Replacing the Mk1 Fuel pump

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[url=https://imoc.co.uk/app.php/kb/viewarticle?a=64&sid=999894761a4f6f1b26b0060b6e6c7d58]Knowledge Base - Replacing the Mk1 Fuel pump[/url]

Replacing the Mk1 Fuel pump

Legal stuff


It is assumed that anyone using this guide as an aide to installing fuel pump into their AW11 is competent to do so, and follows all the relevant safety procedures.

The author does not accept any responsibility or liability whatsoever should damage or injury occur to persons or property as a result of using information contained in this guide.

Safety

This operation must be carried out in a well ventilated area, due to petrol fumes being released.
Ensure all potential sources of ignition are kept well away from the car and work area during this operation !!
Disconnect the battery before starting work


Empty the tank.

There is a drain plug on the bottom of the tank, but removing it means that the fuel comes out in an uncontrolled manner – it also means replacing the sealing washer when you put the plug back in.

A better option is to simply pump it out with the fuel pump ( assuming the reason for swapping the pump isn’t due to the existing one completely failing ). Undo the fuel supply pipe from the fuel rail on the engine, and put the end in a suitable receptacle ( i.e. a fuel can ) – make sure you get the right pipe as disconnecting the fuel return pipe will result in petrol squirting out of the hole on the fuel rail ( supply comes from the fuel filter, return goes direct back to the tank ). Then use a length of wire to apply 12V from the battery to the Fp pin in the engine diagnostic connector – this will start the fuel pump.

Disconnect the electrics

There are two electrical connections to the tank, one for the fuel pump and one for the fuel gauge sender. Both are located under the centre console in the cabin, just in front of the gear lever. Unscrew the centre console, unplug the connectors, and feed them through the rubber grommet in the top of the centre tunnel – this is easier if you unscrew the small metal plate the grommet is fitted into.

Raise the car and support on axle stands – as you need access for the full length of the tank both ends of the car need to be lifted, so 4 axle stands will be needed ( or 2 ramps and 2 stands ) – whatever you do DON’T just rely on jacks while you work under the car !

Remove underbody covers - Unbolt the plastic covers from the underside of the car and engine bay. At the rear this will require unbolting the small metal crossmember.

Unbolt the two crossmembers holding the handbrake mechanism and cables – this can be allowed to just dangle under the car.

Remove pipes
Unbolt the fuel pipe from the bottom of the fuel filter ( easier than removing at the tank end ). The copper washers can be replaced, or reused after heating to red heat to re-soften them ( annealing ).

Unclip the rubber fuel return hose, and the 4 hoses connected to the evaporative separator ( 1a only has 3 – 2nd breather hose from fuel pump goes to air filter box ). Make sure you know which hose goes where !

The two evaporative separators - spot the extra breather connection on the 1b ( black ) one
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Undo the clips on the fuel filler and breather pipes – the filler pipe is really stiff and probably won’t come off the pipe until you’ve moved the tank a bit.

Remove straps
Support the front of the tank with a jack ( the rear will be held up by the pipes ), and undo the straps that hold the tank in the car – one 12mm nut on each. Lower the front of the tank onto something soft e.g. cardboard which won’t scrape the paint when you slide the tank forwards along the ground. You may need to use a bit of force to free the tank and get it to drop down.

At the rear push the tank forwards until the pipes etc attached to the rear of the tank clear the transverse chassis member and the tank is free to drop. Due to the stiffness of the plastic fuel filler pipe this can be quite difficult, but persevere.

Remove pump
Once the tank is out, the pump can be removed. Undo the screw at the rear of the tank that fixes the pipe bracket to the tank ( Phillips screw ), remove the 8mm bolts holding the pump cover, and pull the pump assembly out of the tank.
Image
Tank under the car, pump removed, with handbrake gubbins dangling at the left

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Pump assembly – upper one is OEM pump, lower is a replacement uprated item

The pump itself simply clips into the housing at the bottom, and is held in place by the flexible fuel pipe. The standard electrical connections on the pump are ring terminals secured by nuts, however many replacement pumps use plug connectors which require the original wiring to be removed and the new connectors pop-rivetting into place.
It’s a good idea to check electrical connectivity with a multimeter before re-assembling. :wink:

Reassembly
Check the rubber seal, insert the pump assembly back into the tank, and refit the 8mm bolts. Refix the pipe bracket to the rear of the tank.

Now for the hard part…. :roll:
Lift the rear of the tank into place, making sure all the attached pipes and hoses are in the correct positions and not trapped between the tank and the tunnel. Lift the front of the tank, and working from the back pull the tank into its correct longitudinal position while at the same time positioning the plastic fuel filler pipe back onto the metal pipe. Once in position replace the under tank straps.

Reconnect all the pipes at the rear of the tank. Refit the handbrake crossmembers and the plastic undertrays. Plug the electrical connectors back in, and replace the centre console. Refill the tank, reconnect the fuel supply pipe to the fuel rail, reconnect the battery, and start the engine.

Assuming all is well, remove the axle stands and lower the car.