Regan Brown
If your 70s GM car is not starting, there could be an issue with the fuel system. To check if your car is getting fuel, you can test the fuel pressure up to the fuel rail. This is usually done using a fuel pressure gauge. Simply attach the gauge to the fuel rail, turn the key, and take a reading. If there is no fuel pressure, the fuel pump or the fuel pump circuit could be faulty. Another way to check for fuel delivery is to inspect the wiring on the back of the fuel gauge and the sender unit to ensure they are clean, tight, and free from dirt and corrosion.
| Characteristics | Values |
|---|---|
| How to check if the car is getting fuel | Check the fuel pressure up to the fuel rail using a fuel pressure gauge |
| How to check if your GM vehicle has Active Fuel Management (AFM) | Check the owner's manual, the window sticker, or the digital screen below the tachometer |
| How to test the fuel gauge | Ensure wiring connections are clean, tight, and free from dirt and corrosion; check the fuse; ground the gauge |
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What You'll Learn
Check the owner's manual for Active Fuel Management (AFM)
The owner's manual is one of the primary resources for identifying whether your General Motors (GM) vehicle is equipped with Active Fuel Management (AFM) technology. The manual, provided by the manufacturer, contains detailed information about the vehicle's features and specifications.
To check for AFM, look in the engine and powertrain sections of the manual. There should be a description of the AFM system, its operation, and maintenance tips. The owner's manual will typically include diagrams and explanations to help you understand how AFM works and its benefits. For example, the manual may explain how AFM improves fuel efficiency by reducing the number of active cylinders, which in turn lowers fuel consumption and leads to better overall fuel economy.
In addition to the owner's manual, there are other ways to determine if your GM vehicle has AFM. One way is to examine the window sticker, also known as the Monroney sticker, which is affixed to the car when it's sold new. This sticker lists all the vehicle's standard and optional features, including engine specifications and fuel-saving technologies like AFM. Sales brochures for the vehicle may also highlight AFM as a key selling point for its fuel efficiency benefits.
Another way to tell if your GM vehicle has AFM technology is by checking the dashboard indicators from the driver's seat. Look for the readout on the digital screen below the tachometer, which GM calls the Driver Information Center (DIC). This display was designed to show helpful information, including whether the Active Fuel Management system is in operation. Keep in mind that you may need to toggle through a few screens before you reach the one that shows the Active Fuel Management information. The display will indicate whether the engine runs as a 'V4' or a 'V8'.
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Check the window sticker for fuel-saving technologies
The window sticker, also known as the Monroney sticker, is a label required in the United States to be displayed in all new automobiles. It includes official information about the car, such as the manufacturer's suggested retail price (MSRP), engine and transmission combination, exterior and interior color, model year, and trim level.
One of the key pieces of information on the window sticker is the fuel economy label, which provides estimates of the vehicle's fuel efficiency. This label is also called an EPA label, as the Environmental Protection Agency provides the fuel costs used in the calculations. The fuel economy label allows buyers to compare the mpg numbers of different vehicles. The combined mpg number is the most important figure to note when making comparisons.
In addition to the fuel economy information, the window sticker also lists all the vehicle's standard and optional features, including engine specifications and fuel-saving technologies. This is where you can check for Active Fuel Management (AFM) technology, which improves fuel efficiency by reducing the number of active cylinders. The window sticker will typically include a description of the AFM system, its operation, and maintenance tips, along with diagrams and explanations.
While the window sticker provides valuable information about fuel efficiency and fuel-saving technologies, it is important to note that the fuel cost estimates printed on the sticker may not always be up-to-date. The estimates are typically provided two years in advance, which can lead to discrepancies between the projected and actual fuel costs. Therefore, it is recommended to check online or use the QR code on the sticker to access more accurate and current fuel pricing information.
In summary, checking the window sticker is a quick and effective way to verify the fuel-saving technologies offered in a vehicle. It provides detailed information about the car's fuel efficiency, engine specifications, and features like Active Fuel Management. However, for the most accurate fuel cost estimates, it is advisable to refer to online sources or scan the QR code provided on the sticker.
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Check the dashboard for AFM indicators
One of the easiest ways to check if your GM vehicle has Active Fuel Management (AFM) technology is to check the dashboard for indicators. This can be done from the driver's seat.
To determine if your V6 or V8 GM vehicle has AFM, look for the readout on the digital screen below the tachometer. This display is known as the Driver Information Center (DIC) and was designed to show helpful information, such as whether the Active Fuel Management system is in operation. You may need to toggle through a few screens before you reach the one that shows the Active Fuel Management information. The display will indicate whether the engine runs as a 'V4' or a 'V8'.
If you attempt to get the vehicle to switch to the V4 state, you must stay at a cruising speed below 2000 RPM.
