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Mr.INSANE

Injectors not firing

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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?

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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

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if it fires up with starter fluid' date=' 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[/quote']

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.

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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?

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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?

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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.

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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...

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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.

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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.

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Yeah, I replaced the resistor packs (or dropping resistors) as well. I have noticed a cut, loose wire running down to the frame rail under the master cylinder. But I think that it is one of the wires that ran to the reservoir caps on the MC. I'm really stumped. I'm wondering whether the harness I'm using is from another year model. I had to take a pair of wires from the original harness and add them into the replacement. They plug in under the dash by the steering column, but I haven't traced the wires to find out where they end up. I'll beat my own head in if the problem is on the other end of those two wires. I know that one of the wires originates from the #12 terminal at the ECU. The other ties in to an existing wire. It does not have a terminal of it's own. I don't have my manual with me right now, so I don't know exactly what the #12 terminal runs to. I can check it later, though. Let me know how the megasquirt goes. I have a friend that raves about that setup. I may even decide to go that route.

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I'll let you know how it goes. When I went to get my KA24 TPS from the boneyard, I neglected to pick up the other end of the pigtail, so now it's decision time on how I'm going to wire it. I don't really want to cut the plug off and hard wire the tps in, but I just don't have time to go back to the junkyard and get one. The harness you're describing sounds like the 78 harness, but I can't be sure. The fuel injection relay is different on that year. When I was trying to get it to work with my stock injection, I was never able to get the car to start, so I put the carbs back on. I finally got tired of the carbs and decided it was time for megasquirt. The unit is assembled, but I need to finish construction of my wiring harness now.

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Guest 2ZorNOT2Z
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.

 

Ok I have the same problem. I have a 1975 280Z and it was running great and I got caught in the rain and hit a puddle and then it died as if I was running out of fuel or the Alt. went out with a dead Batt. I check the injectors and got 12V at both terminals. Cleaned all the connectors. when I start it wont crank I get spark and I smell fuel at the exhaust. WTF.

This thing is driving me mad. I know the new stuff you just hook up to a reader and it tells you were its at. What was nissian thinking. Some one Help.:icon2::hs:

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just raising my hand in the roll call of people with the same friggen problem. have replaced ecu, afm, efi harness, fuel rail and injectors. no injector pulse. starts and runs as long as i spray starting fluid. brand new fuel cell with surge tank and walbro pump. bought the car with this problem and would like to get this rustless beauty back on the road. have untaped and checked wiring with schematics. replacement harness was also off another 09/76 car. going bonkers. pleeeeeeaaaassee help! i already have a carbed z car and it smells like crap. would like a nice reliable fuel injected car. lol, maybe i'm asking too much of a 30 year old car.

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Take a noid light and connect it to one side of the injector. Do not disconnect the injector. I just hold the point of the probe in the wire so it pokes through the insulation and makes contact with the wire inside. Then let someone else start the engine.

If the light pulses when you turn the engine over, then electrical should be good. If it does not pulse, then start looking at the electrical. Last time I had this problem, the first thing I did was pull one injector loose and see if it would squirt into a small jar. Until you do this, it's hard to tell what is going on.

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