Sylvie Willis
If you're looking to pump out the fuel tank of your GMT400, there are a few methods you can try. One common suggestion is to use a hand pump siphon to remove the fuel, which can then be stored in buckets or jerry cans. Another method involves jumping the fuel pump relay and using an electric fuel pump and hoses to pump the fuel into a gas can. Additionally, removing the suction tube filter on the gas pump or disconnecting the fuel line and using a rubber hose to direct the fuel into a jerry can are also viable options. It's important to note that some people choose to drop the tank to replace a bad fuel pump or to clean it out properly, but this may not be necessary if you're simply looking to pump out the fuel.
| Characteristics | Values |
|---|---|
| Best way to access the fuel pump | Create a hatch for access |
| How to drain the fuel tank | Disconnect the fuel line, remove the fuel filter, and use an electric fuel pump and hoses to pump into a gas can |
| How to run the fuel pump | Power the fuel pump bypass wire, jump the relay, or crank the engine to keep oil pressure up |
| How to test the fuel pump | Jump from Batt+ to the pump; if it runs, the pump is ok |
| How to check for power issues | Check for power with the ignition switch in the "run" position on the hot on key terminals |
| How to identify a bad relay | If the hot on key terminal lights up and the relay isn't clicking but the pump works, then the relay is bad |
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What You'll Learn
Jump the fuel pump relay
To pump out the fuel tank of a GMT400, one method is to jump the fuel pump relay. This can be done by bypassing the relay with a piece of wire, as shown in the steps below:
- Locate the fuse box: This is usually found under the hood or dashboard of the GMT400.
- Identify the fuel pump relay: It may be a skinny, square-shaped component.
- Check for any issues: Look for any burnt or melted pins, such as Pin 87, which could indicate a problem with the relay.
- Clean or replace the relay: If the pins are dirty, clean them with a small file and needle-nose pliers. If they are burnt, you may need to replace the relay.
- Bypass the relay: Using a piece of wire, connect the positive terminal of the battery to the positive terminal of the fuel pump relay.
- Test the pump: With the wire connected, turn on the ignition switch to the "Run" position and check if the fuel pump runs.
- Verify pump functionality: If the pump runs, it is likely functioning correctly. If it doesn't run, there may be another issue with the fuel system.
It is important to note that this procedure should be done with caution and a basic understanding of automotive systems. Always refer to the GMT400's manual for specific instructions and safety precautions. Additionally, some sources suggest testing the pump outside of the relay circuit by locating the 2-pin connector under the brake booster and temporarily jumping it to the battery using scrap wire and alligator clips.
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Use a hand pump siphon
Using a hand pump siphon to pump out the fuel tank of a GMT400 truck is a safe and effective method. It is a useful skill to have, especially during emergencies when you need to transfer fuel or drain a tank.
Firstly, you must ensure you have the correct safety equipment and are working in a safe environment. Clear the area of any debris or flammable items and remove any sources of flame or sparks. Keep a fire extinguisher nearby and wear a mask or respirator to avoid inhaling dangerous fumes.
Next, you will need to select the correct siphon pump for your application. Most hand pumps work manually, but there are also battery-operated options for certain liquids. Read the instructions for your specific pump to ensure you use it properly.
Once you have your pump, connect the hose to both ends of the pump and fasten the buckles securely. Use the pump on the siphon hose to create suction, drawing out the fuel. Gravity will do most of the work, but you must watch the container carefully as the siphoning process can be quite rapid. Once the container is almost full, raise it to the level of the fuel source to stop the siphoning.
After the process is complete, seal the container tightly to prevent spills, and clean up any spills immediately. Finally, remove the siphon pump and clean it thoroughly before storing it away.
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Disconnect the fuel line
To disconnect the fuel line, you can use a hand pump siphon to remove the fuel from the tank. This is a safe and simple method that can be done without having to get under the vehicle. You will need a few basic tools and a container to catch the fuel.
First, locate the fuel line and the fuse box under the dash. Remove the fuse and insert a wire into the fuel pump slot. Next, remove the fuel line at the filter and attach a length of hose. Pump the fuel into a container, such as a jerry can or gas can. Make sure you have a safe way to store the fuel, such as in another vehicle's empty fuel tank or a designated fuel storage drum.
