I checked the resistance on 2 of my injectors and they were both .25 ohms. This can't be good, can it? I pulled the connector off the injector and just measured across the 2 pins. I haven't had a chance to check them all. I have checked the fuel pressure and it starts at 44 PSI and once I turn the key to off, the pressure drops fairly quick. Would .2 ohms mean they are stuck open or what?

 

I currently have 19# injectors. Can I put 21# or 22# injectors in the car without reprogramming the chip? I know I should change the constant but will it work without running too rich? Can I compansate for it with the fuel pressure regulator?

 

[Would .2 ohms mean they are stuck open or what?]

Yes, I believe that means they are.

It would run rich with 21-22# inj.

 

I went back and checked all the injectors and I was wrong. They all read 16.4-16.5 ohms. Could they still be leaking? I am getting a loud tick from under the hood but only in drive. Dan, I know I would be running rich but would I be able to compensate for that by lowering the fuel pressure?

 

That was 16.4-16.5 ohms.

 

yes you can run larger injectors ie 22# on a 305 changing the injector constant. take for example me.... i'm running 24# lt1 injectors on my 350 just changing the constant and little things here and there. no AFPR here. it's running fine no problems whatsoever.

 

My question is can I do it without changing the constant. Can I compensate for running rich by adjusting the fuel pressure regulator?

 

Understand the ECM can compensate for only so much.

An AFPR shows it most benficial use at WOT, to tune the AF ratio, when the ECM is not trying to compensate.

i/e I run 21lb/hr Accels on my L98 (stock was 22) w/headers and intake upgrades at about 45/46 PSI.

ONly way to know for sure is to try, if too rich, then gives you the best reason to buy some prom burning equipment and bgin tuning

 

unless you have driveability problems, i would leave it alone, if you want to change out the injectors (the aftermarkets are much better as far as tolerances go), i would stay with the stock rating unless you are going to do some major mods in the near future, i.e. port and polish the heads, headers and cat-back.

i recently replaced the injectors on my l98 w/21# accel's, my engine is still stock with the exception of high flow K&N, throttle body collant bypass, TPIS air foil, accel super coil, cap rotor and 8.8mm wires.

it runs like a wild animal.

MD350
89 Formula 350

 

The problem is that I am having drivability problems and a few of the injectors are ticking. Which is not good. They are obviously leaking because my fuel pressure drops off. I am currently at about 265 HP at the crank. The 19# injectors are only good to about 275-280 HP.

 

my injectors "tick" like crazy, which is good as they're opening and closing like they should, if you are saying that they are stuck open, "leaking", you should be running very rich, until the ecm leans the car out so much that it will quit and stall. have you taken a pressure reading on the fuel pressure yet to make sure you are taking a drop? i will idle at 35psi and will rise to 45psi at 3000 rpm.

is this helping? exactly what driveability problems are you having?

MD350
89 Formula 350

 

i see no problem with installing slightly larger injecters and lowering fuel presssure to adjust-people have been doing the exact oppisite for years.especally if you have access to a scanner
pete

 

Once again, and hopefully for the last time (although I know better), there is absolutely NO correalation between the resistance reading of the operating solenoid coil of an injector and the flow characteristics of that injector. Obviously, if you have an injector that has a low resistance coil, it is not serviceable since it will SMOKE the driver transistors in the ECM. And if you have an injector that has overheated so badly that it has melted together and frozen the pintle, you have a possibility of having a leaker and a bad coil at the same time. However, low resistance (or, high, for that matter) says nothing about how an injector will flow. Period. Where anyone ever got that idea is beyond me, but it is simply flat wrong. Unfortunately, that idea has been dissemninated so widely through misinformation that it has become as much legend as Slick 50, intake Tornadoes, and "Neuspeed" and "V-Tec" decals.

AND, a brand-new, out-of-the-GM-box set of injectors will definietly "tick" when actuated if the fuel pressure is correct. Many people cannot hear the noise over the engine noise, but they will make noise.

If you're reading low resistance, you have an electrical problem with the injector. You may or may not also have a mechanical problem with the pintle, screens, check assembly, etcetera that may have flow implications, but the two phenomena are not interdependent. And NO amount of resistance reading will indicate diddly-squat about how an inector will flow in service, unless the coil is completely shorted or open.

I know that nobody believes any of that, so don't take my word for it. Call or email TPIS Specialties, Cruzin' Performance, any reputable fuel injection service, or General Motors Rochester Division for all that it matters. Better check with Denso and Bosch to see if they somehow magically build their injectors differently. Ask their opinions.

 

No flame intended Vader....but having just gone through this with a '91 GTA ...I can vouch for the fact that two injectors were reading 3 ohms and the engine was running dead rich (108 BLM's). Removing the wires from those two injectors did cause the INT & BLM's to come back up to 130-135. I changed the whole set of injectors and now the car runs sweet again. ( I wasn't about to change just two).

 

Sounds like you know the injectors pretty well...What are the likely problems with unknown used injectors that have been laying around for a long time? They all ohm out the same but im wondering what can go wrong mechanically. None of them leak, I've pressure tested the system and there was no dribbling. Can they stick closed? Is that likely? I'm getting ready to try to start the engine for the first time in the next few days and I'm trying to anticipate any problem.

