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Would a bad fuel injector cause plug not to fire? Weird voltages at harness for cylinder 3 compared to other cylinders. No spark at plug. Coil and plug new and tested on other cylinders. I am leaning toward computer. Any ideas?

  • A bad fuel injector will not cause the plug to have an absence of spark. It will cause the engine not to run right, though, due to lack of fuel in that cylinder. – Pᴀᴜʟsᴛᴇʀ2 Aug 6 '14 at 20:59
  • True, Paulster... very literal. Weird voltages can show up on digital meters when they're "not really there" as found by a lower-impedance analog meter, too... you can actually read some pretty high voltages on a wire that's not connected to anything at all if you use a high-impedance digital meter. Induced currents & all that. 293336, check for continuity (low resistance reading) across the injectors' coils, one at a time, with the power off. If #3 injector tells you a significantly different story than the rest, you'd best replace it. – TDHofstetter Aug 6 '14 at 21:29
  • Your best bet in this case is to change the coil with another coil and see if the misfire follows the switched coil. If it follows the coil, get another new one. It is not unheard of to get a bad coil from the parts store. If the same cylinder is not firing, your problem lies in the engine harness wiring. – Pᴀᴜʟsᴛᴇʀ2 Aug 6 '14 at 21:45
  • Coils and plugs have been swapped around. Its is just cylinder 3. Was just curous if the computer would see bad fuel injector and stop plug from firing. Guess I am just hoping it is something cheaper than computer. Basically its either computer or wiring. – user293336 Aug 6 '14 at 23:19
  • You should also check the computer end of the wiring harness for corrosion. Also, while you have the wiring harness plug disconnected from the computer, check resistance between the pin on the connector to the coil. If you have low resistance, the wire between pin to coil is not your problem ... you'd need to look at the computer. If the resistance is high (or infinity) you'll have to run this wire down to see where it is having its issues. You'll have to figure out which pin is for the coil. Also, check to see if there are any recalls on your computer or other things ... you never know. – Pᴀᴜʟsᴛᴇʀ2 Aug 7 '14 at 22:19
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As they are 'pencil coils' on your vehicle, you can transfer the supect coil on to a differant plug. If the coil now works correctly whilst the one it was swopped with starts to 'misfire' on number three plug then you know you are dealing with a fault with No.3 cylinder. Secondly try replacing No3 spark plug with one you have removed and know to be working previously. Thirdly, unplug the No 3 injector-just the electrical connection- and measure its resistence with an Ohm meter. Now compare the resistence of any other injector. Your injector is a simple solonoid and can be tested with an Ohm meter. Open circuit on number 3 injector, or a very much lower reading will pinpoint a faulty injector. If every thing runs to expectations then you very well may have a fault on your wiring harness, or blown power diode(s) in your ECU. In this case, and before deciding on any expensive expenditure, have the vehicle scanned with an OEM/compatable scanner. If you have an analogue volt-amp set, do not use it on any modern vehicle. Its low internal resistence will allow it burn out modern electronics. In passing, an Ohm meter must never be used on any vehicle circuit that includes a Hall generator (three wire sensors for example), as the Ohm meters testing voltage will destroy the Hall generator.

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On Chryslers it's the other way around. When the PCM detects concurrent misfires on a cylinder it'll shutdown injector pulse.

Check pin 1 on the coil harness tan/orange for signal from the PCM and pin 7 on PCM connector 2. If you're seeing voltage drop on the power side of the coil you're gonna have to unwrap some tape and check your splice and wiring.

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If the coil keeps burning through check for cracks inside the threads of spark hole. Sometimes it so small it cant be seen an even the Dodge dealer couldn't find it. Need to inspect with bore cams.

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