Tonight my fuel pressure was fine at 15psi, then very quickly the needle dropped to 10 and right back. About one hour later it fell to 10 and stayed ,but when I hog mash the fuel it goes back to normal. It jerks very quickly when it does act up. I changed the filter but no luck.
I just have about 1300 miles on this lift pump. Could I have got bad fuel? Pump runs fine at key bump, When my last lift pump failed it would cruise at 7psi and 0 wot. Now it holds 15psi but will spike and jump back and forth for a minute then may not do it again for a hour.I have Isspro mechanical gauge. I have spent a small fortune on this truck and may part ways with it.

 

Check the electrical connections in the plug for the lift pump.
They could be corroded.

 

Check your overflow valve at the banjo for the return line on the VP44. If it is sticking or leaking it will allow the fuel pressure to fluctuate like you describe.

The other common source of pressure fluctuation is a sticking bypass valve in the lift pump, and they are not really repairable.

I just do not know how many times I have seen Dodge dealers diagnose a rig as needing a new VP44, and all that is needed is a cheap overflow valve. So, take the time to check that if it is not your lift pump bypass valve.

 

I have a very similar problem. Two days ago I noticed my pressure would quickly drop to 6psi at idle. If I tapped the accelerator it would jump back up to 13 PSI. Today it gave up the ghost. It won't even hold 4 PSI. I am thinking it is the regulator in the pump. I have a new spare so I will change it tomorrow and let you know what I find out.