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Air Injection Pump


mx71

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If all you have to do is pass the emissions tailpipe test then any carb that get's you past it will do. I imagine the stock emissions pass is very low for the ECC carb and will be hard to beat with an other carb. The stock uses the AIS and catalytic converter, the variable primary jet and O2 sensor feedback to run at stoichiometric. It also has EGR ported vacuum. The weber won't have any of that.  

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Mike I run the stock egr and the cheapest catalytic converter I can buy with my Weber.  The last time I failed emissions and all I did was replace the catalytic converter.

 

King cab passed emissions today,  good for 2 more years!!!

 

Here are the last test results after installing a $30 cat.

 

Emission Inspection Results

                                                                       Vehicle                             Test

                                                                    Emissions       Allowed      Result

Hydrocarbons (HC) in grams / mile:                0.95              3.00         Passed

Carbon Monoxide (CO) in grams / mile:          7.79             25.00        Passed

Oxides of Nitrogen (NOX) in grams / mile:      3.16               4.50        Passed

 

Remember this is a non smog legal Weber 32/36 DGEV carburetor.

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If I just have the Hitachi put on it (it's the one with the 6 pin connector), will any air filter housing from 84-86 fit, or are they different depending on the carb?

 

All close enough. Get one from a 2wd. You will need the pipe from the exhaust manifold in order to get the AIS working. .

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The shop is saying new carb because they can't get the crap one that's on it tuned properly.

...u sure that mechanic knows how to tune a carb. Not too many people today know how. Most have retired. We live in an efi world now. I would ask him if he ever tuned a carburator before. How old is this mechanic.
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This is an older family run business that's been here in Boise for 30 years, and are qualified by the state for emissions repairs. I trust that it needs a new carb, as the Holley that's on it looks like junk, and it looks like there's pieces missing from it. I'm just going to have them put on a new (remanufactured) Hitachi and just put it back to stock. In my old age (I'm either 32 or 33 now), I'm now becoming the type of person that likes things stock and starts reliably. I don't care about power or noise. Even though I have no experience with this shop, I trust them. The only smog requirements here are less than 1.2 on the CO, and I was 7.5. All vehicles get tested after 1981, and this is an 85. It passed everywhere else other than not having the injection pump. Test is ever two years, and if you make a good faith effort to repair problem and spend at least $300 (not including replacing removed parts like an EGR valve or AIP), then I qualify for a waiver. This carb install is going to cost at least $1,000, and if all the parts it's supposed to have are put back on it, I'll qualify for the waiver. I didn't want to do it as I had $1,600 in this truck, but I've realized I'm going to keep this truck for a while so it's worth it for me to spend the money on it to have it run right. At this point, I'm more worried about it being right than cheap.

 

Now, will an 84 air cleaner housing for my 85 KC 4x4 manual trans Hitachi carb? There's one on eBay with little details, so not sure if it will fit.

 

http://www.ebay.com/itm/1984-Nissan-Air-Intake-Carb-Breather-Housing-Assembly-720-Truck-Filter-/222550613519?hash=item33d10cde0f:g:cp0AAOSwSlBYxBkI&vxp=mtr

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Family run business is only relevant if someone working there is over 45 and was a mechanic when there were carburetors still. The 720 did not have an air pump so they don't seem to know this. The AIS is a totally passive system using exhaust pulses to draw in air for the catalytic converter. It's a totally passive system using exhaust pulses to draw in fresh air.

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Depends. Already failed because no 'air pump' which I think reads 'missing AIS'. So a new Weber isn't going to fix this and it's still going to have to pass emissions equal to the ECC (feedback) carb and all it's emissions gear on it.

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Depends. Already failed because no 'air pump' which I think reads 'missing AIS'. So a new Weber isn't going to fix this and it's still going to have to pass emissions equal to the ECC (feedback) carb and all it's emissions gear on it.

 

Yep, this.

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It could be tuned lean enough to pass. Air pump ain't stopping it from passing unless strictly visual.

 

Tune it lean. Advance the dizzy to keep it running. Go through test hot. Set back to "stock" with pass slip in hand.

 

It is failing because isn't isn't seen visually. The shop talked to the president of the air board, and the only way they'd pass it is with the stock carb.

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Keep in mind, this is a vehicle from 1985 with unknown maintenance (although it appears well taken care of) with 175,000 miles on it. For all I know, rings are on their way out and blowing oil into the exhaust. Not sure it's worth the risk to throw a weber on it, have it not pass, be out $350 and my time to install it. I'd rather just get it over with. I basically only use this truck to teach my wife to drive a manual, haul dirt bikes and mountain bikes to and from trails, pick up furniture, and transport dogs to and from the vet. I don't care about how much power it has.

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Good news. The shop installed a remanufactured Hitachi carb and it passed the emissions retest. Bad news, some air port on it was broken and they need to replace it, but it passed! Who would have thought a 1985 720 that probably has changed hands multiples times with 176,000 miles would pass?

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