Hello
I recently performed a condition check on our Jabiru 230SP with the 3300 engine. It ran fine before the check, and during I replaced the spark plugs, fuel and air filter. I also verified the head torque at 24 Ft lbs. Now when starting post inspection I get cold cylinders on # 1,2,4. I checked and they are getting spark. Also compressions were decent: 69,60,74. (This was cold obviously). When I did the head torque I did have some bolts move a bit. Is it possible that the heads have recessed a bit? Then again the compressions are ok. I'm kind of lost and would appreciate any feedback!
Thanks!
Hello,
By 3 cold cylinders, do you mean it is only running on 3 cylinders, and 3 aren't firing?
When you normally do a service do you get movement on any of the head bolts? With earlier engines some head recession is inevitable, but if head bolts are kept torqued it shouldn't cause any problems.
Did you check the gap on the spark plugs? It is possible for it to be too wide on a new plug.
Thanks for the reply. Yes when I get it to start it runs extremely rough, and the CHTs on cylinders 1,2,4 are non existent and after shutdown they were physically cold to the touch. I usually get just a bit of movement when I check the torque on the heads. I gapped the plugs to around .020-.023. I’ll try swapping them with another good cylinder and maybe swap harnesses as well. I’m trying to see if it’s an ignition issue or mechanical like collapsed lifters or head recession. Before I installed the valve covers I turned the prop thru by hand and made sure all the valves were indeed moving. Compressions are good on all cylinders also. I’m stumped on this one!
Hello Embmech,
That is strange. Generally it a valve was being held open it would show up on the leakdowns. And if the lifter had collapsed the valve wouldn't move as much as it should, the Jabiru lifter doesn't have enough travel to let the valve not move at all. However this means the cylinder should still fire even if the lifter is collapsed.
I am sure you have probably checked it, but are all the ignition leads going to the right cylinders? Firing order is 1 – 4 – 5 – 2 – 3 – 6.
yes they are going to the correct cylinder per the engine manual. If the leak down check was good and I can see all the valves moving when I turn the prop by hand it almost has to be an ignition issue correct? I checked the harness resistance and was getting anywhere from 2.7 to 4.0
Hello,
One thing to check is that the lifters haven't pumped up. If they have you should be able to tell by doing a leakdown again.
I’ll check compressions again. If I remove the hydraulic lifters I should be able to move the lifter, almost like a spring correct? Should it have some spring to it or be solid?
You will only be able to move them like a spring if there isn't any oil in them. Otherwise they feel solid. With enough continuous pressure they will bleed down slowly. There can be issues both ways. A lifter may not prime with oil if it has leaked away or it can pump up under some circumstances. Both problems cause poor running. Usually this only happens after work has been done on the engine where the lifters are removed or unloaded.
We are having a problem just like this, with cylinders 1 and 2 Cool to the touch, don’t seem to be firing, good compressions and leakdowns.
good spark and have triple checked firing order and changed spark plugs around.
What was the conclusion on this engine?
We haven't received any feedback on if this was the issue with this engine.
What engine do you have @type47?
2012? Type3 Hydraulic lifters
If 2 cylinders aren't firing the engine should be running very roughly.
Things you can check are; Make sure there is no vacuum leaks on the intakes pipes to those cylinders.
With the cylinder at TDC check that the valves are a fully closed (after running the engine) This indicates pumped up lifters.
Check the valves are opening when turning the engine over by hand.
