Resurrection

SD diesels were widely available in the US in the 1981-86 Datsun/Nissan 720 pickups, and in Canada through '87 in the D21 pickup.

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chrwei
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Resurrection

#1

Post by chrwei » 12 years ago

i've picked up a 1981 720KC with an SD22. it's been sitting in a field for 2 years. Guy a bought it from says that it started knocking one day so when got home he parked it to work on at a later time, then had heart problems and just ignored it.

what kind of things do I need to be worried about before trying to make it run again? obviously get old fuel out of tank, inspect hoses, replace filters. should I pull the injectors to inspect/test?

I've read some things here that hint that a mild knock could be caused by some fuel starvation, I did find one hose, between the tank and the lift pump, that was super mushy in the middle but normal on the tips and under the clamps, like it was a gasser fuel line gone soft. what are the chances that this was soft 2 years ago and was collapsing just enough to restrict fuel flow and cause knocking? I'll be inspecting rods and rockers just to be safe though since that's easy. what else could cause a knock? timing?
1981 Datsun 720KC SD22

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asavage
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#2

Post by asavage » 12 years ago

I don't think I've experienced knocking under fuel starvation conditions, and god knows I've certainly had plenty of fuel starvation situations on various diesels over the years.

For a sudden knocking problem that isn't related to over-revving (downshifting to too low a gear, for example: the engine is speed-governed and can't over-rev by itself), I would have the injectors tested first. An injector can begin opening at a much lower pressure than normal, which will give much advanced timing and knock (and is bad for pistons & rings), or it can be leaking, which yields extremely advanced ignition (and is bad for pistons and rings).

Injector service is relatively cheap. Search on "injector gasket*" for more information (and read this thread!), and watch out to avoid breaking the fuel return manifold! It's disturbingly easy to break. Click on the picture below for more info.

Image
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.

chrwei
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#3

Post by chrwei » 12 years ago

I tried to start it and it seemed like only one or 2 cylinders were even trying to fire. pulled the injectors and 2 were bone dry on the tips where the other 2 were wet. stuck injectors or a sign of something else? I read something here about burbing the lines, but if won't run that's not really doable, or should I just crack them all open and turn it over for a sec and then close them all and try again?
1981 Datsun 720KC SD22

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asavage
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#4

Post by asavage » 12 years ago

Have to bled the IP using the factory-specified method (using the hand primer on the top of the lift pump, and opening the two bleed screws on the IP housing)?

See "BLEEDING THE FUEL SYSTEM" (last screenful on that page) for more info.

Do you have a Factory Service Manual? They're cheap (under $40 any day, sometimes half that) and you can use an '82 FSM as well. Watch out for the 1981 FSM, as it doesn't contain the diesel info (in 1981 only they had a Diesel Supplement).

Open the two 10mm-head slotted screws on the top side of the IP, then use the hand primer to move fuel through the IP until NO bubbles appear, then snug the two bleeder screws again.

chrwei
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#5

Post by chrwei » 12 years ago

yes, I did that after replacing the hose and filters.

I don't have an FSM, only one i've even seen for sale so far is for 1980
1981 Datsun 720KC SD22

chrwei
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#6

Post by chrwei » 12 years ago

ok, life got in the way a bit here but back on this.

fuel system is bled, at least up to the IP bleed screws. injection nozzles are good. lift pump is good, not sure how to test the IP except to crack open the connection at the nozzles, and here's what happens:

with everything tight, it really wants to start, but not on all cylinders. it'll run on its own for 10-15 seconds but is really rough.

if I crack open any line except the one next to the firewall it still wants to run and fuel comes out pretty good.

if I crack open the line next to the firewall I get very little fuel out of it and the engine sounds like it has no compression, doesn't want to run at all. I've tried at both the IP side and the nozzle side and has the same effect.

IP needs rebuilt? maybe that leather diaphragm is shot? haven't tried looking at it yet, would this be a symptom of that anyway?

also, how exactly does one adjust the IP timing? the little mark that the FSM says should line up isn't exactly lined up on mine and it never says HOW to adjust it. seems bolted on pretty well, and I don't really see where it would swivel or turn.

and one last thing, when I work the priming pump some fuel comes out around it, could this be letting air in the system?
1981 Datsun 720KC SD22

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asavage
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#7

Post by asavage » 12 years ago

chrwei wrote:injection nozzles are good.
As in, they've been pop tested, and the pattern is good?
if I crack open the line next to the firewall I get very little fuel out of it and the engine sounds like it has no compression, doesn't want to run at all.
Maybe you really do have no or low compression in one or more cylinders. Have you checked the valves to make sure they all have some lash? Perhaps they are very tight (due to someone fooling around with them). Worth a look, as they're easy to check. Or maybe they're extremely loose (a couple of folks have found very bad rocker arm wear).
IP needs rebuilt?
Doubtful, based on what you know so far. The Inline IPs are very durable.
maybe that leather diaphragm is shot?
A shot pneumatic governor diaphragm will (should) have the IP in full-fuel mode. It will still run and still idle, but will give you huge amounts of black (not white) smoke and you can't get it to idle low enough. Does not sound like your current symptom.
also, how exactly does one adjust the IP timing?
See Philip's Inline IP timing writeup.
the little mark that the FSM says should line up isn't exactly lined up on mine and it never says HOW to adjust it. seems bolted on pretty well, and I don't really see where it would swivel or turn.
Four nuts that retain the IP housing to the timing cover, they must be loosened, as well as other stuff. Never try to adjust the timing on a running diesel!
when I work the priming pump some fuel comes out around it, could this be letting air in the system?
The old-style priming pumps leak when in the un-stowed position (ie when you are using it). That is "normal". They can be replaced with a newer style that doesn't leak. See this post for information.

There is no vacuum on the priming pump, so air cannot be drawn into it -- it is not a source of air in the fuel system.
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.

chrwei
Posts:13
Joined:12 years ago

#8

Post by chrwei » 12 years ago

asavage wrote: As in, they've been pop tested, and the pattern is good?
yes, professionally.
Maybe you really do have no or low compression in one or more cylinders. Have you checked the valves to make sure they all have some lash? Perhaps they are very tight (due to someone fooling around with them). Worth a look, as they're easy to check. Or maybe they're extremely loose (a couple of folks have found very bad rocker arm wear).
previous owner said a knock developed while driving and he parked it when he got home, then had heart problems and never looked into not drove it again. first thing I did was a quick inspection of the rockers and push rods and they looked OK, but I didn't check clearances, guess that's next on my agenda.
I should have known to search for "timing" before asking :oops:
1981 Datsun 720KC SD22

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