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The Volvo 700 series is fitted with a fuel pump inside the fuel tank, which moves the fuel out of the tank to the main fuel pump. The car will operate normally using the main fuel pump only, but it will not run with just the in-tank pump. Owners have reported issues with the in-tank fuel pump, such as noise and failure to start when the car is hot. It is possible to replace the in-tank pump, but it is a difficult job and there is a risk of deploying the airbag if the key is in position I or II.
| Characteristics | Values |
|---|---|
| Fuel pump noise | A strange buzzing sound, often intermittent |
| Failure mode | Worn commutator and brushes |
| Replacement part | Rubber Bushings (Volvo p/n 1255018-2) |
| Fuel pre-supply | Volvo 700, 900 |
| Pump size | 135mm length |
| Fuel gauge issue | Gauge reverted to empty when everything was reconnected |
| Fuel pump replacement | Requires a thin wire to hold the pump assembly compressed |
| Fuel pump cost | $50 for the in-tank pump and filter sock, $125 for the main fuel pump |
| Fuel pump replacement time | 4 hours for each pump |
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What You'll Learn
The Volvo 700 series has two fuel pumps
The in-tank pump is located inside the fuel tank and can be replaced. The pump may need to be replaced if it starts to make a strange buzzing sound, which is a symptom of a worn commutator and brushes. The pump can be purchased from Volvo, or a cheaper alternative can be sourced from Scantech, although the latter may differ in design and have additional, unnecessary hoses.
When replacing the in-tank pump, it is recommended to also replace the filter sock, as a new main fuel pump can be quickly destroyed by unfiltered fuel if the in-tank filter sock has deteriorated. It is also recommended to replace the rubber bushings, as this can make a huge difference in the way the car drives and handles. Other parts that may need to be replaced include the hose clamps, the top gasket, and the quick disconnect fitting on the fuel outlet line.
It is important to note that the fuel system is powered whenever the key is in position I or II. Therefore, it is advised to keep the key off when changing the fuel filter to avoid the risk of deploying the airbag while re-installing the fuel pump or fuel filter bracket.
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The car will run with the main fuel pump only
The Volvo 700 series has two fuel pumps that work in series. There is an in-tank fuel pump, which is low pressure, and a main fuel pump, which is high pressure. The in-tank pump lifts the fuel from the tank and sends it to the main pump, which is located under the driver's seat. The main fuel pump is capable of going up to 80 psi, and the fuel pressure regulator keeps the pressure at around 35 psi.
Some Volvo 700 series cars, such as the 1995 940 and all Regina-equipped cars, have a single in-tank main pump. These cars do not have a pre-pump, so the fuel is moved directly from the fuel tank to the engine by the main pump.
It is important to note that if the in-tank pump makes a strange buzzing sound, it may be close to failure. This sound is caused by a worn commutator and brushes, and the pump may need to be replaced.
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The in-tank pump can be removed from inside the car
The Volvo 700 series is fitted with a fuel pump inside the fuel tank. This pre-pump, also called a primary or feed pump, moves the fuel out of the fuel tank to the main fuel pump under the driver's seat. The main pump is a high-pressure pump capable of reaching 80 psi, while the pre-pump is low pressure.
- Grip the outer sleeve of the 90-degree fitting below.
- Push the outer plastic cylindrical sleeve towards the top of the fuel tank send unit.
- Keeping the sleeve pushed forward, push the entire fitting towards the top of the tank.
- Press on the top of the quick-release fitting.
- Pull the quick-release fitting from the send unit's steel tube.
You may need a little penetrating oil to free up the inner o-rings from rust on the tube. If you break this quick disconnect, the part number is "fuel feed line" Volvo p/n 9142814.
In addition to the pump, you will also need to replace the in-tank hose or filter sock. It is also recommended to buy a new top gasket and new hose clamps securing all the hoses on the top of the sender unit.
It is important to note that the car will operate normally using the main fuel pump only, but it will not run with just the in-tank pump.
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A replacement pump may be smaller but have the same flow rate and pressure
The Volvo 700 series is fitted with a fuel pump inside the fuel tank. This pre-pump, also called a primary or feed pump, moves the fuel out of the fuel tank to the main fuel pump under the driver's seat. Most 700/900 series four-cylinder cars with Bosch injection systems have two fuel pumps. The in-tank pump is low pressure, while the main pump under the driver's seat is high pressure.
When replacing the in-tank fuel pump, it is possible that a replacement pump may be smaller but have the same flow rate and pressure. This could be because it is a more efficient smaller pump. However, it is important to note that not all replacement pumps are the same size as the original pump. Some replacement pumps may have a slightly different design and may include a few extra hoses that are not needed.
When choosing a replacement fuel pump, it is important to consider the flow rate and pressure required for your engine. The flow rate of a fuel pump can be affected by the pressure and voltage supplied to the pump. A fuel pump will flow at its highest volume when there is no pressure, and as fuel pressure increases, fuel flow decreases. Therefore, it is recommended to look at a flow chart to determine the flow rate of a pump at a given pressure and voltage.
Additionally, the horsepower of your engine will also determine the fuel flow required. As horsepower increases, the volume of fuel required to support that power also increases. By considering the flow rate, pressure, and horsepower requirements, you can choose a replacement fuel pump that meets the needs of your engine.
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A buzzing sound may indicate pump failure
A buzzing sound coming from your fuel pump is a clear indicator that your pump is close to failing. Usually, a fuel pump makes a low humming sound, which is inaudible to the human ear. However, if you hear a buzzing or whining noise, this is a sign that your pump is malfunctioning. This noise may also be indicative of a dirty fuel tank, with contaminated fuel.
A buzzing sound is not the only indicator of fuel pump failure. If your engine is struggling to start, or stuttering while you are driving, this may be a sign that your fuel pump is not pushing enough fuel through to the engine. This can also cause acceleration lag. In severe cases, your engine will stall due to fuel starvation.
On the other hand, if your fuel pump is pushing too much fuel through to the engine, this can cause power surges, resulting in speed spikes and drops. This will also cause a reduction in your gas mileage, as your engine will burn off the excess fuel.
If your fuel pump has failed completely, your engine will not be able to start, as it will not be able to push any fuel through to the engine.
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Frequently asked questions
Yes, your Volvo 700 series can run without an in-tank fuel pump, as long as the main fuel pump under the driver's seat is functional.
If your in-tank fuel pump is making a strange buzzing sound, it is likely close to failure. The usual failure mode is a worn commutator and brushes.
Partsforvolvosonline and Skandix are two websites that offer parts for Volvo 700 series. You can also try eBay, which has a wide selection of Volvo parts.
It is important to work in a well-ventilated area, free of ignition sources. Additionally, leave the key off when changing the fuel filter to avoid deploying the airbag accidentally.
A hole in the hose of the in-tank fuel pump or a faulty fuel gauge could be causing issues. It is also important to check the fuse for the in-tank fuel pump, as it may be blown.
