Compression testing. Is this a thing?

[IanCC]

Ok, would love to do the compression test thing. Yes i have a spare injector i can adapt (i guess that means remove all internals & seal leak off hole) . But seems to me to get it to seal properly, all the other gubbins needs to go in first, copper washers, heat shield, combustion chambers. Copper washers are use once, yes i know you can heat them up but sometimes there are impurities which melt. Seems all quite problematic and borderline expensive.
Am i overthinking this?

 

[ChromeDome]

What is the reason for doing the test?
What problem do you want to solve?

 

[IanCC]

Engine doesn't run perfect, so have replacement set of injectors to go in. 3gm30f doesn't start perfectly, only goes to 3600 in neutral and blows a little black smoke which i reckon is overfuelling from 25 year old injector springs having softened a little but may not be.
Would like to test compression while swapping.

 

[waynes world]

I do all my engines nowadays. cheap kit about £30, atleast it will tell you the estate of the bores or head.

 

[IanCC]

I do all my engines nowadays. cheap kit about £30, atleast it will tell you the estate of the bores or head.

Where from?
Am i right about all the gubbins in first?

 

[ChromeDome]

Mind the difference diesel/petrol

 

[IanCC]

Mind the difference diesel/petrol

Hmm, not sure what you mean.

 

[waynes world]

Where from?
Am i right about all the gubbins in first?

aslong as the bottom end is built and head on with starter motor to crank it over its all you need. if you get the right diesel kit you can get adaptors to use the glow plugs instead of injector, or use an adaptor for injectors.

compression test kit for sale | eBay

 

[ChromeDome]

Hmm, not sure what you mean.

Testing a petrol is simpler. You just use the spark plug holes and since the compression is far lower, you can even hand-hold the instrument.

Not so with a diesel and the test gear must be for the pressure range.

Plenty vids. One:

 

[bikedaft]

3gm30f has decompression levers, easy if one cylinder is down, not so easy if all 3 are...

 

[IanCC]

3gm30f has decompression levers, easy if one cylinder is down, not so easy if all 3 are...

I don't get what thw decompress levers have to do with it?

 

[bikedaft]

I don't get what thw decompress levers have to do with it?

Run the engine. Decompress one cylinder at a time, whilst going through your tests - if decompressing one cylinder makes less of a difference than the other 2, there's your culprit.

We also have a 3gm30f. In time I will recon the injectors, rather than testing. But then it runs ok at the moment...

Good luck

 

[IanCC]

Not a good idea, as i understand it, carbon can get wrong side of exhaust valve so sticks open to be rammed shut by compression stroke. That's why manual says loosen injector pipes.

I just want to test compression while swapping injectors. They are refurb, cost £20.

 

[scottie]

Old fashioned crude test is loosen injector pipe one at a time will show if one is substantially worse than other in differing rev drop
just break the nut and cover in rag
but if you are feeling really curious than get proper adapter and guage to suit engine

 

[scottie]

Not a good idea, as i understand it, carbon can get wrong side of exhaust valve so sticks open to be rammed shut by compression stroke. That's why manual says loosen injector pipes.

I just want to test compression while swapping injectors. They are refurb, cost £20.

That ridiculously cheap check providence?

 

[IanCC]

That ridiculously cheap check providence?

???

 

[IanCC]

Old fashioned crude test is loosen injector pipe one at a time will show if one is substantially worse than other in differing rev drop
just break the nut and cover in rag
but if you are feeling really curious than get proper adapter and guage to suit engine

Pretty sure there is no such thing as a proper adapter. Much googling and reading of forums.

 

[DinghyMan]

Pretty sure there is no such thing as a proper adapter. Much googling and reading of forums.

There are, depending on the kit you can get dummy injectors and adapters for glow plug holes

I have just been asked to make some adapters for use in place of Volvo Penta KBAL injectors for a customer

 

[IanCC]

There are, depending on the kit you can get dummy injectors and adapters for glow plug holes

I have just been asked to make some adapters for use in place of Volvo Penta KBAL injectors for a customer

I don't have glow plugs, just injectors. Why are you making adapters if they can be bought off the shelf?

 

[davidej]

Run the engine. Decompress one cylinder at a time, whilst going through your tests -
Good luck

The only diesel engine I had with a decompressor would not decompress selectively - only all cylinders together.