I replaced the fuel filter and fuel lines from the tank to the fuel pump but did not replace the fuel pump. I drained the tank and it took forever for all the gas to drain out of the tank. I now have everything back in and the 1983 Mercedes 380SL will not start. Do I need to purge the fuel lines at the engine?

Okay, you need to make sure the fuel pump is getting power and that you have the lines hooked up correctly. Also, when you replace fuel pumps you need to remove the air cleaner and use starter fluid to get the engine started.

the in-line filter is in the fuel line between the tank and the engine, seldom do you have to even touch the tank much less remove it in order to replace that filter. there is a screen on the pump inlet of the
in-tank fuel pump and most likely you are going to have to drop the tank in order to replace the pump or the fuel level sender. make sure there is not a service access hole in the rear of the car such as under the spare tire which could give you access to the top of the tank. on the other hand it is not unusual to find yourself in a situation where a lot of the fuel line must be replaced when you replace the in-line filter. as such you may find yourself with no room to connect the new fuel line to the nipple on top of the tank, without lowering the tank a bit.

There is a strainer filter attached to the fuel pump in the tank however you really need to see how much gas is actually in your tank first. Sounds like a fuel line may be pinched.

JUST DRAIN OUT GASOLINE IN FUEL TANK.CHANGE FUEL FILTER AND.FILL UP TANK WITH DIESEL FUEL. ENGINE WILL RUN ROUGH UNTIL ALL GASOLINE LEAVES THE FUEL LINES.

sounds like the bearings in your fuel pump are going. These bearing are undoubtedly not replaceable without replacing the entire fuel pump.

Fix: replace fuel pump.
Difficulty of fix: moderately advanced. You have to jack up car, drain the tank at the fuel tank drain
and then disconnect fuel lines (3), unbolt the (always rusty) bolts holding the tank, then go at the fuel pump replacement procedure, remembering to replace the fuel pump gasket.

If your car has a hatch in the top of the tank for fuel pump replacement (Hondas do), then use that access to get to the part - otherwise pull the gas tank and replace it that way, While you're in there, replace fuel filter(s) and strainer too (as a matter of course).

If the problem were clogged fuel filter, you'd experience loss of power going uphill, and it would not be able to made to "come back" by mashing on the gas pedal.

Change to Exterior filter not the tank filter. The in tank filter is actually a sock located on the Fuel Pump in the tank. This is rarely a problem. The exterior filter is going to be in-line most likely on the passenger side of the vehicle toward the rear. Easiest way to locate it is to trace the fuel lines back tot eh front of the vehicle from the fuel tank.

The fuel filter (1) is mounted next to the fuel pump module (2), on top of the fuel tank (3)


The fuel delivery system uses quick-connect fittings. The fuel filter mounts to the top of the fuel tank.

1. Properly relieve the fuel system pressure.
   
2. Disconnect the negative battery cable.
   
3. Raise and safely support the vehicle.
   
4. Place a drain pan underneath the fuel filter to catch any spilling fuel that will result from disconnecting the fuel lines.
   

It may be necessary to support the weight of the fuel tank with a block of wood and a floor jack. Once this is accomplished, loosen, but do not remove, the fuel tank strap bolts. Allow the fuel tank to lower just enough to access the fuel line fittings at the fuel pump module.



Disengage the fuel line quick-connect fittings from the fuel pump module


Be sure to place a drain pan underneath the filter line fittings to catch all fuel spillage

Locate the fuel filter in its mounting on top of the fuel tank. Detach the quick-connect fittings from the chassis fuel supply tube and fuel pump module by squeezing the quick-connect fitting retainer tabs together and pulling the fitting assembly away from the fuel line nipple. The retainer will remain on the fuel tube.


Using a 10mm socket, remove the fuel filter mounting bolt ...


