Intermittent Fuel Delivery Leaks - How?

[AnotherOldJeepGuy]

I figure a leak is a leak, so I have some work to do.  But I'd still like to understand an intermittent leak in the fuel injection delivery.  About a week ago I smelled gas, looked, saw one leaky injector.  It appeared to be leaking at the seal into the hole it goes into.  I have had these leaks before, I have replaced 3 of my 6 injectors, and the last time I had it apart I replaced all the o-rings and had no leaks.  But that's not the question, the question is still why intermittent.  I have looked a couple more times over the last few days and the leak has never showed up again.  I looked at both engine hot and cold.  So scratch head.

 

This morning I installed a new battery and started up to make sure the new battery was happy.  I smelled gas again, looked, the aforementioned injector was dry.  But I see dripping fuel from the bottom of the fuel pressure regulator and a small fuel pool under in in the area of the blue outline.  So Alexa, add a new regulator and fuel line quick connect to my shopping list.  But 10 minutes later I decided to look more closely and capture the leak in a pic, it's no longer leaking and the fuel in the pool has dried up.  There is some dampness still visible on the regulator but no active leaking.  Again the intermittent question.  Truck has not been driven or even run long enough to warm up a lot, but still, scratch head more.

 

Anyone care to kill my cat (quench my curiosity for those that don't decode that metaphor)?

[llhat]

i would still plan on replacing the regulator,  be sure to also source the 'kit' for the hard line "o" rings..... 

 

this 'could' be pressure related, as the pressure drops from engine off, the leak threshold is lowered.

"Could" be temperature related..  

waaay out in left field, porosity on the regulator housing...  
good luck!