Fitting a HEI Module in Transistor Ignition Unit 1977 280Z

[HusseinHolland]

4 minutes ago, Captain Obvious said:

Well at this point, the next thing I would do is disable the idle controller system. Pull the low side vacuum hose off and plug both resulting holes. And if that doesn't have any effect, I would disconnect the wire from the coil as well and see if that does anything.

I'm not contesting that the system works fine at idle. I'm concerned that it's not working properly ABOVE idle. Breaking out into some sort of oscillation, or switching between it's different modes when it should not be. Something like that.

Again, just tossing out ideas in the hope that you get to the root of the problem.

Yes, good point. I will do that next, before messing with the fuel rails. I can just disable it entirely (after warming the engine) by unplugging the module. When the IACV is shut, minimal air can bypass, so plugging those shouldn't be necessary for testing the 2.5-3K rpm condition

[Captain Obvious]

2 minutes ago, HusseinHolland said:

 I can just disable it entirely (after warming the engine) by unplugging the module.

Agreed, assuming the valve is mechanically locked with the module unplugged. I don't know if it's a spring loaded vane valve inside or some sort of servo motor driven pintle. As long as the valve position is completely locked with the electronics disconnected, then this would be a good test.

[HusseinHolland]

OK - so here's the problem:

AFR's are way WAY to lean, even when stone cold, it started around 14 & went leaner from there. Normal op temp idle AFR's were 16.5-16.7 range.

I disconnected the CIS system, and predictably it made no difference. 

Regulated fuel pressure is steady @ 36psi, and gets higher as vacuum decreases (when revving the motor off idle). Unplugging each injector in turn, affects the running.

 I'm going to pull the rail & check for any restrictions.  

Edited October 10, 2023 by HusseinHolland

[Patcon]

These cars are known to lean out with age. It's why some people add a resistor pot between the temp sensor and the ECU. Set mixture with the turn of a dial.

@siteunseen

[HusseinHolland]

12 hours ago, Patcon said:

These cars are known to lean out with age. It's why some people add a resistor pot between the temp sensor and the ECU. Set mixture with the turn of a dial.

@siteunseen

I believe it, the issue is that the condition was not present prior to all the recent work, hence the need to revisit the fuel & ignition work I did.

I have not touched the AFM, except to rewire the connector, but that was back in the spring & I drove the car many times after that w/o issue. 

I'll consider making adjustments to the AFM clocking, but not until I've ruled out any issues I may have created.

[Zed Head]

17 hours ago, HusseinHolland said:

OK - so here's the problem:

AFR's are way WAY to lean, even when stone cold, it started around 14 & went leaner from there. Normal op temp idle AFR's were 16.5-16.7 range.

I'd check the coolant temperature sensor resistance.  Compare to the chart from previous.  Check at the ECU connector.

 

[HusseinHolland]

21 hours ago, Zed Head said:

I'd check the coolant temperature sensor resistance.  Compare to the chart from previous.  Check at the ECU connector.

Thanks Z - good idea. I'll do that tomorrow.

EDIT - I need to recheck the TPS setting as well - I had that off when I blocked off the BCDD. Need to verify idle/off idle switch point

I did remove the rails & hoses, blew out the lines. No sign of debris, but at least I've ruled that out. 

Also pulled the plugs & checked that. They're not old, and they look pretty even

The only other thing I'm wondering about, is the AFM - the cover is not fixed, and I've knocked it off several times. I'm wondering if I somehow messed up the sweep. Can't tell if it's actually making contact with the board. Does seem like a stretch, though.

EDIT - looking closely at this pic on the large screen at work, I can see two track marks on the circuit.

Edited October 11, 2023 by HusseinHolland

[siteunseen]

This probably has nothing to do with your current issue but I read the bcdd removal and wanted to ask if you plugged that little hole in the front of the throttle blade? 

 

[HusseinHolland]

 

On 10/11/2023 at 2:53 PM, siteunseen said:

This probably has nothing to do with your current issue but I read the bcdd removal and wanted to ask if you plugged that little hole in the front of the throttle blade? 

