32 replies to this topic

[Mr.INSANE]

So ive been working on this for awhile now today i did some tests first off

Unplugged fuel return line turned it over was bone dry
Unplugged fuel line got sprayed with gas so it works
Did the 9volt trick with coldstart injector no noise its probally gone
9volt on any injector i can hear the injector click and when i turn it over it hits on the cylinder i did that in

Sprayed starter fluid in it starts to hit


My injectors are most likely not firing what could cause this?

[80LS1T]

what kind of engine is this?

[Mr.INSANE]

Oh sorry L28e

[getZ]

if it fires up with starter fluid, you probably have spark so it's probably not the ecu or CAS.

Nissan uses a pull up resistor to 12 volts on all the injectors that tie into a common point. Not sure if all L-28 motors have this, but mine had a resistor pack that connected all the injectors to a 12 volts source. The injectors are always connected to 12 volts. The ecu simply grounds the injectors to fire them

[AK-Z]

if it fires up with starter fluid, you probably have spark so it's probably not the ecu or CAS.

Nissan uses a pull up resistor to 12 volts on all the injectors that tie into a common point. Not sure if all L-28 motors have this, but mine had a resistor pack that connected all the injectors to a 12 volts source. The injectors are always connected to 12 volts. The ecu simply grounds the injectors to fire them

If its a 280zx then it has a CAS modual (non turbo). If its a 280Z then it doesn't have a CAS at all. The ECU get its refference signal from teh spark using the tach signal.

Check to see if your tach blips when cranking. And clean the connector to the ecu. Also check and clean teh TPS and AFM.

[Mr.INSANE]

Tach does blip when cranking

does the elimate a bad ecu?

Also ive been reading up on the 280z efi bible

it did work though but now it just doesnt work at all

also its a stock 280z

[AK-Z]

Ususally the engien won't start is it doesn't have a good signal from the AFM, or TPS. try cleaning those and the ecu connector and see what happens. I don' think its a bad ecu.

[Mr.INSANE]

Cleaned the afm one already ill give the ecu and tps a try

[Mr.INSANE]

alright cleaned afm and related connectors cleaned tps and connector cleaned ecu connector and tryed another tps i had

still a nogo

[getZ]

Maybe you should back up a bit. Does it turnover, stumble and try to fire or is it cranking without ever trying to turnover?

I thought you already established it wasn't firing the injectors, no?

[Mr.INSANE]

cranking without even trying

[getZ]

I'm pretty sure it's not getting fuel then.

As far as the AFM, I know it will stumble and ran crappy but it will try to turnover at least. The Throttle position sensor is not really a sensor but a switch (at least on the later zx engines) so I don't think that would hurt a startup either because if it open or closed the computer wouldn't really care. It would still fire the injectors, but maybe at a different pulse width.

So going back to the injectors again. My 81 turbo motor had a resistor pack from each injector that tied them all to 12 volts. They were all red wires in a bundle that went to a connector. You can also measure each injector and see that you have voltage there (I'm not sure what the exact voltage was because it dropped something over the resistors but I would guess it is something over 9volts.

What year is your engine?

[Mr.INSANE]

76

[TimZ]

Unplugged fuel return line turned it over was bone dry

Why is this? If the pump is making pressure, you should see fuel coming back through the reutrn. Are you sure you have adeqaute fuel pressure?

[Mr.INSANE]

exactly very weird but i can hear the pump spinning up and turning on
and this pump is near new

[Mr.INSANE]

Alright Update

Drained my tank and put in new fuel now theres gas coming out of the return line its dropping alittle gas

Anyone have any new ideas

[zcarcrazy]

Did you ever figure out what your problem was? I've been having the exact same problem with my '77. I've learned that at the connector from the wiring harness, (with the switch on) one pole has current and the other does not. My problem is that both poles on mine have current. This suggests a faulty ground somewhere. I've not been able to locate the bad connection. I've replaced almost every FI component & cleaned every ground source I can find. I still have had no luck. I'm about to take out a loan so that an expert can fix it. Any info I can get is much appreciated.

[veritech-z]

zcarcrazy, your problem sounds like either a short, or a faulty ecu. Do ALL of your injectors have 12 volts to both terminals? If so, That makes me think it may be the ecu. That should make the injectors stick open all the time, right?

Mr. Insane, have you got yours done yet? I know this is an old thread, just curious. That's what my car was doing when I got it, it had 12v to the injectors, 45psi to the rail, but no start. I put some round top su's on it, and am just now in the process of doing a fuel only megasquirt to get back to fuel injection...

[zcarcrazy]

I know that at least two of my injectors have 12V to both terminals. Here is a brief list of things that I have tried/replaced: ECU, wiring harness, cold-start valve, temp sensor, air regulator, AFM, TPS, thermo-time switch, FI/FP relay, fuel filter, & cleaning all terminals and connections that I can find that have anything to do with the FI.

My problem started at idle. The car was idling to keep a weak battery charged. The engine acted as though it was running out of gas. The rpms went up about 300 or so & it just died. I haven't been able to get it running since. It spins freely and will try to start on starting fluid, but the injectors won't pulse.

[veritech-z]

When you did the harness, did you do the resistor packs as well? That's why I hate the bosch fuel injection they used on these cars: no trouble code diagnostics at all makes it difficult to tell at a glance what the problem is. If you have connectors hot on both sides, there has to be a short somewhere there. I just took the injector harness out of my main wiring harness, and the injectors get their power from the resistor packs. If you have a short, it's most like going to be somewhere after that. the ground wires all run straight to the ecu from the injectors. I'm using a 78 harness (different than a 77) for my megasquirt install because I replaced all the injector connectors on it before I realized it's different than the 77 I was attempting to get the factory crap to work on.