LD28 - No power and knocking

Discuss (and cuss) the Nissan LD-series OHC Six diesel engine, popularly available in the US in 1981-83 Datsun/Nissan Maxima Sedans & Wagons.

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LD28 - No power and knocking


Post by Sanfiddy »

Hey guys

So I picked up an old commodore the other day, fitted with an LD28, the guy I got it off had it for years, and stopped driving it when the IP belt broke on his way home. He had various attempts at fixing it, including moving the pump and fitting a new belt. It sat for about a year, then I purchased it, having had this problem before with other LD28's thinking it would be a quick fix of reinstalling the belt correctly.

Got access to the belt, found it wasn't installed right, I set it properly, counting the teeth and starting from 'B' on the IP pulley.

Got it running, Idles fine after a few seconds and sounds normal, but there is a LOT of grey smoke coming from the exhaust, and give it any revs it has a terrible 'diesel knock' sound, and an attempt to drive it found it to have no power.

I'm familiar with these engines, and have plenty of them, But unsure where to start with this issue, I compared the IP position to some other engines I have, and it looks to be back on the original scribed mark. There is other marks from the previous owner however where he has obviously moved it in an attempt to get running. It may need a good bleed on the injectors? But as soon as I crack any the engine dies, I can bleed it other ways but wont have access to the vehicle for a few days so thought id look for any suggestions on here.

What else could the previous owner have adjusted to cause there symptoms? He was a pretty straight up guy and assured me it ran fine before the belt snapping.

Is there a factory setting for the fuel screw ect I can try?

I believe I read somewhere the IP pully can be incorrectly installed on the 'A' position on the keyway, if that was the case would that display these kind of issues?
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Re: LD28 - No power and knocking


Post by Carimbo »

Because the IP has been rotated you probably need to really set the timing to factory specs, using the FSM method. (Sorry I sold my FSM long ago, but it likely outlined the method common to most Bosch VE pumps-- Using a dial gauge screwed into the center port in the IP output distribution head to measure internal piston position at engine TDC.)

Eyeballing scribe marks made by someone in the past may get you somewhat close but not close enough. Very tiny changes in relation to "scribe marks" have large differences in the actual timing setting.

Gray smoke can indicate incomplete combustion, a possible symptom of incorrect timing. Incorrect timing can also cause excessive knocking and low power.

Unless the fuel lines or filter were opened up, there should be no air ingress and therefore no reason to bleed the injectors.

You could try "timing by ear," experimenting with minute repositioning the IP each time, see what that gets you. May get lucky, who knows? :roll:

When twisting the IP, best to first loosen the IP hardlines at the distribution head, then retighten them afterward, to reduce stressing them that could later lead to cracks. Not easy to do without a special "flare-nut"-looking type of bent wrench as those nuts are bunched together blocking easy access.
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