Bad fuel pulse damper? Wont rev past 1k unless a fuel pressure gauge is hooked up

Oh and I suspect the ground is probably balled up shielding from inside the cable. At least one or two of the cam pos sensor wires are shielded. Really, OP should replace the cam pos sensor totally with new DENSO to clean that up. And really pore over the crank post sensor harness carefully, untaping it from the harness in case the PO did funky shit in there too.

 

The cam sensor is completely new, those wires are up above its connector. They do sell a connector for that area, but you still just have to splice it in yourself.

Update:
Got my neighbors help, they were incredible. We ran some jumper wires and bypassed the fuel resistor/ relay, and it still did died. So it's not the ecu shutting off the pump. One guy got under the tank while it was running and it sounded like the pump was operating even as the truck died. Eventually after starting it at least a dozen times it started running longer, and eventually it was just running largely normal until we shut it off. We got it warmed up and in open loop. It still did seem like it was struggling for fuel a bit, but she was running! Never drove it though, and then went for a day trip so it sat for 6 hours. Got back and tried to start it up and it really struggled to even fire, eventually sort of starting but then died.

So from our testing it appears:
-The timing signal and everything else electrical up until the fuel relay is working.
-The pump isn't being shut off, or shutting off itself
But the truck still really struggles for what seems to be fuel. It sounds and smells like it.
- Mass air flow reading on the obd was in spec with the fsm
- The fuel trim was very lean, at one point 90+%, though I don't remember if it dropped to a normal level once it was running, I assume it did and will verify tomorrow.
- Has at least 5 gallons of gas in it.

I feel that at least checking the fuel filter may be a next step? Any other suggestions?

 

Understand:

And I think this is included above:

If the ECU doesn’t get a valid signal from the crank position sensor (not solely the cam position sensor), either because its harness has faults, or the sensor is faulty, it IMMEDIATELY shuts the fuel pump off. No fuel, no run.

Im not sure if this bit has registered yet, but it’s why Bubba and I both (I believe) are pushing you toward that. But maybe I missed something above wher you validate the crank pos sensor and its harness.

 

Yes, I understand this. Considering the truck eventually ran for 5+ minutes I'm willing believe it is probably not that. We have determined that the ecu is not telling the fuel pump to turn off, yet the fuel is still not reaching the engine in large enough amounts. Of course, it could be that the times it ran were because the wires got moved/ jiggled and they managed to send out another signal, though I'd think that would lead to an intermittent style of random starting/ dying, not the very linear continuously getting better and running longer that it was able to do until it was fully operational. I would also think it would lead to the fuel pump turning off, which we believe it did not.

I'm not going to completely write it off, that is what I thought it was for a long time. If I don't find anything mechanically related to a fuel blockage, my neighbor offered to use an oscilloscope to look deeper into the electrical side.

 

I guess next Q: have you pulled the ECU and popped it open to look for damage/corrosion inside? This could be a bad ECU situation. Wouldn’t be the first time.

 

Oooh, no I haven't. That does seem like a good step. I will look into that.
I was reading a thread where a member tried almost everything, but didn't have luck until he swapped in a junkyard one, don't remember which thread it was. Hope its not that!

Thank you shifty and bubba, and everyone else!

 

Yeah, we’ve had a couple people here, when they opened the ECU clamshells they found water or similar damage to the corner of the circuit board. Absence of any sign of damage would be inconclusive but … it’s just a thought.

 

Update:
Replaced fuel filter because it's easy and was suspect. Don't know for sure if it did anything but the truck starts consistently now, and idles great. Here is where it gets weird:
Started it this morning (rough start, but there was air in the lines) and it idled great. Revved it to 2k rpms while in park. Then took it for a test drive and every time I would press on the gas it wouldn't make it past 1k rpm and it would sound like it was dying, proper combustion was NOT occurring, and it would drop down to only 200-400 rpm while driving and then suddenly jump to 1k but wouldn't ever make it past that. Only made it a few hundred feet before turning around and shutting it off.

Then hooked a fuel pressure gauge to it, in place of the fuel pulsation damper, to see if we could get any info on that. Then, it started up great and drove COMPLETELY normal with the gauge in place the whole time, fuel pressure was a steady 46psi. Drove to the gas station, filled up, drove it on the highway, got it up to 60 and 3k+ rpms and it was doing great, running how it was before. Thought that maybe the weird situation from earlier was just some excess air in the fuel lines or something.

Unhooked the fuel pressure gauge, put the dampener back in place, and went back out to test it again. This time it started and idled normal, but AGAIN it couldn't rev past 1k rpm. I would get on the gas, try to rev it up and it would just stick at 1k rpm and if I pushed it harder then it would begin to stutter a little, but not as bad as the first time. When I put it in park it would rev to 2k rpm and then same thing would happen.

So the ONLY thing that changed between the two situations was the fuel pulsation damper, when it drove great/normal it had a fuel pressure gauge hooked up to it instead, and when the damper was put back on, it really struggled. Seems like that would have to be the problem.

Anybody have information on that? I'd never heard of it before and it doesn't seem like a super critical component, but it would appear I am wrong.

Haven't gotten to this yet, maybe something to that as well. Is it located behind the glovebox passenger side?

Edit: Still no check engine lights at all

 

Did some research it appears at least one person had a crank no start or similar not good situation from a fuel damper but there has not been many mentions of it.

FSM mentions that the screw on top of it should be pushed up when there is pressure. Will check on that and update.
It would theoretically seem to me that if the damper wasn't working properly then it may let in just enough fuel to idle nicely but not to drive. ?? Whereas the pressure gauge allows for full flow.

For future reference this thread may be useful: