Slade1

If an injector was exhibiting hhigher than normal resistance outside the normal range, what would the operation of it be like?
Please feel free to voice your input, TPI, TBI, CFI, MPFI, SFI etc on the matter. I don't have access to the necessary equipment, nor do I have the cash or funds to get them or bring it into a shop. In an ideal world, i'd have a scope, lift, all the proper tools and heated garage to do this in.

I've looked up conflicting reports on what the TBI injector resistance is and found vader's response to be 1.2-1.5 ohms, but another conflicting response saying only 1.1-1.3 ohms.

Both my injectors are at 1.6 ohms. Vader's range would have me 6% higher than the max resistance and the other would have 23% higher. This is well outside the standard deviation in my opinion. Would this cause higher BLM counts?

The fact is my injectors are spraying "odd", still cone shape, but not the fine mist I remember. My blm counts have risen to 135-142 range and never go below 128. At WOT with BLM locked at 128, O2 is reading rich numbers all across the board, consistent with a rich mixture. At 2000, 2500 and later rpms there is an odd vibration from the engine. Timing has been returned to stock and fp was added to compensate for the "lean mode".

My theory is this. Since the injectors are producing higher resistance, the injectors are having a hard time opening. This in turn is not allowing a fine mist spray not allowing for a proper fuel mixture. At highway cruising speeds in lean cruise mode, the throttle is low <20% and since the mode is lean, its supposed to reduce fuel, thus lower blm counts, but the improper spray is not allowing proper fuel atomization and causing some cylinders to go lean and some to go rich causing the vibration at those crusing speeds. At WOT, the turbulence associated with WOT allows for better atomization thus revealing the fuel being delivered by a high pressure setting, improper spray injector to be too rich.

The injectors have seen 370000 kms and 15 years of operation. Recently a tune up was performed with no ill effects. (3 - 4weeks ago) Even more recent was an oil change with fuel system cleaner added. ( < 2 weeks ago). The problem began to occur about a week after the oil change.

So my question is, am I crazy with this analysis? I think my injectors are the problem, although I haven't checked FP yet and can't rule out a failing pump. The pump is only 2 years old, replaced with a new stock pump. I replaced the fuel filter already. If the pump were failing though, would not the spray from the injecors come out more like a drip? As it stands, the spray looks strong, just erratic and not a fine mist. WOT and acceleration are strong and quite frankly, the plugs are looking tan/brown not pointing to a lack of fuel.

I will bid on ebay for a replacement injector pod in the mean time. Local junkyards are raided long before I get there due to a local company trying to monopolize f-bodies. (Local being all of freaking ontario, hate that guy). This has the tiny problem of him charging outrageous prices on parts.

Vader

S1,

Injector resistance will vary with temperature.

Another important consideration is the equipment being used to test the injectors. A resistance of that kind, with wire windings and relatively low resistance, should be tested like an electric motor - with a high current ohmmeter. The typical pocket or automotive tester may not provide adequate test current to render a reading that is as accurate as you are seeking. A Simpson or Triplett d'Arsonval meter with a lower ohms/volt and higher current supply for low resistance would be better. Ideally, a bench meter like a VTVM would be the way to go.

Slade1

I have a fluke 87 true rms multimeter.

I checked the resistance when the car had just been run, I'll check when cold too though later today.

As I recall though, for most common metals, resistance increases with temperature.

I wish I had an oscilloscope or something to test the injectors if they truly are opening properly.

When manually opening the throttle, the spray becomes very erratic and turbulent. I can't remember though if it did this before.

Vader

I have an 80-series, an older 8022A, 8024B, and 8026B, and still keep an old Simpson 260 around for high current resistance checks, checking RMS power, dB, and those occasional times when the 2000/S count rates on the Flukes just aren't fast enough to catch those "blips" I'm often too lazy to drag out the Tektronix, isolate it, and plug everything together. I'm also careful with using those $90 probes around hot engine parts, since that could get expensive in a hurry. An o-scope would be a good way to look at the square wave, however.

Remember that fuel pressure will have a lot of bearing on the spray pattern, and that both the injectors are fired once every crank revolution, not every engine cycle.

If your pressure is correct (11-13 PSIG), you might want to remove the top of the injctor pod carefully (so you can reuse the gasket), and remove/inspect the inlet screens for the injectors. You can also manually "fire" the injectors by completing the ground path to them while the ignition is ON and engine is not running. It's a quick way to flood the engine, but should give you a good idea of the actual spray pattern abd flow. You'd have to power up the fuel pump to do that, however. Jumpers, jumpers, everywhere...

You also realize that the pulses width on a warm engine at idle are going to be relatively short, and that the propagation delay of the injector solenoids might be increasing to the point where they no longer comply with those short pulses. Cleaning the injectors can help with that.

All that can occur with injector solenoid resistances that are perfectly acceptable. Also, even though the wire resistance itself may increase with temperature, the insulation resistance can decrease as the windings get hot and start to grow slightly. The wire itself probably rarely fails.