1HZ low compression mystery

[simtoo]

I have a 1HZ diesel that has had low compression in the #1 cylinder since it arrived from AU. It had been sitting around for two years before I purchased it. #1 compression is 430 psi (hot and cold) and rises to 480 psi with a squirt of oil in the cylinder. All other cylinders are 575-600 psi. The engine would put out lots of white smoke at start up for about 10 minutes until warm, then burn clean. If I crack the #1 injector union nut (to stop fuel to the #1 cylinder), the white smoke problem vanishes immediately. It burns no oil in 3000 miles.

I pulled the head and dropped the oil pan expecting to find a broken or stuck piston ring in #1. Instead I found a very healthy looking set of rings and a clean cylinder bore with no sign of abrasion or scoring on the wall. Head gasket looked normal. There were some heavy carbon deposits on the cylinder wall above the piston travel and some carbon on the glow plug. I'm not sure what to do except hone the cylinder, rebuild the head and slap it back together. Any suggestions?? Thanks

 

[Radd Cruisers]

Adjust your valves. Engine must be dead cold - not run for 18 - 24 hours.


~John

 

[simtoo]

I adjusted the valves earlier and no change

 

[simtoo]

Low compression update. I talked to my machinist today and explained the problem and he suggested a bent rod as a possible reason for lower compression and sure enough I had noticed a slight curve to the connecting rod earlier. So with a new rod, it should be a done deal. I will update in a few weeks.

 

[Volcano cruiser]

Low compression update. I talked to my machinist today and explained the problem and he suggested a bent rod as a possible reason for lower compression and sure enough I had noticed a slight curve to the connecting rod earlier. So with a new rod, it should be a done deal. I will update in a few weeks.

My question, how did the rod get bent?

 

[VTCDN]

simtoo

I would of thought that seeing one rod thats curved ,would make me check another just to see ? (the way they go in etc) . All rods I've ever had on a rod resizer were straight and always checked just for that.

They get bent by a hydraulicked cylinder , a gulp of water , Or a real bad leaking fuel nozzle/ oil intake , but that is so rare due to there not running / turning over fast enough ..

If you remove the nozzle and insert a thin rod , measure between cylinders for the differance of total hight , the stroke is the same due to crankshaft.
Next would be a leak down test to see if valves /gaskets or rings are leaking .

No straighting of rods either (for practical thinking) ..

VT

 

[lshobie]

I adjusted the valves on a 1HZ engine that came in from japan, adjusted them before I had even started it up. Turns out that something threw the measurements way off - either carbon, or some corrosion or something, ran like s*** until I returned all the shims back to normal. I'm going to run it for a few more weeks then set the valve shims again.

One shim was way out, caused major blow back into the intake manifold, ran very badly.

Other than that you are looking at taking things apart.