Compression numbers?

[Green1]

In the ongoing saga of my starting problems, I just had a compression test done on my engine... the problem is, neither I, nor the mechanic know what "correct" is.
He measured 320 on 2 cylinders and 340 on the other 2... (I think PSI?)
Anyone know if this is good/bad/ugly??

[Meanman]

the big thing is to not see more than 10% difference between cyllinders (this applies for all internal cumbustion engines). The 300+ numbers seem about right but not 100% sure on the specs for this engine. I think you are good to go!

[Green1]

The mechanic says he doesn't like seeing anything under 400... but he normally does VW diesels not Mitsubishi...

I know that all cylinders low will cause starting (and possibly running) problems, what I don't know is what the actual numbers are...

[josh]

Pardon my ignorance, but doesnt lower compression actually make it easier to start? At least thats how it was with my old golf diesel... the thing started anywhere anytime and had a cracked head and very low compression.

Sorry I cant help with the numbers, I have no idea.

Josh.

[vixentd]

You do not want to see less than 400 on each cylinder. Diesel starts on heat from compression. Much less than that and it will be very hard to start, but it will spin over nicely. In our mild climate it may still start at 300 but as it gets colder will not start.

The rule of 10% applies to gas engines not diesel.

[Green1]

vixen: are those numbers for the 4d56 engine?

[delicat]

G'day Green1

Had your mechanic adjusted the valve clearance before checking the compression? It could impact the results... And I think those numbers are for diesels in general (well, maybe not big rigs but passengers vehicles). Have you checked with the other forums? You can even ask Profister to check on the russian club on your behalf...
Good luck!

[Green1]

I adjusted valve clearances myself. twice. and the valves were adjusted before that by CVI (though they did it on a cold head instead of a whole engine) the starting characteristics haven't changed any...

Basically at this point I have 3 options:
- assume the compression is the problem and... ???
- have the incompetant mechanic take the injection pump off and send it to CVI for a rebuild (hope that's the real problem)
- give up on incompetance, take a week vacation time, and take the vehicle to CVI

[Meanman]

The rule of 10% applies to gas engines not diesel.

Really? so uneven numbers is acceptable? I think not!

[christoph]

The manual states:
Standard................................................1200kPa
minimum.................................................800kPa
Differential Limit between cylinders......100kPa

hope this helps.

[Blue Van Group]

The engine manual posted on the Wiki lists compression at 21:1

[Schwa]

The engine manual posted on the Wiki lists compression at 21:1

That equates (I think) to about 309 PSI

[loki]

lots of different numbers here, I would try calling ccautos, mardy, and/or CVI.

the kpa number works out to 174 psi according to google.

http://www.google.ca/search?hl=en&safe= ... si&spell=1

This next one says 21.50:1

http://www.carfolio.com/specifications/ ... /?car=7986

[Green1]

well... I emailed butch, and he didn't seem to be worried about the numbers at all, as long as they were all within 10% of each other... (and they are)

seems to me like I'm on the low end of acceptable, and compression is likely not my problem... that leaves the injection system in some way, shape, or form...

I've now given up on getting a local solution, as I'm tired of paying people to "fix" the part I specifically tell them not to touch, and isn't causing the problem in the first place! (3 shops have now "fixed" my glow plugs, none has made any difference, (except GCL who physically snapped my temperature sensor in half and burned out all 4 plugs...), and I specifically told the last 2 shops not to touch them!)

I guess I now need to find a way to get the delica to CVI...

[mararmeisto]

The manual states:
Standard................................................1200kPa
minimum.................................................800kPa
Differential Limit between cylinders......100kPa

hope this helps.

Those are for the gasoline engine. Too low.

A little further down the .pdf file are the diesel numbers:

Standard: 3040 kPa @ 2800 rpm
Minimum: 2200 kPa @ 2800 rpm
differential limit: 300 kPa