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Okay. I’m not used to being this confused…and I wish I could borrow Scanner Danner’s tools and IQ for a few minutes on this one.
2005 Dodge Durango with a 4.7 V8. 4WD.
It’s my mothers SUV and she’s been without it for a few weeks.
Kicked up error “open injector circuit #6” and has a bad miss.
Checked wiring and it all appears fine. Did the test with the test light attached to the positive on the battery and probed the wires to locate the ground side switching circuit. The red wire seems to have a rock solid 12volts. Test light is very bright. The other wire when I have the clip attached to the “+” shows a pulse when probed with the test light. The suspect one had NO injector pulse at all. Went and ohm’d out the harness to the computer for the engine. Wiring checked fine.
Ordered in a rebuilt PCU for the Durango. Same error exists on the CEL ?!?!?
Only this time: We have an injector pulse at the injector plug. (Makes sense, the bad computer didn’t have it…the replacement does….)
Now we’ve swapped the #4 injector plug to the #6 and vice versa. Problem goes to #4, number 6 now works fine. So we know the injector is fine.
I’ve checked the injector pulse by just touching the pin in the connector as well with it unplugged. Nice steady flicker on the test light and it looks the same as the other injectors.
We are going to replace the plug with a new one for that injector. I’m not sure that will solve this mystery? I pulled 2 off a salvaged Durango and we have wired in all 3 to that injector. I find it very hard to believe that all 3 plugs would be bad. But I’ll replace it with a new one just to clear that as a possible issue.
Any ideas on this mystery? The crazy part? We tried a used PCU at first and it seemed to run fine until the immob. kicked the engine off. But it only ran for about 5 seconds before it shut the system off. (That PCU had a blown starter circuit that kicked in after the 3rd start….So we put the old one back in and the starter circuit ran fine)
I am not used to being this lost on a project. We now have a rebuilt PCU from a decent company–and I find it even harder to consider that the replacement PCU would have the exact same issue/error the old PCU had. The old PCU had no injector pulse–the replacement one does…..It’s going to the plug to the injector but still showing a miss and ‘open injector circuit’ fault.
What am I missing?
S-
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It’s possible that the injector is bad and caused the driver in the old PCU to fail. Measure the resistance across the terminals of the injector, it should be between 13 and 15 ohms. If you get a reading other than this, check the resistance of working injectors to compare against, they should all be within an ohm or two of each other.
Nailed it.
It’s not often I get fooled by readings and general testing. When this first presented I did a balance test by unplugging injectors and taking readings. The #6 injector passed each test at THAT time. Ohm’d out the same as the neighboring ones, and the wiring when swapped? The injector fired normally, etc…
I redid the plug on the end (it was broken anyway from all the testing..plastic brittle…) And I picked up a used injector from our local salvage yard from a 2003 Durango. (Interchanged fine) Just as a test I plugged it in without having it on the fuel rail. The wife starts the SUV up and no CEL! I can feel the injector fire in my hand, and it was bleeding a bit of fuel out the end. That was the head smack moment. All the normal testing went out the window on that one LOL.
The base of the injector was just about welded into the seat. Thankfully I was able to lift the one rail up without having to remove the entire thing. Wrenched out the bad injector and I had quite a shock. Base of the injector right above the O-Ring was expanded about 1/16″ and had several cracks in it. This injector has the same diameter at the base as the top–picture the bottom 1/2″ of the injector puffed out and full of rust. Couldn’t tell from the outward looks, as this is the part that seats well below the valve cover.
We put it all back together. Light coating of oil on the o-rings (and a new set of o-rings on the replacement injector) Checked for fuel leaks-none. (thank God for that….my track record with injector o-rings suxs). Took it for a test drive, no CEL’s to report..ran smooth as silk.
The company we got the rebuilt PCM did an outstanding job, programmed it with the mileage, vin, everything. Truly plug and drive… I figure the old injector started to dead-short and that took out the driver transistor on the PCM. As we did check for injector pulse and had none with the old computer.
Mom’s very happy and that makes me happy. (it’s Mom’s “Taxi” and she was without it for about a month while I found the time to work on it)
Best regards to the group!!!
S-
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