6x6 Cylinder Compression??

[Summiitt]

One of my 6x6s is finally I believe ready to give its last breath. When I had the new KLR turbo fitted last year, we found signs of dust in the induction system.
Its been going like a train, but in recent weeks has started using about 1 litre of oil/day (150-200km) and is now breathing heavy out of the dipstick.
I bought a motor out of the auctions to suit last year, but having no idea on condition, I want to do a compression test on it (and the old one)
Any tricks in pulling the injectors out to do the test? Im guessing there is no way of telling the condition of the crate motor, I only picked it because it had fresh gaskets on the timing case and tappet cover. A compression test should give me a good indication on overall condition.

[justinc]

Glow plug removal is the normal method

[Blknight.aus]

4bd1 cylinder compression (https://www.aulro.com/afvb/technical-chatter/148051-4bd1-cylinder-compression.html)

310 psi minimum, no more than 441 max 71 difference between cylinders,

The leak down test is more important.

Its also possible that its your turbo bypassing and not the cylinders

[Summiitt]

4bd1 cylinder compression (https://www.aulro.com/afvb/technical-chatter/148051-4bd1-cylinder-compression.html)

310 psi minimum, no more than 441 max 71 difference between cylinders,

The leak down test is more important.

Its also possible that its your turbo bypassing and not the cylinders

Thanks Dave, 310psi minimum seems bloody high, even for a diesel??

I did think about the turbo but its only got about 2000km on a new one, having said that, the first one failed at 4000km.
Given its blowing oil out the dipstick and using 1.5l/day I'm pretty confident its the rings

[Blknight.aus]

Thanks Dave, 310psi minimum seems bloody high, even for a diesel??

I did think about the turbo but its only got about 2000km on a new one, having said that, the first one failed at 4000km.
Given its blowing oil out the dipstick and using 1.5l/day I'm pretty confident its the rings

not really,

17:1ish compression. 14.7 psi for atmospheric pressure.

14.7x17 is 249 PSI and thats before you take in additional pressure from the isentropic phase of the compression stroke.

check the difference between a hot/cold compression test and watch how much higher it gets when the bore and pistons are nice and warm.

310 is also the highest value, I normally allow for 10 hits per cylinder to max out the pressure. IF it takes more than 10 hits to get a maximum gauge reading (assuming the gauges isnt leaking) or you dont hit 300 minimum (allow for gauge error and fitting leakage) in the 10 then its time for a leakdown test.

Dont try a wet test.

[123rover50]

One of my 6x6s is finally I believe ready to give its last breath. When I had the new KLR turbo fitted last year, we found signs of dust in the induction system.
Its been going like a train, but in recent weeks has started using about 1 litre of oil/day (150-200km) and is now breathing heavy out of the dipstick.
I bought a motor out of the auctions to suit last year, but having no idea on condition, I want to do a compression test on it (and the old one)
Any tricks in pulling the injectors out to do the test? Im guessing there is no way of telling the condition of the crate motor, I only picked it because it had fresh gaskets on the timing case and tappet cover. A compression test should give me a good indication on overall condition.

I would have thought the 4x4 and 6x6 with the same Isuzu would have the same compression.
Is that not so?

[Blknight.aus]

I would have thought the 4x4 and 6x6 with the same Isuzu would have the same compression.
Is that not so?


Depends on which spec sheet you want to read for the engine, Compressions listed for the 4bd1 and 4bd1-t is between 16.5 and 18.2.

for rough field maths for diagnositcs if you accept the engine as being either perfect at 16.5, sloppy at 18.2 then the allowable tolerance at 17.5 covers the spectrum of values enough for you to identify issues.