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Halo8u

Transistor Module swap *PLS HELP*

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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.

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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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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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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.

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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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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.

 

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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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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 by Zed Head
pickup coil resistance

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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 LOL.... dizzy could be done for

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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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6 minutes ago, Halo8u said:

 Also, the dizzy is reading 720ohms.... that doesn't sound right compared to 250 LOL.... dizzy could be done for
 

720 is right. I edited my post.

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6 minutes ago, Halo8u said:

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.
 

If you really are getting 12 volts to the center electrode of the cap that would be a sign of a bad coil.  Shorted internally.  Might be your problem, it would probably get worse as the short caused heat.  The distributor cap only sees voltage when spark happens.  It will never see battery voltage.

You might have found it.

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Could be, I put my multimeter in the wire coming out of the coil that goes into the dizzy and have constant 12v from that

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The common test for a short is to measure resistance from one of the terminals, + or -,  to the center terminal.  It should be in the thousands of ohms of resistance.  Like 10,000 ohms.

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I realized after I posted that the center post does see voltage.  Just across very high resistance.  So the 12 volts wasn't wrong, but it was the wrong test.

Your numbers don't look terrible but they might be a sign of a problem that gets worse with heat.  They're not quite right.  Where did you get your specs?  0.2 ohms is very low, even for a GM HEI module.  Spec. is 0.6.  That would create extra heat.

The HEI module does put more work on the coil.  If you have a spare coil it would be worth a swap.  It's not uncommon for coils to fail when they get hot, then work when they cool off.  Ignition modules do the same.

Edited by Zed Head

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Got my specs from MSD's website. Blaster 2 coil is .7ohm primary and 4.5k secondary. I dont even know what primary and secondary means in this application honestly.

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Primary is resistance to voltage passing through the coil and module.  0.2 is low and will cause the module and coil both to get hot.  Heat can cause problems.  If you're sure of that 0.2 number I'd get a new coil.  I would not run that with my parts, and I run some weird stuff some times.

You might even be able to feel the heat buildup by touch while the engine is running.  Put a finger on the module and see if it hurts.

Edited by Zed Head

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Gotcha. And my module is kinda funky looking, discolored in the middle, I would guess heat. But, I need a better heatsink and mounting surface anyways. I'm going to get a new coil and ign module with a heatsink. This setup has seen hell from trying to revive the car. With crappy wiring too. Now that I have new wires, itd be good to start with all fresh parts. I'll order the parts tomorrow and update you when they've arrived and I install them.

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Also my test was from + to - on the coil which I got .2ohms, second test was from + or - (I tried both) to the center. Which I got 5.4kohms. Just to clarify how i reached those numbers.

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Your test procedure is correct.  Discolored module is a sign of overheating.  I think that the manufacturers actually include that in their instructions.  Since it runs now, and ran well before, I'm guessing you'll see good results with new parts.

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Hope so, I hate spending money, but god do I love ordering car parts haha. I'll update you soon. Any recommendation on a specific hei module? I wish I wouldn't have accidentally broken the coil that was originally in the car. It was an old school Mallory.

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The fancy named modules, like Accel and Pertronix, just pass more current and create more heat.  Better spark at 7000 RPM, but if you're not going to be there it's a waste.  I like the decent name brands from the parts stores.  I have a BWD from OReilly Auto right now.  Get on Rockauto and pick a Standard or BWD.  You'll save some money and get a part that will work fine with a 0.7 primary circuit coil. 

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***Update***
Hooked up the new ignition components, car has great spark, and runs. I'm going to also swap out the gas for a higher octane and give an in depth analysis on how it runs with the new components. All in all, I have spark back, and I'm a happy camper :) a few more notes: I went with an 'Accel' ICM, on an ACDelco heatsink and a MSD blaster 2 ign coil. Also used 10g wire for everything.

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