I replaced gas tank, fuel line, fuel pump, carburetor, and still no gas to Carburetor.

This may possibly be due to a fuel issue, although there could alternatively be an electrical issue. Check to make sure you have good spark and good distributor cables and distributor cap (no cracks or cross wire sparking). We had an issue with a car that would die when going at highway speeds. It turned out to be due to a fuel issue from a broken spring in the fuel pump. I don't know if this is related to your issue but you may check your fuel pump by disconnecting the fuel line leading to the carburetor and placing it into a soda bottle. Have someone very briefly turn over the engine and you should see good squirts of gas into the bottle. If the gas only dribbles out there may be a problem with the fuel pump or a plugged fuel line before the fuel pump. It is hard to tell which, but I would guess the fuel pump at this point and replace it. If the gas still dribbles out, unfortunately it was a plugged line somewhere between the fuel tank and the fuel pump (It may be very difficult to find where). Be extremely careful to not spill any gas when doing this, keep free of moving parts, and keep the engine on only for a very short time (a few seconds) to minimize any fire risk. Remember safety first! If the gas is squirting out as it should, the problem may be in your carburetor or a plug in the fuel line after the fuel pump, or a likely candidate - a plugged fuel filter. You may try replacing the fuel filter just on general principles. If the carburetor is the problem, perhaps a few squirts of carburetor cleaner into the air intake of the carburetor might help. In fact, you may try using carburetor cleaner before you try anything else (even before trying the test on your fuel pump) as this is the easiest thing to do first, then do the fuel pump test, next change out your fuel filter, and finally, if this does not help, then you may have a more difficult job of disassembling and rebuilding the carburetor - a job I wouldn't recommend unless you have some experience - or there may be a fuel line plug somewhere else in this part of the system.

Check your float level in carb. & test the valve with the float, check your fuel filters and check your fuel line from the tank or check for dirt in base of tank, lastly check your HT leads to plugs

Are you sure it is a carburetor and not throttle body injection? They do look similar.
If it is a carburetor, there would not be a regulator. The fuel pump will either be a mechanical pump mounted on the engine, or a low volume electric pump in the gas line from gas tank to the engine.
If it is throttle body injection (TBI), yes, there is a fuel pressure regulator, probably located near the throttle body. It will have gas lines connected to it (one line will be a return line back to the gas tank) and a vacuum line. The fuel pressure on TBI systems is not as high as multi point injection, usually around 20 psi. You would have to check the specific pressure requirement for your pathfinder.

Take off the air cleaner cover and look at top of unit. A carburetor should have a choke plate right at top of the carb throat. However some Nissans by '88 had a carburetor without a choke-it used an enricher jet controlled by the ecu for added fuel when starting.. On a TBI, looking down at the unit where the air goes in, you will see one or two injectors with a wiring harness connected to them-each injector will have two wires connected to it.
If still unsure, check engine designation on the under hood label. Carbureted engines will have a s letter designation, injected engines will have letter i. To explain: my '87 Sentra is carbureted, so engine designation is E16s, some same engines were injected, so their designation is E16i.

Fuel line between tank and pump could be blocked. Remove fuel cap and Disconnect fuel line from inlet side of pump and blow back. If line is clear you should hear bubbling from tank filler. It could be that you have picked up a batch of dirty fuel that has clogged the gauze input filter that is inside the fuel tank.

Uncouple the fuel line coming from the pump at the carburetor, place a clean can under the line, and have someone operate the starter--you should have fuel shoot from the line in spurts as the engine turns. If it does, then the entry port on the carburetor is plugged. Remove the float assembly and pull out the float needle valve. Hook the fuel line back to the carburetor and try the starter again, there should be fuel pumping into the float bowl. If not, check to see if there is a filter on the fuel inlet path that may be plugged. If no filter, remove the float needle seat to see if something is blocking the fuel passage. If all else fails, use compressed air to blow backwards through the needle seat (remove the fuel line again). Hope some of this helps!

