"Then they said that I should replace my pump. Ive asked twice and they wont explain why I should replace it."

Because Beckett wants to sell you a new pump. And because the guy didn't want to spend time educating a homeowner on the reasons and then you diddle daddle with your Suntec pump and possibly hurting someone or burning down the house. Your pump has an internal diaphragm cutoff designed to drop out at 80% but they know it won't be constant for a number of reasons so they specify "at some point". The diaphragm comes in a basic repair kit of commonly failed parts, so Beckett doesn't want to give you the idea you can rebuild your pump.

Confirm the solenoid valve has a problem. Put your gauge back on, fire up the furnace then shut it down and at the same time close the shut off valve at the oil inlet (hopefully there is a manual valve right before or after the filter.) If your pressure holds steady without dropping much the solenoid valve is good and the pump diaphragm is bad, or the supply line is not air tight. There will always be a vacuum on the supply line when the oil pump is running so small undetectable leaks will allow air into the line but the viscosity and surface tension won't allow oil to drip out when the pump is off.

Troubleshooting isn't shotgunning and replacing parts until you hit the problem, but by processing information based on knowledge and eliminating other possibilities before replacing parts. In many cases people jump to the least obvious and most complicated and ignore the simplest and most obvious.

The solenoid valve is only used to delay oil in pre purge and Quick stop oil when igniters go off and through post purge. If it leaked smoke and soot would only be visible at start up and not through the entire cycle as you stated in your first post. They should be addressed but it's not the problem causing soot and smoke continuously. For what it's worth the solenoid will leak if gunk builds up on the seats. Taking the nut off the top and removing the coil and then screwing out the stem you will be able to inspect the seals and clean them including inside the valve. If you do end up changing anything in the oil pathway do NOT use Teflon tape and only pipe dope.

Suntec a2va-7116 oil pump has been discontinued by the manufacturer and replaced with Suntec a2va-7116B. The difference is the rubber materials used and the B will have rubber better suited for Biofuel add to the fuel oil. They can add up to 20% biofuel these days and the old rubber fails quicker because of it.

As others had said it's Improper combustion. The reason could be from a long list, and if you must do it yourself google and find the list and go from there. You already confirmed oil pressure so that is good. You want .02 WC, between fire and breach, less than 12% CO2, 500 to 550 stack temp and 0 smoke. Something is out of wack, electrode gap, spray angle, air turbulence, air flow, not enough air in a confined space, house exhaust fans, negative air pressure, dirty blower, motor bearings, low blower motor voltage (does the motor get hot? did you check the current draw on the motor) I could go on.

After cleaning out the soot and replacing nozzle last month it smoked at about 7 after 2 minutes and it keeps getting less until it's at zero smoke after 10 to 12 minutes. Then after a week or two it had to run for 15 minutes to be at about a 1 smoke. So, it's dripping. I just disassembled and reassembled the fuel line today. I had replaced the filter housing and used some old tubing I had laying around a few months ago. I never tested smoke after that. It was at zero in jan 2023. Today i used new line and new fitting and yes i always use goop. I haven't bleed & run it yet. If it still drips, ill get new pump. A2va-7116 served me well and I'll get their equivalent. F beckett. I won't buy from them cuz lousy cs.

I don't understand: "Confirm the solenoid valve has a problem. Put your gauge back on, fire up the furnace then shut it down and at the same time close the shut off valve at the oil inlet (hopefully there is a manual valve right before or after the filter.) If your pressure holds steady without dropping much the solenoid valve is good and the pump diaphragm is bad, or the supply line is not air tight. There will always be a vacuum on the supply line when the oil pump is running so small undetectable leaks will allow air into the line but the viscosity and surface tension won't allow oil to drip out when the pump is off." I think id need to close that valve u mention & remove line from pump & install vacuum gauge & pull a vacuum to test my supply line.

Replaced oil filter fittings and tank fittings. Bleed the bubbles out as i always do. But then i remembered recently I saw on beckett site says bleed for 15 seconds with no bubbles. Ive never done that long. So, i tried that today. Every time i open the bleed valve it runs w\no bubbles for 13 seconds, then off & on bubbles. Never more then 4 sec w\o bubbles. Continues like that until i close valve to empty my container (20-30 seconds). Then when open again it runs w\o bubbles for 13 seconds and repeats bubbles as above. Did that 7 times w\heater on the whole time (never cycled off). 7th time tried a larger container and after about 45 sec w\bleed open, heater cycled off.

Smoke kept varying from 2 to 5 between each bleed. Why no air bubbles for 13 sec each time? Is this a bad pump?