Other ways to determine if your GM vehicle has AFM include examining the window sticker, also known as the Monroney sticker, and the sales brochure. The window sticker, affixed to the car when it's sold new, lists the vehicle's standard and optional features, including engine specifications and fuel-saving technologies like AFM. The owner's manual is another primary resource for identifying whether your GM vehicle is equipped with AFM technology.
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Check the wiring connections for dirt and corrosion
Checking the wiring connections for dirt and corrosion is an important step in ensuring your car's electrical system is functioning properly. Over time, connections can become loose, broken, damaged, or corroded due to vibrations and road conditions such as heat, rain, and snow. This can cause the system to malfunction, so it's crucial to inspect and clean the wiring connections regularly.
To check for dirt and corrosion, start by performing a visual inspection of the wiring connections. Look for any signs of dirt, oil, rust, or corrosion on the connector pins and wires. Pay close attention to the base of the connector, as this is a common place for wiring to break. You can also use a voltmeter to test the wiring connections. Disconnect the connector from the sensor and touch the negative lead of the voltmeter to a good ground source. Then, use the positive lead to probe the connector terminals to check for system voltage.
If you notice any corrosion or damage, it's important to clean or replace the affected parts. You can use a wire brush or battery terminal cleaning tool to clean back to bare metal on the terminal and the attaching area. Ensure that all dirt, corrosion, and paint are removed, leaving only clean, bare metal.
Additionally, you can perform a "quick and dirty" test to diagnose ground issues. Use a set of jumper cables to connect one end to a clean bare metal part of your engine. Then, connect the opposite end of the cable to the chassis ground point. If this fixes the issue, it indicates a problem with the ground cable, and the jumper cable provides an alternative path with lower resistance.
By regularly inspecting and maintaining the wiring connections in your 70s GM car, you can help ensure the electrical system functions properly and prevent potential malfunctions caused by dirt and corrosion.
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Check the fuel pressure with a fuel pressure gauge
To check the fuel pressure with a fuel pressure gauge, you'll first need to install a fuel pressure gauge if you don't have one already. A fuel pressure gauge is normally installed near a fuel line in the engine bay, and plumbed along the fuel line, usually located near the carburetor.
There are two types of mechanical gauges: wet and dry. A wet gauge uses a dial filled with clear oil, such as glycerin, to dampen the effects of the needle's movements and prevent damage to the delicate parts. However, as the engine bay warms up, the oil in the gauge changes temperature, which could affect the reading. A dry gauge lacks this fluid.
If you have a 70s GM car, you may need to rent a master test kit, which comes with several adapters, or buy a standard fuel pressure test kit. You can attach the fuel hose to the fuel pump test point and activate the ignition, then read the vehicle's fuel pressure level. If your vehicle's fuel pressure levels are too high or too low, its performance will drop. You can also bleed the fuel pressure gauge to let out any air before getting your reading.
You can also check the fuel pressure while driving by putting the gauge near the cowl, depending on your hood design. However, plumbing a mechanical gauge into the passenger compartment is not safe. Instead, you can buy an "isolator" that safely transmits the fuel pressure reading, but this is another component that can fail. An electronic gauge can be placed anywhere, even on the dashboard, as the signal is sent via wires.
You can also check the fuel pressure without a gauge by using an OBD II diagnostic scanner tool, which will give you real-time engine fuel pressure readings directly from the fuel pressure sensor. If your car engine will start, take your vehicle for a short 10-minute drive to warm up the engine, as cold engines use more fuel, which can affect fuel pressure readings. If it is a wired scanner, locate the OBD-II socket on your vehicle and plug in the scanner before starting the engine. The socket is usually located under the dashboard and may be covered by some plastic trim. If you have a wireless scanner that connects to an app on your smartphone or tablet, plug in the wireless OBD-II device and connect to it using the app.
If you don't have access to a scanner, you can also check the fuel pipelines that came out from the fuel pump and take fuel to the engine. These pipes are made from fuel line materials and pass underneath the car. Disconnect the hose or pipe that came to the injector's rail and connect the pressure gauge to this pipe with the specific port to ensure there is no pressure leakage. Then, have a helper start up and rev up the car as you check the gauge values.
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Frequently asked questions
You can check the fuel pressure up to the fuel rail by using a fuel pressure gauge. Hook it up to the fuel rail, turn the key on, and take a reading. If there is no fuel pressure, it could be due to a faulty fuel pump or a fuel pump circuit issue.
Check the engine and powertrain sections of your owner's manual. If you do not have the manual, look for a window sticker (Monroney sticker) or refer to the sales brochure. You can also check the dashboard for indicators.
AFM helps to lower fuel consumption and improve overall fuel economy. It does this by reducing the number of active cylinders, which in turn reduces carbon dioxide emissions.
Ensure that all wiring connections are clean, tight, and free from dirt and corrosion. Turn the ignition on and off several times and note if the needle moves. If there is no movement, check the fuse. If the wiring is fine, the issue could be with the sender unit or the in-tank mechanism.
The issue could be with the sending unit or a bad wire.
