Help with an arrangement

After an apparatus areeglo (the chain tensioner was broken and the entire distribution kit broke down the housing the escape valves already arranged and changed several pieces) I turn on my pick -up truck Nissan D21 it despair and the mechanics do not help him

See if it is spark or fuel what you lack to start so we gia where you have to check

If there is a fuel spark and everything ..
new details in the morning light normal (I put new spark plugs) the run the time that is 5 minutes 30 minutes one hour, but after turning it off it the in6Tentum turns back again and does not start at all that once I saw what they did, take away the connections of the injectors and try to start and start shortly after connecting the injector 1 and 3 The next bell connected the injector 2 and 4, stabilizy I took it to take a role and worked perfectly, I turned off the descend for a while and did not want to turn on again tried the above again but it no longer worked only caused that the battery will go down the attempts ....... I don't know what I can do more

If you change the excape and admission valves and give start problems do this

1- Check the caliber of the valves D21 is 8 admission and 10 excape

2- Review the engine compression with a meter

greetings from Costa Rica