Misfires, fuel/air issues. Where to start?

[Zimmerly]

Hey there,
Just an update- I've been really busy lately with projects at work, and with general life as a new dad/new homeowner.
So... with the little time I've had to give this truck attention lately, I took some time on my lunch break to start tracing the orange 12v wire from the fuel pump relay. Just as you said, Road Trip, about 12cm down from the fuse box, the orange wire branched off from the ECM wire. The junction is just barely inside the large loom, and is a little tricky to seperate from the rest... BUT- I can clearly see it is shoddily wraped in electrical tape, with some hanging off, which tells me the condition of this connection is par for the course when dealing with this truck. I got a photo of the wire. I'm going to rewire the connection this weekend.

You must be registered for see images attach

Also, I bought a Denso downstream sensor for my B2-S2 issue. I know I should've gotten all 4 sensors, but I'm running on a low budget and had some other things I needed to buy (rear u-joint, new diff cover, fuel line to fix my vent-to-evap line, misc other things).
I'm hoping this one sensor will get things back in order. If not, I'll buy the other 3.
Hope all is well!

-Jacob

 

[L31MaxExpress]

Hey there,
Just an update- I've been really busy lately with projects at work, and with general life as a new dad/new homeowner.
So... with the little time I've had to give this truck attention lately, I took some time on my lunch break to start tracing the orange 12v wire from the fuel pump relay. Just as you said, Road Trip, about 12cm down from the fuse box, the orange wire branched off from the ECM wire. The junction is just barely inside the large loom, and is a little tricky to seperate from the rest... BUT- I can clearly see it is shoddily wraped in electrical tape, with some hanging off, which tells me the condition of this connection is par for the course when dealing with this truck. I got a photo of the wire. I'm going to rewire the connection this weekend.

You must be registered for see images attach

Also, I bought a Denso downstream sensor for my B2-S2 issue. I know I should've gotten all 4 sensors, but I'm running on a low budget and had some other things I needed to buy (rear u-joint, new diff cover, fuel line to fix my vent-to-evap line, misc other things).
I'm hoping this one sensor will get things back in order. If not, I'll buy the other 3.
Hope all is well!

-Jacob

I see a factory heatshrink with adhesive inside covered splice.

 

[Zimmerly]

I see a factory heatshrink with adhesive inside covered splice.

Wrapped with tape, it does look like factory heat shrink. It's the large amount of unraveled electrical tape below, leading up to it that concerns me. Going to look into it more after work.
Since I'm pretty confident that's where the issue lies, and I have the pump working otherwise, I'm glad this is only a small issue compared to the others I've got.

 

[Road Trip]

Wrapped with tape, it does look like factory heat shrink. It's the large amount of unraveled electrical tape below, leading up to it that concerns me. Going to look into it more after work.
Since I'm pretty confident that's where the issue lies, and I have the pump working otherwise, I'm glad this is only a small issue compared to the others I've got.

I went back through this thread, and the evidence of the PO's hackery that you showed us in reply #24 could have
been initially motivated by a bad connection originating in S101.

So if the current problem description remains a loss of 12v power between the ECM B fuse output (pin G12) and
the fuel pump relay input #87, (pin B1) ...then I think that an eventual inch-by-inch inspection of this power
path will unearth the root cause. (Reply #38) Since the splice in the photo above tells me that you are getting
closer to the actual bad spot. And the good news is that this path is both short and *not* under the
dash. :0)

Just the fact that you have figured out how to jumper power in such a way as to get the fuel pump relay to start
working again tells me that you have a firm grasp of the situation. (!)

Finally, it's good to see that the FSM didn't lie to us about where you would find the factory splice -- it's always good
to verify another data point in the FSM library for future use. Looking forward to the photo of exactly where you track
the power loss down to, followed by a report that fuel pump relay is once again working with the permanently repaired
harness.

Keep up the good work. This GMT400 is going to be better for you having adopted it.

Cheers --