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720 carb running rich


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#1 S..till T..imeless

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Posted 27 December 2017 - 08:34 AM

Does anyone know a good carb guy in los angeles area? My carb guy cant figure it out. Strong gas smell from tail pipe.thank you
1985 720 kc

#2 captain720

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Posted 27 December 2017 - 09:53 AM

Hitachi (stock) or Weber? Nope don't know a carb guy. I would still recommend that you figure it out. It's gonna go a lot easier and be significantly more enjoyable if you can figure out maintenance and stuff out because paying somebody else doesn't always work out.

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1986 and 0 Nissan 720 kc 2wd http://community.ratsun.net/topic/71766-one-wasnt-enough/

 

 

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#3 datzenmike

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Posted 27 December 2017 - 10:52 AM

Looks like an '85 in the avatar. California would be the ECC carb with O2 sensor and the 6 wire round electrical plug at the back.

 

I have to assume this is a rich smell... at idle.  Some things that can cause an over rich idle...

 

 

Float has sunk or stuck or inlet needle valve is obstructed and not closing and the float chamber is over filling and flooding. Look at glass bull's eye on front of carb. Fuel level should be half way up. Look also down the primary barrel while running for gas dripping from the venturi.

 

Choke is on or part on. Take top of air filter off and look when engine fully warmed up. Choke plate should be fully vertical when off.

 

I've seen some pretty dirty air filters in my time but never one that choked the air supply enough to lower the mileage.


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#4 captain720

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Posted 27 December 2017 - 11:14 AM

Looks like an '85 in the avatar. California would be the ECC carb with O2 sensor and the 6 wire round electrical plug at the back.

I have to assume this is a rich smell... at idle. Some things that can cause an over rich idle...


Float has sunk or stuck or inlet needle valve is obstructed and not closing and the float chamber is over filling and flooding. Look at glass bull's eye on front of carb. Fuel level should be half way up. Look also down the primary barrel while running for gas dripping from the venturi.

Choke is on or part on. Take top of air filter off and look when engine fully warmed up. Choke plate should be fully vertical when off.

I've seen some pretty dirty air filters in my time but never one that choked the air supply enough to lower the mileage.


We had one on a 79 C10 that was so clogged up that it wouldn't even run.

1986 and 0 Nissan 720 kc with a 1984 Z24 (third engines the charm?) http://community.rat...y-first-pickup/
1986 and 0 Nissan 720 kc 2wd http://community.ratsun.net/topic/71766-one-wasnt-enough/

 

 

Datsun=Project


#5 datzenmike

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Posted 27 December 2017 - 11:16 AM

I've seen some with oily blow by wetting half the filter.


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#6 S..till T..imeless

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Posted 27 December 2017 - 08:00 PM

85 stock carb,im gonna have to check all those things datzenmike. Thank you. If i were to get a new weber, would that possibly fix the problem?

#7 datzenmike

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Posted 27 December 2017 - 08:03 PM

Not in California. It has to pass emission testing doesn't it? Can't replace anything but with stock parts.

 

 

Guess I had better ask now before we go farther. Is your 'carb guy' familiar with carbs or EFI? EFI would have much less tailpipe smell than a carb vehicle. What you smell may be normal for a 720.  


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#8 S..till T..imeless

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Posted 27 December 2017 - 08:08 PM

I dont know anyone out here with a nissan carb that can pass emissions. They're making harder each year to pass. vehicles from 1974 and older , do not need to have a smog check in California.

#9 racerx

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Posted 27 December 2017 - 08:14 PM

75 and older don't need smog in California. If you do install a weber, it won't pass. 1st is visual, then performance.

#10 racerx

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Posted 27 December 2017 - 08:16 PM

If u can't tune the carb, you have to find a mechanic that knows carbs, specially import ones. Most mechanic s that know carbs are retired or too old. Try adjusting urself before taking it to get smog.

#11 S..till T..imeless

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Posted 27 December 2017 - 08:22 PM

Theres alot of mechanics that work on carbs here in L.A. but they dont want to do deep troubleshooting.

#12 S..till T..imeless

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Posted 27 December 2017 - 08:22 PM

Right away they want to rebuild the carb.

#13 datzenmike

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Posted 27 December 2017 - 08:38 PM

 

 

Float has sunk or stuck or inlet needle valve is obstructed and not closing and the float chamber is over filling and flooding. Look at glass bull's eye on front of carb. Fuel level should be half way up. Look also down the primary barrel while running for gas dripping from the venturi.

 

Choke is on or part on. Take top of air filter off and look when engine fully warmed up. Choke plate should be fully vertical when off.

 

I've seen some pretty dirty air filters in my time but never one that choked the air supply enough to lower the mileage.

 

 

 

Check these first and eliminate the obvious causes.


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#14 S..till T..imeless

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Posted 27 December 2017 - 10:06 PM

Will do, thanks

#15 720_Jeff

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Posted 27 December 2017 - 10:37 PM

I dont know anyone out here with a nissan carb that can pass emissions. They're making harder each year to pass. vehicles from 1974 and older , do not need to have a smog check in California.

 

Mine passes, just passed last year.



#16 S..till T..imeless

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Posted 28 December 2017 - 01:00 PM

Jeff. Who works on your truck. I need to figure this out. They got the smog check points all over here now

#17 datzenmike

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Posted 28 December 2017 - 01:40 PM

First be sure there is a problem. Has it failed emission testing?... you haven't said. Otherwise smelly exhaust isn't much of a sign.

 

Are the plugs black?

Does it blow black smoke?


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#18 S..till T..imeless

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Posted 28 December 2017 - 06:35 PM

Yes, tested emissions. Should be 0.4 . mine tested 4.0 no black smoke. Plugs looked normal.

#19 datzenmike

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Posted 28 December 2017 - 06:51 PM

Was this idle or revved up?


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