My truck has had a really rough idle the whole time I’ve owned it. I recently replace all of the lifter because they were one of the big things that needed replace and when I did replace them I noticed I had two bent push rods. So I replaced 4 pushrods in total just in case. Put it all back together and it ran fine. I just now fixed the return lines so they don’t leak as bad but I think that maybe something else could be the problem. It’s not really missing so much as the whole truck just shakes at idle. Ask questions if you need too

 

Check your compression before you do anything else. You may have a weak cylinder. Does it 'skip' a cylinder when you start it?

 

Install a clear vinyl hose in-line from the fuel filter assembly to the IP. If you have air bubbles in the clear vinyl hose you know you have air intrusion. You can move the clear vinyl hose back between the fuel filter and mechanical lift pump; as well as, between the mechanical lift pump and the fuel tank select valve to ID where your air intrusion is coming from.

FYI, you'll have to make a run to the hardware store to buy hose barbs to install the clear vinyl hose in-line.

 

One advantage of an electric pump mounted near the tank is it eliminates much of the opportunity for air intrusion while running because you're pushing fuel instead of sucking. Pushed fuel cannot mix with air. If there's a hole in the line (between fuel pump and injection pump or anywhere around the filter head) it will immediately show up as a wet leak while running.

 

That's a good point.

 

1. return rail T leaking
2. Fuel heater leaking
3. resistance and voltage drop on starter relay
4. resistance and voltage drop on starter solenoid
5. IP solenoid visual checks
6. 12.5+ on both batteries

You'll be amazed how it's almost never not one of those... Pre-pump and post-return-rail lines and connectors are usually the first suggestion while being the rarest cause.

For injector rails you basically have to install them wrong for even a cheap kit to leak; most people pinch rings and uneven-tighten everything from the cheapest internet kit to billet rails and blame faulty parts..