Thread: 4BD1 Knocking

Originally Posted by Ancient Mariner

The port of the cylinder giving trouble usually looks slightly different just like reading spark plugs as with the diesel test just a crude compare between each cyl

Nothing wrong with a crude compare

Well lokka pretty much summed it up - lifted the head expecting to see a holed piston or snapped conrod, but everything looks good. I knocked up one of the liners when removing the piston, but it's still tight so I tapped it back down. Went over everything that we could without tearing it down further but camshaft is tight, harmonic balancer is good, flywheel, so far as I can see through the wading plug hole is straight and true.

Not much I can do now except reassemble, have to wait for a head gasket to come up from Sydney, then turn her over again and investigate further.

I did a quick check of the injectors before I pulled her apart as Vern suggested and saw no difference - didn't want to run her too long as in low revs, it felt like she was going to tear straight from the engine mounts, and coupled with the blowby I was getting, it seemed at the time that there was a piston issue somewhere.

I'm baffled to be honest, ill reassemble and go through all suggestions one by one. Only thing I can think of is that the clutch has cracked or come loose, but is somehow still working??? Seems like a long shot, but...

Originally Posted by yt110

Mike
Did you check the oil level before removing sump?

Do you have the 2 rubber gaskets on the sump?

Jim

Yes, and yes. Oil level was good, and I'd been watching oil pressure all the way and it hadn't dropped to anywhere near a minimum value. And yes, I have the two rubber gaskets on the sump.

Have a look at this photo.



I found this rag hidden in the intake port inside the head, after this engine ( 300TDi ) was blowing black smoke and acting like it was going to jump clean out of the Disco.
I looked for a air restriction but couldn't see any restriction then felt something catch when I probed the last air intake port with a wire with a hook on it.
After I had removed the rag and replaced all the bits, I started the engine it ran completely normal.

So with black smoke look for a problem with the air flow, White smoke a problem with fuel supply.
.

Originally Posted by Ancient Mariner

The port of the cylinder giving trouble usually looks slightly different just like reading spark plugs as with the diesel test just a crude compare between each cyl

Am i think you may be onto something here as i looked at the head today the valve faces on cyl 2 were cleaner than the other 3 they were looking more like a brownish yellowish colour and the rest were black

The bottom compression ring on no2 piston was fouling as its groove had carbon deposits and was stopping it from turning freely so it had a good clean better than all the other bits anyway to get the ring mooving freely

No2 injector looked like it had extra crud on it also so we may be on a winner no2 cyl is the problem

To me it looks like no2 injector is more like a stream of diesel rather than a mist and this is causing the cyl to not fire properly and cause a knocking and shaking action which has fouled the rings on no2 from not firing at the right time and has caused the blow by

Only tomoro will tell as i will take an injector from my county motor with me just to try once its running then we can try and solve the riddle


Well after today's effort its allmost back together all clean and torqued up only the rockers and push rods then the plumbing for the injection and turbo fill it up with water (for the test run) and see what we find

It is starting to come together, a dribbling injector letting improperly burn fuel down past the piston gumming up the rings.
With one injector faulty, the timing is essentially out in that one cylinder, with a sharp explosion and not evenly burning causes a knock at that stroke of the crankshaft.

What has upset that one injector?
Is there rubbish or dirt caught inside the injector, maybe it's left over residue/tar from dirty injector line insides?

In hindsight, I wonder if a cracking of each injector line in turn would have been a quick way of localising the fault to that number two cylinder injector.

It's interesting to me that the fault in this engine read like the fault that I described with the rag blocking the one air intake port of that 300TDi, again the fuel in that number four cylinder didn't burnt smoothly causing a out of time knock in that cylinder.

About finding the rag in the 300TDi cylinder head, I did write this up in another thread but I didn't find it with the Google search this time around.

Originally Posted by wrinklearthur

It is starting to come together, a dribbling injector letting improperly burn fuel down past the piston gumming up the rings.
With one injector faulty, the timing is essentially out in that one cylinder, with a sharp explosion and not evenly burning causes a knock at that stroke of the crankshaft.

What has upset that one injector?
Is there rubbish or dirt caught inside the injector, maybe it's left over residue/tar from dirty injector line insides?

In hindsight, I wonder if a cracking of each injector line in turn would have been a quick way of localising the fault to that number two cylinder injector.

It's interesting to me that the fault in this engine read like the fault that I described with the rag blocking the one air intake port of that 300TDi, again the fuel in that number four cylinder didn't burnt smoothly causing a out of time knock in that cylinder.

About finding the rag in the 300TDi cylinder head, I did write this up in another thread but I didn't find it with the Google search this time around.

If I had have seen it running before it was pulled to bits cracking off injectors would have been my first test after a quick visual and listen to it run

1 / Check for air most important effects 2+3 2 / crack the injectors 3/remove the exhaust maniifold and run 4/ start swearing. Only applies to real diesels no rubber bands or electrickery