1986 Nissan 300zx No Injector Pulse - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 9 (permalink) Old 02-12-2019, 04:59 PM Thread Starter
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1986 Nissan 300zx No Injector Pulse

Good afternoon,

I have a 1986 Nissan 300zx with a 1985 VG30E (non-turbo) I have been working on for a while now.
I was able to get the car to crank and I know I'm getting fuel pressure, spark, and the starter is working.
My issue right now is that the car isn't sending the pulse signal to the injectors.

I have checked the green relay on the passenger side by the battery and it is activating, I have changed the crank angle sensor and distributor as someone told me they control both spark and pulse.
I know that the ECU I have in the car is working as it came from a running car and the lights for diagnostics are on.

I can only think that the problem is coming from 1 of the following:
-The engine wiring harness is not connected properly to the main interior harness and ECU
-There is a grounding issue somewhere preventing the injectors from getting pulse
-The ecu got damaged at some point since being removed from another vehicle

If anyone has any other ideas as to where else my issue could be I would greatly appreciate it.
I would also like to know if anyone either has images of how the connections for the engine wiring harness should be inside the engine bay and inside the passenger area to discard any potential issues there.

Thank you!
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post #2 of 9 (permalink) Old 02-17-2019, 10:55 AM
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It sounds like you're on the right track. How did you determine no injector pulse? I honestly doubt the ecu is bad. The engine wiring harness is isolated from the main harness. It goes directly to the ecu. You may want to perform the crank angle sensor checks from the fsm, starting on EF & EC-50. The electrical section of the fsm will help you with the engine harness connections.

Last edited by Oscillation; 02-17-2019 at 10:57 AM.
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post #3 of 9 (permalink) Old 02-24-2019, 05:48 PM Thread Starter
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Ok so I got an ECU from a salvage yard to check, and no luck, though I already figured it was a longshot.
I also checked the pulse by using a light bulb connected to the injector connector while attempting to crank.
Additionally, we found that after disconnecting the battery, unplugging the ECU, and waiting for a bit before reconnecting everything, the car will get pulse on the injectors and can run for a few minutes at full force.

I was separating the cable bundles of the engine harness to the ECU and found a few black badly spliced cables that, according to the multimeter, were ground. I'm thinking I will probably have to remove all the shieldings for the bundles, check all the cables, then re-shield them after fixing anything that looks wonky.

Thanks, and sorry for the long time before responding, this is a university project that is mainly worked on the weekends.
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post #4 of 9 (permalink) Old 02-27-2019, 07:15 PM
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Do you have a scope type device that can capture the actual electrical pulse?

1984 300zx non-turbo
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post #5 of 9 (permalink) Old 03-05-2019, 11:34 PM Thread Starter
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is there a way to check that with a multimeter?
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post #6 of 9 (permalink) Old 03-06-2019, 07:30 PM
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Quote:
Originally Posted by EnduranceEagle View Post
is there a way to check that with a multimeter?

No, you need a scope. What is the voltage, using a multi-meter on the two wires at the injectors?

1984 300zx non-turbo

Last edited by thansen; 03-06-2019 at 07:33 PM.
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post #7 of 9 (permalink) Old 03-06-2019, 07:40 PM Thread Starter
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The red wire gives 12.3V, but the green wire (supposed to control signal) isn't sending a ground signal.
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post #8 of 9 (permalink) Old 03-07-2019, 01:38 AM
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Quote:
Originally Posted by EnduranceEagle View Post
The red wire gives 12.3V, but the green wire (supposed to control signal) isn't sending a ground signal.

You won't see the injection pulses with a digital multi-meter. Let me do some quick math...



At 100 HP a NA engine will burn about 6 gallons of gas per hour or 6.3 cc/ second.
The NA injector is rated 180cc/min or 3cc/second. Using 6 of them 18 cc/second.
So at a output rate of 100 HP the injectors are open about 1/3 of the time. If your engine is doing 4500 RPM at this point, that is 75 rotations per second or 13.3 ms per rotation. The fuel system will be injecting once per rotation for about 4.4 ms.



At lower RPM and throttle position, let say IDLE 750 RPM and 2 HP, or 12.5 rotations per second, 80 ms per rotation. The injector pulse would be 2 % of 1/3 of 80 ms or 0.53 ms.

This might give you some idea what the injector pulse should look like. A sub 1 ms pulse in a 80 ms cycle. If the fuel system is running in group mode both those number would be doubled, 4 cycle engine, 1 pulse per power stroke.


At Idle, the ground pulse should be about 1 ms long in an 160 ms cycle. You won't see this on a DMM.



There is startability diagnostic in the FSM section EFEC. This gets into fuel pressure and fuel injection harness checking.

1984 300zx non-turbo

Last edited by thansen; 03-07-2019 at 01:44 AM.
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post #9 of 9 (permalink) Old 03-08-2019, 12:32 PM Thread Starter
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Quote:
Originally Posted by thansen View Post
No, you need a scope.
Do you know what type of scope I would need to buy (like amazon link or exactly what its called)

I will check that and things I would like to check include:
-FPR
-Wiring harness (again)
-ECU (Again)
-electronic pickup coil (again)

and see if any of those are the culprits.

On a side note, my team members and I removed all the emissions items around the plenum, could that have affected anything?

Thanks
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