85 720 electric choke

[Shaun]

85 Nissan 720 and I have a 6 wire plug California carb. My choke valve is not opening all the way so my fast idle cam is not swinging out the way either. Is there a way to test with a multimeter if so how. From what I read in the book says to bend the linkage but I’m not sure which one to bend

[datzenmike]

 

 

 

 

Automatic choke heater is a BLUE wire (Nissan uses an L because B is black and already used)

 

Check that it has 12 v when engine running. Engine HAS to be running.

 

It's a common problem with the 72's0 6 wire plug for the wires to break inside the insulation so you may have 12 v on the harness but not at the heater itself, so check and expect this. Let me know if you do have 12 v on the heater itself..

[Shaun]

Thank you for the help I’ll let ya know what I find

[Shaun]

Hey datzenmike so I checked voltage for my choke heater while running and I’m not getting any voltage I also noticed bottom of carb turning white so I checked that plug and I’m not getting any voltage there either and when my truck is running and I unplug 6 pin connector the engine dies but if I leave it unplugged it’ll start back up and run 

[datzenmike]

Well the relay for the choke needs a charging alternator to work properly. Often the 720 alternator has been replaced or the original alternator is not 100% and the relay can't work properly. What I have done before is to connect the Blue choke wire on the carb to the Red idle cut solenoid beside it and just forget the relay. This is another switched source of power.

 

Bottom of carb turning white??? Is this frost? in cold weather? This means that the ATC (air temperature control) system isn't working. The ATC consists of a sheet metal shield on the side of the hot exhaust, a 'stove pipe' to conduct heated air up to the air filter snorkel. In the end of the snorkel is a vacuum operated servo that pulls a flap open to allow exhaust warmed air into the carburetor.  This vacuum signal is regulated by a thermostat inside the air filter housing. It mixes cold outside air with heated air and keeps it at a constant 100F.

 

See if the 'stove pipe' is missing or the vacuum line to the intake is plugged or missing. Warming the air when it's cold out will make it run and idle better during warm up and after and will stop carb icing. The frost is caused by the additional cooling of the intake air by the evaporation of the gas mixture. If near freezing this cooling effect can drop the carb base well below freezing and moisture in the air inside and outside will collect on it just like the inside of your freezer.  

[Shaun]

Well that explains it then because last week my battery light came on and I can hear the relay buzzing every so often I put a meter on battery and with truck off I got 12.6 volts running I got 18.4 volts that’s way to high

[Shaun]

Oh and I am missing that stove pipe peice that hooks from air cleaner to manifold. But isn’t there a heater on bottom of carb that heats the fuel 

[datzenmike]

I think you can probably buy that 'stove pipe' by the foot. Too big a diameter you can hose clamp it on.

 

Yes, some later years had a heated screen under the primary barrel. For instant heating as the exhaust does take a couple of minutes to warm up. 

 

56 minutes ago, Shaun said:

Well that explains it then because last week my battery light came on and I can hear the relay buzzing every so often I put a meter on battery and with truck off I got 12.6 volts running I got 18.4 volts that’s way to high

 

18 v is not good for electronics or for the battery. You'll just cook it.

[Shaun]

WOW!!! #amazed  I have been a industrial maintenance technician for 10years and I’m a firm believer in the saying u learn something new everyday and in this case I most certainly did. Anyway I put a new alternator on my 720 and ran like a dream choke started working like it’s supposed too idles and runs great now. Thank u so much for all the help.this forum is the best forum I’ve ever been on

[datzenmike]

Well stick around.