Injectors?- pcm ?
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Injectors?- pcm ? Thought I would try this here first. Friend has a strange problem with his 5.3engine. It has 2001 intake and injectors#25317669 I believe. It has PCM # ending in #411. PCM was re-programmed to be stand alone with 2 front oxygen sensors and the usual deletes. The problem is the #2 cylinder on passenger side runs extremely rich. So rich in fact, it backfired and blew muffler on that side. Thinking the injector was bad, we tried to confirm by switching it to another cylinder. It ran clean on that cylinder and the one we relaced it with promply started doing the same thing...running rich. We tried switching coils and plug wires with no success either. We checked ohms on injectors and all seem to be somewhat out of spec, reading up around 14.8 into the 15 range instead of the 11 to 13 range recommended. Could this be a factor? If so, why just one injector? He tried a noid light and it blinks on the bad one just like the rest. Plug on that one cylinder runs black carbon, smells like gas, all others run clean. Could PCM do this on only one cylinder? Anybody ever run into anything like this? Any suggestions to try? I might add, the engine starts and runs fine except uses a lot of fuel (duh). Afraid it's going to ruin rings on that cylinder. Thanks, Ron
Last edited by rojs234; Jan 11, 2011 at 09:39 AM. Reason: Had the injector # wrong
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Thanks for the reply. We had considered the O2 sensors, but I couldn't see how it could affect just one injector on a bank of cylinders. I always thought the O2 sensor sampled the exhaust for the side it was on and adjusted the four injectors accordingly. I might also add that it is showing no codes. It's got us baffled.
I read a thread in the force induction section where his did the same thing with an after market AEM computer. It put so much gas in that one cylinder that it caused the starter to kick back and brake one of the starter mounting holes in the block. He was using 160lb injectors though.
I would check the harness. Pull the connectors off the PCM and injectors. check the resistance of the wires running to the injector (PCM to injector plug), and then to ground (either end to ground). Most fuel injection systems have injectors hotwired and then pull-up to ground to fire the injector. If you get a ground signal it would hold the injector open. You could also buy a fuel injector tester and plug it in and see if the light stays lit.
Correcto.. Thanks for the reply. We had considered the O2 sensors, but I couldn't see how it could affect just one injector on a bank of cylinders. I always thought the O2 sensor sampled the exhaust for the side it was on and adjusted the four injectors accordingly. I might also add that it is showing no codes. It's got us baffled.
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I would check the harness. Pull the connectors off the PCM and injectors. check the resistance of the wires running to the injector (PCM to injector plug), and then to ground (either end to ground). Most fuel injection systems have injectors hotwired and then pull-up to ground to fire the injector. If you get a ground signal it would hold the injector open. You could also buy a fuel injector tester and plug it in and see if the light stays lit.
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See if I am understanding you correctly. I should check each individual wire from the PCM to the injector to see what resistance each wire has, and then hook it back up at PCM and check from the injector end to see if it has continuity with chassis ground? And then reverse and check from injector to ground? If wire shows any continuity with ground it would hold injector open, right? But as I said above...would a noid light blink if wire was grounded? I am curious to see the results of your suggestion, so we will definately give it a try. Thanks...Ron
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Anyway, thanks for confirming the way the sensors work. Ron Thread Starter
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I would only worry about the individual cylinder you are having trouble with, but the goal here is to check continuity the entire length of the wire run from the PCM to the injector connector. Then check each wire so that it has not picked up a nick or other ground path. The noid light would show a constant light (i.e. hanging an injector open).
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We will post the results, but at this point I have pretty well run out of things to try. I guess a different PCM is the only other thing that makes sense. Anybody got any other ideas?
