E.C.C Control Unit - correct behavior - inspection lamp

[spddm0n]

I'm doing some carb/fuel mixture diagnosis on my 720 and ran into an explanation in the FSM about the behavior of the inspection lamp on the ECC (ECU) under the driver seat when performing this diagnosis.  It says the lamp should light 4 times in 10 seconds, while doing this test.  My light doesn't blink at all, except to light up and stay on then I first tern on the key to ON.  

 

Does anyone know what the correct behavior is on the inspection lamp, that I could check to ensure the ECC is working correctly?  Does it "store" error codes or the like - like an OBDI ECU?

 

 

 

Thanks!

[datzenmike]

The Z24i with throttle body injection stores error codes that can be retrieved. The procedure is in the manual. The ECC (electronic control carb, I'm not sure) Do you have the 

'85 FSM?

[spddm0n]

Hey Mike -

 

I have the Z24(S) carbureted model with the Hitachi carb with electronic feedback.

 

I’m not sure how to tell if my ECC is working correctly, based on the behavior. I do have the ‘85 FSM, but it doesn't describe the procedure to check it (that I can find), except for the page shown in the images above.

 

 

Edited June 21, 2019 by spddm0n
Clarity

[spddm0n]

Hey Mike - 

 

Thanks for the above reply.  I edited that reply just now, because it didn't make sense.  I didn't realize who had replied, and I included a lot of info that you would have already known, so I was repeating myself. 😉

 

I didn't know what E.E.C. was an acronym for either.  Ironically, the FSM uses a lot of acronyms, many which are not spelled out in full meaning. 🙂  I find it odd it is considered a Carb Control module.  There are a variety of other switches and sensors that would have nothing to do with the carb (I would think).  Such as...the clutch switch.  Ironically, I did pull out the clutch switch (as it seemed to not be working correctly), and the engine began to stumble.  ??  

 

I'm still searching for a way to test the ECC.  Perhaps, I'll simply remove it and see if the engine will run.

[sTanTruck]

Hey @spddm0n Did you ever end up figuring out how to test the ECC module? I am in a similar boat currently and trying to work through this issue. 

Thanks

[Sephakrid]

I really need to start going to bed at more reasonable times instead of posting at 3AM!

 

Anyway, this is a page from a 1984 FSM that I found to be pretty helpful. It provides an overview of all the inputs that affect whether the solenoid is active.

 

 

The '86 FSM also has some more tests for the E.C.C. control unit:

 

 

Hopefully this helps! The system predates OBDI I believe, and it doesn't seem to store any information.

[datzenmike]

The Z24i in the later D1 Hardbody can store error codes. The Z24i in the April '85 and on 720 might also, I don't now. There is a procedure for extracting the codes.

 

The ECC carburetor used on all California emissions trucks does not. As shown above there are test procedures to check the wiring continuity and some limited function and this can point to a failed part but the proof is in replacing it. Without storing codes, an intermittent problem or one only while driving goes unknown. 

 

The ECC carburetor uses a solenoid primary jet. The solenoid pulses on and off many times a second tailoring the mixture with feedback from the O₂ sensor  to keep the mixture close to stochiometric for excellent emissions and economy. It's not in closed loop mode during warm up or at full throttle. This is the cross over from true carburetor to EFI.