fuel system troubles

Are you sure that all 6 ignition wires are routed to the right plugs? Is the coil pack functioning properly and are the ignition wires good? Have you tried replacing the spark plugs that are not firing? What condition were the tips in when you pulled them? Is the Check Engine light illuminated and are there any engine computer codes set?

Bob

Now that you mention it, I haven't checked that but I have no reason to believe that they are wrong. Disconnecting #4 injector wire improves running, so I don't suspect the ignition system. I will be checking this, though.

Brand new plugs and wires, just finished this job yesterday. I noticed that #4 makes bigger sparks than #2, but I don't know what that means in this situation.

They looked pretty worn, but now the plugs are new.

No light and no codes.

I checked to make sure, and the wires are indeed routed correctly.

As bad as this vehicle is running the check engine lite should be on!!! you mention nothing about this or even checking for fault codes. I would think that by disconnecting the #4 injector and the fact that is smooths out some would be the injector driver circuit is causing the injector to remain open and dumping in to much fuel. The injector gets 12v from the ASD relay and is grounded by the PCM. make sure the wire from the injector (ground) to the pcm is not shorted to ground. If this were the case a #4 injector circuit fault code would have been generated.

Just a thought

Glenn Beasley Chrysler Tech

If you were to trace the wire from the injector to the PCM. disconnect the injector#4 connector and the PCM C1 connector (LB/BR pin 16 ) and check for a short to ground

Glenn

I did mention that there were no fault codes, and that the injectors click as they should, indicating that they are getting a pulsating signal. I forgot to mention the absence of the check engine light.

It would set a fault code if the fuel pressure was to high or to low. P0171 P0172 1/1 fuel system lean and 1/1 fuel system rich. But does not just point to the fuel pressure. It wont just condemn the fuel pressure. You would still have to check the basics for this code such as coolant temp, mechanical problems and upstream 02 sensors

Glenn

I know from experience that an intermittently failing/failed fuel pump (low pressure) on a '96 will not set a fault code in 1000 miles of drive/die/restart/drive highway travel over 2 plus days. Every dealer within 600 miles of here knew exactly what the problem was, but none was sure enough to replace the pump if they couldn't make it quit while they had the pressure gauge hooked up. Never did set a code. Also never quit with a gauge in place :-)

As you say, IF you get a code from fuel pressure, it will be a sec> It would set a fault code if the fuel pressure was to high or to low. P01= 71

That's really interesting, because it is obviously getting too much fuel, so much so that it cannot burn it. I know the spark plugs are working because I pulled the wires off and watched the sparks jump to the tip of the plug, meaning that there is spark in the cylinder. I listened to the injectors clicking, meaning that they are operating properly. So the problem is either too high fuel pressure or an injector that doesn't close all the way. The resistance on the injector coil is correct.

I guess I need to buy a fuel pressure gauge, unless somebody can think of another problem that would cause excessive fuel delivery WITHOUT setting a computer code.

Just because the injector is ticking does not mean it is opening and closing. If one cylinder is getting to much fuel I don't think it would set a fault code for high fuel pressure because it would only be effecting one cylinder. Maybe going back to basics is needed. A compression test of the effected cylinder? A scan test with a good scanner.

Glenn

It won't set a mixture code if the fuel pump just 'up and quits'. It also won't set a code if the pressure is only slightly high or low. With gas pouring out of the tail pipe, it will NOT set a code because it'll likely never achieve closed loop and can't know what the mixture is doing.

It will, however, definitely set a code if the pressure is off far enough that the PCM can no longer correct the mixture.

If it's misfiring, it 'should' set a misfire code. However, if the battery has been disconnected and the adaptive numerator has not been relearned since, misfire detection will be disabled. It would also be disabled if the engine is operating outside the normal paramaters that misfire detection occurs in.

Not likely that a fuel pressure problem would affect only 1 or 2 cylinders.

OK, this is interesting because the battery has been in and out a couple of times as I worked on basic tuneup items.

If disconnecting the power would disrupt normal codes, I'm starting to think it may be something more obvious like an oxygen sensor.

My last post obviously went over your head.

While fuel pressure is not monitored, it WILL cause a code if it's high enough, or low enough, to cause the PCM to determine it can't keep fuel trim within spec. The resulting code would be 'Fuel system rich' or 'Fuel system lean'.

Yes. Fuel pressure alone WILL cause a code to be set.

Stop right there.

Now, before you start thinking again, go back and read what you quoted. Now, tell me where I said disconnecting power would disrupt normal codes.

That's right, I didn't say that. I said MISFIRE DETECTION would be disabled if the PCM hasn't relearned the adaptive numerator since the battery was disconnected.

OK. Resume thinking and take it to somebody that knows what he's doing.