94, starts and dies, then misses?

[Thor]

I have a 94 chev with 295,000, 195,000 on a new engine. Truck has been awesome for the last 8 years. Truck starts right up in the morning, runs about 15 seconds, dies. Restarts if I crank and pump throttle for 20 seconds. Never had it quit twice but runs rough and misses, and this never goes away. Tried a new lift pump, is my IP shot after this many miles? Can I bypass OP switch to rule the OP switch? If its not the OP switch, can a GM shop plug into the computer and check IP if it's not throwing codes? Also this does have a new FSD, but when that went, it only died when hot, this is opposite. Bottom line, I don't want to put in a new IP, unless I know for sure it toast. Thanks guys.

[a5150nut]

Thor, welcome to TDP.

You can pull your own codes on a 94. You need a paper clip or short peice of wire bent in a u shape. Under the steering colum is a plug receptical and you want to connect the two top right pins in the connector. Now turn on your ignition switch and count the flashes of the Sevice Engine light. 1, 1,2, 1, 1,2 1, 1,2 says everything is good and working. Any other combinations will flash 3 times then on to the next. Write these down and let us know what you read. And don't forget to remove the jumper when your done.

[Thor]

The service engine light just flashes 1,2 1,2 1.2. was going to try to bypass OP switch but it has 3 wires going to it. One lite test light brite, middle one was dim, and the third did not lite at all. What two would I jump to bypass this? Or any more ideas? Thanks