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HybridZ

Injectors not firing


Mr.INSANE

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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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  • 9 months later...
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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  • 8 months later...

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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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.

 

wish i could say that i hadn't tried this. fuel pressure is great, press regulator is good and i have fuel cycling back to the cell, getting no light show when probing with tester.dunno how this is possible since the wiring harness has been replaced, checked th0oroughly, and had all connection points cleaned. would dropping resistor problem throw off the pulse width? or would it totally kill any pulse (my current problem). please and thank you to anyone who can help.

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When you say that you are getting no light shown when probing with tester, is this when the engine is cranking?. If the engine is not cranking over during the test, you should not be getting a light on the probe. Make sure that the ground wire on the probe is connected to one side of the injector and the other side of the probe (needle) is pushed into the other wire. This will place the tester in parallel with the injector.

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When you say that you are getting no light shown when probing with tester, is this when the engine is cranking?. If the engine is not cranking over during the test, you should not be getting a light on the probe. Make sure that the ground wire on the probe is connected to one side of the injector and the other side of the probe (needle) is pushed into the other wire. This will place the tester in parallel with the injector.

yep, this is with the engine turning over. connected as described. at my wits end with this car.

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With the ignition on, what are the voltages to each wire on the injector?

If you are not getting a pulse, there has to be a bad connection someware. If all the injectors are not getting a pulse, look for the wire locations that are common. Like the dropping resistors .It has a single wire

that connects both the injector dropping resistor and the fuel pump dropping resistor. When I look at the wire diagram for the 75z, the wire goes to the fuel pump and gets power when the pump is turned on. There are several connectors located between the fuel pump and the dropping resistors. If you have power at the fuel pump and none at the injector, you probably have a bad connection on that line.

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With the ignition on, what are the voltages to each wire on the injector?

If you are not getting a pulse, there has to be a bad connection someware. If all the injectors are not getting a pulse, look for the wire locations that are common. Like the dropping resistors .It has a single wire

that connects both the injector dropping resistor and the fuel pump dropping resistor. When I look at the wire diagram for the 75z, the wire goes to the fuel pump and gets power when the pump is turned on. There are several connectors located between the fuel pump and the dropping resistors. If you have power at the fuel pump and none at the injector, you probably have a bad connection on that line.

 

i will definitely have to check that out. the pump is on a switch along with the fans and elec. water pump, but as i recall, the pump didn't turn on with the ignition before i installed the aftermarket setup. i'll let you know how it checks out. i may actually get a chance to work on it tomorrow.

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240swapped,

You got that thing running. I noticed on another thread that the AFM can cause the fuel pump to not turn on if it is not work propely. Just another thing to look at.

hehe, if that's the problem then i have 3 bad AFM's! took one of my buddy's 77 and it works for him and not myself. :-(

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