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Fuel Pump Testing and Replacement
 

Pelican Technical Article:

Fuel Pump Testing and Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$75 to $530

Talent:

***

Tools:

10mm socket, 19mm, 17mm, 8mm, 7mm wrenches, hose pinchers, Philips screwdriver

Applicable Models:

Porsche 993 Carrera (1995-98)
Porsche 993 Carrera 4 (1995-98)
Porsche 993 Carrera 4S (1996-98)
Porsche 993 Carrera S (1998)
Porsche 993 Targa (1996-98)
Porsche 993 Turbo (1996-97)

Parts Required:

Fuel pump

Hot Tip:

Use all precautions when working around fuel

Performance Gain:

Better running engine

Complementary Modification:

Test your fuel pressures

A faulty or failing fuel pump can cause poor engine performance, stumbling or stalling under acceleration or just a general lack of power. If the pump fails the engine will not run at all. The pump is an axial-flow design that uses the fuel to cool it while it is being pumped through so you do not want to let the fuel get too low in the tank or run out as fuel starvation issues can also lead to damaging the pump.

The fuel pump is located under the front right side of the vehicle near the tank. It has a protective plate over it that you can remove without removing any of the other under trays. When replacing, work in a well ventilated area, working outdoors is a good choice. Do not use incandescent work lights or power tools and DO NOT smoke: fuel and fuel vapors are highly combustible.

You will need to safely raise and support the vehicle, please see our article on safely raising and supporting your Porsche 993. Lift and support the vehicle as high as you can safely get it as you are going to want space to work under the car.

The fuel pump panel is held in place by a series of 10mm nuts and bolts (red arrows).
Figure 1

The fuel pump panel is held in place by a series of 10mm nuts and bolts (red arrows). It can be removed without removing any of the other panels.

With the hardware removed, tilt the panel down and pull it back and out from the front panel.
Figure 2

With the hardware removed, tilt the panel down and pull it back and out from the front panel.

You now have access to the fuel pump, lines and mount (red arrow) without removing any other panels.
Figure 3

You now have access to the fuel pump, lines and mount (red arrow) without removing any other panels. It is a tight fit in there so be glad you raised the car as high as you safely could.

The pump is covered in a rubber sound deadening protector and is mounted to the bracket with a large hose clamp.
Figure 4

The pump is covered in a rubber sound deadening protector and is mounted to the bracket with a large hose clamp. You will need to remove the three 10mm bolts holding the bracket in place and these bolts have rubber isolators and washers so take care when removing them and do not lose any parts.

Move the fuel lines and slip the pump up into the body of the opening until the wiring and banjo clear the body work and then lower that end first.
Figure 5

Move the fuel lines and slip the pump up into the body of the opening until the wiring and banjo clear the body work and then lower that end first.

With the unit out, pinch off the fuel line from the tank to the input side of the pump (red arrow).
Figure 6

With the unit out, pinch off the fuel line from the tank to the input side of the pump (red arrow).

Before you replace an expensive pump make sure it is getting power.
Figure 7

Before you replace an expensive pump make sure it is getting power. Remove the rubber protectors and place your voltmeter ends on the positive (yellow arrow) and the ground (red arrow). Bypass the fuel pump relay (please our article on preforming fuel tests for this information) and you should be getting 12 volts. If you are getting power and the connections are good then you have a bad pump or a bad ground. Use an 8mm and remove the ground and a 7mm wrench to remove the positive wires.

Check the continuity of the ground wire separately and if it is good then you have a bad pump.
Figure 8

Check the continuity of the ground wire separately and if it is good then you have a bad pump.

While supporting the 17mm nut on the base of the filter use a 19mm wrench and loosen the capping nut holding the banjo bolt on (yellow arrow).
Figure 9

While supporting the 17mm nut on the base of the filter use a 19mm wrench and loosen the capping nut holding the banjo bolt on (yellow arrow). Be prepared to catch and dispose of the fuel that will escape out. Even though you have pinched the line off the fuel in the pump will escape. There is very little room to work with the 17mm wrench and sometimes the fitting will loosen at the check valve. If that is the case go to the next step.

Next use a 7mm wrench and loosen the hose clamp on the supply line; again be prepared to catch the fuel that will escape.
Figure 10

Next use a 7mm wrench and loosen the hose clamp on the supply line; again be prepared to catch the fuel that will escape. Remove the hose and if your output connection loosened at the check valve you can now just spin the pump around the check valve until it is off, giving you much more room to separate the banjo bolt.

Take the filter to your bench and loosen the hose clamp and separate the pump from the base (red arrow).
Figure 11

Take the filter to your bench and loosen the hose clamp and separate the pump from the base (red arrow).

Thankfully Porsche designed a cap for the rubber cover making it easy to take off the old pump and install it on your new pump.
Figure 12

Thankfully Porsche designed a cap for the rubber cover making it easy to take off the old pump and install it on your new pump.

When installing the new pump make sure to use new crush washers.
Figure 13

When installing the new pump make sure to use new crush washers. Installation is the reverse of removal and make sure to check for any leaks before you button everything back up.

Comments and Suggestions:
Larry Comments: Is this the same process for my 1991 911 Carrera 2?
May 12, 2017
  Followup from the Pelican Staff: Yes. - Nick at Pelican Parts  
KNS Comments: Nice tech article, I followed it for my Fuel Pump replacement. I did, however, have to trim down my 17mm wrench to fit on the pump while getting the cap nut off.
February 26, 2017
  Followup from the Pelican Staff: Nice work! Thanks for the additional info, we appreciate your contribution to the DIY community! - Casey at Pelican Parts  

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Page last updated: Tue 12/12/2017 03:16:58 AM