Fuel Pump Information and Replacement
How to safely depressurize the fuel system, remove, and install the Bosch in-tank fuel pump on 944 models, with fuse locations for each generation.
Auxiliary fuse box — early cars
| № | Rating | Protected circuit |
|---|---|---|
| 2 | 16 A | Fuel pump |
Central electric panel — later cars (1985.5+), by fuse number
| № | Rating | Protected circuit |
|---|---|---|
| 34 | 15 A | Fuel pump, oxygen sensor |
Numbered by official fuse number 1–41 (the late fuse list). The factory does not publish a 1:1 map between these numbers and the physical carrier positions, so this logical view is ordered by number; see the physical Type-2 carrier for the as-installed layout. Fuses 12, 26, 27, 29 and 35 are unpopulated.
Introduction
The Bosch fuel pumps used in these cars are generally highly reliable. If a fuel pump requires replacement, it is worth investigating whether a secondary issue caused the failure before simply installing a new pump. Known causes of premature pump failure include a clogged fuel filter and a failing fuel pressure regulator.
After installing a new pump, performing a fuel pressure check (FUEL-01) and a pump delivery rate check (FUEL-04) is recommended. These tests verify the condition of the full fuel system and can identify problems that might cause early failure of the new pump.
Tools
- Metric wrench and socket set
- Catch rags
- Hose clamp pliers or locking pliers
- Jack stands and floor jack, or ramps
Removal
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Depressurize the fuel system: a. Remove the fuel pump fuse. On 1985.5 and newer cars, the fuel pump is supplied via the DME relay through Fuse 34 (15A) on the Central Electric Panel under the hood. On early cars, the pump is supplied via Fuse 2 on the Auxiliary Fuse Panel (under dash, driver's side, left-hand drive). b. Attempt to start the engine — it may or may not start. If it does start, allow it to run until it stops from fuel starvation.
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Disconnect the battery negative lead.
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Raise the rear of the vehicle and support on jack stands or ramps.
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If equipped with a fuel pump cover at the bottom of the fuel tank, remove it. The cover is held by a strap and a single 13 mm bolt near the wheel well.
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Disconnect the electrical leads from the fuel pump. Depending on the model, there may be a direct lead connection or a two-prong plug connector near the pump.
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Using hose clamp pliers or locking pliers, clamp the fuel line from the fuel tank to the suction side of the pump. If regular locking pliers are used, wrap the fuel line to prevent the teeth from damaging it.
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Loosen the hose clamp on the fuel pump suction line and disconnect the line from the pump. Have catch rags and a container ready for residual fuel.
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Using the appropriate wrenches, disconnect the discharge line from the fuel pump.
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Loosen the hose clamp holding the fuel pump in its holder and slide the pump out.
Installation
- Compare the fittings on the new pump to the old pump. Transfer any fittings not supplied with the new pump.
- Slide the new fuel pump into the holder. Tighten the clamp that holds the pump in place. Do not overtighten — excessive clamping force can damage the pump motor housing.
- Attach the suction line and discharge line to the new pump.
- Remove the hose clamp from the suction line.
- Connect the electrical leads.
- Connect the battery negative lead.
- Install the fuel pump fuse (see Removal section for fuse location).
- Start the vehicle to verify pump operation and check for fuel system leaks.
- If equipped, install the fuel pump cover.
- Remove the vehicle from jack stands or ramps.