Diagnosing black smoke under load on 300tdi?

Hi everyone,

My 300tdi has a lot of black smoke when under load (I mean a lot!). The engine has done this since I owned it, but since I recently took it out of my discovery, and put it in my 110, including disco gearbox and transfer box, the longer ratios, plus slightly larger tyres are causing the engine to be under load more often and therefore more black smoke.

Here’s my state of play:
I’ve done all the filters. The fuel pump still has its security band thing on, so I don’t think anyone has mucked about with the pump. The smoke issue was present with both the disco and defender air routing. EGR valve has been blanked off.

Here’s some suspect things:
my temp gauge climbs to about 1/3 up from cold and stays there. Same on disco and defender (stuck open thermostat maybe?) - would this cause the smoke?
Oily hoses coming off the bottom of the intercooler - blocked/restricted cyclone breather? One of the turbo intake hoses (the elbow that goes into the turbo) burst a few months ago and I had to limp the car home. Could my intercooler be full of soot due to that?

The engine runs beautifully. Did in the discovery, and does in the 110 (it replaced a knacked 2.5na so feels like a rocket regardless!). Puff of smoke on start. No smoke on idle, or when revving the engine in neutral.

Obviously I could start replacing bits, and I already ordered a replacement thermostat ready to check if the old one is stuck. But would love some other directions to explore.

Thanks!

How about the boost pin, is that original and running in the correct place?

It's fuel, or to be more pecise, too much fuel.
The thermostst won't effect it although diesels are more efficient when warm than cold.

Intercoolers can gum up as there is always a little oil from the turbo bearings getting through.
Too much fuel can also be too little air, but your description sounds like too much fuel.

I'd start by unscrewing the fuel pin by 1 full turn (you said the security band was still on but that nominally stops it screwing in).

Well yes it's too much fuel for the amount of air it is getting, so turbo could be the issue , or a hole in the intercooler or pipes. I put a bicycle valve in my top boost hose linked to the manual gauge inside the cab in my D1 300 tdi - cheap and is a needed for diagnosing issue's

That's where i would start before injector replacement and pump refurb etc.

Oily pipes on the whole air circuit is "normal". If it's dripping oil then that's an issue .

Come up with any answers yet?

Still smoking?

If you can, fit a boost gauge to the "spare" / blanked port on the back of the inlet manifold.

Assuming you're not burning oil (are you loosing oil) then it's a fuel air ratio issue.

If you're not seeing enough air at the manifold when under load then that will be it.


...however

The way the setup works is that the pressure from the turbo works on the injection pump diaphragm and the fueling is (partially) increased by the air pressure itself. There are scenarios where you may see pressure at the IP but not the manifold, but they would not be common.

A cheap boost gauge and the banjo for the back of the manifold would help you though.

Anyway, back to the IP -

The pin on the bottom of the diaphragm in the IP is an asymmetric cone. Rotating this cone alters how the fuel comes in under boost. I don't reckon this is your issue, however, rotating the cone will reduce the fueling under boost.

But then if the turbo is actually putting the pressure to the inlet manifold, its unlikely that a bit of extra fuel would create real issues.

So then we are back to inlet pressure monitoring. Expect around 15psi ish on a stock engine. Should leap up to 10 or 11 almost instantly under load and then progress further as the revs rise.

Hi everyone,

Sorry for the slow update - I was busy getting married (of course, the One-Ten was the wedding car). I’ve since sorted out the thermostat (it was stuck open) which made a bit of difference. However, I’ve now done about 1500 miles since the conversion, and just after I posted the first time about this issue, it developed a loud squeal on the turbo. This squeal has slowly been getting worse.

I’m guessing the turbo was struggling, hence too much fuel, but now it’s actually noticeable. I think I’m going to get the turbo rebuilt/serviced, then if the smoke since exists, look at the pump. I don’t want to adjust anything until I’m sure the turbo is at 100%!

Thanks all for the advice - I’ll update once I’ve actually managed to get the turbo sorted

Congratulations on the wedding.
Probably best not to drive if the turbo is squealing, you don't want it coming apart while driving.
Think you can get a cartridge to swap over.