Checking Fuel Pressure On Gmc Jimmy: Step-By-Step Guide

If you're having trouble with your GMC Jimmy, you may need to check the fuel pressure. This can be done by locating the fuel pressure check valve, which is usually found on one of the fuel lines on top of the engine. In some GMC models, it may be on the passenger side with a green cap, while in others, it may be on the driver's side with a black cap. Once you've located the fuel pressure check valve, you can use a fuel pressure tester to determine if your GMC Jimmy is running at the correct fuel pressure. It's important to note that different models and years of the GMC Jimmy may have different fuel pressure requirements, so it's always best to consult a repair manual or a mechanic for specific instructions.

Locating the fuel pressure check valve

First, it's important to know that the fuel pressure check valve is typically located on the engine of your GMC Jimmy. In your case, since you mentioned having a 2000 GMC Jimmy SLT 4.3 4x4, the fuel pressure check valve will be on the passenger side of the engine.

Now, when you open the hood and look at the engine, you'll want to look for the fuel lines. There should be two silver fuel lines on top of the engine. The fuel pressure check valve will be on the larger of these two fuel lines. So, make sure to identify the larger silver fuel line.

Additionally, you may notice a green cap on one of the fuel lines. This green cap is part of the EVAP system and is not the fuel pressure check valve you're looking for. The fuel pressure check valve will have a black cap instead.

To make sure you've found the correct valve, look for a steel line near the rear of the engine, close to the distributor on the driver's side. The fuel pressure check valve should be on this steel line.

Once you've located the fuel pressure check valve, you can proceed with checking the fuel pressure on your GMC Jimmy. Remember to exercise caution when working on your vehicle and refer to a repair manual or seek professional assistance if needed.

Identifying the correct check valve

To identify the correct check valve on your GMC Jimmy, you'll need to locate the fuel pressure check valve, which can be found on the fuel lines on top of the engine. Here's a step-by-step guide to help you identify the correct check valve:

• Open the hood of your GMC Jimmy and locate the engine.
• Look for the fuel lines on top of the engine. There should be two silver fuel lines, one larger than the other.
• The fuel pressure check valve is usually located on the larger of the two silver fuel lines.
• You can also refer to a component location diagram for your specific model of GMC Jimmy to identify the correct check valve. These diagrams can be found in repair manuals or online forums.
• Once you've located the correct fuel line, look for the check valve on that line. It will have a cap, which is usually black or green. The black cap indicates the correct check valve, while the green cap is typically for the EVAP system.
• If you're still unsure, you can consult a mechanic or a GMC dealer for further assistance in identifying the correct check valve.

It's important to note that the fuel pressure check valve may vary depending on the year and model of your GMC Jimmy, so it's always a good idea to consult a professional or refer to vehicle-specific documentation.

Testing fuel pressure

Step 1: Locate the Fuel Pressure Check Valve

The first step is to locate the fuel pressure check valve on your GMC Jimmy. According to a user on the Blazer Forum, it can be found on the "black cap on a steel line rear of the engine near the distributor driver's side." It is important to accurately identify the correct valve, as there may be other similar-looking valves in the engine bay.

Step 2: Connect a Fuel Pressure Gauge

Once you have located the fuel pressure check valve, you will need to connect a fuel pressure gauge to it. Ensure that you have a suitable gauge that can measure the pressure accurately. You may need to purchase or borrow one if you don't already own one.

Step 3: Run the Engine and Observe the Gauge

With the fuel pressure gauge connected, start your GMC Jimmy's engine and observe the reading on the gauge. A stable reading of around 55-60 psi (pounds per square inch) is considered normal for a GMC Jimmy with a 4.3L engine. If the pressure is significantly lower or higher, it may indicate an issue with the fuel pump or other components in the fuel system.

Step 4: Compare with Specifications

Compare the fuel pressure reading you obtained with the specifications provided by GMC for your specific model and year of the Jimmy. This will help you determine if the fuel pressure is within the acceptable range. You can refer to online forums, repair manuals, or consult a GMC dealer for the specific fuel pressure values.

