Transistor Module swap *PLS HELP*

[Halo8u]

The car will idle low, only if the dizzy is turned all the way counterclockwise. Unsure if that's advanced or retarded. It will idle around 1k to 1100RPM. But I get a very low vacuum reading that way, and the car stumbles. If it's around the middle of the adjustment area, it idles for a moment, then dies. When I get home I will run a voltage check.

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[Halo8u]

Another clue, the tach drops first and then the engine dies. Immediately after. So now I'm almost 100% sure it's something to do with the ignition system, i.e. a swapped wire or a poor ground. What all is involved with adjusting the air gap?

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[Zed Head]

4 hours ago, Halo8u said:

The car will idle low, only if the dizzy is turned all the way counterclockwise. Unsure if that's advanced or retarded. It will idle around 1k to 1100RPM. But I get a very low vacuum reading that way, and the car stumbles. If it's around the middle of the adjustment area, it idles for a moment, then dies. When I get home I will run a voltage check.

Swap the wires at the G and W terminals on the HEI module.  

The air gap procedure is shown in the Engine Electrical chapter.

[Halo8u]

So I rewired all of my ignition system. Confirmed 12v at coil. But my leads coming off my dizzy are getting 1.3V in the "On" position. Pretty certain my wiring is correct, could I have burnt out my hei module when I rewired it? Not sure what's going on

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[Halo8u]

Additional note** old wires were pretty crusty, that's my reason for rewiring it. And to tidy up my engine bay too. Air gap looked in spec

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[Zed Head]

Not sure what to recommend here.  I've offered ideas but then you do something else instead.  Did you swap G and W?  Not clear what the problem is now.  Is it still the idle problem or is it something new?  Why do you think the HEI module might be burnt out?  Does it not work at all now?

The distributor leads don't have a possible power supply unless they're connected the the G and W terminals.  Try touching your meter leads together and see what voltage reading you get.  Maybe you have a meter problem. 

Might want to just resummarize your situation.

[Halo8u]

Let me break down what happened.
-attempted to swap wires on 'G' and 'W'
-depinned my 'G' lead when pulling it
-rewired it, car did the same thing even when switched.
-tested my positive lead coming from my harness to my unit, turned out I was getting a fluctuating voltage, and it would cut out after a few seconds.
-decided to clean up my old crusty wires and rewire everything
-ran a new 12v to my unit, confirmed 12v
-now I'm at a loss
So im not sure what the coil and ballast resistor are supposed to read, but I'm getting 12v on both posts of my ignition coil, and 12v on my + and - on my ballast resistor. I could be wrong, probably am, but naturally I would think I would have 0v on my - lead on my coil, and my ballast resistor. Lack of knowledge and from so much digging has me at a loss.


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[Zed Head]

When the engine is not running you'll get the same voltage on both sides of the coil.  So that's correct.  

Seems like your ignition system might be okay and you have some other problem.  There are a variety of possibilities.  I went back through the thread and you have made progress.  You have spark and it does run.  But, I see that you have an E88 head, which means that you have carbs.  So, that's a whole new twist for a 75 280Z.  Do you know what type of fuel pump you're using?  Electric or mechanical?  Have you measured fuel pressure?  What shape are the carbs in?

Maybe start a new thread about carbs.  People with carbs and Pertronix on a 240Z might not even look at this thread.  But they'd have the answers.

 

[Halo8u]

Fuel pump is electric in working order. I have it wired manually to a switch. I have an Edelbrock 5-7psi 38gph pump running to a holley 4 barrel 390cfm carb. Fuel and air seems not to be the issue as it was running great aside from spark cutting out (I have dialed in the carb as well). The ignition system is almost completely isolated from the cars harness aside from a few wires (tach, and a few grounds). That's the reason I'm thinking it's the ignition module itself. It had spark before, now it doesnt after the rewire.

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[Zed Head]

On 4/12/2018 at 4:35 AM, Halo8u said:

Update: life always finds a way to get in the way of the Z. I was finally able to get to Z to run. First time in 20+ years. The gm hei unit works great. However I'm not getting anything to the tach. I've looked at the wiring diagrams, and seem to have it hooked up correctly. Did anyone else have this issue when doing the gm hei swap? Thanks in advance.

Alright, so I've gone back to a known good spot, above.  As I understand it, you eventually hooked up the blue wire and it started working.  Maybe it's that temp sensor?  Who knows.

"Welp, I'm a dummy. I didn't have the blue wire hooked to the coil. It works great now. Perfect response. Now just to figure out this temp sensor. I bought a new one today. Hope it works."

Then, some things happened.

"Hey guys, so I'm back with more issues haha. So I've been wrenching on the Z for months. It's getting really close to driving condition. I'm just running into another spark issue now. The car cranks, runs, and is quite rev happy when the carb is dialed in. But I seem to have an issue where the car will start, then die maybe 3 seconds of running if the idle is anything under 1500RPM. After I tried all sorts of carb tuning, and idle adjustments, it still wont idle correctly. I pulled a plug wire and did a spark check. Very strong spark, but after a few seconds of running, it stops sparking, and dies."

So, maybe the HEI module did get damaged.  It's hard to say.  You sound confident that you're losing spark, causing the engine to die.  You might make sure that the module itself is not losing power.  Put your meter on the B terminal of the module and see if it is getting lost before it does.  It will show low current, like 10 volts, while the engine is running, but should jump to 12 when the engine dies, if it's not losing power.

One other possibility is the pickup coil in the distributor.  They have been known to have wiring problems.  One odd one is that the vacuum advance moving the breaker plate causes the wires to shor out.  Maybe disconnect your vacuum advance to be sure.  Measure resistance of the red and green distributor wires also, not voltage.  Should be about 720 ohms, per FSM.

Sorry.  Thought you had it back there in March.

Edited August 16, 2018 by Zed Head
pickup coil resistance

[Halo8u]

Well now I can't get any spark to start it and check haha. And yeah, I thought it was good in March too. Weird thing is that it idled fine back then too. Idling at 800-900 perfect. It just started doing this weird spark drop thing recently, and I haven't messed with any wiring. Kinda pointing towards a faulty piece of equipment rather than a wiring issue. Either dizzy or the ign module. Also, the dizzy is reading 720ohms.... that doesn't sound right compared to 250 .... dizzy could be done for

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[Halo8u]

I'm getting full 12v from the coil to the dizzy cap. So the coil is fine, so my issue is now leading me to a distributor issue, maybe.

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