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Datsun 620 l20b oil problems

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jholl8fy
Novice

Aug 19, 2011, 12:46 PM

Post #1 of 10 (2512 views)
Datsun 620 l20b oil problems Sign In

So I recently bought a 77' Datsun 620. Runs solid, but when I brought it home I checked the oil and the dipstick showed that it was way too low. I wanted to change the oil anyway so I did, I filled it with oil until the dipstick read that it was around where it should be, but after I drove it for a bit it started spitting out black smoke and backfiring, a sign that I added too much oil. I drained about a quart until the dipstick is reading about what it was -- way too low -- but it's still acting like there's too much. Will this problem resolve itself assuming I have a good amount of oil in it? Also is there any other way to check oil levels if my dipstick doesn't give a good read? Thanks.


Hammer Time
Ultimate Carjunky / Moderator
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Aug 19, 2011, 12:52 PM

Post #2 of 10 (2509 views)
Re: Datsun 620 l20b oil problems Sign In


Quote
I drove it for a bit it started spitting out black smoke and backfiring, a sign that I added too much oil.


OH really?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



jholl8fy
Novice

Aug 19, 2011, 4:15 PM

Post #3 of 10 (2489 views)
Re: Datsun 620 l20b oil problems Sign In

?


Hammer Time
Ultimate Carjunky / Moderator
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Aug 19, 2011, 4:28 PM

Post #4 of 10 (2483 views)
Re: Datsun 620 l20b oil problems Sign In

I don't know in what world those symptoms indicate too much oil.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



jholl8fy
Novice

Aug 21, 2011, 10:50 AM

Post #5 of 10 (2466 views)
Re: Datsun 620 l20b oil problems Sign In

I wont pretend to be a mechanical genius that's just what I was told by another mechanic I spoke with, any ideas you might have as to what could be causing the problem? I do think it's strange that it ran without any problems or symptoms prior to the day I changed the oil. It wasn't immediate it was about two hours after driving with the new oil change. I'm wondering if there could be a blown gasket somewhere that's causing a fuel problem. I don't know any productive input would be very appreciated.


Hammer Time
Ultimate Carjunky / Moderator
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Aug 21, 2011, 11:19 AM

Post #6 of 10 (2464 views)
Re: Datsun 620 l20b oil problems Sign In

Black smoke is generally a indication of too much fuel. Since your truck is not fuel injected, the problem is likely coming from a problem in the carburetor.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



jholl8fy
Novice

Aug 21, 2011, 11:24 AM

Post #7 of 10 (2461 views)
Re: Datsun 620 l20b oil problems Sign In

Thank you for your responses. Also as an update, my truck won't accelerate hardly at all. I drove it once around the block and even in third gear was unable to get past 20mph. I don't know if this changes anything, read some issues online that sound similar stating that it may be an issue with the catalytic converter.


Hammer Time
Ultimate Carjunky / Moderator
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Aug 21, 2011, 11:33 AM

Post #8 of 10 (2458 views)
Re: Datsun 620 l20b oil problems Sign In

Catalytic Converters don't cause smoke but the smoke will eventually ruin the converter if you don't get the situation resolved. You will likely need a new carb.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Ultimate Carjunky / Moderator
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Aug 21, 2011, 11:39 AM

Post #9 of 10 (2454 views)
Re: Datsun 620 l20b oil problems Sign In

You check to see if the carb was flooding over. A float needle that isn't seating will cause the bowl in the carb to overflow with fuel and come out of the annular booster in throttle bore causing the engine to run extremely rich and miss.





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(This post was edited by Discretesignals on Aug 21, 2011, 11:40 AM)


jholl8fy
Novice

Aug 23, 2011, 4:48 PM

Post #10 of 10 (2433 views)
Re: Datsun 620 l20b oil problems Sign In

Thanks for the input guys, I haven't had to much time to play around with it but I did check the spark plugs and they are completely black but not oily. I'm thinking that might be more evidence suggesting it's running too rich. I was going to replace the carb anyway with a weber at some point and a friend recommended replacing the fuel filter, so I'll keep you posted after I do that. Thanks again.






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