Noid light staying lit KOEO with new injectors | AEM
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azfiveoh
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Noid light staying lit KOEO with new injectors

I have a 30-2710 box installed with a 30-1400 series 1 EMS and recently switched to high impedence injectors.  After installing the new injectors I found that one of the injectors did not appear to be firing.  After checking the wiring I used a noid light to test the pulse going to the injector and found that the noid light is staying on KOEO for this particular injector.  Bypassing the P&H box yeilds the same results. There is not short to ground in the wiring harness.  The problem does not follow the injector as I have swapped injectors to different cylinders but the problem remains at the same cylinder.

Do I have a faulty computer, faulty injector driver box, or is there another test that I need to run to determine the problem component.

Thanks, in advance, for any help.

AEM_NS
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Did you test for short to

Did you test for short to ground with harness disconnected from EMS?  If yes and there was truly no short to ground, then it sounds like the injector driver in the EMS may be bad.

azfiveoh
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I disconnected the harness

I disconnected the harness from the EMS and the injector and tested for a short to ground between the two pins, there was no continuity to ground.  Are there any resistance tests I can run to deterimine if there is truly a problem with the EMS?

Interestingly, with the car running the injector is not dumping fuel into the car.  The car runs lean and has a miss, just as one would expect with an injector that is not flowing.  With the noid light staying on I would have expected the injector to have been flowing at full flow and flooding the car.

 

AEM_NS
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Perhaps its only enough

Perhaps its only enough current to light the light and not open the injector.  You've eliminated the p&h box from the equation, yes?  You could maybe try checking the resistance of other known good injector outputs and compare them to the potentially bad one.  We never bother with checking the outputs with a multimeter - we'd just put the EMS on a test bench.    

azfiveoh
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Thanks for the guidance.  I

Thanks for the guidance.  I have elimated the P&H box and the problem still exists.  I've compared resistance from the all injector outputs and they're all about the same, there's nothing inheretly different about the faulty injector driver until key power is applied and the output goes to ground.  The only thing I haven't done is remove the pin from the harness corresponding to the faulty injector, replace it with a test lead, and check that lead for continuity to ground KOEO.  I think it would be only foolproof way to eliminate, or verify, the EMS as the problem.
 

azfiveoh
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I pulled the pin from the

I pulled the pin from the main connector and wired in a test pin to the EMS output for the injector in question.  I tested the resistance and continutity to ground on the wire coming from the test pin and it matched the other working injector outputs.  I'm pretty confident that the computer is not the problem.  The noid light goes solid once the injector driver box is plugged in.  Is there any way to test the output from the injector driver box?  There's no continuity to ground on the output from the driver box, but something is happening when I plug it in.

AEM_NS
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A simple check would be to

A simple check would be to just tap the inj input to ground.  The output should go to ground whenever the input is to ground.

azfiveoh
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AEM_NS, I did some more

AEM_NS, I did some more testing last night and found something interesteing.  I switched injector pins for 6 and 7 (6 is the malfunctioning injector output) at the EMS to see if the problem moved to injector 7, and it did not. I suspect this rules out the EMS as the source of the issue, is that a safe presumption?  I swapped pins 6 and 7 back to their correct locations at the EMS and swapped pins 6 and 7 at the output of the injector driver box. Doing this moved the problem to injector 7.  At this point I thought the problem was with the injector 6 output from the injector driver. Oddly, when I disconnect the injector driver output from the injection harness and test the output from injector 6 for continuity to ground with KOEO it does not show continuity to ground.  Somehow, connecting the injector harness to the output side of the injector driver causes the output from injector 6 to go to ground.  I thought something might be wrong with the connector between the harness and the driver box so I removed the output wire for injector 6 and wired in the output from injector 9 and the problem goes away.

Any thoughts on what might be happening?  Something caused the output for injector 6 to go fail and before I plug everything back in and fire up the car I'd like to understand what caused the failure and insure that I have solved the problem.

Thanks for your continued help.

 

 

AEM_NS
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Sounds like the driver output

Sounds like the driver output might be bad.  Without physically looking at it and/or testing it, I can only guess what's going on with it.  If you're now using high impedance injectors, I'd consider removing the P&H driver box to eliminate it as an unnecessary step between the EMS and the injectors.

azfiveoh
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I was planning on doing that

I was planning on doing that but when I tested the coils on the injectors they all came back at 9 ohms.  While it's still above the 7 ohm definitional value of high impedance, it's pretty far off of the 14-16 ohm coil resistance one would normally expect to find on a high impedance injector.  I left the P&H driver in just to be on the safe side.

I did measure resistance to ground on the injector outputs of the EMS and all of them have some resistance to ground KOEO.  As a result, there is a very faint glow coming from the noid light from any injector tested when the P&H driver is removed.  There is no glow from the noid light when the P&H driver is connected.  The noid light was built with an LED and requires very little current to light up.  Should I expect some resistance to ground from the EMS injector outputs KOEO or is there a problem?

azfiveoh
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After doing some more testing

After doing some more testing last night it's safe to say there is a problem with the P&H driver box.  As soon as power is applied to the driver box the output for injector 6 goes straight to ground.  What are some typical causes of failures that result in an injector output going straight to ground in the P&H driver box?  Before starting the car again it would be good to check for other underlying issues that may have led to the failure of the P&H driver box.  Thanks for your help.

AEM_NS
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You should be okay to run 9

You should be okay to run 9 ohm injectors directly from the EMS.  The P&H box hasn't been very failure prone so we've not had a reason to do an investigative failure analysis.  At least you've got a few spare ins and outs to use.

azfiveoh
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I'll try it both ways and see

I'll try it both ways and see what happens, thanks for confirming that the EMS is safe to use directly with a 9ohm injector.  I've had the P&H box for years and it's been rock solid.  I found it odd that the simple act of swapping injectors caused this problem and am concerned that there is an underlying issue for the failure or an unknown compatibility issue with Injector Dynamics brand injectors.  It may be coincidence, but I find that very hard to believe.

azfiveoh
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I did some testing and found

I did some testing and found an issue that I don't understand. Cylinders 3 and 6 are not working even though the noid light is flashing for both cylinders. Swapping injectors does not solve the issue. I wired new injector outputs from the EMS (9 and 10) to the P&H driver and it did not change anything. What's odd is that if I swap injector plugs between injectors 6 and 7 such that the plug from the harness for injector 6 is clipped to injector 7 and vice versa both injectors work. I have not tried swapping wires for injector 3 as it requires removing the upper intake manifold. When I swap the plugs back to the proper injectors number 6 no longer works. Since the noid light works it's safe to say there is no wiring issue. What would cause the P&H driver box to act this way?