A couple years ago I gave the TBs a few turns, not exactly sure how many and a day or so ago I gave them two turns.
Now when I start truck the motor doesn’t even run at all on its on It does when apply direct power from battery in video below.
I checked the pressure sensor as per a thread from another forum. Said to unplug sensor and start vehicle. If it raises then the sensor is bad. It didn’t raise so I guess that may rule out the sensor.
The video sound indicates an unhappy pump. The cause of unhappiness is far from clear. However, it did not sound fatal to me and may or may not be the pump itself. For example, a downstream blockage may be preventing or limiting discharge volume and this would result in the rising pitch of the sound of pump as it builds up pressure until it switches itself off due to overpressure or other self-protection. This may result in the Height Control Accumulator not being recharged, hindering raising of the vehicle. Or there may be problems in the Control Valve Assembly or the Pump Attenuator or the Pressure Sensor or even the AHC Electronic Control Unit (ECU) itself. Checking the electrical condition of the Pressure Sensor is done very easily with a multi-metre – see Factory Service Manual (FSM) references further below. I suspect that the Pressure Sensor is working and this is what is preventing pump operation for self-protection -- but it is better to check it properly.
The pump is a simple robust positive-displacement gear pump. Diagrams of the pump and other AHC components can be found in the FSM at the pathway given below.
You are giving yourself a very hard time without a scanning tool to do some basic diagnostics and also identify the Diagnostic Trouble Codes (DTC’s) which will be present in this situation. It also means that all that we onlookers can do is offer wild best guesses with insufficient information – as I have done above.
If you are not confident about getting Techstream to work or if it takes too long to get the required cable, then may I suggest going to an auto store and buy a cheap Bluetooth dongle which plugs into the DLC3 diagnostic below the dash next to the brake pedal, then download and use the app described at this link:
AHC rough ride, with readouts from ecu
This arrangement is not as capable as Techstream but it is simple and it will get you to the AHC Electronic Control Unit (ECU) on a plug-and-play basis.
Then you may be able see whatever DTC’s are listed and also see what, if any, pressure readings can be obtained. Note that AHC pressure readings depend on being able to drop the vehicle down to “LO” and then raise back to “N” – which currently you are unable to do because the vehicle will not raise -- but you may see something.
You also do need to look at the relevant parts of the Factory Service Manual (FSM).
To do this, go to
https://lc100e.github.io/manual/ . To start, find your way to AHC general description and diagrams by following the tabs along the pathway depicted below. Diagrams of AHC components and an explanation of how they work are found here:
Next, follow another pathway to the “Problems Symptoms Table” as shown below. This lists various symptoms and gives a lead as to the possible causes. As stated at the top of this Table, it is best to work through these methodically
in the order given in the table, rather than start in the middle with a guess.
Details of all of the Diagnostic Trouble Codes also are found in this section of the FSM, as well as details on how to check the Pressure Sensor on the AHC Pump with a multi-meter (without removing the Sensor).
The “Repair Manual” section of the FSM also explains how to go about removal of various items. In this section, scroll all the way down until you reach the "Active Height Control" sections.
As
@ramangain already suggested, if you are inclined to remove and dismantle the AHC Pump (not difficult), this will first require depressurising the AHC system by very gently carefully opening the bleeder valves and catching the fluid with a hose leading to a container. Be very aware that the stored pressure is quite high and the vehicle will drop suddenly to the bump stops. As
@ramangain noted, this also would provide an opportunity to open the bleeder at the Height Control Accumulator (long black cylinder on Left side chassis rail) and briefly start the pump again and observe whether fluid is being pumped, or not. Releasing fluid from all four ‘globes’ also would give you a good idea of the condition of the existing AHC fluid.
The attached Technical Service Bulletin (TSB) may be helpful, although it mainly applies to older vehicles.
Anyway, always happy to try to help -- please keep us all posted.