Starting problems with 1992 gmc c1500. 350 tbi
 

Hi, I have a 1992 GMC C1500 with the 5.7 TBI 2x4.

Recently I have experienced starting issues. Get in it starts and runs great, drive it to town go in store for 10 to 30 mins come back turns over but not running . Let it sit for a while to cool off play with the key turn on and off and fires up and runs good. Then it may work fine for a few days or it may continue to do it. I took it by the parts store and the ran the codes, it threw a fuel pump code, Code 42 (Electric Spark Timing circuit)(EST), and a o2 sensor code. So i changed the fuel pump. Took it back yesterday because it has not been near as bad maybe once a week or so. It only had a o2 sensor code on it but nothing else. Well i go to leave and it wont start, it turns over but wont start. So i waited about an hour still wont start. I went in and purchased A Ignition Module as per what the parts guy said it probably needed a few weeks ago when it threw code 42. So i put it on and it fired right up no problem. I wanted to make sure i got to the house before I turned it off. So I did and it would not start again. This morning it started and ran fine. What i have found so far is that it only does it when the truck is warm. I dont think its a fuel problem. But i have no idea.

Any suggestions?

Thanks in advanced