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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 23086
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have an MG ZR Diesel with L Series engine . It is difficult

I have an MG... Show More
I have an MG ZR Diesel with L Series engine . It is difficult to start when cold . When it starts it runs lumpy for a couple of seconds after which it runs smoothly . The Turbo does not seem to boost power when you accelerate on the road and when you hold the throttle down and it is pulling hard theres lots of black smoke coming out of exaust . I have had it put on diagnostics and they could not find the fault. They said that the EML should come on and when it does to bring it back to check it . As I have been using it now for 3 weeks since and the light still has not come on co you suggest what is causing this
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I'd check that you're getting full power to the glow-plugs, they pull a lot of current so take care when checking but see if the relay is clicking when the ignition is turned on first and also check the fuse if this is OK check to see if the engine earth strap is also OK.

You can test the glow-plugs with a multimeter by measuring the resistance across the plug ( between the power connection and the body) it should be around 4-8ohms if its tending to infinity / open circuit the plug is faulty or by using a clip on current clamp, either on the supply wire to glow plugs or onto engine earth, with glow plug light on you should see 15-20amps for each glow plug fitted, 4 cylinders would be approximately 60-80amps.

Also if its not injecting at all then check the connections to the crankshaft sensor, unplug it and check for corroded contacts and broken wiring, and consider fitting a new sensor - do the same for the cam position sensor

If the EGR valve is stuck open then this too can effect starting so try disconnecting it to see if this helps or changes anything

Could also be an injector leaking fuel back through the overspill pipe, so not getting enough fuel pressure to tell ECU to fire the injectors, this is trickier to find and you’ll need the garage to do a ‘run back’ test to identify which one is the issue

Lastly it’s also worth considering fitting a new fuel filter as if only slightly blocked this can lower fuel supply pressure and choke the main pump, the pump will be more sensitive to this when its cold as diesel thickens considerably with low temperatures.

Customer reply replied 3 years ago.

I have checked wires on sensors and cleaned terminals. I have disconnected EGR and it does not make any difference . I took pipe from Turbo to Rad off and this had a lot of oil in it could this mean that the Turbo itself is the cause of the problems.


if there's a lot oil as this would be an indication that the turbo oil seal is starting to fail and a replacement / rebuilt turbo may well be required. Have a feel of the turbine wheel - there should be no play radially at all - but a little bit of axial / end to end float is normal