94 6.5 Hard Start, Sputtering Issues

[85spraybomb]

Hi guys, I have a 94 K3500 Ext Cab 6.5 Auto 4wd.
I had been having issues with it sputtering under throttle, I assumed fuel related.
So I went ahead and replaced the tank, added a pre
Filter setup between the tank and lift pump, also installed a new 93 AcDelco EP158 lift pump, also removed the factory FFM and installed a spin on fuel filter setup in the engine bay along with a larger inlet fitting. The truck also has a new lift pump harness from PT Wiring solutions. I can get the truck to run, sometimes it will run well, other times it will begin to spit and sputter and shut off, at that point it will become very hard to restart, although it will restart it doesn't run clear.
I've exhausted all options I could think of.
I'm leaning towards the injection pump being bad. But I'm looking for suggestions and opinions.
Thank you

[DmaxMaverick]

Welcome aboard!

Or, it could simply be air getting into the system. You've done a lot of messing around with it. Install a clear line at the IP return outlet in a loop. Watch for bubbles.

[Cazmatt]

My truck was running like that, died after five minutes. Would not restart till it cooled some, and struggled to stay but for a bit. So I replaced the PMD with a long harness, and it stayed running. Now I’m just suffering from S code EGR syndrome. Not sure if your 94 is set up the same, but maybe that’s it.

[GMC-John]

I just bought a '94 TD as a non-running truck. I finally realized that the FSD (PMD) was an issue but I didn't want to remove the top of the intake manifold to change it out. I bought an $83 PMD relocating kit on Amazon to move it under the front bumper. After installation the engine stqrted within 5 seconds of cranking. I was able to leave the old PMD on the fuel pump by just sticking the new extension cable connector in the gap between the PMD and the manifold. Once around the block I noticed that under a medium load or more it would misfire and buck at a very random manor. I called up one of the nationally known diesel suppliers and the owner told me that I had a bad oil pressure switch. I was very skeptical at first but I had already bought this part for the truck so I decided to put it on even though it looks like a substantial effort. I had already replaced my '94 lift pump with the '93 spec lift pump and tested it on the truck with remote 12V power. It worked beautifully. I bought the special Lisle #13250 socket to get this done (was on the shelf at O'Reillys). This socket makes the job very easy and it was done in 15 minutes. I hit the switch and all popping and miss-firing stopped. Come to find out the bad oil pressure switch was not giving 12Volts to my new lift pump when the truck was in the runniing position.....only the start position. Hope this helps.