Turbo boost

How does the ECM control boost pressure on the TD5? There are no electrical components on the turbo as it is driven off exhaust gases. I ask as my 90 has an intermitant fault sometimes it goes great pulling very well from 1000 revs and other times it seems to pull far less well as if lower on power or boost. Also when it is not behaving the engine sounds different, it appears to rattle more instead of a nice deep engine note(lack of turbo boost present?). If i turn it off for a couple of minutes and then re start usually it runs fine again???? Had anew turbo and MAF sensor...systematically renewing all the sensors under the bonnet. Oh yes, EGR disconnected to eliminate this from the equation.

Thanks

Ian

Hmmm, would try taking it to a turbo diesel specialist, ideally a Lndy one. If you're in Yorkshire, Twisted Performance in Thirsk can do diagnostics and give you a quick tune up as well

ian2988 said:

How does the ECM control boost pressure on the TD5? T

Thanks

Ian

Click to expand...

It doesn't on the Defender TD5, but it does on the Discovery TD5.

So you could screw it up a bit in the Defender.
It won't go up much though.

CharlesY

Could be a failing fuel pump,check the pressure,(4 bar constant) if thats OK then live data on Testbook should show whats wrong.Increase max boost over 225 kpa on Disco or Defender and the ECU will cut fuelling to save the engine,resulting in "kangarooing" as the boost dies off then fuel is restored,overboosts,cuts fuel etc.

whats the best way to check the fuel pressure? fit an inline guage of some description? I take it that LR testbook does not check fuel pressure? It has never kangarooed and can drive badly right from initial start up and so wouldn't really get a chance to overboost. Lack of fuel could leed to low boost though... What a pain!
What usually causes the fuel pressure problems, the regulator or the pump itself?

Yep,gauge tee'd in.Usually pump failing but the way to test for a poor regulator is to gradually clamp off the return and see what it can achieve.

If yer having a run of luck like mine it'll be the pump. Heavy money unless you know someone with a replacement part used...

Still got 5 months warranty but dealer scratching their heads trying to find fault, so i thought i would find it for them, then they can foot the bill...