Take to a garage and you will soon find out that "bad joke" is the wrong name for this. All gas must be removed and gas tank dropped and cleaned. you can only hope that that will fix it. Fuel pump, line and injectors may also need attention.

remove the fuel line from the carb, put it into a bottle, crank the engine, If the bottle has fuel in it the fuel pump is working properly, if not, check the filter, and the fuel lines to the tank!!!

Quick explanation of your fuel system:

An automotive fuel system consists of everything between the fuel tank and the carburetor or fuel injection unit. This includes the tank itself, all the lines, one or more fuel filters, a fuel pump (mechanical, electric, or both), and the carburetor or fuel injection unit.
With the exception of the carburetor or fuel injection unit, the fuel system is quite simple in operation. Fuel is drawn or pumped from the tank through the fuel line by the fuel pump, which forces it through the fuel filter, and from there to the carburetor/injection unit where it is distributed to the cylinders.

So with that info...try first to clean your spark plugs.
Next, replace your fuel filter.
After that, depending on a carburetor/fuel injection, try an additive that cleans the injectors. For the carburetor, try a half of can of what is called "Seafoam". It comes in a metal can available everywhere, including Walmart. It is worth the $6-8 and also will "dry" out your fuel from water. Very good product.

After that, get back to us and let us know how your Toyota is running.

The mechanic should check the fuel lines or gas hose from the tank going to the carburetor and from carburetor going to the engine. and also check on the first or primary filter ,the secondary filter, the spray nozzle assembly and the carburetor . if there is a dirt it should be cleaned if there is a spare parts that is worn out it should be replace and if there is a corroded parts then clean it also .After it then also check if there is a loose connection of the hose then reconnect the connection of the fuel lines or gas hose should be tighten that it will not spill gas.But still don't forget to check the screws or the bleeder screws of the carburetor check if there is a dirt and if there is a worn out screw's or bleeder screws .if there is then clean it with a clean gas if there is a worn out replace it. the throttle should also be check if it is been stock there fore you have to repair it if worn out already then replace it.If the carburetor is dirty gas can't pass to the engine normally or some times no gas is going to the engine.That is why you should clean it or replace the worn out parts . But then you have also to check the gas that you are using to your car. If the gas is diluted or dirty then it can be the cause of the problem. Change the gas and buy or get a clean gas that is not diluted or dirty because sometimes dirty gas or fuel can give malfunctioning to the carburetor assembly.

1. Disconnect the negative battery cable.
   
2. Disconnect fuel tank hose at the fuel pump, and plug the hose with a bolt or wooden dowel to keep any fuel from flowing out wires. Check the hose and if it is frayed or cracked, replace it with new fuel line hose.
   
3. Disconnect the outlet line to the carburetor. Use a wrench on the fuel pump fitting and another on the line nut.
   
4. Remove the two attaching bolts and remove the old fuel pump. Clean off any old gasket material from the mounting surface of the engine.
   

Installation:

1. Apply a coat of gasket sealer on both sides of the new gasket. Put the attaching bolts through the new pump and slip the gasket over the bolts.
   
2. Install the new pump on the engine. Make sure that the rocker arm in the pump is against the eccentric inside the engine, or that the push rod is correctly installed in both the engine and the fuel pump. If the push rod slides out, you can pack it with some heavy grease to hold it in place while you install the pump.
   
3. Attach the fuel outlet line that runs to the carburetor. If it's difficult to connect, remove the other end of the line from the carburetor. Connect the line to the fuel pump, and then reattach the other end to the carburetor. Use a wrench to hold the fuel pump fitting and tighten the line nut with another wrench.
   
4. Attach the fuel inlet hose from the gas tank, and the vapor return hose (if the vehicle is equipped with one). Tighten all clamps.
   
5. Reconnect the battery ground cable, start the vehicle and check for leaks.
   

Hope that works