1976 280Z Fuel Issues Troubleshooting

[EuroDat]

Hi Paul, It's a pity you're having issues with the TIU mod. I ran mine from 2014 up to October last year with I had the good fortune to buy a 280ZX unit.

A couple of suggestions.

You are running a 0.3 ohm flamethrower coil with the resistor. That coil should have 12 volts, the HEI has a current limiting function to get the maximum out of the coil.

The blue wire should go straight to the negative post on the coil, or via the end terminal on the resistor, if you want to keep the original look.

Not mentioned in the instruction, but check the reluctor air gap. That is crucial for the HEI because the HEI needs 0.5 volts to trigger and too big a gap will quickly drop the cranking volfage to 0.3 volts.

The other thing that can give you problems is the reluctor in the dizzy. If it is old and the insulation is starting the break up, it will not generate the voltage required to trigger the HEI. When you crank the engjne, it will generate 0.5 volts and will reach around 28 volts a high rpm. That high voltage can bridge poor insulation and cause your problem.

Edited August 4, 2023 by EuroDat

[Paulytunes]

4 hours ago, EuroDat said:

Hi Paul, It's a pity you're having issues with the TIU mod. I ran mine from 2014 up to October last year with I had the good fortune to buy a 280ZX unit.

A couple of suggestions.

You are running a 0.3 ohm flamethrower coil with the resistor. That coil should have 12 volts, the HEI has current a limiting function to get the maximum out of the coil.

The blue wire should go straight to the negative post on the coil, or via the end terminal on the resistor, if you want to keep the original look.

Not mentioned in the instruction, but check the reluctor air gap. That is crucial for the HEI because the HEI needs 0.5 volts to trigger and too big a gap will quickly drop the cranking volfage to 0.3 volts.

The other thing that can give you problems is the reluctor in the dizzy. If it is old and the insulation is starting the bream up, it will not generate the voltage required to trigger the HEI. When you crank the engjne, it will generate 0.5 volts and will reach around 28 volts a high rpm. That high voltage can bridge poor jnsulation and cause your problem.

Chas,

Thanks for the suggestions and your excellent write up that got me this far. The blue wire is attached to the end terminal on the resistor.  Should I try and bypass the resistor and connect straight to the coil?

I will also look into trying to adjust the reluctor air gaps.  To add insult to injury, I opened up the hood to find that the condenser wire was broken.  Old and brittle, I guess they do snap.  I doubt this is contributing to the issue, but I guess I will be shopping for a new one.

[Zed Head]

On 8/2/2023 at 7:13 PM, Paulytunes said:

anytime I exceed 2000rpm, the engine immediately stalls.

If you have a manual transmission just leave it in gear and watch the tachometer.  If the tachometer is still showing proper engine speed as the car slows down then the ignition system is still producing spark.  If the tach goes to zero but the engine is still turning then it's not.

You said that it starts back up.  Do you mean that the engine restarts by itself as RPM drop below 2000?  Or that you have to pull over, wait, and use the starter?  

[Paulytunes]

3 hours ago, Zed Head said:

If you have a manual transmission just leave it in gear and watch the tachometer.  If the tachometer is still showing proper engine speed as the car slows down then the ignition system is still producing spark.  If the tach goes to zero but the engine is still turning then it's not.

You said that it starts back up.  Do you mean that the engine restarts by itself as RPM drop below 2000?  Or that you have to pull over, wait, and use the starter?  

All testing since the module swap has thus far been in the garage with the Z parked and handbrake on.  Test procedure has been as follows:  Reconnect negative battery terminal.  Start the car and let it warm up.  Once idle normalizes around 800rpm, apply throttle and observe.  With the HEI module, when I rev past 2000rpm, the tach needle drops quickly to zero and the car stalls - this happens quickly, like the system gets overloaded and shuts itself off.  Restart is only accomplished by turning the key and re-engaging the starter.  

[Zed Head]

Have you checked the ground from the module mounting point with a meter?  Your drawing shows a wire but the area under the dash is not full of good grounding spots.  It's often pretty crusty under there too.  One of the few things that can cause quick heat buildup is electricity.

p.s. heat could be causing the module to fail.  Higher PRM passes more current through the module.  More current = more heat.  Not sure if a bad ground could cause more heat but it might.

Edited August 4, 2023 by Zed Head

[EuroDat]

On 8/4/2023 at 3:55 AM, Paulytunes said:

Chas,

Thanks for the suggestions and your excellent write up that got me this far. The blue wire is attached to the end terminal on the resistor.  Should I try and bypass the resistor and connect straight to the coil?

I will also look into trying to adjust the reluctor air gaps.  To add insult to injury, I opened up the hood to find that the condenser wire was broken.  Old and brittle, I guess they do snap.  I doubt this is contributing to the issue, but I guess I will be shopping for a new one.

 

Hi Paul,

I would bypass the resistor or bridge it over if you are looking for the original look. I bridged mine in the photos. The condensor should not be an issue, it's more a noise supressor than anything else.

Like Zed Head said. It could be a heat issue. You could try and mount the HEI module with the heat sink plate next to the coil. Then you have the shortest circuit to the coil and good grounds in the area. Once you know it works, then you can more to fitting the module in the original position.

The HEI will get hot, and the flame thrower in no exception, but heat is not a good thing in these units. The high resistance the resisitor is generating will not let the HEI function as it was designed. Not helping.

Btw: My TIU was overheating when failing. Like yours it would leave me stranded on the side of the road. A quick spray with very cold circuit cleaner would bring it back to life almost instantly. A passenger (my wife) could spray it and the engine would come back on after a second or two.

Edited August 5, 2023 by EuroDat
Forgot to post photo

[Paulytunes]

5 hours ago, EuroDat said:

Hi Paul,

I would bypass the resistor or bridge it over if you aee looking for the original look. I bridged mine in the photos. The condensor should not be an issue, it's more a noise supressor than anything else.

Like Zed Head said. It could be a heat issue. You could try and mount the HEI module with the heat sink plate next to the coil. Then you have the shortest circuit to the coil and good grounds in the area. Once you know it works, then you can more to fitting the module in the original position.

The HEI will get hot, and the flame thrower in no exception, but heat is not a good thing in these units. The high resistance the resisitor is generating will not let the HEI function as it was designed. Not helping.

Btw: My TIU was overheating when failing. Like yours it would leave me stranded on the side of the road. A quick spray with very cold circuit cleaner would bring it back to life almost instantly. A passenger (my wife) could spray it and the engine would come back on after a second or two.

Well, I had some time this morning, so I bypassed the resistor.  That seems to have done the trick!!!  No more stalling after a high RPM pull.  Thanks so much for all the help!  This forum is awesome!!  I am going to go for a morning test drive to verify.

[Paulytunes]

...and after a ~20 minute test drive, everything seems operating as it should.  Now on to resolving the known issues and corrections.