1997 Chevy Truck engine surging

you failed to mention it hasn't electronic fuel injection pump let me know what you so I can assist you

Yes sir, it has an electronic fuel injection pump, of which I have replaced the PMD and relocated the PMD to the top of the wheel well just above power brakes.

I'm going to have to apologize but I'm a little bit confused the PMD that you're referring to I'm assuming is the injection pump cam signal sensor is that correct? I need to know that before we can move any further.

I do not know exactly what it does, but it is a Stanadyne Pump Mounted Driver. This is the part that everyone talks about it going out due to high heat in its factory location. So I replaced it and bought the relocation/heat sink kit for it.The PMD is part #DIPDT76301 @ dieselcare.net

okay I am on the same page with you now, the PMD is an aftermarket injection pump cam signal sensor, need to ask you a few more questions was the trucks surging before you installed this aftermarket PMD? how was the truck running when it had the original injection pump cam signal sensor? or do it just not run anymore so you replace it with the PMD? the reason I'm asking you these questions is you may have a defective PMD, or a wiring harness going to it. Also make sure the wiring harness has not been damaged by heat or that you are running the wiring harness to close to possibly the glow relay or other electrical components that may cause it to malfunction. furthermore get back to me and give me a little more background on when it started and what you did before it started and after.