6.9 Fuel delivery issue

[Tomstill8569]

So I have had the typical fuel delivery problems as the next 6.8 IDI owner. Here is where I am at now. 6 an fuel line tank to pre filter, 6an fuel line prefilter to Holly Red fuel pump, 6an fuel line pump to marine 10 micron water separator, 6 an fuel line to factory fuel filter assembly. This was all installed this weekend. Fuel injector return line kit install less the 2 months ago. All is dry around the injectors.

The truck starts right up no bobble no stumble. It runs perfectly smooth with zero surging. I was so happy with results…then.

Today running down the road it just cut out. It took 5 or 6 key turns for it to start back up, like it was out of gas. Now it is hot here in TX right now 100’s. It was like a vapor lock on a hot rod.

Any thoughts would be appreciated. Am I looking at an injector pump? New injectors? I don’t want to throw good money after bad.

 

[IDIBRONCO]

The first thing that I'd recommend is a good, quality fuel pressure gauge. Those can be invaluable in diagnosing fuel delivery issues. They can even help to diagnose a dying injector pump if it's returning too much fuel back to the tank. I LOVE mine and will install one on every truck that I own from now on.
Now to your question. It could be the IP, I don't think that it's the injectors, it could even be a loose electrical connection. I don't know about an IP just shutting off from excess wear, but the next time that it happens, pour some cool water over the IP. If it starts easier, then that's your problem. The IP and injectors should be replaced at the same time, ideally. They wear internally at the same rate.

 

[Tomstill8569]

Installed fuel pressure gauge with everything else. Guage is at input to fuel filter. It is between 3 & 4 psi when at idle.

 

[IDIBRONCO]

That seems a little low. What is the pressure when you rev the engine? How about while you're driving? I ask because an electric pump won't build pressure as engine RPM rises. It's possible that the IP just, plain ran out of fuel. I like mine to be 4-6 PSI while I'm driving at highway speeds.

 

[Tomstill8569]

I thought it is low as well. It is a new Holly red and is 3 - 4 psi from install across all rpm’s. I don’t know about psi driving. The guage is under the hood. I am going to turn up the pump and see what that does. Maybe it was set low from factory.

 

[IDIBRONCO]

That could be. I have my gauge inside the cab so I can watch it. My sender in located before the factory filter too. I don't want 100% accuracy, just an baseline to watch for. Damage can occur if the IP is run out of fuel very many times. I lost one to a bad mechanical lift pump last summer.