Z24 Carb Choke Issue

[Benannah]

Hey all, I recently noticed my truck running a little bit differently lately and noticed that the choke isnt opening all the way when warm. For the past few months I noticed that my engine would sometimes run a little weird - sometimes idling high until I tap the gas or occationally going on fits of idling at 2000 rpm or higher for a day only to work properly the next day.

 

The past few days though the problems have been getting a little worse. Often when I turn off the truck after it is warm it will continue sputtering and trying to run for maybe 5 more seconds than usual. Then today the engine was idling at 2000 rpm while warm and it would not drop down in rpm. Occationally when I would tap the gas, the engine would hesitate and sound like it wanted to stall for a second before reving it up. I looked at the choke and found that it does not open fully. Even when the truck is warmed up to proper operating temperature. See the attached video of the carburetor to see what it's like. I took the video when the engine was warmed up and also noticed that manually opening the choke seemed to have little effect on the idle speed.

 

Please let me know what any of you think the issue could be. It is still drivable, but really annoying and I'm sure its awful for gas milage. Thanks!

 

 

[datzenmike]

Choke heater would seem to not be working.

 

This thing...

 

 

Be sure it's plugged in.

It should have 12v on the wire to it, BUT only when engine is running.

 

 

Normally there is a relay that supplies this 12v but it is designed in such a way that it only does this if the engine is running.  Up to you, but you could run a +12 volt jumper from any switched source such as the idle cut solenoid to allow the heater to work any time the ignition is on.

[Benannah]

Thank you for the advice! I'll look into that when I get a chance. What do you think would be the most likely issue? Wiring? Relay? Choke Heater itself? Thanks again for the help! This forum has been a life saver!

[Benannah]

Also, I’m having a hard time finding the auto choke relay. Does anyone know where I might find that? Thanks!

[datzenmike]

It's up under the right side of the dash on the kick panel and above the fuel pump relay. Remember, it will only be ON when the engine is running. If it's buzzin, this usually indicates a problem with the alternator.g

 

Get a meter and check the choke heater wire (disconnected)on the carburetor with the engine running. If there's power then the relay isn't on... this doesn't mean the relay is bad. Possibly the alternator isn't charging properly.

[Benannah]

Alright, thanks for the tip! I’ll check it when the weather finally clears up here

[Benannah]

I was able to locate the relay, but have been unable to test much else as I do not have a multimeter right now, but I’ll track one down later. I’ve heard that if the relay would likely buzz if the alternator is the issue and I do not hear any buzz. However, I do not hear and click when I turn the car on either. Is there some way to temporarily bypass the relay to test if the relay is receiving power and the rest of the circuit works? If the relay is not receiving power, where would one even start with tracking that down? Thanks again for the help!

[datzenmike]

Even a test lamp will do to show power is getting to the choke heater.

 

#2 fuse, second over form the left side.

[Benannah]

Alright, I will check that. As for the relay, I noticed it has a small Philips head screw on the underside of it near the terminals. Does anyone know what this would do? Could this be an adjustment screw?

[datzenmike]

Screw??? Does not sound stock. Can you post a picture?

 

Relays connect things so either connected or not connected. There is no adjustment to partly connect something electrical.

 

They should look like these in black, brown, gray or blue. Choke heater should be Black. The actual heater fan relay is also Black so swap them see if the problem goes away. The heater relay is on top of the fuse box, second over from the far right side, just to the left of the headlight relay.

 

 

 

[Crashtd420]

12 hours ago, Benannah said:

Alright, I will check that. As for the relay, I noticed it has a small Philips head screw on the underside of it near the terminals. Does anyone know what this would do? Could this be an adjustment screw?

That sounds like a flasher relay to me...

Those are available with little screw to adjust the flash rate.

 

[Benannah]

https://www.bwdbrand.com/en/ecatalog?partdetail=R801

 

here is a link to a replacement relay for the auto choke and it has the same screw on it. Could not find the data sheet for it…

 

I also tested the relay and it it does appear to work properly. I will do the test that Datsunmike recommended when I get off class. Is it possible that the relay isn’t receiving any power? Loose wire maybe?

Edited November 6, 2024 by Benannah
Fixed link

[Benannah]

I did try to swap the relays as mike recommended, but they were unable to swap as the center pin would not allow them to fit into the others socket

[Benannah]

Relay Diagram

 

here is a diagram of the relay according to my repair manual - it appears to work exactly as pictured.

[Crashtd420]

That screw looks like it just holding that bottom plate on.... 

Does look to be the correct relay....

 

 

[Crashtd420]

40 minutes ago, Benannah said:

Relay Diagram

 

here is a diagram of the relay according to my repair manual - it appears to work exactly as pictured.

 

[Benannah]

That is the correct relay. Screw could just be holding it together, but I couldn’t find a way to disassemble it. Regardless it seems to be working properly. Going to test the truck now 🤷‍♂️

[datzenmike]

I guess some have a screw in it. I don't ever remember seeing one or I would have tried taking apart from curiosity. All of the ones I had were sealed or glued together.

 

[Benannah]

https://drive.google.com/file/d/1V6z-atCn03W0ncUAsojkoNj4Ks-ZHOoF/view?usp=drivesdk
 

I tested the voltage across the two pins by my thumb and was only getting 9.5v. This was consistent whether the relay was connected or not. Those pins are connected to the auto choke heater. Where do I go from here?

[Benannah]

Apologies for the confusion, those were not the wires I needed. I found the power wire being sent to the choke heater (from the relay) and it is indeed receiving 14v when the engine is running. The relay is not switching off this power. When checking the leads to the relay I found that the voltage across the relay coil is only .5v but this makes sense to me since they are wires from the ignition and from the alternator. Adding more confusion, removing the relay does shut off power to the choke heater, but does not open the choke? I’m sorry this is taking so long, but I’m just utterly confused…

[Benannah]

I can hear/feel the relay click when I turn the ignition on, but the second the engine starts, it shuts back off again…

[datzenmike]

If there is power to the choke heater on the carburetor, then it's simply not working and needs replacing.

 

Below... Behind that spring is a heater coil. If you remove and wire to 12v and a ground it should get very hot to the touch if working. 

 

[Benannah]

Good to know, I will take a look at that. As a little bit of a test to see if it will work, I checked the resistance as described in the manual pictured below and initially read 80 ohms, but every time I would read a different resistance ranging from 13 ohms to a couple hundred ohms. Now I’m consistently measuring upwards of a mega ohm. Sounds like the coil may be bad, but I will disassemble to confirm when able.

 

If it is the case that the coil you mention is bad, what would be the course of action you recommend?

 

As a side note, I’m still a little confused about if the choke heater is supposed to receive power when the truck is running. You said that it’s not supposed to, but the manual seems to make it sound like it is supposed to? Sorry, I’m a little new to working with carburetors and am a little confused.

 

Repair Manual Photo

[datzenmike]

As I see it this is most useful in very cold weather. You co out on a cold morning and start your truck, then go back in to finish you coffee or whatever. Unknown to you the engine stalls but without the relay, the choke heater continues to heat the choke and turn it off. You come out and try to restart a stone cold engine without a choke. If you have ever tried this in freezing weather you know what a bitch this can be, and if you get it going you have to remain there and keep it running.

 

The choke relay senses if the engine is not running and turns the choke heater off.

[Benannah]

Alright, thank you for the tip! I will see what I can do and let you all know the result!