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 Post subject: 1977 Datsun B210 Poor MPG ~Please help
PostPosted: Sun Oct 03, 2010 4:42 pm 

Joined: Wed Sep 08, 2010 8:01 am
Posts: 14
Location: Rolla, MO
Alright, so my Datsun B210(automatic trans) has a new distributor, a new fuel pump, a new condenser, new points, new spark plugs, new carburetor and new wires and yet it is barely getting 17 mpg. I'm pretty sure it should be getting around 30 mpg. Any suggestions as to what I should do/check?


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 Post subject:
PostPosted: Sun Oct 03, 2010 5:31 pm 

Joined: Tue Aug 04, 2009 8:46 pm
Posts: 82
Location: austin tx
are you having any other problems? smoke, sluggish behaviors, dried cement in your trunk?


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 Post subject: Re:
PostPosted: Sun Oct 03, 2010 8:26 pm 

Joined: Wed Sep 08, 2010 8:01 am
Posts: 14
Location: Rolla, MO
Sadly, no dried cement in my trunk. Darn.

My car does have a lot of trouble going up hills though, but I assumed that since it has such a tiny engine it just doesn't have much power to chug up big hills.

It drives in town fine, just slow acceleration, but once again, I thought simply because it is an "impressive" 4 cylinder engine.

The exhaust has been pretty horrid lately, and I know it is not the fuel mixture since I had it recently adjusted to its proper specs (before it was too rich).

On the highway it can go about 65 max. After that it struggles.

When I bought the car they said it had not been driven for a while. I have been driving it for 3 months with no improvement and I have put in fuel treatments/cleaners.

Thats all the info I can think about that might be helpful.


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 Post subject:
PostPosted: Sun Oct 03, 2010 9:32 pm 
Maybe a plugged exhaust system?

Mark


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 Post subject:
PostPosted: Sun Oct 03, 2010 9:35 pm 
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Joined: Fri Oct 12, 2007 8:57 pm
Posts: 8459
Location: Fort Worth, TX, USA
Yeah, I'd start looking at the exhaust system. Plugged catalytic converter maybe? If it ran too rich for too long, that can happen.


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 Post subject:
PostPosted: Sun Oct 03, 2010 10:46 pm 

Joined: Tue Aug 04, 2009 8:46 pm
Posts: 82
Location: austin tx
you shouldnt be having acceleration problems with a healthy a14, its a small motor holds up well enough. personally i would start with the PCV valve, i had one that broke open and had all the problems your describing although my idle was almost nonexistent too. does the exhaust generally only occure on acceleration?


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 Post subject:
PostPosted: Tue Oct 05, 2010 3:52 pm 

Joined: Wed Sep 08, 2010 8:01 am
Posts: 14
Location: Rolla, MO
datsunfreak wrote:
Yeah, I'd start looking at the exhaust system. Plugged catalytic converter maybe? If it ran too rich for too long, that can happen.


My car has no catalytic converter. My exhaust looks normal, it just smells bad sometimes but I didn't notice the smell today. The idle is very firm/normal.

I took it to a few mechanics, and they said that I will have to redo the fuel mixture after a while since it is a new carb(seals expand and all that).

They also said it might not be getting the mpg it should because the gas in the USA now has ethanol in it (which is not good for my engine apparently or any car still using a carb)


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 Post subject:
PostPosted: Tue Oct 05, 2010 7:31 pm 
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Location: Fort Worth, TX, USA
gcq4nb wrote:

My car has no catalytic converter. My exhaust looks normal, it just smells bad sometimes but I didn't notice the smell today. The idle is very firm/normal.


Are you 100% sure? I know most '77 Datsuns didn't, but problems with the cat will also cause it to have a really bad smell... :P


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 Post subject:
PostPosted: Wed Oct 06, 2010 1:48 pm 

Joined: Wed Sep 08, 2010 8:01 am
Posts: 14
Location: Rolla, MO
datsunfreak wrote:
gcq4nb wrote:

My car has no catalytic converter. My exhaust looks normal, it just smells bad sometimes but I didn't notice the smell today. The idle is very firm/normal.


Are you 100% sure? I know most '77 Datsuns didn't, but problems with the cat will also cause it to have a really bad smell... :P


100% sure, I had a mechanic that specializes in exhaust systems look into the plugged converter theory, and he said there wasn't even one installed.

Plus I looked myself.


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 Post subject:
PostPosted: Wed Oct 06, 2010 3:03 pm 

Joined: Tue Aug 04, 2009 8:46 pm
Posts: 82
Location: austin tx
sorry, but did you check the PCV valve yet? its located just below the carburetor on the in intake manifold connected to the only hose thats coming out of the back of the motor, pull the hose off and stick a screwdriver in the valve, it should feel like poking a spring.

that ethanol shouldnt have that much of an effect -i still get about 28 mpg on my '76, and your loss in power proves other problems.


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 Post subject:
PostPosted: Wed Oct 06, 2010 4:11 pm 
Have you checked/set the timing? If the exhaust checked out, maybe the timing is retarded, causing the last of power? Maybe installed the new dizzy a tooth off? Have you checked the valve lash? May have a tight valve causing a compression loss? Both are super easy to check.

Mark


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 Post subject:
PostPosted: Fri Dec 17, 2010 11:20 am 

Joined: Wed Sep 08, 2010 8:01 am
Posts: 14
Location: Rolla, MO
Sorry guys, I have been dead to the world thanks to school x.x, alright, so acceleration and power is fine now, no more exhaust problems either.

The main concern now is still mpg. I was getting 20 (yay it improved) but now that we have hit winter time in missouri, it plummeted to 10mpg. I know the cold will affect it, but not THAT much!

One thought I had was a bad coil spring, but I have no idea how to check that on an automatic choke. Any ideas guys?


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 Post subject:
PostPosted: Fri Dec 17, 2010 11:22 am 

Joined: Wed Sep 08, 2010 8:01 am
Posts: 14
Location: Rolla, MO
Datsunrides wrote:
Have you checked/set the timing? If the exhaust checked out, maybe the timing is retarded, causing the last of power? Maybe installed the new dizzy a tooth off? Have you checked the valve lash? May have a tight valve causing a compression loss? Both are super easy to check.

Mark


Oh and timing is good and I have no idea how to check a tight valve


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