83 280ZX starts but won't run - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 59 (permalink) Old 01-29-2017, 06:12 PM Thread Starter
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83 280ZX starts but won't run

Hi Guys, I just joined this forum and was looking for some help. (sorry for the long post)

Vehicle
1983 280ZX (original owner)
Non-turbo
5 Speed
Coupe
98,000 miles

Background
About 9 years ago I stupidly crossed jumper cables while jump-starting the car and as you might suspect, fried the ECU. I got too busy with other things and the car just sat till now. I recently sent the ECU out to Motor Sports and got a replacement unit.

Problem
The car starts but dies within 2-3 seconds

Question
Based on what I've done below what am I over looking? Are there any more fuseable links in the car? Anything else I should be checking?

What I've replaced
  • ECU
  • All injectors and rubber fuel lines
  • Fuel filter (after pumping out 8 gallons of 9 year old fuel)
  • Battery
What I've checked
  • Fuel tank for rust or contaminants (none found! who would have thought after sitting for 9 years with gas in it)
  • Fuel pressure is ~36 psi (before, during and after starting)
  • Checked all injector connections with a noid light
  • General visual inspection of engine compartment vacum lines
  • Fuseable links in the engine compartment
FSM Tests (with multimeter)
  • Throttle Valve Switch test
  • Air Flow Meter test including a manual test of the flapper valve
  • Air Temp Sensor test
  • Cylinder Head Temp Sensor test
  • Exhaust Gas Sensor Circuit test
  • Thermotime Switch test
  • Control Unit Ground Circuit test
  • Air Regulator Circuit test
  • Cold Start Valve test
  • Injector Circuit test
  • Ignition Coil Trigger Input test
  • EFI Relay & Fuel Pump Relay test
  • Ignition Start Signal test
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post #2 of 59 (permalink) Old 01-29-2017, 07:37 PM
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How long does it run before it dies, after starting? Have you confirmed that the injectors have power? You said "Circuit test" but there's no detail about power to the injectors.
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post #3 of 59 (permalink) Old 01-29-2017, 08:44 PM Thread Starter
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It will run about 2-3 seconds after you release the key from the "start" position. I did check the injectors circuits with a noid light while cranking the engine over with the starter, all of them indicated power
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post #4 of 59 (permalink) Old 01-29-2017, 09:05 PM
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did you check the cold start injector on the throttle body?

73 240Z very orange
Dual Weber DGV's, header and 2.5 exhaust
Electronic dizzy with G.M. HEI module
Tokico Struts/Springs, Full Poly U bushings
Daily driver, all work done by me
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post #5 of 59 (permalink) Old 01-29-2017, 09:20 PM
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Quote:
Originally Posted by Kevin280ZCar View Post
It will run about 2-3 seconds after you release the key from the "start" position. I did check the injectors circuits with a noid light while cranking the engine over with the starter, all of them indicated power
I think that you're not clear on how the injector circuit tests works. The light is supposed to flash as the injector circuit to ground is completed. So a sequence of tests be to use a meter to confirm battery power to the injectors when the key is on, and then a second test using an injector connector and noid light to see if current flows, causing a flash. You can have power but no injection if the ECU isn't grounding the circuit.
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post #6 of 59 (permalink) Old 01-29-2017, 09:24 PM Thread Starter
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I did check the cold start valve with a multimeter through the ECU 35 pin connector and also checked it at the connector on the valve for resistance. Is there any other check I should do to this valve?
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post #7 of 59 (permalink) Old 01-29-2017, 09:34 PM Thread Starter
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Yep - the noid light was flashing on each injector connector as the engine rotated. I assumed the circuit test done from the ECU 35 pin connector was to test the harness.

I'll check for power to the injectors with the key on next -- thanks
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post #8 of 59 (permalink) Old 01-29-2017, 09:43 PM
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If you're getting flashing then there's power. So the question is why is no fuel passing through the injectors, to keep the engine running. Were they flashing after you let go of the key, when the engine started? Or did they stop?

See the process? You had fuel in the engine when it started. Why didn't fuel keep flowing and the engine keep running? If the injectors were flashing then maybe no fuel was passing through the injectors. Or maybe the injector stopped flashing when you let go of the key. Add those details in and you'll figure it out.

The fuel is just sitting inside the injectors under pressure waiting to get out when they open.
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post #9 of 59 (permalink) Old 01-29-2017, 10:01 PM Thread Starter
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Got it -- I'll go back an do the noid check again. It runs for so short a period it may be hard to tell

Thanks for you reply(s)
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post #10 of 59 (permalink) Old 01-30-2017, 10:26 AM Thread Starter
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Quote:
Originally Posted by pdx280 View Post
If you're getting flashing then there's power. So the question is why is no fuel passing through the injectors, to keep the engine running. Were they flashing after you let go of the key, when the engine started? Or did they stop?

See the process? You had fuel in the engine when it started. Why didn't fuel keep flowing and the engine keep running? If the injectors were flashing then maybe no fuel was passing through the injectors. Or maybe the injector stopped flashing when you let go of the key. Add those details in and you'll figure it out.

The fuel is just sitting inside the injectors under pressure waiting to get out when they open.
Just thinking sitting here at work (wishing I was working on my car). If the noid light is flashing while key is in the start position and then stops flashing when you release the key to the on position --- does that tell you its the ECU computer or could it be something else?

Last edited by Kevin280ZCar; 01-30-2017 at 10:28 AM.
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