Both Alternator maxi fuses were blown. It appears the PO removed all the maxi fuses and replaced them randomly, as nothing was in its correct place. the maxi fuses were supposed to be 60 each, and they were 30 and 40 amps, no wonder they blew. After replacing those, the fuel pump is running at 35 lbs pressure again. I am theorizing that the fuel pump was running low pressure due to running low voltage, since the alternator wasn’t really part of the equation. I am back to wondering if the fuel injectors are dirty or plugged.
I retested for spark, and I have spark on all cylinders, but occasionally when starting the truck it will have no spark at all when cranking, but if I cycle the key off and on, it will have spark the second time.
ECM?
Scrap my earlier suggestion about dual circuits. A schematic shows a common power source for all 6 injectors.
What I would do is check for power at the iffy injector plugs and that a ground circuit exists for each one through the PCM. This could be done with a test light or VOM at the injector plugs.
A Noid light is beneficial to a point. If power exists and no pulsing ground is shown (which is what pulses the injectors) there may be a problem with the PCM. That’s all assuming there is not a compression issue involving the engine. Hope that helps.
I am checking compression this afternoon, and I will pull the fuel rail to inspect the injectors for physical blockage. The ecm is looking more and more suspect.
@dockrat100
pulling the fuel rail to inspect for physical blockage may or may not work. You might see EXTREME blockage.
The best way is for a mechanic to perform an injector balance test
What you can do . . . without removing the rail, I believe . . . is measure the resistance of all 6 injectors. I don’t know what the specs are, but they should all be identical
When I pull the fuel rail, I intend to swap the injectors around to see if the problem moves with the injectors.
That sounds like a good plan
The good news is, I found what ails the Jeep. The bad news is, it has 0 compression on cylinder4. I think that’s a wrap for this vehicle.
@dockrat100
What is the cause of 0 compression?
Blown head gasket?
Burnt/damaged valves?
All cylinders had good compression but #4. (by good, I mean between 130 and 145.) I don’t know why this one has no compression, but the piston is moving in the cylinder, so the connecting rod isn’t broken. If I had to guess, I would say a valve is stuck open, but that is over my head.
The head gasket was just replaced a month ago, so I hope it isn’t that, but I guess it could be.
Ya gonna pull the valve cover and have a look-see?
Just a wild guess, but something similar happened to by dad years ago. His Ford truck was running fine, then one day he went to start it and it ran horribly, missing like crazy. It turned out some neighborhood kids had changed around his spark plug wires as a practical joke. As a first order of business OP should verify the spark plug wires are connected to the correct plugs.
It is, I think, either a bent valve sticking, or a gaping hole in the top of the piston. I will pull the valve cover this week and see if all my valves, especially #4, are moving properly.
I would think that a valve stuck open would cause a loud clacking noise due to increased valve lash.
A zero reading usually means a valve issue or disentegrated piston. Hate to be a downer, but those compression numbers on the other cylinders are low.
Did this engine suffer overheating and that is the reason for a head gasket replacement?
I will add that in some cases coolant entering the combustion chamber can be very corrosive and will flat eat the heads off of valves.
The worst example of that I’ve ever seen was when I worked for VW and had to do a warranty engine overhaul on a new car that didn’t even have 500 miles on it. It was wiped and then some.
There was a story behind this one but it wasn’t VW’s fault. This problem was inflicted by more than one person although the new car owner could be forgiven for their part in this debacle and I certainly didn’t fault them. Stinking salesmen… 
The engine did get overheated by the PO, causing the blown head gasket. At this point, I am seriously questioning if the mechanic who replaced the head gasket did the appropriate machine shop work before putting the new head on. (The old head was cracked.)
@dockrat100
The new head . . . was it brand new?
Or just new to the vehicle?
Were any of the old valves reused?
I am sure it was a used head, valves were probably reused. It was supposed to go to the machine shop and get checked out, now I am seriously wondering if that ever happened.
I just used a compression gauge to air up the cylinder, and I am getting no leakage through the cylinder to the crankcase, and no leakage to the intake. I am getting air out the tailpipe, so it appears that an exhaust valve is stuck open. I will do more testing to verify this.
I’m sure you know this, but on the cylinder being checked you do have the came lobes in the correct position with both valves (in theory anyway) being closed?
When an engine runs fine and then runs rough suddenly, and you find a leak-down test reveals there’s a problem with an exhaust valve in a certain cylinder, I remove the valve cover to see if there’s a broken valve spring for that exhaust valve.
Tester