Purge Pump overhaul

Lotus Excel - Purge Pump rebuild

This short article describe the steps necessary to resurrect a dead airbox purge pump. Note - this is only present on later cars and is intended to make hot starting easier.

  • Tools required : 10mm spanner, soldering iron, "prising implement".

  • Other item required : replacement motor (see below), glue to reassemble the motor housing, may also need superglue to resurrect vibration proof mounts.

Difficulty : low

Time required : approx. 30 minutes (max.)

Purge Pump in place

Purge pump situated on wing near pedal box

Step 1 : unbolt the purge pump from the mounting bracket. It is attached by "vibration proof" mounts which are held in place by 10mm nuts with shakeproof washers. Once the nuts have slackened by about one turn, they can be undone by hand.

Step 2 : disconnect the two air hoses and the electrical plug.

The pump should now be free to come out of the engine bay.

Step 3 - prise off the end cap of the motor housing - this is the end with the electrical cable protruding. It may take some force to remove, but it will come off eventually to reveal the scene of devastation where the old motor sits. Given the state of the cap on mine, it seems the motor has been replaced at least once before. My motor was so bad that the hub and brushes came out with the cable.

Step 4 - extract the old motor. Again, this may take some "persuasion" as the motor shaft is a tight fit in the fan, but it does pull free eventually. Clean up the inside of the housing.

Old motor inside housing. Cap fell off.

Old motor inside housing. Cap fell off.

Old motor vs. new showing wiring

Swap electrical cables from old to new

Step 5 - swap electrical cables over (Excel wiring is Blue for Live, Black for earth - my replacement motor came with Brown & Black for live and Black for earth) by unsoldering and resoldering. Be careful not to disconnect the suppression capacitor during this process. Also make sure that the replacement cable has enough "slack" to allow the cap to fit between the cables and the motor hub when it is replaced (there is a casting in the cap which centres the motor by sliding over the projecting plastic hub cover on the end of the motor). The replacement motor is a RE360 type and commonly sold as a MFA/Como drills motor.

Step 6 - Transfer the black plastic/rubber cap from the old motor shaft to the new motor and insert replacement motor into housing and into fan. It helps if the hole for the drive shaft is properly centred. A certain amount of force may be required to get the drive shaft into the fan, so holding the pump assembly in a vice or similar can be useful. It is also a good idea to use a stick, screwdriver or similar implement through the front inlet to hold the fan in place while you push the motor in. If the motor shaft is loose in the fan a blob of glue may help.

RE360 motor

The new RE360 motor

Step 7 - refit cap using an appropriate glue to get a good seal. Silicone sealant did not work well for me as the pump housing was a little greasy. Bostik seems to hold OK.

Step 8 - reconnect wiring to loom in engine bay and refit air hoses.

Step 9 - reattach pump to mounting bracket.

Step 10 - drive until the engine is warm and check that the pump runs when the ignition is turned off. It may also be helpful to check that the pump is blowing in the correct direction at this stage (fumes should be sucked out of the airbox).