Z20s long crank/rough starting from cold issue

[DatsunD21]

Hi all, 

Coming to you guys from New Zealand, 
Hoping for some advice, long crank/rough start issues. 
 

Truck: 1986 Nissan Datsun D21 Navara, 2.0L, Z20s, 4x4. 

 

When I turn the key I have to give it full pedal to the floor while cranking otherwise it will die out immediately, if I keep the pedal to the floor then it will gulp and sputter to life (and rev super high because my foots on the floor), if I try reducing the gas in this first 30 odd seconds of starting her up it will just die out. After 30-60 seconds of full revs, I can let off the pedal completely and it idles just fine, and I can turn it off and start it again first pop no long crank, but only when it’s warmed up like that. 
 

what I think it might be: 

-I took the carb off recently when I had a fuel pump issue and I may not have adjusted everything right, I’m thinking maybe I messed up the choke? I certainly moved the idle mixture screw (or whatever the sharp screw with the spring around it is called) and I’m not sure I’ve adjusted it back right 
-The carb hasn’t had a clean for as long as I’ve had it

 

background info that might be useful: 

-it’s the stock hitachi carb 

-when I bought it a couple years ago it had a decently long crank from cold but never needed the pedal to the floor but it did have a smaller battery in it 380CCA or something like this 

-I previously reversed the polarity by mistake on the battery, this resulted in a problem with the indicator lights which I had to fix, and It also made the Fuel pump housing wires in the gas tank go bad and this was replaced with an external pump recently

-spark plugs, ignition wires and fuel filter all replaced recently 

-battery changed to larger 600cca 

 

 

 

 

[datzenmike]

Take the air filter housing off. Choke plate should be part closed after the engine sits all night and engine is dead cold. Watch while someone steps on the gas pedal and releases it. If working and set up right, the choke flap should snap fully closed and the fast idle cam should drop into position holding the throttle open slightly. See what you get.

 

At this point, (normally) with foot off the gas engine will start with a couple of turns. Idle will climb to 1,800-2,200 RPM on the fast idle. Normally.

 

In extreme cold days try stepping on the gas 2 or 3 times. This will squirt raw fuel in from the accelerator pump to richen the mixture.

 

 

Set/checking idle mixture on a fully warmed up engine... (assume the valves are adjusted and ignition timing is set)

 

Lower the idle as much as possible it makes small adjustments easier to notice.

Turn idle mix screw in (leaner) till the idle quality drops off.

Turn the other way out (richer) till it drops off.

There may be a half turn where there is no noticeable change. Set in the middle of this range.

Idle hopefully went higher, so reduce the idle speed and repeat the in and out looking for the best idle quality. 

This may take as many a 8 tries but when you can't improve the idle quality any farther and the idle speed is around 700 you're done.

[DatsunD21]

Thanks for that advice DatzenMike, I will try this out when I get a chance next

[DatsunD21]

It looks like the choke is working properly? I am unfamiliar with the fast idle cam. 

 

How does this look to you DatzenMike? 

[datzenmike]

That's the correct position when the engine is warmed up.

[DatsunD21]

Okay so if that was from cold and not running , should I have another look while trying to start it? 

[datzenmike]

When cold starting it should be like this...

 

and not this...

 

Is that flap free to move if you hold the throttle half open? Spray the linkages liberally with WD-40 and work everything back and forth on the back of the carburetor.

[DatsunD21]

Update: you were 100% right on the choke being the issue, I held it closed by hand and it started like a dream 

 

however, the mechanism that is supposed to keep the choke closed must have an issue, it’s just super limp, maybe when I removed the carb I messed with something in the system… I can’t seem to figure it out

 

Here is a video link as I dont see the old option to add video to the post, I have used a 3rd party website to host the video it might have an ad in it unfortunately let me know if its not working 

 

 

https://streamable.com/voihp9

 

 

[datzenmike]

Maybe you had the choke apart?

 

 

 

When taken apart and then put back, that J shape must engage the linkage inside the choke heater housing. You'll figure it out.

[DatsunD21]

Okay great I will try this, thank you for your help!

[datzenmike]

When properly engaged when you turn the black housing the choke will close or open. On a cold engine turn till the choke closes while holding the throttle part open to disengage the interlock. This will get you close. I leave the three screws just tight enough that you can turn it by hand. The choke is now set for whatever temperature it is now and will need to be turned richer as the weather gets colder.