Where is ecu located on a 91 chevy 2500?

What is your question?

I have a truck that was running fine, turned off and wont start. Thought it was fuel pump at first but pump is good, replaced the two injectors, rotoe, plugs, fuel pump sensor gaskets, temp sensor and cap still looks new. It cranks but wont start. Was told maybe it is ecu but if fuel is coming thru injectors does that not mean ecu is ok?

How long has your 1991 GMC C1500 had this problem?

A couple months