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Nissan diesel engines, and the people who love them
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Post Number:#1  PostPosted: Tue Oct 04, 2016 2:13 pm 
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Hi there, been lurking for a little while. Pleased to meet you guys. Recently I was in the market for a nice diesel pickup. I was looking for something in the 20k range and while looking at a Dodge pickup, I saw a listing for a Datsun. $900 later, I drag home a 1981 Datsun king cab.

Questions I have are that the thing idles high, I did whittle it down to the smoke screw. I will adjust it but my other concern is that while driving the truck, it accelerates through the gears on its own. It's almost like it's running away but it stops as soon as I go into neutral. I would like to hear some advice as to what is going on.

Thanks in advance


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Post Number:#2  PostPosted: Tue Oct 04, 2016 8:06 pm 
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Eplascen92 wrote:
Hi there, been lurking for a little while. Pleased to meet you guys. Recently I was in the market for a nice diesel pickup. I was looking for something in the 20k range and while looking at a Dodge pickup, I saw a listing for a Datsun. $900 later, I drag home a 1981 Datsun king cab.

Questions I have are that the thing idles high, I did whittle it down to the smoke screw. I will adjust it but my other concern is that while driving the truck, it accelerates through the gears on its own. It's almost like it's running away but it stops as soon as I go into neutral. I would like to hear some advice as to what is going on.

Thanks in advance


Welcome, where are you located?

Two things, there is an idle adjustment screw on the throttle body(carb looking thing), and you need to check the vacuum line that comes off the throttle body, if that line is cracked or has any type of vacuum leak it will do what you are describing.
Does it blow a lot of black smoke at an idle?
How about when driving it, does it blow black smoke?
I would not mess with the smoke screw a lot till you know everything else is as it should be.

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Post Number:#3  PostPosted: Tue Oct 04, 2016 10:35 pm 
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I'm in Greeley Colorado, north east of Denver. I will look into those two things. I get no black really at all really, just white when it's stone cold. What do I do to the screw on the throttle body?


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Post Number:#4  PostPosted: Thu Oct 06, 2016 12:12 pm 
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Eplascen92 wrote:
I'm in Greeley Colorado, north east of Denver. I will look into those two things. I get no black really at all really, just white when it's stone cold. What do I do to the screw on the throttle body?


It is just an idle adjustment screw(10mm), basically it controls how much air the engine gets, less air, lower idle speed, but everything else needs to be in serviceable condition, if that vacuum line going from the throttle body to the injection pump is cracked or leaks for any reason, the rack will think the pedal is being pressed, but since it is not being pressed it will only rev as high as the amount of air it can get threw the closed butterfly valve in the throttle body.
You have to understand that these diesel engine injection pumps are controlled by vacuum, if there is a leak in the vacuum line between the throttle body and the injection pump things will not work properly, as the vacuum from the venturi in the throttle body pulls the injection pump back to the idle position.
I hope you understand what I am trying to say, you should pull the cover off the throttle body and look down the hole, you will see the butterfly valve and a small venturi/hole, that venturi/hole creates a lot of vacuum when the engine is running and the butterfly is closed, it pulls air thru that venturi very fast creating vacuum, when the butterfly valve opens(press on pedal) the air gets past the venturi as the butterfly valve is open and then the venturi creates less vacuum, less vacuum, more fuel and more air as the butterfly valve is open, when the butterfly valve is all the way open, there is hardly any vacuum being created by the venturi, so the injection pump rack moves to the richest position.

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Post Number:#5  PostPosted: Fri Oct 07, 2016 12:15 pm 
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I appreciate the help, I went through the vacuum lines and replaced them along with a governor diaphragm and now she runs cherry. Fluctuating idle and white smoke went away completely.


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Post Number:#6  PostPosted: Fri Oct 07, 2016 11:28 pm 
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Eplascen92 wrote:
I appreciate the help, I went through the vacuum lines and replaced them along with a governor diaphragm and now she runs cherry. Fluctuating idle and white smoke went away completely.


I am happy that I could help you, them vacuum lines and that diaphragm are important, I didn't think to mention it, but if has a crack, it would cause the same issue.
Another thing about the diaphragm is that the old ones get dried out and and stiff, now that you have a new one, it may over all be more responsive as it is more flexible.
I believe that cod liver oil should be added to the injection pump side of the diaphragm, maybe someone else will chime in on this subject, I myself might learn something.
Mine puffs white smoke out when I first start it in the morning when it is cold outside, not so much in the summer, what counts is that when it quits missing when first started, the white smoke should also go away, as that smoke is un-burnt fuel.
Now that you have that issue figured out, if it blows a lot of black smoke, you may have to put the smoke screw back where it was if you adjusted it before.

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Post Number:#7  PostPosted: Sat Oct 08, 2016 6:24 am 
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And just in case your not sure.

Out is less in is more with that smoke screw.
Tiny TINY adjustments make a huge difference.

1/4 to 1/8th turns at a time is all it needs.

Good to hear it's running again.

I'm kinda glad I don't have that "device" on mine.

P

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Post Number:#8  PostPosted: Tue Oct 11, 2016 10:13 am 
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I'm extremely happy, it only smokes slightly on startup and at wide open throttle. I've been daily driving it roughly 60 miles since last Friday. While it isn't as plush as my 2008 civic, it gets the job done with a little worse fuel economy. I'll play around with it and see if I could get the smoke down a bit.



Thank you guys for all your knowledge, it is much appreciated.


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Post Number:#9  PostPosted: Tue Oct 11, 2016 7:09 pm 
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plenzen wrote:
And just in case your not sure.

Out is less in is more with that smoke screw.
Tiny TINY adjustments make a huge difference.

1/4 to 1/8th turns at a time is all it needs.

Good to hear it's running again.

I'm kinda glad I don't have that "device" on mine.

P


I would have to agree with this statement, the racks total throw is 9/16ths of an inch, and that includes the fuel cutoff position which takes up quite a bit of the movement, so even a 32nd of an inch can be a 10 percent or more difference at the rack itself, that is a lot.

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Post Number:#10  PostPosted: Sat Oct 15, 2016 6:21 pm 
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Location: Canada
I use power steering fluid on my governor diaphragm. That's been in it for almost 13 years now and everything still works fine...

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Post Number:#11  PostPosted: Sat Oct 22, 2016 8:06 pm 
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I'm just wondering what you used for power steering fluid. Most older power steering units used auto transmission fluid. Red, and corrosive to many items, paint being one of them. I'm assuming you used the clear stuff that is sold as power steering fluid.

Don


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