Auto choke test help

[dom14]

Hi Guys,

Vehicle is an RB30 Patrol, carby model.

I've been trying to find out how to test the auto choke bimetal piece.

I performed following tests on it.

1)I applied +12V to blue wire and -12V to the end bit of the bimetal spring for few minutes.
No movement of the bimetal spring

2)I checked the continuity of the heater circuit with a multimeter.
It shows as open circuit. No resistance reading of any kind.

3)I checked the power to the blue wire from the socket at the vehicle end, there's no power to the blue wire, even when ignition on. I'm not sure whether the power to the blue wire is activated via a tachometric relay.
As the carby is out now, I can't test that(or may be I can by cranking the engine?!). But, somehow, I doubt the power to the auto choke is activated via a tachometric relay.

Any help/guide will be appreciated as I'm a fair bit lost atm. :)

Cheers
Dom

[garett]

i know this isn't checking the choke but can you remove the choke butterfly and test it on the car ?? you might need to hold the throttle open with your foot until it warms a bit but if you still have issues its not your choke ...

[dom14]

i know this isn't checking the choke but can you remove the choke butterfly and test it on the car ?? you might need to hold the throttle open with your foot until it warms a bit but if you still have issues its not your choke ...

Hi mate,
I didn't quite understand it. Did you mean to take the choke butterfly out and put the carby back on and start the engine?
I reckon it's possible to start without the choke, even though I might have to crank it for a while.

Does this above No: 3 scenario make any sense to you??!!
How come the choke wire not get any power at all when ignition's on?

[garett]

i have disconnected my choke i just use the heater in mine (different carby) works like a diesel's glow pulgs only it heats the throat of the carby. then pump the throttle a couple times hold it open a bit and she fires up pretty much straight away ... when its cold i gotta hold the throttle open for a min or two to keep in running but i dont mind this.

yeah take off the butterfly and start the car or just make sure it cant close.

[dom14]

Ok, cool. Yeah, i can do it without having to take the butterfly out. I simply have to remove the choke bimetal spring disk assembly and fully open the choke manually and leave it at that setting. I can use a piece of string or something to make sure it stays that way.
I've considered a manual choke setup for a while, am still considering it.
First I would have to understand how the existing choke system works.

For example I'm bit puzzled at the above test results and I have to figure out why.

Either the tests show a failing electrical and mechanical issues of the choke circuit

or

I don't have a clue about how the auto choke works in this carby, from electrical point of view.

I'm looking into the electrical diagram of the RB30 Patrol now, and see if it can shed some light on this issue.

[dom14]

I found out there's an auto choke relay. So, I did few tests on it. It has five pins and the pin No-5 is not connected to anything.
Pin 1 & 2 are the supply lines. Pin 3 & 4(as well as pin 5) are the switch lines.
However, only 1, 2, 3 and 4 are used. Pin 3 & 4 are always connected and when pin 1 & 2 get powered, pin 3 & 4 get disconnected.
I have no idea how this helps to activate the auto choke bimetal heater.
Also, pin 1 & 2 only gets 9.6 V, not 12V. That also puzzles me.

[dom14]

Auto chokes(on both carbys) are fubar, according to the tests that I've done so far. They fail all the electric tests that I've done so far.
Looks like the auto choke hasn't been working for a while and has been a part contributor to the problems with the carby.

I'm currently looking into see whether I can open up the sealed auto choke heat unit and replace a heat element with a compatible unit or whether I should hook up a manual choke setup with a cable.

[dom14]

This is the link to the auto choke repair thread.

http://www.nissanpatrol.com.au/forums/showthread.php?35187-RB30-Patrol-auto-choke-repair&p=633467#post633467