[FIXED] 1983 280ZX Starts but dies in 2-3 Seconds

Hi all -- looking for some trouble shooting help here. Back about 10 years ago I was trying to jump start the car and crossed the jumper cables and fried the ECU. Life got in the way and the car sat until now. I have the car to the point that I've changed the Injectors (new) and have gone through the fuel system to make sure all the gunk was cleaned out and filter changed. I sent the ECU out to be fixed and they sent out a remanufactured one. Now the car starts but dies within 2-3 seconds. I've done all the Factory Service Manual checks in the book and everything led me back to a bad ECU so I sent it back for warranty and the company sent me back another replacement, unfortunately without telling me if the one I sent them was good or bad. I just put the unit in the vehicle but its doing the same as before (starts then dies). I put a noid light on the injectors and the light comes on (dimly) when I'm starting the car but I have to say I really can't see the light flashing/pulsing until the car starts dying-out and then I can see the light pulsing as the RPM's drop. I don't know if this is correct or not?? I don't think the injectors are firing because I took out a couple plugs and cranked the engine but I couldn't smell any gas fumes. Not sure where to go from here as all the Factory Service Manual tests are showing good. I think the reason the car starts at all is this vehicle has a Cold Start Valve that adds extra gas when the engine is starting and when you release the key this circuit turns off so the car is essentially running on the fuel the Cold Start Valve provides not the injectors.

A few things that spring to mind are:
1 does the car car have any sort of immobiliser? is the key chipped type? if the ecu is not coded to that then it may be intentionally shutting down the injectors
2 if jumpers leads were crossed there may other damaged components or even blown fuses.
3 try hot wiring the cold start valve to see if the engine stays running

Hope that helps Regards Nigel

Thanks Nigel -- the car is too old to have a chip in the key. I've checked all the harnesses, fusible links and fuses so think I'm good there. I guess since the car will start and idle for 2-3 seconds I'm down to an injector issue of some sort and since I've tried two ECU's now and still have the same problem I need to figure out why the injectors are not firing.

Moving this topic guys

Looked around for any rodent damage? Any other fuses possibly blown?

What is your fuel pressure?

On some cars of this era the fuel pump supply and sometimes ignition was wired through a relay driven from the oil pressure switch.
When cranking the relay was bypassed by the ignition switch and the pump energised/
When the engine fired and the the key was released and engine running the oil pressure at the oil pressure switch should be sufficient to operate it and energise the relay and hold the pump on.

Thanks Fudgie -- I've been over the car pretty good and don't see any rodent damage and I checked all the fuses

Thanks Karma -- My fuel pressure is 32psi

Thanks Karma - I checked the wiring diagram for the car and don't see a tie-in to the oil pressure switch.

...distributor if i dont remember wrong is responsible for fuel injection could ve been damaged

Thanks -- I know that the ECU controls the injectors by providing a ground to the circuit and it does this by counting the RPM's of the engine through a signal from the coil. There might be a problem in the distributor but I'm not sure how to check that??

Have you checked the positive side of the coil and injectors are getting battery voltage when the key is released from the start position? ie KOEO (Key On Engine Off).

As to fuel pressue I would expect more pressure, whats the Nissan spec ? 3bar???????

Thanks Andy -- With the key in the "on" position I have 12v at the injector connectors. The Factory Service Manual says 30 PSI for fuel pressure at idle. For some reason the ECU is not applying the ground signal/connection for the circuit to be completed. I put a jumper on each of the injector pins at the ECU 35 pin connector (one at a time) and if I tap it to ground the injector fires. Given that I've put in two ECU's (both remanufactured units from Fuel Injection Corp) I have to think the ECU is good. The ECU is supposed to get a signal from the coil basically telling it that the engine is running and what RPM the engine is operating and I have continuity on the signal wire coming from the coil to the ECU.

Is it fitted with an old style flap air flow sensor ? the flap can stick and cause problems.

Thanks Andy -- yes it does. I took a look at that and the flapper operates smoothly and passes the electrical tests in the FSM

[Fixed] All my trouble shooting kept coming back as the ECU was bad so I sent the ECU back for warranty (2nd time). They gave me a bit of static about taking it back again since the issue I had wasn't changing at all. I've been waiting for 4 weeks now for it to be repaired/replaced when I noticed a used ECU pop up on eBay so I took a flyer and bought it. I put this unit in last weekend and the car started right up! Can't tell you how infuriating it is to get bad parts, not once but twice and paying extra for what was supposed to be repaired and tested parts!! It really makes you question your trouble shooting and wasted a lot of time checking and rechecking things.
Thanks to all who sent in suggestions and to ScannerDanner for your videos on YouTube. I looked at the EFI trouble shooting vids several times and they were very helpful.

Slapped a [FIXED] on this one.

Kevin_280ZX wrote: Can't tell you how infuriating it is to get bad parts, not once but twice and paying extra for what was supposed to be repaired and tested parts!! It really makes you question your trouble shooting and wasted a lot of time checking and rechecking things.

Been there, done that.