 

I did both openings 1/8" NPT & M5x1

Fixed the running issues!

https://youtu.be/pvHhBw-u9Ro

First I checked the ECT (cold, 70ºF) - 2160 ohms at the sensor

at the ECU : 2180 ohms

 

Normal OP temp 263 ohms. Values within normal range according to Datsun chart (thanks, ZedHead)

 

I could swap it out for a Volvo one - & make it (marginally) fatter when cold.... Might need to do that depending on how the cold starts are now.

 

Anyway, after that I went back to thinking about what could cause the hunting. I realized that when I did the TPS trigger signal, I didn't confirm that the relay I added had diode protection to prevent interference with the stock circuitry. I simply added a diode inline from the TPS to the relay to test the operation.

 

With that in place, the hunting at 2.5K went away. So that aspect was resolved (YAY!) (Thanks also to @Captain Obvious for questioning the off idle interaction . The system still runs lean though. I don't know if all the cleaning out of coking in the TB & clearing other passages has made it leaner. I certainly didn't feel the lean running condition before I started all the mods. I looked at the AFM adjustment, and that made no meaningful difference.

Manifold vacuum at idle is good.

Regulated Fuel pressure is good

 

While I cogitated on how to address this, I added the AC switch plate

 

 

and added carpet mat stays

 

So, I decided that instead of futzing with the AFM to try & tweak the AFR's 2 whole points richer, I decided to just raise the regulated pressure to 3bar - using a Volvo regulator of course  As you can see form the video above, that brought the AFR's right where they need to be.

new regulated fuel pressure under vacuum. Rises to 3bar with vacuum removed.

Having confirmed the pressure is consistent & vacuum works I installed a nylon feed line & quick connect in the intake. Old FPR location is bridged with new hose above it.

 

Bay

 

Now I know the system is fully operational, I will revise the return setup, it is overly long - didn't want to cut down the hose that had to connect to the rail return until I knew it would work.

With the fueling resolved, I'll switch the HEI module back & see if I can get that aspect resolved 

Edited October 14, 2023 by HusseinHolland

[HusseinHolland]

So, I shouldn't have declared it resolved. 😞

Started fine cold, but as the engine warmed, pretty quickly the AFR's climbed back into the 16 range, so it would seem possible that there is an issue with the ECT.

I tried plugging in a Volvo ECT, and with it pressed against the t/stat housing the AFR's were where I wanted them to be - 14.5-7 range at idle, so I swapped it out after the engine cooled. With it installed in the cooling system,  the AFR's went even leaner. I'll order a new ECT, just to safe. I'm going to have to investigate a thorough functional test of the AFM also.

[Zed Head]

How does it run?  The typical no-AFR-gauge sign of a lean mixture is bucking and popping back through the intake manifold at part throttle acceleration.  Don't get too focused on the numbers on the LED screen.

If you're certain it's lean you could try the resistance tuning for the temperature sensor, that was previously mentioned.  You can insert it in between the bullet connectors on the engine and let it hang for a quick test.

http://www.atlanticz.ca/zclub/techtips/tempsensorpot/index.html

 

[HusseinHolland]

1 hour ago, Zed Head said:

How does it run?  The typical no-AFR-gauge sign of a lean mixture is bucking and popping back through the intake manifold at part throttle acceleration.  Don't get too focused on the numbers on the LED screen.

If you're certain it's lean you could try the resistance tuning for the temperature sensor, that was previously mentioned.  You can insert it in between the bullet connectors on the engine and let it hang for a quick test.

http://www.atlanticz.ca/zclub/techtips/tempsensorpot/index.html

 

It's way too lean, you can feel the lean miss. To stop this HEI thread from going even further into left field, I started posting in the existing AFM / lean running thread.

Thank you for the link - I'll look at adding a POT - that seems like a practical way to make adjustments to the eng. temp ECU input