Einleitung

Besides all the rubber fuel lines you see under the hood every time you check your oil, there are three rubber fuel lines at the rear of the car just under the fuel tank. These often get neglected and can end up leaking. This is obviously bad for your fuel economy, and can also lead to degradation of your axle boots. To replace them you'll need to drain the tank. Learn how to do all this with this guide.

Before replacing any of the lines at the rear of the car the fuel tank must be drained of any fuel. It is obviously best to perform this work when the fuel tank is near empty to avoid having to store too much fuel during the rest of the job. The tank is most easily drained from the main fuel feed line which comes out of the bottom of the tank just above the rear passenger side axle.
  • Before replacing any of the lines at the rear of the car the fuel tank must be drained of any fuel. It is obviously best to perform this work when the fuel tank is near empty to avoid having to store too much fuel during the rest of the job.

  • The tank is most easily drained from the main fuel feed line which comes out of the bottom of the tank just above the rear passenger side axle.

  • It has a metal fitting on the top end that threads in to the tank screen.

  • The other end is rubber hose and clamps to the main metal feed line going towards the front of the car.

  • To limit fuel spillage when removing the clamped rubber end of the line, pinch the fuel hose between some vice grips as pictured.

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Position your catch container near the main fuel feed line. Using a container that you can insert a long funnel in will be helpful. It should be large enough to hold the amount of fuel you estimate to be in the tank. Or, you should have multiple containers on hand.
  • Position your catch container near the main fuel feed line. Using a container that you can insert a long funnel in will be helpful. It should be large enough to hold the amount of fuel you estimate to be in the tank. Or, you should have multiple containers on hand.

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Next, unscrew the hose clamp at the rubber end of the main fuel feed line. This usually takes a Phillips or flathead screwdriver. Then pull that end of hose off the metal fuel line (fuel should not flow out thanks to the vice grip pinching the line). Aim the hose at your catch container/funnel. Then remove the vice grip and let the fuel flow in to the container.
  • Next, unscrew the hose clamp at the rubber end of the main fuel feed line. This usually takes a Phillips or flathead screwdriver.

  • Then pull that end of hose off the metal fuel line (fuel should not flow out thanks to the vice grip pinching the line). Aim the hose at your catch container/funnel. Then remove the vice grip and let the fuel flow in to the container.

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Once the tank is fully drained you will need to use a 19mm wrench to remove the main fuel feed line from the tank.
  • Once the tank is fully drained you will need to use a 19mm wrench to remove the main fuel feed line from the tank.

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You will be left with an opening in the bottom of the tank. This will likely slowly drip for some time. Leave a catch pan underneath or place some shop towels or rags underneath to catch the drips.
  • You will be left with an opening in the bottom of the tank. This will likely slowly drip for some time. Leave a catch pan underneath or place some shop towels or rags underneath to catch the drips.

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Next, you'll remove the two short lengths of fuel hose for the tank return lines.
  • Next, you'll remove the two short lengths of fuel hose for the tank return lines.

  • If the clamps look as rusty as these, consider spraying them with some penetrating lubricant before removing them.

What are the size of the two fuel hoses? I read somewhere that the vent hose was bigger. Is that true?

matthew.callaham95 - Antwort

The steel lines that cross from the fuel tank drain hose to behind the driver side tire- which route up to the block can be replaced with flexible 300+ psi plastic tubing & then reconnected using proper clamps to the rubber connections?

Steve Smith - Antwort

Loosen all four of the hose clamps on both fuel lines using a Phillips or flathead screwdriver as needed.
  • Loosen all four of the hose clamps on both fuel lines using a Phillips or flathead screwdriver as needed.

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With all four clamps loosened, pull both lines off. You can see here what the metal fuel lines look like with the lines removed.
  • With all four clamps loosened, pull both lines off. You can see here what the metal fuel lines look like with the lines removed.

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Now it is time to proceed with installation of the new lines. Installation is generally the reverse of removal. However, following are some helpful tips.
  • Now it is time to proceed with installation of the new lines. Installation is generally the reverse of removal. However, following are some helpful tips.

  • Start with the main fuel feed line. It has a metal fitting on one end that screws in to the tank. Screw this in, the opposite of removal.

  • The new line likely comes with excess rubber line. You should cut the hose short enough to avoid touching any other parts like the axles or differential, but long enough to make a graceful bend to the fuel line it attaches to. Use your best judgement, and start longer than you think. You can always make it shorter.

  • Then, clamp the rubber end to the metal fuel line. Use a new hose clamp, if available.

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Next, cut new lengths of hose to fit the rear return lines. Use the old hose as a guide for cutting your new lengths.
  • Next, cut new lengths of hose to fit the rear return lines. Use the old hose as a guide for cutting your new lengths.

  • Push the fuel line over the metal hose ends with the clamps over the new line. Then tighten the clamps. Be mindful that the clamps don't touch the adjacent line at the risk of the clamp rubbing through the line over time.

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You can now proceed to refill your fuel tank with the fuel you drained.
  • You can now proceed to refill your fuel tank with the fuel you drained.

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Abschluss

When done, check for leaks. Go for a drive, and check for leaks again.

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Nicolas Siemsen

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On my w123, the short rubber lines (fuel grade rubber) were 9mm inside diameter and the other one was standard 5/16" rubber fuel line. The tank screen came out with the other fuel line so I used a tiny brass brush and carefully cleaned it as well & re installed with the new hose as he shows in the guide. Guide was helpful, thanks!

Frank - Antwort

Frank, glad to hear it was helpful!

Nicolas Siemsen -

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