Checking Fuel Pressure: Volvo 240 Maintenance Guide

Checking the fuel pressure on a Volvo 240 can be a complex process. The fuel pressure should be between 35 psi at idle and 43 psi at wide-open throttle. There is no Schrader valve in the fuel system of Volvo 240s, so it is necessary to use a banjo fitting between the hard and flexible fuel lines or create a tee fitting with a Schrader valve. It is important to take precautions when checking fuel pressure, such as wrapping the fuel line connection with rags and jumping fuses 4 and 6 to check for leaks before starting the car. High fuel pressure can be caused by a faulty fuel pressure regulator or obstructions in the fuel return line.

Installing an inline fuel pressure gauge

To install an inline fuel pressure gauge on a Volvo 240, you will need to first relieve the fuel pressure from the system. To do this, run the car for about 15 seconds with fuse 6 (main fuel pump) removed. Then, turn off the car, put fuse 6 back in, remove fuse 4 (primary fuel pump), and turn the car on again. Wait for the engine to stall and then turn off the car.

Next, disconnect the negative battery terminal and install the inline fuel pressure gauge. Reconnect the negative battery terminal and use a jumper with an on/off switch and a 20-amp fuse to short out the fuel pump relay harness and test the fuel pump. Jump the red/yellow wire and the red wire, turn on the ignition, and turn the jumper switch on.

If the fuel pump is working, you should be able to hear it and see the installed gauge building up pressure. Check the fuel pressure reading on the gauge and ensure it is within the proper range for your Volvo 240, which is between 35 psi at idle and 43 psi wide-open throttle.

Note that installing an inline fuel pressure gauge requires cutting into the fuel feed hose, so it is recommended to purchase a new hose if you are not satisfied with the inline gauge and want to remove it. Additionally, always take proper safety precautions when working with fuel systems, such as performing the work in a well-ventilated area away from any sources of ignition.

Locating the fuel pressure regulator

On the 1993 Volvo 240, the fuel pressure regulator is positioned at the end of the fuel rail. For this specific model, the Volvo part number for the fuel pressure regulator is 3517064, and it is also known to use the Bosch OE version with part number 0280160294.

For the 1991 Volvo 240 with the B200F injection engine, the fuel pressure regulator is located on top of the engine and has a small-diameter vacuum hose connecting to the intake manifold.

On the 1987 Volvo 240, the factory method for testing fuel pressure involves using a banjo fitting between the hard and flexible fuel lines.

It is important to note that the fuel lines on the Volvo 240 do not have a Schrader valve, which is commonly found on other cars, making it more challenging to check fuel pressure directly at the fuel rail.

When locating and working on the fuel pressure regulator, exercise extreme caution as fuel and fuel vapors are highly flammable. Ensure the engine is off and the area is well-ventilated before proceeding with any repairs or maintenance.

Testing the fuel pump

Step 1: Check the Power Source

First, check the power or voltage at the source by measuring the right-side terminal of the tank pump fuse. With the motor running, the expected voltage should be between 13 and 14 volts.

Step 2: Test the Pump

To test the pump itself, apply battery power to the load side of the tank pump fuse. This can be done by connecting a jumper wire from fuse 6 (either side) to the left side of fuse 4 for 1985 or newer models. This will power up the main pump, and you should be able to hear it running under the car.

Step 3: Listen for the Pump

If you are unable to hear the tank pump in a quiet environment, it is most likely not working. Try listening at the filler neck with the gas cap off, but be cautious as this can be challenging if the car is on a busy road.

Step 4: Spark Test

If you are still unsure, try the spark test. Connect the power at the fuse, and you should see a tiny spark, indicating that the pump is responding. Alternatively, use a test light in series to indicate current. Remember to disconnect the oxygen sensor heater if using this method.

Step 5: Fully Rule Out the Tank Pump

To completely rule out the tank pump, you must be able to hear the pump running smoothly and evenly. Rap on the sender top or the tank bottom while powering the pump with a jumper; if the pump takes off running, it confirms that the pump was stuck or not working properly.

Step 6: Check the Wiring

Before reassembling, check the wiring to ensure the gray wire mates with the car's harness gray wire, and the black wire mates with the yellow/red wire. Getting the wiring wrong could result in the fuel gauge not dropping, and the pump not working as expected.

Checking for leaks

To check for leaks in your 1990 Volvo 240, you should jumper fuses 4 and 6 to run both pumps and check for leaks before starting the car.

A common source of leakage is the timing-cover oil seal at the crankshaft-pulley end of the engine. When the engine is running fast, oil leaks most from the seal, less when idling. Check for signs of oil sprayed out sideways in line with the oil seal or pulley onto adjacent parts of the bodywork or engine. Also, look at the underside of the engine beneath the seal and on the sump pan for oil streaks starting at the lower edge of the seal. If the timing-cover oil seal is leaking, it will need to be replaced, ensuring that the rotating parts it is in contact with are smooth and free of burrs or raised metal.

Another area to check for leaks is the crankshaft rear oil seal, which is usually hidden by the flywheel and clutch housing. The only visible sign of a leak is a drip from the bottom of the clutch housing. If the seal is leaking badly, there may be clutch judder or slip caused by oil spraying on the clutch. The only cure is to replace the seal, which involves removing either the gearbox or the engine, a job best left to a garage.

Using a tee fitting

To check the fuel pressure on a Volvo 240, you can use a tee fitting placed between the supply hose and the fuel rail. This method requires a tee fitting with a Schrader valve on top. The tee fitting can be purchased or made from old fuel rails and feed hoses from junkers. Cut the last few inches off the male-threaded end of the fuel rail and a similar amount off the high-pressure line coming from the firewall. Place the tee in the middle and connect it to the fuel rail and supply hose.

This method is effective for diagnosing fuel pressure issues but should not be left installed permanently as it may develop leaks over time. It is important to exercise caution when working with fuel lines to avoid any safety hazards. Ensure you have the necessary tools and knowledge before attempting to check the fuel pressure on your Volvo 240.

The ideal fuel pressure for a Volvo 240 varies depending on the engine's revolutions per minute (RPM) and should be between 35 and 43 PSI. At idle, the fuel pressure should be around 35 PSI, while at wide-open throttle, it should be closer to 43 PSI.

It is also important to consider the age and condition of your Volvo 240's fuel system. Older models may have rusted fuel tanks, pumps, and lines, which can affect fuel pressure and overall engine performance. Regular maintenance and replacement of fuel system components are crucial to ensure optimal fuel pressure and engine performance.

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