HEI Upgrade not working on '78 280Z

[bullitt01]

The TIU on my bone stock'78 280Z bit the dust so I decided to replace it with a GM HEI unit. The one I got was new and from a '83 Buick Regal V6 in case anyone thinks it matters.

I took the 5-pin connector off the old TIU circuit board and wired the HEI unit to it so I could just plug it in the wiring harness like the old TIU. I wired the 4 pins and ground on the HEI to the appropriate pins on the old connector and confirmed I had good conductivity through the connector. When I plug it in the car won't start. It cranks but has no spark. The seatbelt buzzer doesn't even come on when you turn the key on.

Has anyone installed a HEI unit this way before? I checked that I had things wired to the right spots 100 times. All the HEI installations I've seen have been in the engine bay next to the cool. Will

It just not work the way I want to do it? I don't see why it shouldn't. Do I need a HEI unit from a specific car? Sorry for my ignorance. Thanks for the help.

[Zed Head]

First, you need to show us how you wired it.  Did you follow Eurodat's guide?  He installed his the way that you did.  It is possible.  But no guesses can be made without knowing exactly what you did.  At least make a list of the wire colors and where you attached them to the module.  

 

Second, have you confirmed that you have the basics, like power to the coil with the key On?

 

Third, did the seat belt buzzer work before?  If it did, you might have blown a fuse or a fusible link.  The seat belt buzzer shouldn't have anything at all to do with the ignition module.  So that might be a clue that you bumped or shorted something.

Edited November 3, 2015 by Zed Head

[bullitt01]

I did follow EuroDats guide, except the '78 has a 5-pin connector on the TIU instead of that individual wire thing the '77 has. The buzzer worked before. What I was trying to convey is that nothing works now. It's like the ignition isn't even being turned on. The fusible links are brand new. With the key on there is 12V at the positive side of the coil, but no spark when cranking. In case it helps, the car just shut off one day and hasn't started since. I decided it was the TIU via process of elimination, I could be wrong. When I get home tonight I will draw a diagram of exactly what I did.

[Zed Head]

 In case it helps, the car just shut off one day and hasn't started since. I decided it was the TIU via process of elimination, I could be wrong. 

I think that you might be wrong.  Some basic troubleshooting with a meter should find the answer.

 

Although, a sketch of the wiring would tell if the module should work.  Some of us have pondered the 280Z ignition systems far too deeply.

Edited November 3, 2015 by Zed Head

[EuroDat]

Can you post some photos of the mod you did? Photos can make the difference.

The 78 wiring is the same as the 77. They both use 5 of the 6 pins in the plug. The 78 uses hard pins instead of wire between the terminal block and the board. You need cut the hard pins and then solder the wiring to these hard pins. The base plate might be a little different.

There are some checks you should try before swapping too many parts.

1. Disconnect the plug at the TIU

2. Check the black wire is grounded.

3. With the ignition key ON, check for battery voltage at the Black/White striped wire.

4. Check the resistance across the red & green wies. Should be about 725ohms iirc.

5. Use the multi meter (analoge needle type works best) on low voltage setting (preferably lower than 5volt scale) and check for small voltage spikes across the red and green wires while cranking the engine. You should see 3 small voltages peaks per revolution.

6. Remove the HT lead from the distributor cap and connect it to a spare spark plug (or remove one from the engine).

a: Connect a jumper wire to the coil ( - ). Turn the key on and tap the junper wire rapidly on the car frame. You should see the spark plug sparking when you tap the wire. Be carefull for shocks from the coil.

b: You could also do this test through the blue wire and black ground wire at the TIU terminal block to check the blue wire works correctly.

7. Check coil resistance. It should be under 1.0 ohm across + & - terminals. Higher resistance can mess up the HEI unit.

If all these checks work out, then the HEI is not wired correctly of it is damaged. If you fry one, they sometimes come back to life, but not for long. So if you have any doubts about the module, I would change it.

Sucess

[Zed Head]

The buzzer worked before. What I was trying to convey is that nothing works now. It's like the ignition isn't even being turned on.

 

With the key on there is 12V at the positive side of the coil, but no spark when cranking

Just to draw out another detail.  Clarity on what exactly is happening will help a lot.  You've lost the buzzer and, apparently, some other things - "like the ignition isn't even being turned on".  But 12 volts at the coil only happens when the ignition is on, so that statement is a little unclear.  Also, you should measure both sides of the coil.  It will tell you if there's continuity through the coil circuit.  You should see battery voltage on both + and -.

 

Anyway, the answer's there somewhere.  Diagnose first, fix second.

[Zed Head]

And, since I'm here, before I sign off, might as well mention the distributor.  If you have power to the coil and the module is right, then you should get spark.  The distributor is connected directly to the module and will make it trigger if it's right.  There are several things to look at there, easy to do.

 

There are just so many small things that you could confirm are right, if you use the meter and work through the tests.  There's a flow chart in the FSM.  Super easy, and it's the only good "process of elimination" to use.

[bullitt01]

I did all the checks except #6 that EuroDat suggests. They all

checked out ok. I wired the HEI exactly the same as EuroDats diagram in his walkthrough.

I work 60 hours a week and have 2 children under the age of 3 so I don't exactly get much time to tinker with the car. Next chance I get I will do check #6 and I will clean all the grounds and see where that gets me.

[Zed Head]

You can get a new module for ~$20 at OReilly Auto.  They do go bad (I've had one), maybe that's why the Regal was in the yard .  If it doesn't fix the problem, at least you'll have a spare.

 

 

But do #6 first. It will test everything before the module.  And you don't need a spare spark plug (in case you don't have one handy), you can just place the metal end of the HT lead ( the center coil wire) close to a ground and look for spark.  Each time you tap the jumper from the coil (-) to ground you're doing exactly what the module would do.  Each tap to ground should cause a spark from the coil's center wire.  If you get spark that way, the module should be able to do the same.

[TomoHawk]

I haven't seen much of the HEI stuff lately, so could you  post a link to EuroDats diagram or the thread it's in?

[bullitt01]

I had a couple minutes to tinker with the car today. I did test #6 from the post above and got no spark out of the coil. Also, the battery was putting out 12V but the cool had 10.4V at the (+) post and 2.1V at the (-) post. Also, with the ignition on the HEI and coil both got hot. Is that normal?

[Zed Head]

No, that's bad.  Sounds like the coil is grounded all of the time.  Either through a bad module or incorrect wiring.  If you turn the key off you'll find that the coil negative terminal has continuity to ground.  Something is shorting power to ground all of the time.

 

It does explain the "no-spark" though.