think your choke is controlled these days by a vacuum motor, gone are the days of funky big springs ontop of the intake manifold...been out of circulation so long couldn't even tell you what/how this cold start needing enrichment is accomplished.

Throttle body injestion on all GM trucks in 87. Aside from the choke being nonexistent the only thing I would cross off on bobs list is the airfilter. A tuneup (plugs, wires, cap, rotor, fuel filter) could quite possibly fix the issue. Air filter and PCV valve are also part of a tuneup and won't hurt to also replace. If a tuneup doesn't fix it then it could be a vacuum issue, fuel delivery issue, mechanical timing issue, or electrical timing issue. To quote bob the list goes on and if all mentioned check out good then post about it.

Let me rephrase that. All GM trucks from 1987 and newer came stock with electronic fuel injection.

Try pulling codes.

check your fuel pressure, sounds like your fuel pump is weak causing engine to stall, fuel injectors need about 55 p.s.i. for the fuel injectors to open and spray fuel in cylinders, a easy way to check is spray carb cleaner in air intake with someone starting engine, if engine stays running while spraying carb cleaner you know you have a fuel problem, be care when doing this if engine happens to backfire you could have some flames, (be carefull )

Throttle body injection...... 11-13 psi

sorry, john you are right thinging of newer with mulit-port fuel injection

I tried to put that as nicely as possible, others won't. You should easily be able to remove the air cleaner and see the injectors squirt while someone cranks the engine. To test pressure you will have to use an adapter at the fuel filter fitting under the drivers door. Pretty sure it doesn't have a schrader valve. It should hold that pressure for quite some time also. Ideally it should hold forever.

I remembered a similar issue and found the thread. The person in this link had many similar issues to you and it turned out to be a fuel pump. Read through and see if anything seems familiar, pasting a link through my phone adds spaces so be sure to delete them... http:// www.cargurus.com/Cars/ Discussion-t14325_ds534062