Pump pressure can not increase pressure by turning screw in,only has 1 lb pressure so shuts off

something wrong here. your incoming pressure is 4 psi ( tank pressure to the pump and you use a pump to boost pressure to a maximum of 65 psi at which point the pump is shut off ( all taps close off)
yet with no pumps running the pressure goes up to 100 psi
Find where you are getting pressure in that is making the pump leak
if you have 100 psi to the pump when it is turned off, then it would not be turning on ( power on) as the shut off pressure is set at 65 psi and the line pressure is 100 psi

I assume this has an electric blower and probably electric fuel pump? Does it have a fuel filter somewhere in the system? I'd try to return the fuel pressure adj. screw to factory setting. I'm guessing screw in decreased flow rate and out increases flow rate. If fuel pressure is measured on the burner side, then increasing flow rate should increase pressure. It's intuitively backwards. What does customer service say? Usually, they are helpful. They need to know there's a customer problem.

If in the past your system can build-up pressure up to 40 psi even if the supply valve is open and water is being used in your house, then your pump impeller maybe already worn out that's why its pumping capacity was reduced.

First of all are you running kerosene or diesel ? If you are using diesel, it does not burn as clean as kerosene which causes that burning rich smell. If you are going to use diesel, just use #1 diesel only but still may have a little rich smell. Don't use die red off road diesel. If you are using kerosene and want to check your air pressure on your pump, you will need a 10 lb. test gauge with a 1/8" NPT male pipe thread on the end of the gauge.There are 2 plugs on the back plate. Do not remove the upper plug with the hole in it. This is the adjustment screw for pressure. Clockwise increases pressure, counter clockwise decreases pressure. With the heater unplugged,remove the lower plug. Screw the test gauge in and start the heater. Check the pressure. Most are set between 5 1/2 and 6 lb. of pressure. Check your owners manual to see what your setting should be. If your pressure does not change, you have a worn pump and it would have to be repaired. Once you have the correct setting, unplug the heater, remove the gauge and install the plug back. If you feel that you are not qualified to perform this procedure, send it in to a local repair center.

Your unit has a air pump behind the electric fan motor. This pump is what produces low pressure air across the nozzle which causes a suction for the fuel pick up tube from the tank. Check your fuel filter first. If you are not getting any fuel spraying out the end of the heater, your air pump needs to be looked at. There are carbon vanes on a rotor inside the pump. They could be stuck in the slots of the rotor. Don't mess with any of the plastic plugs on the back cover unless you have the tools to test. Just remove the steel screws that hold the cover on. There will be another set of screw inside,remove them to get to the rotor and carbon vanes. If they are not stuck, your air pump may just need to be turned up. You will need a 10 lb. pressure gauge to test the pressure. It screws in to the 1/8" threaded hole (usually has a plasic plug) thats where the gauge screws in. The pressure on most heaters is 5.5 to 6 lbs. setting. The adjustment is the plug above the gauge test port. Turn clockwise to increase pressure/ counter clockwise to decrease pressure. Be careful because this will also increase more fuel to the combustion chamber. If turned up to high, you will get a large flame shooting out the end of the heater. If you do not have experience with working on the heater, and do not feel comfortable doing it, get someone else to help you that does. Good luck.

This could be caused by low pump pressure but is more likely a bad control board part # 104068-02.

If you put your finger over the pump adjustment screw on the back of the motor you should be able to hear an increase in the sound of the heater.

If you need service help you can call 1-800-475-5660

Sometimes a new tank the blatter will be kinda sealed to the sides of the tank.the amount of air in the tank s/b equal to the cut in pressure of the pressure switch.(40 lb) that would be (60 lb) cut out if you messed with the little screw on the pressure switch you have a problem.there must be the 20 psi of differance between start and stop.

28-45 when running
35-45 key engine off
check your fuel filter for blockage

sounds like high pressure stop. increase screw in pressure regulator. or use more water.

Yes 90 series pumps will run pretty close to 6000 psi. there are cross port reliefs built into the endcap of the pump and usually a POR valve as well. so the POR should be set at 3000, the cross ports in the pump should be set higher than this. There may also be a "transmission block" which is a seperate block with hot oil shuttle and cross port reliefs. Make sure these reliefs are also set higher than the POR valve in the pump. There may also be cross port reliefs in the motor. These too must be set higher than the POR valve in the pump. If you system overheats after increasing the pressure setting of the POR valve, you are probably loosing oil across one of the cross port relief valves.
Please visit http://hansonhydraulics.blogspot.com for more information. I** If am electric motor is being used to drive this pump, be sure you have sufficient horse power for this increased load. **