fuel return line

[catjim813]

All, when checking the to see if the fuel return line is blocked, when you disconnect the line from the fuel tank should it be a strong stream of fuel coming from the tank?  The flow on the return line from the tank was very similar to the stream of fuel going to the fuel pump.  69 280 sl.  I will now start at the front of the engine with compressed air to see if I hear the bubbles in the tank. 

[Jordan]

Someone can correct me if I'm wrong but you should be getting about a litre of fuel every 15 seconds with only the pump running.  It's a pretty steady stream.  Just get a graduated container and run the pump for 15 seconds and see what you get. 

[Tyler S]

If your tank is very full you will get fuel from the tank side of the return line, Or if your tank has any pressure in it. Crack your gascap loose for your tests so you dont over pressure your tank.

[Benz Dr.]

You should get fuel even if your tank is low on fuel. The return line sits at the bottom of the tank so it will not run out very fast once the fuel level goes down. At some point there will be fuel in the tank but it won't come out of the return line. The line going to the fuel pump should drain the tank completely.

I would do a fuel volume test at the end of the return line before it enters the tank if you think there's a problem anywhere in the return system.

[Shvegel]

Dan has the right idea.  Blowing air through the return line might just create enough static electricity to cause a spark.

[catjim813]

Thanks to all of you for your replies.  I will test the system this weekend and respond back to the group. 

[catjim813]

All, I checked the return line and I am getting a small stream with the just the pump running and a bit stronger stream with the engine running.   It only equals a quarter of a liter in 15 seconds either way.  Is it best to replace the lines or try to roto rooter them? Also where is the best place to buy replacement fuel lines.  Thanks in advance.

[Tyler S]

Others here have had success using a guitar string to clear the blockages. Disconnect the rubber lines on both sides and use a combination of compressed air, some sort of carb cleaner, and the guitar string to ream out the steel lines.
I used a thin electricians fish tape once to do this on a different vehicle.