Thread: MSD 72lb injector help. -- Injectors bad or tune?

Hey,

Got the MSD 72lb injectors installed on my car today. The car idles really bad. It seems like a few of the injectors are not firing or firing out of order. My AFRs are non-existant and the car idles really bad with bouncing idle and low vacuum. I even pulled a few of the spark plug wires to see if I could pinpoint which one was not firing and it seemed to make no difference. I even pulled 3 of them and the car seemed to not change its idle. It seemed like no matter which one I pulled it sounded the same.

All the injectors have resistors on them. All of the resistors are on the skinny wire. I made sure to wire skiny-skiny fat-fat from my injectors to the harness. I'm guessing skinny is power and fat is ground. Anyways, does it matter how you wire up the injectors to your harness with regard to which wire the resistor is on? In other words, if the resistor is on the power wire on the injector and you connect that to the ground on the harness, will that work and visa-versa?

Any other ideas? All I did was replace the fuel rail from a stock highport to a JWT. I have a Nismo FPR so it bolted up no problem to it. Not sure if I missed something? The other thing I was considering is that these injectors may be 50#(as you can't visually tell the difference) and the tune I have is for 72#, but I'd guess the car wouldn't run his horrible if the tune was wrong, but I'm going to try a 50# tune and see if that makes any difference.

@Ben: Did you run these injectors while you owned them? any issues? I thought you said you ran them for a little bit, but I deleted all those PMs so I don't recall.

Thanks!

If your ecu is tuned for the injectors that you have then there has to be something up with your wiring why didnt you just use a resistor box instead of individual resistors?

This is the way it came to me. I thought it would work?

Also, the 72lb and 50lb MSD injectors look exactly the same..even the 96lbs I think. It could be the injectors are 50#, but even if they were I don't think the car would be acting this bad w/a 72# tune.

-G

Yeah they all look the same but if I remember correctly 50lb injectors are high impedance and 72lb and 96lb injectors are low impedance.

ahh so the 50# injectors don't need resistors? Well, if that's the case then these have got to be 72# unless someone wired these resistors in to 50# injectors and if that's the case then it would probably explain why it's messed up, but I'm doubting that scenario, but it is a possibility...

When I had 96lb injectors in my turbo car I got a resistor box from a late 80's early 90's model Acura Legend then followed the wires from the injectors on my B13 until they all spliced into one then i installed the resistor box there. I may do a write-up some time in the future it is such a cleaner looking install this way also early 90's mitsubishi eclipse resistor boxes work well too.

Any advice I should check w/my wiring? Polarity and such doesn't matter with the resistor does it? It could be that not all the resistors are on the power wire as I never checked that(I checked one), but I'm assuming they are. If they are, as long as I have all the wires connected the same it should work, right? The car does idle, but it idles bad. So it at least starts. I actually seem to notice the car running fine for the first few seconds of the start and then it gets pretty bad after about 10 seconds. Almost seems like a huge vacuum leak. I checked all of the injector seals on the intake manifold and they are all pressed down pretty good. I did notice w/the JWT fuel rail and bracket I can't get the injectors to seat fully, they do move around a bit up and down but no fuel leaks. I have the injector clips facing the firewall, I wouldn't think that would cause any issues. I was thinking maybe the angle or orientation of the injector is not shooting straight but that doesn't make much sense to me...as you can tell - I'm grabbing at straws here lol

-G

From what I remember you have to wire in the resistors either all on the positive side of the injectors or all on the negative side you can't mismatch them.

OK I'll check tomorrow that the resistors are all wired on the power/skinny-wire side tomorrow. Also, for me to re-wire these into my harness again I'll need another injector harness as I'm out of wire so I may go to the jyard tomorrow to pick one up. '95-'99 G20 should be the same I think.

Ok bro keep me posted.