McFerg Posted August 31, 2020 Report Share Posted August 31, 2020 Hi y’all. I rebuilt my ‘86 720 carb then found that it’s’ choke connecting rod was busted. I ordered a cheap $75 carb from Amazon to pilfer the connecting rod from it, but found that the carb is different from mine. My trucks carb has a vacuum nipple on the fuel Reservoir side that the new one did not. I was watching a YouTube rebuild by JNH Classics and noticed that his carb matches the Amazon Purchase. Did the previous owner put in a different carb? If so where would the Vaccuum hose go that connected to the carb nipple? Is this nipple exclusive to my ‘86 720? It does have AC. Is that the difference? Here is a link to a pic of my carb and the Amazon carb to see the difference https://www.amazon.com/photos/shared/yPDi7ANjRdal8bPW71eHpw.uC24BIU0ccYC31PDC5FWrX here is the Pic of the two differences between the choke connectors. https://www.amazon.com/photos/shared/JeMEcWtMTdCyu1x-_9WcSA.EmN8Bmd6opTqKee499Z9w_ thanks for the help. 2 Quote Link to comment
datzenmike Posted August 31, 2020 Report Share Posted August 31, 2020 Yours is a California specific carburetor. It's not a vacuum line but a vent from the float chamber and any escaping fumes are directed to the charcoal canister over on the distributor side and stored there. Next time the engine starts the stored canister fumes from the carburetor and gas tank are purged into the intake and burned. You'll have to point to the choke part, I can't see the difference. 1 Quote Link to comment
McFerg Posted August 31, 2020 Author Report Share Posted August 31, 2020 thank you Mike. So most any carb at My CA “pick and Pull“ should be the same. Good to know. I will head down to one when I get some time. here’s the circled pic of the different choke top. It may not be a big deal. https://www.amazon.com/photos/shared/jttVTS7tQiqiyopzoU2aBA.lBfF-ZOfF7aKoPoLBIErm6 1 Quote Link to comment
Charlie69 Posted August 31, 2020 Report Share Posted August 31, 2020 Your 86 720 Has a feed back Carb and you will be looking for 85/86 720 carb. Mike might know if any other Nissans used the feed back carb. It has a 6 wire plug on it, the 81 to 84 has a 2 wire plug and are not feed back carbs. 1 Quote Link to comment
datzenmike Posted August 31, 2020 Report Share Posted August 31, 2020 ECC (electronically controlled carburetor) or feedback carbs were used in California and maybe Nevada as they were lower emission. 1 1 Quote Link to comment
Charlie69 Posted September 1, 2020 Report Share Posted September 1, 2020 My 86 is from Salt Lake city Utah and it is California emissions. My 85 720 ST was California emissions. From my understanding if the Datsun/Nissan came to the country through a California port it has California Emissions. Quote Link to comment
datzenmike Posted September 1, 2020 Report Share Posted September 1, 2020 Makes sense if sold in California but Utah doesn't have a port. lol 1 Quote Link to comment
Charlie69 Posted September 25, 2020 Report Share Posted September 25, 2020 Hense the Cal port! LOL Quote Link to comment
mtkingcab3 Posted November 10, 2020 Report Share Posted November 10, 2020 I'm working on replacing the carb on my '86 720 KingCab and have ordered probably the same amazon carb that @McFerg ordered so I thought I'd continue my carb question in this forum - let me know if there is a better place. The serial number on my old carb is 2KT60-47 but I have not been able to find the same carb online. The one I bought is serial number 2KT60-55 and looks like it is the same size and fit, but with some differences. My main issue is the wiring harness plugs are different - the new is oval, while the old is round. My questions are 1) any thoughts on what to do about the wiring harness and 2) any pro tips or things I should be aware of while putting this new carb in? My old carb is a California carb like McFergs so the conversation above was really useful to understand some of the differences. Wiring: See old round plug and oval new plug: https://photos.app.goo.gl/y5qw72VRWnyGN3Pp9 Thanks for any thoughts. My truck - https://photos.app.goo.gl/GQPRSgVHs5qyya4q8 1 Quote Link to comment
datzenmike Posted November 11, 2020 Report Share Posted November 11, 2020 All California carbs are ECC electronic control carburetors. AKA a feedback carb. It will have 6 wires to connect. There's no way that 2 wire will work. Well to be fair you could connect the red and blue wires and it will run but would never pass emissions. Your carb has a solenoid in the primary jet that vibrates opens and closed as needed by the small computer under the driver's seat with feedback from the O2 sensor (and others) in the exhaust to keep the air fuel ratio at optimum. What's wrong with it? The stock carb is known to have wires break at the plug. When there is a failure in the system it defaults to a limp home mode of extra rich. The symptoms are very poor mileage and performance. 1 Quote Link to comment
