ISPKI Posted May 7, 2014 Share Posted May 7, 2014 Hello Hybrids!!! I am finally back after moving around throughout winter. Long story short, I now have my first house with a garage and will be diving back into my 77 280z. It has been a while since I worked on it so I will start a new thread and see where I get with it. I have narrowed my issue down to the fuel injectors. They do not fire on their own. The vehicle starts off the cold start injector and then immediately dies. Spark plugs are working fine. I am able to manually fire each injector. The car was driving before I took it off the road to do some exhaust work. I also replaced the fusible links with a midi fuse box and moved the battery to the cab and added fuse holders for the lines running through the dropping resistors. I have performed all of the tests from the Bible and replaced the ECU which did not help. I need to know what can prevent the injectors from operating while the car is running. J came up with a hunch when measuring voltage. The battery voltage has dropped below 12v (11.73v I believe) with the new electrical work so I am curious if the injectors will simply refuse to function when the voltage is that low. The battery cables are now much longer than they used to be and have a bulkhead connector for the injector wires. I am think that the connector may be creating a huge resistance jump in the system. Quote Link to comment Share on other sites More sharing options...
Domzs Posted May 7, 2014 Share Posted May 7, 2014 Double check your work , since it was fine until you worked on it . Make sure to use correct size wires/cables . Since the battery is further away from the original location , the wires used must be large enough to carry the work load . Pics will be helpful . Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 7, 2014 Share Posted May 7, 2014 Probably a Pin 1 problem. The ECU needs to know what's going on. Quote Link to comment Share on other sites More sharing options...
ISPKI Posted May 7, 2014 Author Share Posted May 7, 2014 I bumped the battery cable size from the original 4awg to 1awg and soldered new copper contacts. I will take some photos of the setup tomorrow. Pin 1 is going to negative coil post correct? I believe I had verified that it has continuity but was not sure if I could check the signal coming from the coil. Can I just leave the meter on the pin while cranking to see if it is receiving a signal? Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 7, 2014 Share Posted May 7, 2014 Pin 1 at the ECU connector needs to be connected to coil negative, and the tachometer and its resistor need to be in place. The tachometer is also connected to coil negative and has an effect on the Pin 1 signal to the ECU. I don't know exactly what range the ECU works in so a meter reading probably wouldn't tell very much. Quote Link to comment Share on other sites More sharing options...
Nigel Posted May 7, 2014 Share Posted May 7, 2014 added fuse holders for the lines running through the dropping resistors. Can you explain this in more detail? Quote Link to comment Share on other sites More sharing options...
ISPKI Posted May 7, 2014 Author Share Posted May 7, 2014 The wires that connect the fuel injectors to the battery and run through the dropping resistors had badly corroded fusible links. I replaced the links with glass AGU(?) Fuses. There is one connecting to negative on the battery and the other to positive. Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 7, 2014 Share Posted May 7, 2014 If you strike the coil, every third strike firing the coil, the injectors should fire. If not, then as stated above check Pin 1. If that input to the ECU is good...your ECU is toast. That said, make sure the wires for the ECU from the battery are correct. One is positive, one negative. They don't both go to hot, and obviously if they're hooked up backwards...poof! Quote Link to comment Share on other sites More sharing options...
SUNNY Z Posted May 13, 2014 Share Posted May 13, 2014 Might be as simple as a separated wire? Check continuity from your ECU to the injectors. I have no knowledge of the stock wiring, but i've had wires separate before. Quote Link to comment Share on other sites More sharing options...
ISPKI Posted May 15, 2014 Author Share Posted May 15, 2014 I checked pin 1 continuity to negative coil post and it checked out. I also checked from negative coil post to ground to make sure the wire hadnt chaffed and was contacting the body somewhere and that checked out. I have continuity from ECU to injectors as that is actually how I was manually firing each injector, by grounding it at the ECU plug. I have the original ECU which was working previously and a brand new ECU that I swapped in because my testing pointed to the ECU being bad. However, new ECU did not solve the issue. Tony: Which wires from the Battery to the ECU are you referring to? There appears to be several according to the diagram on EF-25 factory service manual. 5, 16, 17, 35 all go to battery ground, while 4, 10, and 20 run through the power relay to the + battery terminal. I want to make sure I am reading this schematic correctly: On EF-25, the wires that provide power to the injectors goes first into the power relay (connection #70 at the power relay). They exit the relay as #43 and run to the dropping resistors which then divide 12v to each injector. Quote Link to comment Share on other sites More sharing options...
ISPKI Posted May 17, 2014 Author Share Posted May 17, 2014 OK. Exciting update. I cut out the battery cables and replaced with new ones. Moved the battery back to it's factory location and wired everything back up and now the car starts. I put some fresh 93 octane in it and got it to idle, but it idles pretty poorly. I rotated the distributor clockwise and it started to smooth out the further I rotated it. It was very smooth at almost the max adjustment on the dizzy but if I gave it any gas, it would pop out the intake while revving up. When I rotate the dizzy counterclockwise, it wont idle. Also - I have a vacuum gauge hooked up to it and it is sitting at between 10 and 14psi depending on where I adjust the dizzy. More clockwise = higher vacuum, but I also noticed that the vacuum empties as soon as the car shuts off. Shouldnt the engine hold vacuum unless there is a vacuum leak? Quote Link to comment Share on other sites More sharing options...
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