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.

[Paulytunes]

Bumping this thread back up because my 280Z is now in a non-running state and this time, I think it is a fuel issue.  All was going well until about a week before Memorial Day.  I was noticing a whine coming from the rear of the car.  

I was planning on taking the car to a car show at work in late May and headed out to take a Friday evening drive, with plans to prep it for the show over the weekend.  Well, I never made it out of the driveway.  The car started to run rough and then stalled.  I tried to start it again, and it would first sputter, then start, run rough, then die.  Eventually it would just crank and crank and crank and nothing. 

I went through the fuel injection bible religiously, tested for spark, injectors, relays, ECU, etc.  All of this troubleshooting ruled out everything but the fuel delivery/pumping.  I bought and installed a pressure gauge after the engine fuel filter, and after the car sat for awhile, I got it to start again.  Fuel pressure at the filter discharge is ~25 to 26 PSIG, about 10 PSIG less of where it should be.  "Fuel pump, it's gotta be that," or so I thought. 

Well, upon inspection, the installed pump is an aftermarket one (a Carter 6203BE, 150421A-12).  Online research indicates that this pump is rated for half the flow rate of the stock 280Z, and applications are typical for many vintage European cars (BMW, Jaguar, Triumph, Fiat, Lancia, Eagle Renault).  It was also pretty poorly installed in the original bracket, so it could bang around every time I encountered a bump.  One of the previous owners also installed the wrong type of fuel hose clamps.  Ugh. 

So I decide to buy an aftermarket pump that has the right flow rate and will fit.  Shocker: It doesn't without significant line rework.  While I was at it, I decided to install a pre-filter (the Fram see-thru one) from the tank the to suction line of the pump.  After a few gasoline showers, and thinking all is good to go, I install everything back and try to start it up.  One problem:  Gas isn't getting to the replacement pump.  I also notice that the pre-filter is only about half full of gasoline.  Shouldn't it be fully flooded?  Despite multiple attempts and adding about 3 additional gallons of gas to the tank, I cannot get the new pump to prime.  I am now wondering if there's something (rust or delaminated coating blocking the tank outlet.  Has anyone had a similar experience?  Am I heading down the road to a new gas tank?         

[Paulytunes]

I forgot to mention that the way I got it to start again was with some quick start fluid sprayed into the air intake.

[Zed Head]

Any chance that you have the pump installed backward?  They typically have a check valve on the outlet end.

Also, if you wire it backward it will spin backward.

If it was mine, I would disconnect the hose from the tank and see if fuel flows freely.  If it does, then reconnect it to the pump and disconnect the outlet side of the pump.  Gravity should fill the pump and fuel should come out of the outlet of the pump through the check valve.  That would be the priming step.  Once it is full of liquid it should push it up to the filter and rail.

 

[Paulytunes]

8 hours ago, Zed Head said:

Any chance that you have the pump installed backward?  They typically have a check valve on the outlet end.

Also, if you wire it backward it will spin backward.

If it was mine, I would disconnect the hose from the tank and see if fuel flows freely.  If it does, then reconnect it to the pump and disconnect the outlet side of the pump.  Gravity should fill the pump and fuel should come out of the outlet of the pump through the check valve.  That would be the priming step.  Once it is full of liquid it should push it up to the filter and rail.

 

I checked both orientations, no flow through the pump after multiple attempts.  I wired it up to match the replacement pump, 1976 wiring diagram, and the FSM - green is positive, grey/black is negative.  I verified the pump is getting power.

Fuel does seem to flow pretty freely out of the hose when I disconnect the prefilter.  After thinking about it, I am wondering if the issue may be the prefilter.  I may just connect the outlet hose to the pump inlet and see if that works.  The pump installation instructions say to prime it by starting the car without the pump outlet open and verify fuel flow out of the pump discharge.