mtkingcab3 Posted November 11, 2020 Report Share Posted November 11, 2020 Thanks for the quick response Mike. Don't necessarily need it to pass emissions as I'm not in California anymore (in Montana now). Summary of issue: The truck would warm up in high idle as normal but once it was warm and the high idle stopped, the truck would idle itself down until it quit running. I can fire it right back up again with no issues, but won't stay running without giving it a little gas. Figured it was a vacuum leak, so had a look at the carb and found this hole in (what I am pretty sure is - but please correct me if I am wrong) the choke housing and assumed that was the source of the leak - hence the replacement. Photo of broken housing - https://photos.app.goo.gl/DNCbAXakVxWnjah69 1 Quote Link to comment
datzenmike Posted November 11, 2020 Report Share Posted November 11, 2020 Yup the choke cover, but this won't affect it if broken. With engine off have someone turn ignition on off on off but not start, while you listen near rear of carb. What you should hear is a soft clicking noise coming from the carb. Does it? 1 Quote Link to comment
mtkingcab3 Posted November 11, 2020 Report Share Posted November 11, 2020 Just tried - didn't hear anything sounds coming from the carb. Only heard the fuel pump 1 Quote Link to comment
datzenmike Posted November 11, 2020 Report Share Posted November 11, 2020 OK what you should here is the idle cut solenoid AKA ANTI DIESELING SOLENOID opening in the ON position to allow fuel down into the idle circuit. No solenoid, no fuel... no idle. Try wiggling the wires to the connector as they can break inside the insulation. Pull the round plug apart and test for 12v on the Red/Yellow wire on the harness side of the plug with the key in the ON position. If no voltage check the 15 amp fuse, second fuse in from the left side. If voltage is there plug back in and see is there is power on the Red wire on the carburetor side. See what you get 1 Quote Link to comment
mtkingcab3 Posted November 12, 2020 Report Share Posted November 12, 2020 Hi Mike, thanks for getting back to me. I had a chance to test the plugs today, and I have 11.55v on the harness side (R/Y wire) and 0v on the carburator side (Red wire). All fuses are intact. Any suggestions? Thanks! Taylor 1 Quote Link to comment
datzenmike Posted November 12, 2020 Report Share Posted November 12, 2020 These ECC carbs are known for problems with the plug. Nissan saved 1/2 a cent buy using wires that were too short so any time the plug is un coupled it pulls on them and they can break inside. Look at the pins on both sides of the plug are the damaged? Look on the carburetor side... is the wire broken off the back side of the pin connector? 1 Quote Link to comment
mtkingcab3 Posted November 12, 2020 Report Share Posted November 12, 2020 Hi Mike, Just had a look - all pins are in place and feel solid. No broken or cracked wires between the plug and the carb. -Taylor 1 Quote Link to comment
datzenmike Posted November 12, 2020 Report Share Posted November 12, 2020 But you did say power on one side and not on the other. 1 Quote Link to comment
mtkingcab3 Posted November 12, 2020 Report Share Posted November 12, 2020 Yep - read 12v on the harness side plug (female end) and didn't pick up any readings on the carb side plug (male end)... not sure what that means 1 Quote Link to comment
datzenmike Posted November 12, 2020 Report Share Posted November 12, 2020 It means that power is not going through the plug to the other side where it certainly should be. This should be an easy fix. 1 Quote Link to comment
mtkingcab3 Posted November 13, 2020 Report Share Posted November 13, 2020 Sounds like I'll rewire the new carb to fit the old harness but without the emission control wiring. Looking at the 6 wire schematic above, and seeing the new carb has 2 wires (a blue and a red wire) it looks like those are the two wires to focus on from the old wiring system. I think I have a decent idea of whats needed - we'll see how it goes and let you know. Thanks again for the help flushing things out. 1 Quote Link to comment
datzenmike Posted November 13, 2020 Report Share Posted November 13, 2020 Red is the idle cut or anti dieseling solenoid. The Blue wire is for the electric choke. 2 Quote Link to comment
McFerg Posted July 13, 2021 Author Report Share Posted July 13, 2021 On 11/12/2020 at 5:50 PM, mtkingcab3 said: Sounds like I'll rewire the new carb to fit the old harness but without the emission control wiring. Looking at the 6 wire schematic above, and seeing the new carb has 2 wires (a blue and a red wire) it looks like those are the two wires to focus on from the old wiring system. I think I have a decent idea of whats needed - we'll see how it goes and let you know. Thanks again for the help flushing things out. Curious how this Carb has been working out for you? I ended up sending mine back but have now registered the truck in Idaho to avoid the Smog check. I Will need to change my stock carb as it seems to be in "Limp Home" Mode, so i figure I'll throw one of these on it or possibly put forth the $500 or so for a weber. Has the China carb been working well for you? 1 Quote Link to comment
Charlie69 Posted July 13, 2021 Report Share Posted July 13, 2021 China Weber knock offs have a 50% chance of working out of the box. Quote Link to comment
datzenmike Posted July 13, 2021 Report Share Posted July 13, 2021 Charlie you are such an optimist!!! Most would say a 50% chance of bad in the box. 1 Quote Link to comment
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