Alternatively, you can disconnect the fuel line directly. This method may require some special tools, such as plastic angled disconnectors or a small screwdriver, depending on the type of clips securing the fuel lines. If your GMT400 has a TBI engine, you can disconnect the fuel line by pulling the line back, inserting the tool, and then pulling back on the line until you hear a click. If your vehicle has a Vortec engine, you will need to pull the Schrader valve instead.
Once the fuel line is disconnected, you can run a rubber hose into a container and jump the fuel pump at the relay or fuse panel to drain the tank. This method allows you to drain the tank without having to get under the vehicle or remove the tank.
It is important to note that fuel system pressures can be high, especially in Vortec engines, so exercise caution when working on the fuel lines. Additionally, always prioritize safety when working with flammable liquids like fuel. Ensure proper ventilation and take the necessary precautions to avoid any potential hazards.
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Replace the fuel filter
To replace the fuel filter on your GMT400, it is recommended to do so every 6,000 miles or twice a year. The process is relatively straightforward and should not take long.
Firstly, ensure your tank is not totally full, and depressurise your fuel line. Park your vehicle on a hill or slant, not downhill. You will need lots of rags, as fuel will get everywhere. There are two fittings on each side of the filter. Unscrew these, then remove the filter. To install the new filter, simply reverse the process. Screw in the new filter and reconnect the fittings.
If you have a diesel GMT400, the process is slightly different. The diesel filters take less than five minutes. Unscrew the cartridge, clean out the fuel in the bowl, then screw in a new cartridge. Finally, open the air bleeder and run the lift pump to get rid of the air.
You can also take this opportunity to change the fuel lines from the tank to the filter. Nylon kits are available to purchase and are preferable to steel, as they are easier to work with and will never rust.
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Use a squeeze bulb siphon hose
A squeeze bulb siphon hose is a cheap and effective way to pump out a fuel tank. It is a simple process, but there are some important steps to follow to ensure it is done safely and correctly.
Firstly, you need to locate a gas can or another closed container to siphon the fuel into. It is important to use a closed container, as gasoline fumes can be hazardous to your health, and spilling gasoline is dangerous.
Next, you need to prepare your squeeze bulb siphon hose. Ensure that you have clear plastic tubing that is approximately 1 inch (2.5 cm) in diameter. Check that the tubing is not damaged and that you are using the correct ends for the liquid to enter and exit. If arranged backward, the pump will push air into the gas tank.
Now you are ready to start siphoning. Place the source end of the tubing into the fuel tank, ensuring that it is below the fuel level. Point the bulb in the right direction, and squeeze it a few times to start the siphon action. You may need to squeeze a few times to get the fuel flowing, but once it starts, gravity will do the rest of the work.
Monitor the flow of fuel and keep an eye on the gas can to ensure it does not overflow. When you want to stop siphoning, cover the long tube with your thumb, raise it above the level of the gas in the tank, and remove it. Finally, close your gas tank and seal your gas can to prevent any fumes from escaping.
Using a squeeze bulb siphon hose is a straightforward and inexpensive way to pump out a fuel tank, and it can be a handy skill to have in various situations, such as running out of gas or winterizing a vehicle.
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Frequently asked questions
You can disconnect the fuel line (TBI) or pull the Schrader valve (Vortec) and run a rubber hose into a jerry can. You will also need to jump the fuel pump at the relay or fuse panel.
The most common reason to drain a fuel tank is to replace a bad fuel pump. You can use a hand pump siphon to remove the fuel and store it in buckets or another car's tank.
First, test the pump by jumping from Batt+ to the pump. If the pump runs, it is ok. Next, check for power with the ignition switch in run on the hot on key terminals. If they don't go hot, no signal to run the pump is being received. If the hot on the key terminal lights up and the relay isn't clicking, the relay is bad.
The ECM/PCM primes the pump for a few seconds when it sees pressure. If pressure is not detected, it will continue to run the pump. To run the fuel pump, you can power the fuel pump bypass wire, jump the relay, or crank the engine to keep oil pressure up.
You can use the fuel pump to empty the tank and then drop and clean it. Remember to replace the fuel filter and the sock on the electric fuel pump.
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