MTDI Rover pump unstable idle

[240zdan]

Fitted a rover pump to my 1z along with some Bosio sprint 520s.
Pump is brand new from Bosch so its fresh. Timing is set to about 1.35mm.

Runs great, tons of power, a bit smokey. Main issue I have right now is idle. I can set the idle to about 1000rpm using the Stop screw but then if I load up the motor (for example let out the clutch a bit in 1st and push it back in.) the idle will drop to 700 and stay there. I know these pumps like to idle low but when this happens I see a bit of smoke out of the tailpipe and the idle gets pretty shakey and no more of that diesel clatter.. A quick blip of the throttle will bring the idle back up to a steady and smooth 1000rpm. There is no binding or funny business with the throttle cable.

I would like it to just idle consistently at 1k, this is better for offroad as well as this engines currently being used in a Toyota truck.

Any ideas? My old AAZ would idle at 1k all day long without missing a beat.

[240zdan]

Starting to suspect its a bad injector, going to build a pop tester this weekend and test them. When the idle settles it ALMOST sounds like its running on three cylinders, and I get a bit of lope too. Motor overall doesn't idle smooth and shakes the truck a bit more compared to my AAZ. It being a TDI I would expect a much smoother running motor.


Another symptom... I get a puff of black smoke on startup hot or cold. Engine fires up instantly though. Is this leading towards an improperly set injector or that just a normal thing for  a landy pump and larger nozzles?

[vanbcguy]

Who built your injectors?

M-TDIs are actually a lot more sensitive to injector imbalance than you might think. The combination of high pressure and a large pump plunger makes for a very short duration; unbalanced injectors can be a bit more apparent than on an IDI motor.  Actual electronic TDIs have injector compensation in the pump controlled by the ECU and are slightly more tolerant of mismatched injectors.

To see if you are in fact running on 3 cyls try loosening off the injector lines one by one with the engine running, you should have the revs drop as the injector stops firing.  This is like yanking the spark plug wire one cylinder at a time on a gasser to see if one isn't firing - if you find one where there's no change in how the engine is running when you loosen up the line you've found your culprit.

Puff of black on startup is normal.  Some versions of the LR300 pump had a linkage that would reduce fueling in this scenario - I had that version and removed it to get the top back on my pump easier then discovered just how much it had been helping.  I have a pretty scary cloud at startup...   The mechanical pumps go to full fueling until the flyweights in the pump spin fast enough to kick the governor lever back over which is what causes the startup smoke.

Finally around idle speed, the factory idle speed is apparently around 720RPM for some versions of the Land Rover pump, so the fact that it's trying to settle down there isn't that surprising.  You may need to stretch the idle spring out a little; I actually need to do this myself.  My engine is pretty smooth at 1K but shakes like crazy around 900 and lower.

[240zdan]

Wow... that was a very helpful post. I was starting to suspect it was the idle return spring.

I threw the nozzles in without pop testing them. I know... I will pull them out and get them balanced regardless.
I tried loosening the injector lines one by one and the revs drop equally on each cylinder, however.

I would like to stretch the idle spring a bit to maintain a higher idle, the low idle can get annoying in traffic. Right now I just turn up the stereo and enjoy the massage.

BTW, I am located in Vancouver as well.
Thanks.