Oil pump plunger and guide pin

[Colonel Blink]

Sorry chaps, but another couple of questions...

Firstly, concerning the oil pump guide pin (the 1948 on two part type), does the reduced diameter end of the pin go into the threaded holder, or is that in fact a hardened tip which is meant to go to the oil pump plunger groove? Mine has it in the holder and the end which has been in the plunger groove is showing wear. If that's is the wrong way round then I can simply invert it.....!

Secondly, how much tooth wear on the plunger constitutes too much? I would class mine as showing 'significant wear' but I also think it could fall into the class of 'if that is 28 years of wear (it hasn't run in at least 43 years) then there is no need to replace it considering its likely usage from here on' . Just wondered what the more experienced think?

Many thanks!

[Duncan]

I wouldn't have said that your pump is that worn, the guide pin was installed the correct way around with the reduced end in the the hollow bolt, replacements for both are available from the usual sources

[Joker_Bones]

This is the oil pump plunger from the G80 engine I recently assembled. My opinion was that it was serviceable so I refitted it.

IMG_20230818_170858.jpg

[Colonel Blink]

Thanking you most kindly, gentlemen!

I will therefore assume that the reduced diameter is in order to create a small reservoir of oil to ensure the guide pin doesn't seize in the holder; and that my pump is servicable for a few thousand miles.

So I need a new guide pin at £4.63 and don't need a new oil pump plunger at £132.00...... better than the other way around!!!

[Joker_Bones]

There was a thread recently about some guide pins in the supply chain that are too long, another member believed this had caused his pump plunger to seize, shearing off some of the splines.
Suggest you check/compare the length/projection of the new guide pin when fitted in the housing screw.

[Colonel Blink]

There was a thread recently about some guide pins in the supply chain that are too long, another member believed this had caused his pump plunger to seize, shearing off some of the splines.
Suggest you check/compare the length/projection of the new guide pin when fitted in the housing screw.

Thanks for the warning! This is the sort of tip which makes forums like this so wonderful.

[SPRIDDLER]

I will therefore assume that the reduced diameter is in order to create a small reservoir of oil to ensure the guide pin doesn't seize in the holder;

There was a thread recently about some guide pins in the supply chain that are too long, another member believed this had caused his pump plunger to seize, shearing off some of the splines.
Suggest you check/compare the length/projection of the new guide pin when fitted in the housing screw.

The oil in the guide pin holder also seems to act like a hydraulic spring or buffer, maintaining slight pressure under the pin to keep it in permanent contact against the plunger.

[Colonel Blink]

The oil in the guide pin holder also seems to act like a hydraulic spring or buffer, maintaining slight pressure under the pin to keep it in permanent contact against the plunger.

I noticed that when I removed the old one!