I installed the Walbro 392 pump kit and Draw Straw 3 weeks ago. Up until yesterday, I was getting 23 psi at idle, 22 psi cruising & 16 psi wot. Now when starting the truck, it jumps up to 23 psi and then jumps a little up and down...then drops to 18 psi. When I give it throttle, it jumps back up to 23 psi. Driving down the road it's fine but once I let off the throttle, it jumps back down to 18 psi. Get on the peddle and it jumps back up to 23 psi. What the heck?

 

I Installed the same fuel system minus the draw straw. Mine was mint for like a week then it was dropping down to nothing when I would punch it. I changed the gauge and sending unit. It was good for another 2 hours then dropped down again. So I called rich and he told me to check the connections, they were good. I put some injectors in and the pressure was good again for a week. Called him agin he told me to replace the bypass valve on the injection pump. Good but some times if its real cold I can drop it for the fist minute or 2. I am going to call him again and see whats up. What gets me is that its not all the time It will do it then it wont. But I notice before It does it it will fluctuate like you said.

 

What's strange is the pressure should drop when I give it throttle...not increase. Let me know what you find out.

 

Ok...after work, I started my truck and sat there for a few minutes watching the fuel pressure. When the grid heaters kicked on, the fuel pressure would shoot up to 23 psi. When the grids kicked off, the fuel pressure would go down to about 19 psi. Does that sound like an electrical thing because it should be doing the opposite? At least that's what it used to do.