I have a new to me 1999 Ram with the 318. I have been going through maintenance so far...plugs, wires, cap, rotor, oil and diff fluid change. I am having some trouble when I start the truck for the first time each day. It starts very rough and takes a few tries to start, once it is started, it runs great though. I can stop the truck and try to start it again later on in the day and it will start just fine but if I let it sit overnight I will run into the starting issue again. Figuring it might be fuel pressure related I hooked up my fuel pressure test gauge and tried to start the truck. Turned the key to prime the pump and the gauge went from 0-20, next prime 20-40, next turn of the key it started right up and idled at 49psi. I took the truck for a drive and came back, still at 49psi. The minute I turn off the truck, the pressure starts to drop and after a few minutes it's down to 0. Am I right to assume the issue is either the regulator or check valve in the pump? At first I thought it might have been leaky injectors but I'm not so sure about that now. Should I be looking into anything else relating to the rough start and low pressure or should I just go ahead and buy a new pump? Thanks in advance guys!

 

The pump should prime to full pressure faster than that.... it may just be getting weak. 49 PSI is correct though....

It isn't a return style fuel system though, so, likely it's a check valve in the line. WHERE in the line it is though, I'm not sure. You can download a factory service manual for your truck from here. Might be some info in there about it....

Welcome to DF!