# No electric current in Fuel Injector



## shabbarraza2000 (Jan 17, 2015)

Hi Mates,
I have a funny problem with my car, it works well when ambient temperature is below 20 C but when it hot then its seems that engine is miss firing. The detail of car is given below, 
Nissan, Pulsar, ST/N16, 5D Hatchback, 2002, 1.8L, 4 SP Automatic, 92 kw, 161 Nm, European make
Its really strange that when outdoor temperature is 20C the car runs smooth but as soon as the weather gets hot the car mis firing. I check this even in the first start in the morning and after dozen of try I come to conclusion that weather is somehow related to the problem with car. 
Anyways I took the car to the mechanics and he check the car computer, spark plugs, fuel injector and finally diagnose that fuel injector 3 and 4 are not working (counting from driver toward passenger side). As the fuel injector is quite expensive so I clean the fuel injectors by watching a video on youtube successfully and found out the even the fuel injectors were little Clough but they were working fine ( I mean when I connect them with battery they start spiting the cleaning fuel). When I put the fuel injector back the car was still not working in hot weather (just to clarify that car radiator is working fine and the temperature needle is in the middle). So I Did a screw driver test by listening the clicks of fuel injector and found out the fuel injector number three is not working. Further when I test the wire coming into the fuel injector number three I found out that there is no electricity is coming in the fuel injector to work. 
Now I am stuck that what is the problem, if the connections is loose then why it work in the cold weather? 
Wiring looks fine as the car is only 109,000 km on clock, which is ok for this much old car.
I am not in a mood to mess with the wiring as it all seems to be good and professionally done. 
Someone told me that I might be because of car computer that when it heat it don’t work well, but there is not warning light on the dash board.
Please help me out, I tried to be as much as descriptive.  
Thanks you very much.
Syed


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## rogoman (Dec 16, 2004)

There are two wires to each fuel injector, a black/red wire that supplies a constant 12 v. The other wire connects to the ECM which will see a pulse to activate the injector.

You can use a volt meter to check the 12v wire and a 'noid' light to check for a pulse on the other wire. If there's no pulse, then the ECU might be at fault. Check the harness connector at each injector for tightness and oxidation on the pins; also check the harness connector at the ECU.

All four 12v wires go to a common connection which then connects to a 10 amp fuse block. If there's no 12v at those injectors, then wherever the common connection is might be the source of the problem.


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## shabbarraza2000 (Jan 17, 2015)

Hi Rogoman,
First of all I am really thankful to you for the reply. 
I have done what you have said.
Only my one injector is not working, other three are working fine. (I did the screw driver test to find the bad injector).
I unplug the harness connecter from that fuel injector and check with the volt meter, after starting the engine, no voltage is shown. Its mean that circuit is not complete. But I am unable to identify whether the 12 volt wire is bad or the other one. Is there any other way to find that which wire is bad ? I guess the other wire is bad as the three injectors are working therefore 12v wire much be good ... just a hypothesis.

Further, I open the ECU unit and take the two blocks of wire and put it back and make sure they are tight enough, I guess their was some anioxident oil on the pin of the ECU too.
I visually inspect the ECU and it looks fine, but if there is some electronics wrong with ECU then it is hard to visually inspect. (FYI: there is no warning light on dashboard. 

I am planning the change the ECU first before messing with the wiring.

Please comment.

Kind regards,


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## smj999smj (Jan 1, 2006)

Replacing the ECU before checking the wiring if not a good idea. It's best to identify the problem first and replace the ECU only if everything else has been tested and confirmed ok. The reason for this is if a wire is shorted, it may cause the ECU to burn out. If you replace the ECU without fixing the short, it can damage the replacement ECU and it will void the warranty.
You don't need to start the engine to test power to the injector. Just turn the key "on" and with the injector unplugged, use a 12v test light (connected to ground) to confirm power at one of the terminals in the plug. If you confirm power on one wire and not the other, you know the other wire is the ground circuit that goes to the ECU; the ECU uses drivers to pulse the circuit to ground to "fire" the fuel injector. To check the ground circuit to the ECU, you will need to get a diagram of the ECU harness connectors, unplug the ECU, locate the wire in the connector and test the wire between the ECU and injector with an ohmmeter and also make sure it's not shorted to groun. 
If you have power at both wires of the injector harness connector, then the two wires are likely shorted together and you'll need to trace the short.
If you have no power to the incident injector, but power to the other injectors, you'll need to trace the wire back (after identifying which wire it is) to find the "open" in the circuit. You'll probably find a break somewhere in that wire that will need to be repaired. 
If you have power to the incident injector, and the ground circuit to the ECU test good, then replace the ECU.


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## shabbarraza2000 (Jan 17, 2015)

Thanks Smj999smj for the reply.

I have understand what you have written, probably I will do it will a voltmeter as I have seen it in the manual of the vehicle for the location of ECU and the pins associated with the fuel injectors.
Probably I will do it at the weekend and update you guys.
Let see what will be the diagnose, finger crossed.

Kind regards,


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## shabbarraza2000 (Jan 17, 2015)

Hi, 
Just to give quick update.
Yesterday I used the voltmeter to check the 12 v in the injectors. I turn the ignition key on, with out starting the car, and confirm the 12.XX volts are coming in each injector, including the one which is not working.
So the neutral coming from the ECU have some problem.
hopefully on this weekend I will check if their is a problem in the wire going from injector to ECU. This will be a simple continuity check. If the wire found to be OK then the only thing is ECU is not working properly. 
Please pass your comment.
Kind regards,


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## shabbarraza2000 (Jan 17, 2015)

Hi,
I checked the connectivity between injector and the other end to the ECU harness point and found the positive connectivity. Now I am sure that the problem is in ECU.

Is that anyway I can repair ECU ?


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