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Fuel Pump Stator Anti-Rotation Mod

Lucas/Bosch Fuel Pump Stator Anti-Rotation Mod

One possible problem with the Lucas/Bosch EFI fuel pump -- although at present there is no evidence that it actually occurs, it's just theory -- is that the pump stator may rotate within the pump housing.  There is no anti-rotation feature between the stator and the magnet case, and there is no anti-rotation feature between the stator and the outer aluminum can.  The crimping of the aluminum can to hold the whole assembly together is done in such a way as to not compress the parts together inside the can.  This may be deliberate; the stator may be intended to slip if the impellor gets jammed or some such.

Experience with this pump seems to confirm this; as long as everything else is working fine, the pump keeps on working fine.  As soon as the pickup in the surge tank gets plugged up, the pump starts making noise, and may continue to make noise even after the surge tank pickup is cleaned.  Perhaps the higher torque load caused by the suction problems causes the stator to start slipping in the housing, and once slipped it's easier to keep slipping.

If all of those assumptions have any merit at all, it may be possible to fix this pump when it gets noisy.  Simply tear it apart, install some sort of anti-rotation feature to hold the pump still inside the housing, reassemble with a new O-ring and reinstall.

Since the outside of the pump stator is square, making sure it doesn't rotate is simple: just install an obstruction for one corner of that square to run into if it tries to turn.

One simple anti-rotation fix is to drill and tap a hole in the magnet case near the end that the pump slides into and put a screw in it so that the corner of the stator will hit the head of the screw.  That has been done in this picture:

The screw used here is an 8-32.  Both the screw and the two split ring lock washers under it are stainless steel, just because that's the kind of guy Palm is; many of the other parts in this pump are ferrous steel, so perhaps a cheaper fastener will work fine.  The round head is actually the optimum configuration here due to the angle at which the corner of the pump stator runs into it.

The screw was installed from the inside outward, and the portion of the screw extending beyond the outside surface of the magnet case was ground off flush.  The number of lockwashers used under the screw head was carefully selected; by providing enough washers to make the head stand up high enough, the screw cannot back out because it runs into the side of the square stator before the threads clear the inside surface of the magnet case.  Hence, the screw and washers cannot come loose and go rattling around inside the works.

If you screw up a hole, just move over and drill another.  Holes all through this magnet case wouldn't hurt a thing, so you could make a dozen tries at getting one drilled and tapped properly without hurting anything.

It would probably be a good idea to try to clean all the filings and drilling chips out of this housing -- and of course they're gonna try to stick to the magnets and make your life miserable.  Any chips left behind would hopefully end up in the fuel filter, but they might damage the brushes or check valve within this pump before they get there.


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