Through the black coating = metal on metal inside the pump

The follower is completely external to the pump innards. If that swarf has gone anywhere it's in the engine/sump and it would be microns of material, not enough to cause damage.
 
The follower is completely external to the pump innards. If that swarf has gone anywhere it's in the engine/sump and it would be microns of material, not enough to cause damage.

What I meant is that once the black coating is worn through, the metal cam lobe is in contact with the metal of the follower.

I didn't word it very well lol
 
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Well why do people change it then?

They run a fine tolerance, if that tolerance is not met then the fuel pressure cannot be achieved and the engine runs lean. The early followers wore through, losing a lot of fuel pressure.
These engines require such high pressure as the use direct injection technology which requires high pressure to atomise the fuel in as fine a form as it can.
 
This is the worst one I've seen:



And just because the bluing has worn off the face doesn't mean they're f*cked.
 
And just because the bluing has worn off the face doesn't mean they're f*cked.

Perhaps not but it makes it a little more difficult to judge the amount of wear. If the coating does nothing, why bother with it in the first place?
 
I'm not saying it does absolutely nothing. It'll be a preventative surface coating used to decrease wear. They are still made of steel underneith.
 
Guys your getting too paranoid about the cam followers , the coating on top of the followers is microns thick , the whole follower face is hardened , the coating is designed to give minimum friction between the cam lobe and follower on every revolution , wear is inevatable.

When people keep going on about metal to metal the faces are already metal to metal so I don't see why you say this ?
Most wear is from an Inbalance between the 2 hardness figures of the cam and the follower , one will eventually start to erode and wear the other away.

If the follower was too hard the cam would soon wear away and vice versa.
In the real world things wear out I would suggest most cam followers have either broken or worn prematurely from either a manufacturing fault either with the material or the hardening process , or poor fitting of the cam follower , maybe poor timing , or a very poor oil service regime.
Things fail for a reason and until the real
Cause is found just changing a part could result in the same issue happening again.


I agree cam followers need changing mine was changed at 40 k with minimal wear.
To the op
Your issue maybe something as simple as changing your low pressure sensor on the side of the fuel pump , it also depends on what your map is requesting ?