... then remove the fuel filter from the top of the fuel tank

1. Remove the fuel filter mounting bolt and remove the fuel filter from the fuel tank.
   

To install:

1. Install the fuel filter on the top of the fuel tank and tighten the mounting bolt.
   
2. The fuel supply tube (to chassis fuel line), return tube (to pump module) and fuel supply (to fuel filter) tube are permanently attached to the fuel filter. The quick-connect fitting ends of the fuel supply and return tubes are of different sizes.
   
3. Apply a light coating of 30W engine oil to the nipples of the fuel filter.
   
4. Push the quick-connect fitting over the fuel line until the retainer seats and clicks into place. Be sure the retainer tabs have locked into the case of the fitting.
   
5. If necessary, raise the fuel tank and tighten the fuel tank strap bolts.
   
6. Lower the vehicle. Start the engine and check for leaks.
   

You must remove the fuel tank in order to replace the fuel pump. Drain the tank of as much fuel as possible with a hand pump. Disconnect the positive + battery cable. Disconnect the fuel lines and the electrical connections. Remove the fuel tank, and then remove the old pump. Clean off any old gasket and then reinstall the new pump. Reinstall the tank and then replace the fuel filter. A partially clogged fuel filter will cause a pump to fail prematurely.

I would lean towards the pump. Some fuel pumps can be expensive, and it can be dangerous to work on fuel tanks, make sure your fuel tank is empty if you are going to remove it (they are deceivingly heavy)

from the description you gave, I would say your fuel pump is dying, and starting to fail. The whining noise is it struggling to do its job. You might find someone that can service the fuel pump (clean it, inspect it, fix worn out components and contacts, otherwise get it replaced.

My recommendation: Get a service technician (aka Mechanic) to take a look and ensure it is the fuel pump that has failed before you go buy a new one (because it may be a couple hundred dollars).
I hope this helps, Let me know what you find out.

PS - If you have never replaced the fuel filter, do it, they are rather cheap and easy to replace.

The combination Fuel Filter/Fuel Pressure Regulator is located on the fuel pump module. The fuel pump module is located on top of fuel tank.

The filter/regulator may be removed without removing fuel pump module although fuel tank must be removed.

REMOVAL

1. Remove fuel tank. Refer to Fuel Tank Removal/Installation.
2. Clean area around filter/regulator.
3. Disconnect fuel line at filter/regulator. Refer to Quick-Connect Fittings for procedures.
4. Remove retainer clamp from top of filter/regulator. Clamp snaps to tabs on pump module. Discard old clamp.
5. Pry filter/regulator from top of pump module with 2 screwdrivers. Unit is snapped into module
6. Discard gasket below filter/regulator.
   1. Before discarding filter/regulator assembly, inspect assembly to verify that O-rings are intact. If the smallest of the two O-rings can not be found on bottom of filter/regulator, it may be necessary to remove it from the fuel inlet passage in fuel pump module.
   INSTALLATION
   
   1. Clean recessed area in pump module where filter/regulator is to be installed.
   2. Obtain new filter/regulator (two new O-rings should already be installed)
   3. Apply a small amount of clean engine oil to O-rings. Do not install O-rings separately into fuel pump module. They will be damaged when installing filter/regulator.
   4. Install new gasket to top of fuel pump module.
   5. Press new filter/regulator into top of pump module until it snaps into position (a positive click must be heard or felt).
   6. The arrow molded into top of fuel pump module should be pointed towards front of vehicle (12 O'clock position).
   7. Rotate filter/regulator until fuel supply tube (fitting) is pointed towards front of vehicle (12 O'clock position).
   8. Install new retainer clamp (clamp snaps over top of filter/regulator and locks to flanges on pump module).
   9. Connect fuel line at filter/regulator. Refer to Quick-Connect Fittings for procedures.
   10. Install fuel tank. Refer to Fuel Tank Removal/Installation.

WARNING: THE FUEL SYSTEM IS UNDER CONSTANT FUEL PRESSURE EVEN WITH THE ENGINE OFF. THIS PRESSURE MUST BE RELEASED BEFORE SERVICING FUEL TANK .

