Smoke and No power: first place to look?

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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1693power
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Smoke and No power: first place to look?

#1

Post by 1693power » 1 year ago

A couple years ago I saw an old circa 83 Maxima sedan (US version) in town making a heck of a noise. At first I thought it badly needed an exhaust manifold, until it drove by me close enough for me to read the "diesel "badging. I'm an antique semi truck guy, so I found it very intriguing.

The car turned up at the shade tree mechanic down the street from me 6-12 mos. later. I looked it over and tried to buy it, but the owner didn't want to sell it.

Fast forward another 6-12 mos., and I checked in with the mechanic, and he says the engine is smoking and has no power and he thought it probably needed rings, but he was not a diesel mechanic.

From my background in semi-truck diesels, I generally understand diesel engines and air fuel ratio valves, things like that which will deprive the engine of fuel until it has sufficient air, to avoid smoke. I know that when those valves or the diaphragms in them go bad, loss of power and smoke can result.

I am going to go over to look at the car soon and evaluate the amount and color of the smoke. I assume that these cars have a vacuum pump to operate HVAC controls? Is there an emissions device on this engine, in the pump or a vacuum dookickey which I should go to first? My barely-informed gut feeling is that something like that has gone wrong. Any direction in this matter would be very helpful thank you. I'd love to get this car, haul it to our truck shows, and rumble back-and-forth to the hotel in it.
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asavage
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Re: Smoke and No power: first place to look?

#2

Post by asavage » 1 year ago

1693power wrote:
1 year ago
A couple years ago I saw an old circa 83 Maxima sedan (US version) in town making a heck of a noise. At first I thought it badly needed an exhaust manifold, until it drove by me close enough for me to read the "diesel "badging.
Starting only with this: this is not a particularly noisy diesel, when running properly. The LD28 is not a very smoky engine, until you get some miles on the injection pump and its internal lift pump fails to develop enough housing pressure to advance the delivery timing: black smoke under load.

However, banging noise that is louder than normal diesel noise may be a failed injector. Google "diesel nailing".

Beyond that guess, diesels that smoke can be "anything". Lots of contributing factors.

No turbo, so forget about fuel control based on air delivery.
I assume that these cars have a vacuum pump to operate HVAC controls? Is there an emissions device on this engine, in the pump or a vacuum dookickey which I should go to first?
There's a very rudimentary EGR system that as part of its operation has a real intake throttle valve, up at the air cleaner box. That throttle valve is diaphagm-operated, and defaults to open, so even if there's a vacuum system failure (eg the power brake booster isn't working: failed vacuum pump on the back of the alternator, or more likely somebody left a vacuum hose disconnected), that throttle valve won't cause an intake restriction.

One likely contributor could be a stuffed-up intake manifold. The EGR, combined with crankcase ventilation recirculation, plugs up the intake runners. That's quite common, messy a couple of hours to fix but cheap, but that will only give you smoke and lack of power at higher revs & loads, not just tooling around town at normal speeds.
I am going to go over to look at the car soon and evaluate the amount and color of the smoke.
As you know, important clues from the color & amount, and if those change from cold engine to hot. If it comes up on less than all six cylinders, the GP's bus bar is likely corroded and missing a segment. It's aluminum and a common failure point on these older rigs. A former member here made up some in copper, they were very nice, but you can use std. wiring techniques and bypass the bad section. Of course, it'll smoke grey bad until it warms up a bit, just like any GP-equipped diesel with a bad/non-op GP.
My barely-informed gut feeling is that something like that has gone wrong. Any direction in this matter would be very helpful thank you.
You have come to the right place. Back when I owned my Maxima diesels, I wrote tons on them, and all that I know is pretty much on this site somewhere. Try the Search feature, and spend a couple hours reading, it'll bring you up to speed. I sold all mine long ago, and am beginning to forget things, so I would probably have to use Search as well . . .

1983 has the four-speed overdrive transmission (or the rare 5-speed manual? Not in the Wagon, though), so from that perspective it's the "best" year. The EGR system is two-stage in 1983. See viewtopic.php?p=4#p4_MY_differences for more differences (you'll have to scroll down a bit; the internal links don't seem to be working right now, I'll have to look into that).
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

Carimbo
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Re: Smoke and No power: first place to look?

#3

Post by Carimbo » 1 year ago

What color smoke?

My advice: start with the easy things that we like to inconveniently overlook in our attempts to complexify everything.
Fuel filter, air filter, especially the fuel filter. WARNING: May take several 100's of pump strokes on that primer button to get the system primed again to start.

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asavage
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Re: Smoke and No power: first place to look?

#4

Post by asavage » 1 year ago

Carimbo wrote:
1 year ago
Fuel filter [ . . . ] WARNING: May take several 100's of pump strokes on that primer button to get the system primed again to start.
If the primer even works anymore. Many don't. When replacing the fuel filter, be prepared with a Mity-Vac setup (what I use), or temporarily install a pusher electric fuel pump (which is completely unneccessary after priming is completed).
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

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