All fuel injected models use similar fuel pumps, although the pumping capacity will vary depending on the type of fuel injection and size of the engine. Beginning in the middle of the 1976 production year, a second fuel feed fuel pump was fitted inside the fuel tank and is integral with the fuel tank sender unit.
The purpose of the fuel feed pump is to supply fuel under lower pressure to the main fuel pump. This arrangement reduces the possibility of vapor lock and relieves some of the strain on the external pump. This in-tank pump can be fitted on earlier model continuous (mechanical) fuel injected vehicles.
Because of the need for constant fuel pressure in the continuous fuel injection system, a fuel accumulator is installed between the fuel pump and the engine. The accumulator smooths out fuel pump pulsing and maintains fuel pressure in the line after the engine is stopped to insure quick start-ups.
On both continuous and electronic fuel injected models, the fuel pump is a wet type, roller fuel pump. As the pump motor spins, the rollers are forced outwards by centrifugal force and ride against the eccentrically shaped pump chambers. Fuel is drawn into the cavities between the rollers and forced outward to the line under pressure.
Volvo states that a no-start condition may occasionally occur when the engine has not been started for an extended period of time. This may be due to the fuel pump sticking in one position because of foreign matter, or corrosion forming on the rotor shaft or commutator and brushes. It is very important to clean the fuel tank pick-up screen or filter at the recommended intervals to prevent water condensation and foreign matter from entering the pump. As an additional corrosion prevention measure, add an alcohol solution or gas line antifreeze to the fuel, especially in winter months or if storing the car for a period of weeks or months. When the pump does become stuck in one position for any of the above reasons, first try the simplest method to free it. With the ignition switched ON try to free the pump by lightly tapping on its casing with a length of hardwood such as a hammer handle. This simply loosens the binding material within the pump and allows the motor to turn the pumping mechanism. It is one of the few occasions when a bit of controlled violence will cure an electrical problem.
TESTING & ADJUSTMENT
No adjustment may be made to the fuel pump. If the pump is not functioning properly, it must be discarded and replaced. To check the function of the fuel pump, the pump should be connected to a pressure gauge. Be careful not to switch the electrical leads. If the pump fails to develop its proper pressure, or if it cannot pump deliver that pressure at its specified amperage, it must be replaced. It is recommended that you consult your dealer or other reputable repair facility for accurate testing of the fuel pump pressure and amperage.
REMOVAL & INSTALLATION
See Figures 1, 2, 3, 4 and 5
The fuel pump is located either in front of or beside the fuel tank. On continuous fuel injection models, it is located with the fuel accumulator.
- Remove the gas cap. Remove the electrical lead from the pump as well as the plate to which the pump is mounted if necessary.
- Clean around the hose connections. After labeling the fuel lines, pinch them shut, loosen the hose clamps and disconnect the lines. Take care not to crush or damage the hoses when pinching them.
- Loosen the retaining nuts and remove the pump from its rubber mounts.
- Install the new pump on its rubber mounts and tighten the retaining nuts.
- Reconnect the fuel lines, tighten the hose clamps, and remove the pinchers.
- Mount the plate beneath the car and connect the electrical lead.
- Start the engine and check for leaks.