Two different procedures may be used to drain fuel tank (lowering tank or using DRB scan tool).

The quickest draining procedure involves lowering the fuel tank.

As an alternative procedure, the electric fuel pump may be activated allowing tank to be drained at fuel rail connection. Refer to DRB scan tool for fuel pump activation procedures. Before disconnecting fuel line at fuel rail, release fuel pressure. Refer to the Fuel System Pressure Release Procedure for procedures. Attach end of special test hose tool number 6541, 6539, 6631 or 6923 at fuel rail disconnection (tool number will depend on model and/or engine application). Position opposite end of this hose tool to an approved gasoline draining station. Activate fuel pump and drain tank until empty.

If electric fuel pump is not operating, tank must be lowered for fuel draining. Refer to following procedures.

FUEL TANK REMOVAL

1. Disconnect negative battery cable at battery.
2. Release fuel system pressure. Refer to the Fuel System Pressure Release.
3. Raise and support vehicle.
4. If Equipped: Remove fuel tank skid plate.
5. Remove 4 fuel hose shield mounting bolts and remove fuel hose shield from body.
   1. Remove fuel tank fill hose and vent hose clamps at fuel tank filler tube. Remove both hoses at fuel filler tube.
   2. Remove exhaust tailpipe heat shield mounting bolts and remove shield. CAUTION: To protect fuel tank from exhaust heat, this shield must reinstalled after tank installation.
   3. Place a hydraulic jack to bottom of fuel tank. WARNING: PLACE A SHOP TOWEL AROUND FUEL LINES TO CATCH ANY EXCESS FUEL .
      1. Disconnect fuel supply line from fuel extension line near front of fuel tank. Refer to Fuel Tubes/Lines/Hoses and Clamps. Also refer to Quick-Connect Fittings for procedures.
      2. Disconnect EVAP canister vent line near front of tank.
      3. Disconnect fuel pump module electrical connector (pigtail harness) near front of tank. Harness connector is clipped to body.
         1. Remove two fuel tank strap nuts. Position both tank support straps away from tank.
         2. Carefully lower right side of tank while feeding both fuel hoses through access hole in body. Fuel Tank Full And Not Drained Using DRB Scan Tool: To prevent fuel loss through hoses, keep left side of tank higher than right side while lowering. Do not allow hose openings to drop lower than top of tank.
         3. Continue lowering tank until clear of vehicle. Place tank on floor with left side (hose side) higher than right side
            1. Drain tank by removing fuel fill hose at tank. Fuel fill hose is largest of 2 hoses. Insert the drain hose (from an approved gasoline draining station) into hose opening. Drain tank until empty.
            2. If fuel pump module removal is necessary, refer to Fuel Pump Module Removal/installation for procedures.
            INSTALLATION
            
            1. If fuel pump module is being installed, refer to Fuel Pump Module Removal/installation for procedures.
            2. Install fuel fill/vent hoses to tank fittings. To prevent hose from kinking, rotate each hose until index mark on hose is aligned to index tang on fuel tank.
            3. Install hose clamps to hoses. Position clamps between index marks on each hose.
            4. Position fuel tank to hydraulic jack.
            5. Raise tank into position while guiding fuel fill and vent hoses into and through access hole in body.
            6. Continue raising tank until positioned to body.
            7. Attach two fuel tank mounting straps and mounting nuts. Tighten nuts to 10 Nm (90 in. lbs.) torque. Do not over tighten nuts.
            8. Install both fuel hoses to fuel fill tube. Tighten both retaining clamps.
            9. Position fuel hose shield to body. Install and tighten 4 mounting bolts.
            10. Connect fuel pump module pigtail harness electrical connector near front of tank.
            11. Connect fuel pump module supply line near front of tank. Refer to Quick-Connect Fittings for procedures.
            12. Connect EVAP hose near front of tank.
            13. Install exhaust tailpipe heat shield.
            1. Install fuel tank skid plate (if equipped).
            1. Lower vehicle and connect battery cable to battery.