Model D55141 The pump PSI runs at 27.5, but the tank pressure remains at 0. The motor seems to be laboring.

This could possibly be, you have some water from condensation buildup inside the tank, liquid does not compress. Before this next step make sure the tank is to 0 psi! Now, there should be a relief valve Wingnut on the bottom. Loosen the wing nut and drain as needed. Then retighten the wingnut (Do not overtighten). Plug the compressor in and try it. My second suggestion is, the psi adjustment pressure knob could be faulty replace as needed!

Most likely in tank check valve is leaking or belt is slipping. Belt tension easy to check, should not deflect with thumb pressure. Check valve should not let air escape out of tank. Easy to check. Run compressor till pressure builds to around 50 psi. Then unplug machine from power outlet. Listen for air leaking out of tank. In bad cases, air will actually leak out of intake filter. Replace check valve as needed. Good luck

The gauge is bad. Injector pumps need tons of pressure cause deisel compression is high

You should have a test port on the Fuel Supply rail, use a tool from a local auto parts "Tool Loaner program" where you can borrow tools for free,w/a deposit of course,then follow the steps provided;

MPI Fuel System Pressure Test

The MPI fuel system used in vehicles equipped with a 4.OL engine employs a vacuum balanced pressure regulator. Fuel pressure should be approximately 55-69 kPa (8-10 psi) lower with the vacuum line attached to the regulator than with the vacuum line disconnected. System fuel should be 214 kPa (31 psi) with the vacuum line connected to the regulator and 269 kPa (39 psi) with the vacuum line disconnected. CAUTION: Some fuel may be discharged when connecting fuel gauge to fuel rail.

1. Connect a 0-414 kPa (0-60 psi) fuel pressure gauge to test port pressure fitting on fuel rail (Fig. 7).
2. Remove vacuum line from pressure regulator.
3. Start the vehicle.
4. Note gauge reading. With vacuum line disconnected, fuel pressure should be approximately 269 kPa (39 psi).
5. Connect vacuum line to pressure regulator. Note gauge reading. Fuel pressure should be approximately 214 kPa (31 psi).
6. If fuel pressure is not approximately 55-69 kPa (8-10 psi) higher with vacuum line removed from regulator, inspect pressure regulator vacuum line for leaks, kinks or blockage. CAUTION: Fuel pressure will rise to as much as 655 kPa (95 psi) when the fuel return tine is pinched shut, shut engine down immediately after pinching oft fuel return line.
7. If fuel pressure is low, momentarily pinch shut the hose section of the fuel return line. If fuel pressure remains low, inspect the fuel supply line, fuel filter, and fuel rail inlet for blockage. If fuel pressure rises replace fuel pressure regulator.
8. If fuel pressure is above specifications, inspect the fuel return line for kinks and blockage.

Capacity Test

1. Remove the cap from the pressure test port in the fuel rail.
2. Connect a 0-414 kPa (0-60 psi) fuel pressure gauge to the pressure fitting on the fuel rail (Fig. 7).
3. Start the vehicle. Pressure should be approxi- mately 214 kPa (31 psi) with the vacuum hose connected to the pressure regulator and 269 kPa (39 psi) with the vacuum hose removed from the pressure regulator.
4. If the pressure is not to specification, check the following before replacing the fuel pressure regulator:

• 4a - Inspect the fuel supply and return lines/hoses for kinks or restricting bends
• 4b - Check the fuel pump flow rate. A good fuel pump will deliver at least 1 liter of fuel per minute with the fuel return line pinched off. If the fuel pump does not pump adequately, then inspect the fuel system for a plugged fuel filter or fuel pump inlet filter (sock). Fuel pump flow rate can be done by connecting one end of an old A/C gauge hose to the fuel test port on the fuel rail and inserting the other end of the hose into a container of at least 1 liter capacity. Run the fuel pump by installing a jumper wire into diagnostic connector terminals D1-5 and D1-6. Be sure to pinch off the fuel return line or most of the fuel will be returned to the fuel tank.

Try examining the pressure switch first. If it's cycling on/off abnormally, it's probably the pressure switch.

Is the petcock down below open or closed? If open, then screw it closed. Also, is the compressor portion connected to the motor working as it should? As the motor reciprocates, it should operate the compressor piston that pumps air pressure into the tank. Maybe something is broken there.

Hi
your pressure switch is bad. so it isnt cutting off the compressor. the part number is N003306SV and can be obtained from Dewalt on Servicenet.
Detail

Good luck and hope this helps

Check to ensure that the storage tank has no fluid in it, open the drain valve and blow it out. There may also be an inlet air filter on the compressor, make sure that is clean and there are no obstructions.

There is a line running from the pump assembly to the tank. At the tank the compressed air passes a check valve. This valve prevents the air from escaping back along the same line. After the tank reaches max psi the motor shuts off. What is undoubtedly happening or rather not happening with your compressor is the unloader valve is not functioning properly.

The unloader valve is what bleeds off the pressure that remain in the compression chamber after the motor shut off. If the unloader valve fails to bleed the excess psi off then the piston has to work against your minimum psi. or around 80psi.

This is your large load.
The unloader valve is comprised of a mechanical trigger at the switch and a small air line that runs from the switch back to the tank check valve or up at the pump manifold.

Often it is enough to clean the small mechanism and make sure all the small parts are free from corrosion or damage.
However you may need to replace it.
Hope this helps.

Usually you cannot adjust the cut out pressure of the tank/motor itself, this is why they have regulators, which regulates the pressure flowing down the air lines (regulators like these dont regulate actual tank pressure cutout). To regulate air flow using the regulator knob, you actually have to have air flowing through the hose while you make the regulator/pressure adjustments as regulators regulate pressure DOWNSTREAM from the actual regulator itself.. so air flowing through is a must. Attach an air blower or something similar and let air start flowing through the hose. Now turn your regulator knob in the "-" direction to decrease regulated pressure. It is best to bring pressure all the way down to "0" first, then open the regulator up (by turning to the "+" side) and pressure will rise until you get to the desired pressure needed for the air tool in use. The tank pressure will still be between 80-125 PSI as the motor regulates and keeps the pressure in the tank between these values automatically, but your line/hose air flow pressure will remain at the regulated pressure (say 40 PSI or whatever you set using the regulator knob).

Hope that helps and makes sense.

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