Injector Resistance Question.

[Booster-Shot]

Hey well I went and tested my injector resistance because my car has been throwing a cel and what do you know, my #3 cylinder has no resistance. I was really confused when this happened though because I had just replaced my injectors about a month ago. (I replaced them because of this same problem) Do I have a bad injector or is there something that could be causing my injector to have no resistance? I dont want to have to buy another new injector if something else is causing it to do this. -Thanks

 

[steve]

Yes that injector is shot.
I assume your running 450cc injectors. Perhaps your running them too hard (>90% IDC) and burning them up.

Steve

 

[Booster-Shot]

That would suck if I was, when it happened I was completely stock. But there is something else thats confusing me as well.

It says in my Chiltons manual that the 450 injectors are supposed to read at about 2-3 ohms. Well when I went to check my other injectors they were reading at around 8ohms. Does anyone know what this could be?

 

[steve]

If you were measuring something other than the original OEM injectors then the factory spec doesn't need apply.

Steve

 

[Booster-Shot]

Alright so even though Im running 450's, because they are not from the factory they have different readings? Generally would 8ohms be an alright reading? I was getting worried that they were running too high.

 

[dsm-onster]

Alright so even though Im running 450's, because they are not from the factory they have different readings? Generally would 8ohms be an alright reading? I was getting worried that they were running too high.

Turbo DSMs run low impedance or peak and hold injectors. 2-3 ohms is acceptable.

You can run a high impedence or 8-13 ohm injector, but in all likelyhood you'll run a bit lean at idle and slight throttle in any cylinder you put one in because of the high deadtime associated with high impedence or saturated injectors. You cannot run low impedence injectors in a high impedence setup without a resistor pack (a resistor between the ecu and injector that brings the total resistance to 8-13 ohms).

I am pretty sure 1G and 2G dsms have a resistor pack. Mitsu chose to run a high impedence ecu with peak and hold injectors . The na cars have high impedence injectors and consequently have no resistor pack.

But, in the midst of all my babel, you should be getting 2-3 ohms as a reading with stock injectors or any direct replacement upgrades.

 

[Booster-Shot]

Turbo DSMs run low impedance or peak and hold injectors. 2-3 ohms is acceptable.

You can run a high impedence or 8-13 ohm injector, but in all likelyhood you'll run a bit lean at idle and slight throttle in any cylinder you put one in because of the high deadtime associated with high impedence or saturated injectors. You cannot run low impedence injectors in a high impedence setup without a resistor pack (a resistor between the ecu and injector that brings the total resistance to 8-13 ohms).

I am pretty sure 1G and 2G dsms have a resistor pack. Mitsu chose to run a high impedence ecu with peak and hold injectors . The na cars have high impedence injectors and consequently have no resistor pack.

But, in the midst of all my babel, you should be getting 2-3 ohms as a reading with stock injectors or any direct replacement upgrades.

Yeah my car does have a resistor pack. So, assuming this could my resistor pack be shot? Is this why my other injectors would be reading so high? Would this in turn cause my injectors to eventually go out? Because like I said I these are a new set and I dont know why they would go out already. - Thanks

 

[psychlow]

If the resistor pack was dead, it would fry the transistor drivers in the ECU, not your injectors. Low impedence injectors are made to soak up 4-7.2 amps (a lot.) If the injectors are burning up, it's because they're driven at too high a voltage, or too high a duty cycle.

 

[Booster-Shot]

...so what can I do about that? WTF

 

[psychlow]

First order of business: Figure out what type of injectors you have. If they all came from the vendor reading 8 ohms, you need to remove the resistor pack to use those injectors. If that was the case, I'm surprised they even work(ed) at all.

Second: check your alternator output voltage with the car running. Use a multimeter or a voltmeter and disconnect the negative battery terminal while the car is running, and measure the voltage between the positive and negative terminals. If it's above 14.4V, you need a new alternator (or you can replace the alternator's internal voltage regulator, but you'd have to disassemble the alternator).

Third check injector duty cycles at WOT. If they're above 90%, you either need to fix boost leaks, turn the boost down, or upgrade your injectors.