Thanks

Steve Huddleston

 

vader...in reviewing the posts, i don't see where anyone made a correlation between resistance and flow. it appears that the thread was going along parrallel paths. i do appreciate the additional info on injector operation though.

don...i agree, change the whole set once and for all, i had 3 bad injectors recently, the car was not driven for 7 years prior to my purchasing it, a nice set of 21# accel's was just the ticket.

stevie...when you say used injectors laying around, where these the oem's in the car or spares that you got from somebody? if spares, spend the $250 and get a fresh set from summit or jegs, if oem's in the car, watch for a very rough idle, as don stated, and i have done also, you can isolate the injectors by unplugging the suspected bad ones, just don't lose the connector weatherproofing gasket. good luck on the startup.

 

I can't imagine that if I am sitting in the car, in drive and moving that I should be able to hear the injector, but I can. That much tick is not normal. It can't be. I don't remember making any coorelation between flow and resistance. I was just trying provide as much information about what was going on.

 

and it's not.... but an injector shouldn't tick that LOUD. a lifter can but an injector ??? u sure it's not a lifter or an exhaust leak?

 

I'm pretty sure it is an injector. I only have 2-3 injectors that are ticking. The loud tick sounds like it is comming from the same area that one of the injectors are at.

 

Dyno,

No flame taken. And I wouldn't have bothered to change just a couple of the early design Multec injectors either. Just throw them in the recycle bin.

As I mentioned, a low resistance injector may indeed have suffered internal damage from the overheating coil, and this could easily lock the core in an open position. However, the two phenomena are not always related. The same injector could have been "locked" in the closed position just as easily by the melting solenoid insulation. In other words, and injector that has 12 ohms of coil resistance will not necessarily flow any more or less than one that has 16 ohms resistance. I have read many posts where it is apparent that some would believe that the 12 ohm injector would flow 25% more than the 16 ohm injector, based solely on the solenoid coil resistance. Nothing could be further from the truth.

Additionally, even if the injectors that failed didn't suffer a melt-down and lock open, the system can still go rich from nearly static injectors. If you study the system, you'll see that the injectors are "banked" in sets of four (three, on V-6 MPFIs). The ECM has an in ternal or external connection (depending on year) that connects the two banks so that one switching transistor can operate the entire set. The primary power is fused from two sources, but the ground path for each bank is through the same switch.

If any one of those injectors has a low-resistance path to ground from a coil insulation failure, all the injectors will go "static" as soon as the ignition power is switched on. Even if the failure is not a ground, the high current through the switching transistor can cause the transistor to saturate, maintaing a constant forward bias on the base through the internal resistance change effect on the emitter-base bias resistor or emitter resistor in a thermal runaway condition. Reverse bias of the junction would be very slow, if at all, so the injectors would either remain energized (grounded) or the turn off would be very slow. That's just elementary transistor theory in action. As soon as the current is reduced from either shutting off the source (ignition) removing the excessive load (shorted injector) the system operation could return to a normal cut-off of the base-emitter bias.

What you experienced is completely normal. The exact same thing can happen in a push-pull audio amplifier stage if the voice coil of a loudspeaker is shorted or suffers thermal breakdown of the insulation. Pop in a new speaker, and everything on that channel return to normal (if you didn't fry the finals of the amplifier).

 

As for the ticking of the injectors, what can I say? I guess I'm just lucky, but all of mine tick - an LB9, two LT1s, A V-6 MPFI, a 122 four-banger, and even a few that I no longer have like TBIs have all ticked. Other owners must have experienced similar noises at simlar levels, since GM has had TSBs to advise their service technicians of the "problem" when owners complain of it.

 

So you're saying that an injector tick that can be heard from inside the car at 2000+ RPM is normal. It wasn't that loud until recently.

 

replace the set and be done with it. enjoy better driveability, performance, & gas mileage. report back with results

 

At 2K RPM? No. At 1k and below, yes. I missed the part about the 2,000 RPM noise. There should be enough other engine noise at that point to mask the injector sounds, although I've heard that some of the Denso injectors can be pretty noisy.

 

It just started a few days ago. It wasn't that noisy before. It started after I replaced the transmission and screwed up the timing. I can't seem to adjust the minimum idle without the car dieing either. What a mess. Will bad injectors screw up the timing or cause the car to stall at idle?

 

go back to the source, the car was running fine...work was done...now it runs crappy...start with what you changed or altered, tranny and timing. i doubt the injectors decided to go south just because work was done on the car. i think you're chasing the wrong problem.

MD350
89 Formula 350

 

FWIW, it might help.

Back when I was wrenchin' for GM, we saw alot of complaints on ALL sorts of vehicles for the "infamous ticking".. shoot, even years later I bought my wife a '96 GP w/ only 10k miles on it, and the injectors on that 3.1 sounded like a busted rocker...ESPECIALLY when cold started.... but it was normal..or like Vader said, and we were lucky...just got rid of that car for a new truck in Feb '03 and it had 130k on it and ran PERFECT....still TICKED like a SOB, but ran perfect


One thing that seemed to help on some cars was to replace / lubricate the injector O-rings, and sometimes just moving the injector around without taking 'em out...just turning it a bit this way or that way would lessen the noise...I'm guessing the ticking amplfied off the intake itself...


HTH