Step 5: Troubleshooting

If the fuel pressure is outside the acceptable range, there may be an issue with the fuel pump, fuel filter, or other components in the fuel system. In such cases, further troubleshooting and diagnosis are required. It is recommended to consult a qualified mechanic who can perform a thorough inspection and make any necessary repairs or replacements.

Understanding the fuel pump relay

The fuel pump relay is an essential component for any combustion engine vehicle. It is an electromagnetic switch that uses low current to control a higher current circuit. The relay is typically controlled by the ignition or the power control module. When the ignition is turned on, the relay supplies electricity to the fuel pump, and when the ignition is shut off, it powers down the fuel pump.

The fuel pump relay is usually located in the fuse box in the engine bay, but it can also be found under the hood, on the firewall, or near the steering column. It is a cube-shaped object with prongs like an electrical plug.

A bad fuel pump relay will result in the fuel pump malfunctioning and can cause startup issues. Some common symptoms of a failing fuel pump relay include:

• The engine cranks but doesn't start
• The fuel pump runs continuously even when the key is out of the ignition
• The check engine light is illuminated
• The engine stalls
• The vehicle loses power while driving
• No noise from the fuel pump when the ignition is turned on

To diagnose a bad fuel pump relay, you can perform a visual inspection of the relay and check for signs of corrosion and overheating. You can also use a digital multimeter to test the relay by setting it to the Ohms scale or 'continuity' and connecting the leads to the power circuit pins. If you detect zero ohms or any resistance value, the relay has shorted power pins and needs to be replaced.

The cost of replacing a fuel pump relay ranges from $90 to $150, with the part itself costing less than $20. It is a relatively simple DIY repair that can be done at home.

Replacing the fuel pump

Step 1: Run the fuel tank empty

Firstly, run the fuel tank empty if possible. The GMC Jimmy's tank does not have a drain plug, but if the pump is still operating, then running the tank dry is the only method. An empty tank is lighter than a full one, making removal easier.

Step 2: Remove the fuel tank's protective shield

Unbolt the fuel tank's protective shield by turning its hex-head bolts in a counterclockwise direction. The shield will then slide out, exposing the tank's bolts.

Step 3: Disconnect the electrical and fuel line connections

Disconnect the electrical and fuel line connections to the tank's fuel pump, located on the top centre front of the tank. There are two or three different-sized fuel lines and one wiring adapter plug that must be disconnected. The hoses come off by pinching or unscrewing their hose clamps, and the plug simply pulls free once its catch is depressed.

Step 4: Unbolt the fuel tank

Unbolt the fuel tank by turning the bolts that hold it to the frame counterclockwise. The tank should be supported with a jack during this process, as once the tank is freed it will drop from the frame. Lower the tank out of the truck and use the jacks to set it aside for further work.

Step 5: Unscrew the fuel pump

Unscrew the two screws holding the fuel pump to the tank by turning them in a counterclockwise direction. Once they are out, the pump can be gently pulled upwards and out of the tank. Some residual fuel may spill out, so have a towel handy.

Step 6: Install the new fuel pump

Replace the fuel pump by lowering it into place inside the tank, then securing its screws in a clockwise direction. The plastic fuel pump may be easily damaged by turning the screws too far, so only tighten them enough to seal the pump to the tank.

Step 7: Reinstall the fuel tank

Replace the fuel tank into the truck with the jack(s), and tighten the bolts that secure it to the frame in a clockwise direction.

Step 8: Reconnect the fuel lines and adapter plug

Reconnect the fuel lines and adapter plug. The fuel lines are sized for their nipple fittings and should only fit onto the nipple they were designed for. Tighten each one with a hose clamp. The wiring adapter plug should make a "snap" sound when it is properly seated.

Step 9: Fill the tank and test the new pump

Fill the tank with fuel and test the new pump. The pump should make an audible whine as the truck is started, and the whine should stop after a couple of seconds. The pump might make a softer sound after the truck is started—this is normal.

Frequently asked questions