Couldn't find a fuel pressure tester in my neck of the woods with the proper adapter that the Haynes manual indicated I needed to pinpoint the problem. Since it was so on-off, on-off it made sense that the fuel pump may be going if they do quit in that way, so I replaced the fuel pump and the rotted fuel vent tube (just replaced it with a length of 3/4 i/d heater hose, some gasket maker and hose clamps). Pretty sure nowhere on that filler pipe/vent assembly is leaking.

Unfortunately, despite the truck starting and working fine several times yesterday after the fuel pump replacement...it didn't start this morning. I can hear this fuel pump come on every time the key is turned to run, and I tried cycling the key on and off several times to prime it but still didn't start. Where's the next best place to look? I had already replaced the plugs, wires, cap and rotor with no change.

 

Update: bought a normal fuel pressure tester to at least see what was going on overall. Relieved the system pressure, attached the tester and with the ignition to Run the fuel pump primed it up to 46psi, within the 44-54psi range the book says it should be. Started the truck (yes, it actually started now for some reason) and it went up to 50psi, stayed like that for a minute or two that I let the truck run. Turned it off and it went back down to 46psi.

Now, the book says to wait 5min and if the pressure falls below 30psi you have a leak. Well it was still above 44 after 5min and now, 30min later its still above 40. Is this normal performance? Or should it hold just about that 46-50psi when the engine was on/freshly shutoff indefinetely?

When I relieved the fuel system pressure the truck actually started which it hadn't done all morning. Of course it died when it ran out of fuel pressure, the only thing that was different was that I had plugged in the block heater in the morning (it wasn't cold today, 40F or 10C) and now the coolant must be warmer than it was first thing. Why that might make it start I have no idea. My Scanguage still told me the truck was in Open loop mode (at least with ignition off, haven't started it again because I want to see where the FP goes after a few hours).

I'm out of ideas. It has spark, it has the fuel pressure the book says it should..now just going to wait and see how much the pressure drops over several hours, then maybe do the same thing to my Jeep and compare.

 

Well, I got down to testing the ignition coil and pickup coil (cam position sensor) and discovered the ignition coil primary resistance was over spec. Went to test it again later in the evening to see if it being wet out made a difference and as the girlfriend cranked the truck over in the dark twilight I could see a 1/4" spark jumping around the body of the coil.

Replaced the coil (why did they have to use philips head bolts on that...hello vice grips!) put some new hex head bolts in and the truck has been running great for a week or so now. Thanks guys!