Yea but not on a 1st gen Cummins apparently the only thing that causes a 1st gen to loose prime is the lift pump
Or sucking air.....

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So then, can you please explain how air can get into the system from the return side?

A old sticky faulty injector can cause it, though its very very
unusual....atmospheric pressure is more than 0, but it can happen. If a injector sticks open for any length of time AFTER POPOFF OCCURS, you can get air.
If air can get into injector lines, why not the returns? Is there some magical law that keeps it safe?

 

Well I must have an odd ball 12V mine has a Tee in the return line from the injectors and where does that other line on the Tee go, ahh yeah the injection pump.
Must be some after market hot up thingy.

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Motaxraca33, by chance are you keeping an eye on your engine oil level? If it is rising there is a chance you have a bad seal on the input shaft. Not real familiar with this seal but if it leaks fuel it could leak air back into the pump.

 

Maybe you should put a check valve in there, then!

Must be some gravity/suction drain-back thing.

Better yet, you and Screamin Metal boy should team up and submit a fuel system design change to Cummins. Must be some kind of miracle any of them are running at all with this egregious flaw in the fuel return line.

 

Well who had razor blades for breakfast then? Very sharp today.
Just pointing out that air does NOT have to flow back past the injectors to get to the injection pump as per the earlier post it has direct access via the bleed line.
Having seen many "impossible" things happen in the mechanical world any thing is possible.
Just trying to give some constructive help to a man in need, may be a bit of a stretch but it may help. Any constructive input?

 

• How to check for air in fuel lines on a Ford 6.9 & 7.3 IDI Diesel ...
  
  
  
  How to check for air in fuel lines on a Ford 6.9 & 7.3 IDI Diesel - YouTube
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  Jul 10, 2012 ... Each fuel injector has a return line cap that is attached with 2 o-rings, and over time these can either leak fuel or suck air....both will cause your ...

There's several instances were you can suck air at the return....just go ahead though and believe what you want to believe....it can even happen to a Cummins....Been there, Done that....


Better yet, you and Screamin Metal boy should team up and submit a fuel system design change to Cummins. Must be some kind of miracle any of them are running at all with this egregious flaw in the fuel return line.

How did you know I was a Powertrain Engineer at Dodge?

 

NP,
So what flaw in the Cummins design were you re-engineering when you added a check valve in the delivery line? Fuel can only flow back when something (AIR?) takes it's place. So where was the air coming from in your case?

 

Can we get back to the OP's truck

 

Great idea. Too bad we have to waste time barking up the wrong tree. Just to clarify, surely nobody thinks the pump return is an open drain do they? Chime right in now if you still believe a single word about the return should have ever been uttered.

 

Ok guys... I'm sitting here in the hospital kind of drugged up on pain meds confused at what I'm reading! Lol should I put a check valve in the return line just after the "T"? I have rubber hose there anyways. A local shop has a one way flow check valve for 42 bucks... Would that eliminate any possible drain back and losing prime on the return side? Just to keep fuel at the injectors so hopefully it starts up every time! And I found a tiny leak at one of the compression fittings where i connected the lines together... It didn't start up again after sitting overnight, that's when I found the leak.

 

Just curious, How did we get from fuel system troubleshooting to drugged up in the hospital?