Restored engine rough idle.

[Mick.source]

Hi all been restoring my VW t25 Westfalia for four years now, rebuilt the engine, re bored, new pistons etc etc.
I now have a problem, engine starts fine but when you rev when cold as the video it seems to run on three cylinders and rough ideal after some time it eventually goes back into its natural rhythm, when rough idling increased white smoke.
I have fitted new glow plugs, new injector nozzles, re-checked pump timing, etc etc.
Any ideas  
Video

[Robsey]

White smoke would normally infer coolant in the combustion chamber.

Possibly a gasket or seal that has not been seated properly during assembly.

Best way to know, is to remove and look at the plugs. See if one is unusually clean, or at least different in appearance to others.

[Mick.source]

Taken the diesel injectors out all look the same and quite clean.
The white smoke does disapear once warm so dont think its coolant, also coolant level; hasn't changed.

[colinthefox]

Whenever I have had white smoke on starting a diesel, it has mostly been due to injection a smidge too far retarded. Are you using whatever cold start device is provided? All this does is to advance the timing for starting. I know you say it sounds like just one cylinder, but try advancing injection a tiny bit and it might well be OK. The smoking cylinder will be the one with the lowest compression.

[mioba]

Tbf sound just fine.
If it drives fine, no power loss - then doubt its a cylinder issue.

My jx has always smoked a tad on start.

Did you clean the rocker cover mesh and the pcv. check turbo return is good (any kinks) otherwise oil holds in turbo and blows out exhaust.

[Mick.source]

Thanks for you reply.
OK long story, drove it round the block smoke was terrible and yes the diagnosis was the turbo  drain just couldn't gravity drain quick enough so i placed a valve on the pressure side to the turbo to reduce the flow seem to work ok.
I started the van today first time since October started well, and went straight into a decent idle, after about one minute then revved similar to the video the engine went into a rough idle worse that the video as if it was on three cylinders went back to the original idle about a minute later. Had to wait about 10 minutes before i could rev it without this rough idle, its doing my head in, tried with the choke (lever by steering wheel) in and out.
I am getting to the stage where i think it is either poor compression or a worn Bosch diesel pump, both expensive.
I am prepared to spend the money as long as it does the trick.
 

[Mick.source]

Sorry forgot to ask what is the PCV?

[colinthefox]

When you were building the engine, did you rebuild the cylinder head, and when or if you did the head have you checked the valve clearances?

[mioba]

Placing a valve on the turbo inlet is not wise. Ot feeds the turbo oil to lube and cool it.
Get a new return line - 52 notes from BW. 5 mins to change ensuring it flows downwards.
a king in turbo drain = oil cant get out so it backs up and goes out of exhaust - change it before you fry your turbo.

PCV is the mushroom on the rocker cover. Cleaned mine recently - took almost a can of brake cleaner.

Do a compression test.

Worn fuel pump = loads of smoke.

[Mick.source]

Yes re built the cylinder head new stem seals etc didn't check the valve clearances.

Fitted new turbo drain that made no difference, even made my own drain using see through tube so i could see the oil flow, when i revved the engine you could see the oil back up to the turbo, the inside of the hose to engine was caked in oil. The turbo is fitted with new turbine. 

[mioba]

if a proper jx head the tappets are a service item to be set

[colinthefox]

Yes re built the cylinder head new stem seals etc didn't check the valve clearances.

OK. Can I recommend you check the valve clearances next with feeler gauges. Before you take any action to correct them, if you would list them here, I may be able to help.
 

[RogerT]

Did you fit a JR head? I note previous posts to that effect.

[Mick.source]

yes i fitted a jr head

[mioba]

i have also a JR head and it sounds the same.
if you fancy a drive up to Nottingham to compare then you are welcome.