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Discussion Starter · #1 ·
I have a 1914cc motor in my bus that I'm having a few running issues with which I'm trying to get to the bottom of it.

The engine was built a number of years ago, however it had a replacement set of barrels/pistons and the cam was changed 3000 miles ago.

I recently did a compression test on it, 3 out of the 4 cylinders came back around 80 and the 4th was around 100 on the compression test.

I checked the valve clearances at the same time.

Just trying to figure out what and where I need to start looking.
 

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I checked the valve clearances at the same time.
Was that before, or after the compression test ?
Battery fully charged and spinnng the engine over quickly on all four pulls ? (a weak battery can give you lower figures on the last one/s)
All plugs removed and throttle held fully open during the tests ?
Are you having some other engine trouble ?

Dave.
 

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Discussion Starter · #3 ·
Yeah the valve clearances were checked cold.

The compression test was done with all the plugs removed and upto temperature.

Yeah full battery as far as I'm aware, ill put it back on charge and give it another go to confirm they're the same.

It's a fuel injected turbo engine with crank trigger which I think could benefit from having the map checked over as it doesn't seem to run smoothly. The turbo has begun to get oil in all 3 outlets, I removed the turbo and had it checked over and apparently its all good. There is no oil in the exhaust system prior to the turbo.

The turbo engineers believed there were other engine problems, possible piston rings or parts and I was just trying to rule out certain parts before digging deeper.
 

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Yeah full battery as far as I'm aware, ill put it back on charge and give it another go to confirm they're the same.
If you do the readings again but in the reverse order from the first time, but the readings still match, then they're valid readings.
If each reading is slightly lower than the one before, then it's your cranking speed dropping.
I put the battery charger on before and then leave it on during the testing to help keep battery voltage as steady as possible.

Dave.
 

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Usual trick is test one cylinder then squirt some engine oil into the cylinder and re- test, if pressures rise then it's a ring sealing issue, if they stay the same then it's a problem with the top end - heads / valves.

Dave.
 

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Discussion Starter · #8 ·
Yeah didn't find any oil in the manifold just carbon/soot. Only oil was within the turbo inlets/outlets and silencer.

Batteries on charge and ill do the compression test again tomorrow.
 

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Yeah didn't find any oil in the manifold just carbon/soot. Only oil was within the turbo inlets/outlets and silencer.

Batteries on charge and ill do the compression test again tomorrow.
Oil found in the inlet of the turbo could be ingested from crank breather, if fitted to inlet somewhere, but can also be the turbo seal leaking. On the exhaust side it's definitely the seal leaking from my experience. If the turbo can't drain then back pressure will cause oil to force it's way out of the seals but this also happens if too much oil is going to the turbo as many turbos from the factory have a restrictor in the feed line to ensure this doesn't occur. The turbo place you went too should have picked up on this and informed of the reasons for oil in the inlet/exhaust.
 

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Discussion Starter · #10 ·
They checked it over and said there were no issues with the turbo.

The inlet side isn't connected to the breather, just hosing to an air filter.

My next step was going to check the oil pump return to make sure that it works. I knownit powers up and I can hear the pump working when the ignition is on just not sure how effective it is.
 

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They checked it over and said there were no issues with the turbo.

The inlet side isn't connected to the breather, just hosing to an air filter.

My next step was going to check the oil pump return to make sure that it works. I knownit powers up and I can hear the pump working when the ignition is on just not sure how effective it is.
Fair enough they checked that the bearing n seals were all good but I would have thought they'd have given suggestions for the oil in the inlet and exhaust.

Anyhoo, is the turbo low mount? If it's low mount and using a scavenge pump direct off the turbo drain then this can be an issue. Better to have a small sump for the oil to collect in that the scavenge pump can draw from. ;)
 

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Discussion Starter · #13 ·
It has a small reservoir below the turbo for the oil to drain into, then oil pipe to the pump before its returned to the case.

I'm looking at changing the header to move the position of the turbo higher so the oil can return to the sump by gravity and then remove the pump to simplify it and remove possible failures.
 
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