How do I check and/or replace this...
"The problem with the earlier pumps was that they had a tendency to shear off the splines inside the oil pump drive gear ( the one that is driven from the auxiliary driveshaft in the cyl. block). I'd suggest carefully checking the splines inside this drive gear and renew if in any doubt."
Thanks again!
If the length of the splines on the oil pump driveshaft (the bit that goes up into the cylinder block) is iirc approximately 8mm on the early pumps and approx. 13mm on the later pumps. I'd expect your car being 1976 to have the longer splines already. I don't know if there was any difference in pumps after about 1979 (as I finished working in a Fiat dealers at that time) so I'd suggest you follow the recommendation of your chosen parts supplier as regards which pump to fit.
Re:- the oil pump drive gear, which drops into the block and is driven by the auxiliary driveshaft. The drive teeth don't usually wear much but the internal drive splines (probably more correctly referred as serrations?) can wear. If you look inside you'll see just how much the splines are engaged by the oil pump driveshaft as they'll be shiny. If you notice any narrowing of the splines, best change it. Also put the drive gear onto the oil pump, only as far as it would normally engage, and try for rotational fit, any undue slack, best change the drive gear. I always fitted a new drive gear if it showed any signs of spline wear and always fitted a new one if fitting a new pump.
One point I think is important and I don't think it's mentioned in 'shop manuals:- when fitting the oil pump to the cylinder block, I always fit the drive gear without the auxiliary driveshaft in place to 'centralise' the oil pump driveshaft with it's drivegear. You can then rotate the oil pump via the drivegear and check it drives the pump without any binding before tightening the pump mounting bolts.
Another tip :- I ground the teeth from an old oil pump drive gear and brazed a length of rod into the upper splines where the distributor shaft would normally engage. With the engine reassembled but distributor removed, I could extract the oil pump drivegear, fit my 'special tool' and spin it with an electric/air drill to prime the oil system (all crankshaft bearings, camshaft bearings, cam lobes etc) before a first start. (with the outer teeth removed from the old oil pump drivegear, it clears the auxiliary driveshaft teeth so can be spun to drive the oil pump). Iirc you spin the 'special tool' clockwise (whatever is the same direction as the distributor).
Or you can simply spin over the engine with the spark plugs removed until the oil pressure light is extinguished, if you prefer.
P.S. Ask as many questions as you like, I'd prefer you to ask beforehand if unsure about anything, rather than have your job go 'pearshaped'. :bang:
I'm not on here all the time, but I'm happy to help out whenever I am.
Hth,
AL.
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