Friday, June 20, 2014

Spare Engine - Oil Pump Inspection

As I had the clutch housing off already, I thought it would be quite interesting to have a look at the oil pump and see how it worked and also if it was still usable.

The oil pump is located behind the clutch housing cover and it held in place with three small bolts which were easily removed. However to get at the oil pump while the engine is still in the car would be very tricky as the clutch and it's housing are in the way and getting them out with the engine in situ would be a nightmare. If anyone has managed it, I take my hat off to you as this is how difficult I found it even with the engine on the bench.

Oil pump location.

Once it was off, I could get the thing to pieces.

Once it was all cleaned up, I could see the genius of it's design was it's simplicity.

The engine turns the inner wheel, which drives the outer eccentric wheel. As they rotate together, oil comes in one side, moves under the central wheel and is then squashed as the space shrinks out through a hole in the engine block.

The whole design does have an Achilles heel though and that is the gap between the blades of the inner wheel and the lobes of the outer wheel being out of spec. I looked up the tolerance and it was 15 thou or less.

I checked each of the gaps as I rotated the inner wheel and alas I was able to easily fit a 20 thou feeler gauge in the gap meaning that this particular pump is now an ornament. If I were rebuilding the engine, I would not risk putting this back in given how difficult it is to get to once the engine is back together and back in the car.

Oh well, at least I was able to examine how it works and appreciate the brilliance of it's design even if it was beyond repair. Also just knowing the location of where the oil pump is and how it can fall below spec is useful info also. I can only hope that I never have to replace one while the engine is in the car.

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