Injectors not firing

[micronot]

I have a 92 Grand Am with the 3.3 engine. I was having the same problem. I found that when I manually fired the injectors (by grounding signal wire) that the car was able to start, but would eventually act up again.

So I came across your posting and I took an ohm meter to the injectors. 4 of them were about 9 ohms, one was about 11, and the last one was ~4.5ohms. So I disconnected the one at 4.5ohms and the car started up. I reconnected it and it would try to start but wouldn't. I disconnected it again and it started right up.

I haven't replaced that injector yet, to see if it cures the problem, but it seems to be the right track. I was going to replace the computer to see if that cleared it up, but now I will be trying that injector first. My computer was occasionally throwing codes 26,27, and 28 related to a "quad driver". I am not even sure what that controls. Perhaps the failing injector was causing this?

[BNaylor]

Welcome to AF.

Your post has been moved to the Pontiac Grand Am forum.

[xeroinfinity]

Hi micronot,

probley is that injector shorting the pulse signal so none fire when its connected.

It might be best to replace them all as their ohm readings are all different. Should be able to find a set for relatively cheaper then buying one at a time.

[micronot]

I ended up replacing 4 of the 6 injectors. Afterwards the car started right up and ran fine for 3 days. Now I am getting the same problem intermittently. I am getting spark, so I assume the crank sensor is good. I am pulling codes 27 & 28, not sure if its related.

Could the bad injectors have weakened the injector drivers in the ECM? I hate guessing and replacing parts that aren't bad, but I am stumped on this one.

[micronot]

I found a TBS that says:

"Many fuel-injected General Motors' engines are equipped with Multec injectors. Some of these injectors experienced shorting problems in the windings, especially if the fuel contained some alcohol. If the injectors become shorted they draw excessive current. General Motors' P4 PCMs have a sense line connected to the quad driver that operates the injectors. When this sense line experiences excessive current flow, the quad driver shuts off and stops firing the injectors."

I am getting codes 27 & 28, which my Chiltons book says are Quad Circuit Driver failures.

I put some fuel injector cleaner in the car. Perhaps this caused some of the problem? I know some injector cleaners contain alcohol.

I replaced the shorted injectors. But I am still occasionally getting this problem. None of the injectors are reading low ohms now. Is it possible that the bad injectors did some damage to the ecm?

[xeroinfinity]

It's quiet possible the ECM is flaking out still. It's also possible your crank sensor is starting to fail.

The Quad driver is just a name for 4 on-off switchs aranged in a group. A driver code means that an expected value is not present when it’s suppose to be.

So I'd double check the injector harness for breaks/shorts in the wires and make sure all ground wires are tight. And make sure all your fuses are good, and or making contact.
Then if the problem pursists might visualy check the ECM and its wires for any burnt spots, and on the circuit board.
Other wise the ECM may need tested/checked by the dealership.

ps- you probly should have replaced all of the injectors.