QuestionQUESTION: Hi Roland. I have a 1988 Chrysler LeBaron convertible 2.5L 3spd auto, and I'm experiencing an issue with the engine not shutting off when the key is turned off and removed. My ignition lock cylinder had not been working properly for many years. I wasn't able to turn the key to lock the wheel or to the Acc position, and I was able to start and turn off the car without the key. First I thought maybe this started causing the problem. I replaced the lock cylinder, and it fixed the issues I was having with the original but not the engine issue. I then replaced the ignition switch with a new one from Napa, even though the original looked fine. No signs of corrosion or heat damage. The new switch functions properly, but the engine still won't turn off. To get it to shut off, I unplug the square, black plastic relay on the fender wall, which I think is the ASD relay. I'm not sure what is causing this. The battery also drains if I leave it connected, and when I reconnect it I can hear the relays immediately click and the chime go off inside once or twice. The fuel pump must prime immediately then, too, because when I put the key in and turn it to Run, I don't hear it prime.
One thing worth mentioning, is that prior to this issue happening I replaced rusted fuel lines. I had to unplug the fuel pump and sending unit to drop the tank enough to get the lines off. Those two plugs are the only electrical things I had to mess with. They plugged back in fine and don't seem damaged in anyway.
Any ideas?
Josh
ANSWER: Hi Josh,
For the engine to keep running the voltage to the single module engine controller has to still be present. That voltage is controlled by the ignition switch so either the switch is failing to open when shut off, or there is voltage getting to the smec via another wire that it shares between the switch and the controller. So go to fuses #2,3,4 and verify that they show 0V when the key is Off. If not, then remove them one at a time and check to see if the other two fuses ever go Off. If not, then remove all three fuses and check for voltage at the black/orange wire at the ignition switch when it is turned off.
Similarly, check fuse #13 and the dark blue wire at the ignition switch. Both the dark blue wire and the black/orange wire have to be 'cold' when the switch is off or the engine will keep running.
Let me know what you find.
Roland
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QUESTION: Thanks Roland. I will borrow a multimeter after work and test the fuses you mentioned this evening and get back to you. As far as testing the switch wires, how do I go about that?
Josh
ANSWER: Same as the fuses: one lead to the wire/fuse and one lead to chassis metal. See if there is or is not 12v on the item being tested.
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QUESTION: Roland, I've the checked the fuses and they are all at 0 volts except for #13, which is a 5 amp fuse for the gauges and speed control. Removing 2, 3 and 4 didn't turn off #13. I removed #13 and when I plug it back in, the fuel pump primes. Also, the low oil light stays illuminated even with #13 pulled.
Josh
AnswerHi Josh,
Knowing that 2,3,4 are showing 0 volts means one section of ignition switch is working, but that fuse 13 shows 12 volts, suggests that a dark blue wire at a separate section of the ignition switch is getting 12 volts when it shouldn't (assuming the key is in the "off" position) because of a defective switch section OR the switch could be OK and that something which is supposed to get 12 volts from that dark blue wire is getting it when it shouldn't due to a short circuit between the wire and a separate 12 volt source. Unfortunately that dark blue wire connects to many locations so finding a short will be difficult. So first lets check the ignition switch:
Go back in the steering column and go to the switch. At the switch notice where there is a red wire attached and where there is a dark blue wire attached. Then remove the plugs on the ignition switch and do a test of the switch as follows: connect one lead of the multi-meter to the pin where the red wire was attached and the other lead to where the dark blue wire was attached. Then set the multi-meter to read ohms and see what the readings are when the key is in the off position, and when it is in the run position.
If it reads infinite ohms and 0 ohms, respectively then the switch is not the problem. otherwise it is.
If it is not the problem then reattach the two plugs of the switch to the switch, and with the switch in the off position, go to the dark blue wire's connection point at its plug and measure the voltage on the wire. If it reads 0 volts, fine, if it reads 12v then something that is connected to the dark blue wire is carrying 12 volts which shouldn't be there. That essentially by-passes the purpose of the ignition switch and explains why the engine keeps running when you turn it off. The trick will be to find which of many things is shorted to a rouge 12 volt source.
Roland
