Fuel Injectors with low resistance

[06goat75]

Working on tracking down a hesitation on the '95 LQ1.  Mainly when it is cold, but still has some hesitation during acceleration.

Looking at the 3 fuel injectors under the cover (haven't checked the back 3 yet), 2 of the 3 are showing a low resistance of ~10.5 ohms.  Third one is showing the accurate 12.2 ohms.  Car was warm, but not hot.

What does low resistance mean for a fuel injector?  Been looking a bit online, and can't find a definitive answer.  What happens with a fuel injector with low resistance, will it still work (hence, the car is running decent), just on its way out?  Or just not working good at low RPM (hence the hesitation?)

Have a set of 17lb injectors for my Fiero w/ a Camaro 3.4 pushrod (ACCEL 150617), but doubt I'm lucky enough they will work!

Edited April 1, 2020 by 06goat75

[55trucker]

The Rochester injector for the '95 LQ1 is a 17090844, this is a 29lbs. high impedance multi tip injector. High impedance would be 12-16 ohms, low would be 1-5 ohms.

When the impedance begins to fall away the injector actually begins to react quicker to electrical impulse. This will upset the fuel delivery with respect to all of the other injectors that are responding *normally*.

The ECM is expecting to allow a certain amperage flow to each injector, the lower the impedance the higher the current to that injector which can cause excess heat to that injector winding (not necessarily a good thing).

Edited April 1, 2020 by 55trucker

[06goat75]

33 minutes ago, 55trucker said:

The Rochester injector for the '95 LQ1 is a 17090844, this is a 29lbs. high impedance multi tip injector. High impedance would be 12-16 ohms, low would be 1-5 ohms.

When the impedance begins to fall away the injector actually begins to react quicker to electrical impulse. This will upset the fuel delivery with respect to all of the other injectors that are responding *normally*.

The ECM is expecting to allow a certain amperage flow to each injector, the lower the impedance the higher the current to that injector which can cause excess heat to that injector winding (not necessarily a good thing).

 

Thanks for the PN.  Now to do some shopping.

I guess with a higher current to the injector, theoretically it might stay open a fraction longer, causing a bit more fuel flow, resulting in it bogging down a bit (too much fuel) when the accelerator is pressed from idle?  Am I thinking about that the right way?

 

[55trucker]

For example.....at 13v the amps flowing thru a 12 ohm resistor is approx 1.1 amp, the same 13v on a 10 ohm resistor is 1.3 amps, not much difference but how much is too much over what given length of time over what general heat environment before the windings suffer from heat?

The fuel is supposed to keep the injector cool.

as for bogging, the ECM should be able to cover off the fuel flow in closed loop & stay within the programmed tables, in a sequential environment each injector fires on it's own, not so in a multi-port batch firing environment.

[06goat75]

So, in all reality, a fuel injector showing 10 ohms of resistance, is on its way out, but still flowing fuel within a spec the ECM can compensate for.  Just running hot.

[White93z34]

I don't know what the spec is, exactly. I just know 10ohm is probably still ok... I'd keep an eye on it.

When they go bad they'll usually drop to 1ohm or less and at that point they short the driver and no injector pulse to all of them.