Compression testing a Perkins 4-108

The injectors do not have threads on, there is a saddle over the top of injector that compresses a copper washer under the injector. That's what gives you the seal. Compression test is easy as you can use a compression tester with a conical rubber end and hold it firmly in injector hole as engine rotates. I think you are getting confused with a petrol engine.

Saddle by the way is held down by two nuts on two 5/16 unf studs.
 
Just wondering for future information, would the copper washer need replacing with new (or annealling) on refit? I assume that one would not just put the old one back in again, or am I wrong? Just interested in case I need to do the same in the future.
 
mikehibb said:
Just wondering for future information, would the copper washer need replacing with new (or annealling) on refit? I assume that one would not just put the old one back in again, or am I wrong? Just interested in case I need to do the same in the future.
Click to expand...

You should always re-anneal the washers before putting back in or if they have a lip where they have been compressed replace with new. New washers need annealling aswell.
 
Pete735 said:
The injectors do not have threads on, there is a saddle over the top of injector that compresses a copper washer under the injector. That's what gives you the seal. Compression test is easy as you can use a compression tester with a conical rubber end and hold it firmly in injector hole as engine rotates. I think you are getting confused with a petrol engine.

Saddle by the way is held down by two nuts on two 5/16 unf studs.
Click to expand...
There seems to be some confusion here. You definitely can't hold the rubber cone type of a petrol engine type compression tester into the hole where the injector fits on a diesel engine and get it to work properly.

Firstly the compression is too great and you will never hold in it place and get a meaningful reading.

Secondly the tester itself isn't anywhere near the right scale!

I have a diesel engine compression tester and you need to bolt it in place to get a proper reading. Either use a bridge piece to hold the nozzle down against a copper washer, or mine has a variety of different threads to fit a variety of injection threaded holes. (Sadly none of them match my current engine!)
 
I went a dug around a bit more. Didn't think you could hold in a tester as you can with a petrol engine. Pressures about 300 psi in a perk 4-108 so a petrol guage will probably explode at that pressure and with about 1/2 square inch of surface area there has to be about 70kg pushing up on the tester. Had a closer look at a diesel test set and realise they come with a bunch of adaptors and a yoke.

Didn't realise how the injectors were held in ( should have looked at the manual :) )

Thanks for the tip on the seating washers, thought that may be the case.
 
So if I was re-building an engine, I'd get all my new washers, heat 'em up and let them cool down prior to fitting, on the basis that I don't know what state they were in when I bought them.
does this also apply to the washers used to seal the swan neck's on my injection pump and all the other washers on the connections between fuel pipes and injectors etc etc?

Can you anneal the original washers and re-use?
 
yes you can ( and are supposed to ) re anneal old copper washers.

A DIY'ers guide

New washers ( from a quality supplier ) should be supplied pre-annealed but since it takes minutes to do .........


In annealing of copper ( and other non ferrous metals ), the heating is the important part. The rate of cooling is immaterial.

Whether you allow it to cool naturally or drop it into water makes no difference to the final softness.

Traditionally, you drop it into water because that's the way its always been done, but it is not necessary. It's only a matter of convenience.

Overheating can cause the copper to become very brittle.
 
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gardenshed said:
So if I was re-building an engine, I'd get all my new washers, heat 'em up and let them cool down prior to fitting, on the basis that I don't know what state they were in when I bought them.
does this also apply to the washers used to seal the swan neck's on my injection pump and all the other washers on the connections between fuel pipes and injectors etc etc?

Can you anneal the original washers and re-use?
Click to expand...
If they look to be in good condition , there is no reason why not.

A little research on annealing copper says that (unlike other metals) the rate of cooling is not important - the heating to cherry red is the important bit. Allowing them to cool in air, or dunking them in water produces the same results I am told.

You learn something every day.
 
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