JCB 3c II fuel in the oil - fuel pumps?

[kardigen]

OK, here is the link to the recording. It runs at 800/1000/1200 RPMs.
https://drive.google.com/file/d/1LlpEK9CSNtHkxy8WSPcGoODXaQEupEZE/view?usp=drive_link

How does it sound to you? You may hear a metallic noise which comes from the exhaust cap, just ignore it. Also, I don't think the exhaust is original. I think it was changed.

[Billy26F5]

I think one cylinder isn't firing very well, check all the injector lines are tight, it would be nice to see how it sounds under a bit of load. Looks like you have a DPA injector pump there. Also see if loosening one injector line at a time you notice differences in running or not, you'll need to run around 1200 rpm for that sort of test probably. If an injector has failed you'll get this diesel in oil issue, so if one injector seems to be worse you probably want to test it, if it fails you'll need to replace all the nozzles as otherwise there will be too many differences. Also worth checking in the rocker cover, just in case. Very nice JCB, once fixed you'll really enjoy it! The exhaust is not original, the silencer was large and completely under the bonnet with only a short pipe coming up from it.
Sandy

[kardigen]

Thanks, Sandy for the advice!
Injectors are tight, no leakage. I'll cut off all injector lines one by one to check if this makes any difference.

if an injector has failed you'll get this diesel in oil issue

Do I understand correctly? So if there is not enough compression or enough fuel to ignite then it doesn't fire out and it just flushes fuel through the piston seal due to the next compression pressure. Sth like that?

Also, can you explain what do you mean by

worth checking in the rocker cover, just in case

? Do you mean the rockers gaps etc?

Thanks,
Marcin

[Billy26F5]

I'm actually referring to a dribling injector or similar, the fuel can't burn properly due to the atomisation being poor and it passes down into the oil as it can seep through the rings easily. Although it's unlikely there is a chance a push rod might have bent which could also cause a sound like that, but it probaby is worth checking tappet clearances while you're there anyway. But do check that the new lift pump is ok, as it's still the most likely reason for diesel in oil. Keen to see how it runs when testing the injector lines.
Sandy

[essexpete]

Perhaps run a little ATF through the fuel before doing anything expensive. Helps lubricate and clean. TBH I did not think it sounded too bad.

[Billy26F5]

See what you think of the accelerations, it sounds pretty clear one cylinder is not the same, also the exhaust cap is moving as if a cylinder is not firing properly. The ATF trick might sort things but not if they're serious (make sure you don't overdo it as ATF is not designed for use as fuel). Really keen to see what it sounds like under load. When you loosen the injector lines make sure fuel is coming out as if not you have a delivery valve issue.
Sandy

[kardigen]

Hi. Finally, I had some time to look into it. I've loosened delivery lines one by one and indeed seems that one of the cylinders does not stroke. The delivery line seems to work fine - passing fuel under pressure some pressure. I'd assume that it may be partly clogged injector, or sth with the valve clearance. I wish I had the equipment to check compression... Any other advices?

[Billy26F5]

You can check compression without a tester, just turn over the engine with the starter and the stop control pulled out and if one cylinder is different you need to check tappet clearances, if it's all regular then test the injector.
Sandy

[kardigen]

Update. It turned out that one of the rocker's arm and shaft connecting rods got loose, popped out somehow and stuck in the way that one of the valves was always open... I was lucky it did not break anything in the engine. It bent a little though (unfortunately I have no pictures ). So I took it out, made it straight, and checked all the other rods, rocker arms, slits, etc... basically, I reassembled the engine head and reset everything to the correct settings and now it works great! No more fuel in the oil. Oil is nice and clean. I have checked a few times after reassembly if the settings are still correct, nothing is getting loose, or the rod I made straight back is bending again, etc. All seems good so far.

Great thanks to Sandy for help. Thanks!

[gecko.cx]

Good save - that could have been expensive.