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Discussion Starter #1
I've got a 95 Dakota Sport with the 3.9L v6 engine. A few days ago it just sputtered to a stop and wouldn't crank again. I thought it was the fuel pump (had problems with it prior) so I replaced that. I also replaced the main computer (ECM or PCM. I'm not sure of the proper term.) I tried to crank and got nothing. It would spin but wouldn't even try to start. I've got pressure at the fuel rail but the plugs aren't wet so no fuel is going into the motor. I pulled one of the plugs out and it doesn't spark at all. Within the past 6 months, I've replaced the coil, distributor, rotor, plug wires, and plugs. It's been running fine but now it won't do anything. I read about the crankshaft position sensor and the crankcase position sensor and replaced both. I checked the voltage at the coil and going into the coil, there were 2 volts between the wires when cranking and nothing between either wire and either terminal on the battery. All the relays are good, but I've been seeing 3 positive terminals going into the relay and one negative. Is that how it's supposed to be? Could there be another sensor that's bad? The truck also doesn't show any codes whatsoever.
 

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It's really acting like it's not seeing the crankshaft position sensor pulses.

Did you replace with a Mopar, or a generic aftermarket, crank position sensor?

(Also, I presume in the body, you mean replacing both the crank and the cam position sensors, not two crank position sensors ... )

Have you checked compared to the factory service manual's wiring diagrams at the ASD relay?

Have you tried another relay in place of the current ASD? It's not impossible that a approx-25 year old relay may be failing.

RwP
 

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Discussion Starter #3
It's really acting like it's not seeing the crankshaft position sensor pulses.

Did you replace with a Mopar, or a generic aftermarket, crank position sensor?

(Also, I presume in the body, you mean replacing both the crank and the cam position sensors, not two crank position sensors ... )

Have you checked compared to the factory service manual's wiring diagrams at the ASD relay?

Have you tried another relay in place of the current ASD? It's not impossible that a approx-25 year old relay may be failing.

RwP
I did replace the crank position sensor with the BWD brand sensor from Advance Auto. Yes, I did replace both, I guess I just mistyped. I have tried other relays and all the wiring lines up with the factory wiring diagram. My dad thinks it might have something to do with the ignition switch. Could that be a potential problem?
 

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It could be; try checking the voltages where they should be when the ignition switch is on.

Also, with the negative battery cable off the battery, try removing/installing the connector to your ECU three or four times, then reconnect the battery and see if that makes a difference.

As to "three positive and one negative" ... there's one from the ignition switch which is keyed with the key (pin A), one is pulled low by the ECU during the 2 second prime or while the engine is "running" (i.e., the ECU sees crank pulses) (pin C), there's one hot all the time (pin B), and one that feeds all the stuff switched (pin D). Which ones did you see positive? And how did you measure it - if with a multi meter, or a LED light, it might easily show "positive" even when it's not really due to the low load of the test equipment.

I'd try a Mopar crank position sensor; a lot of folks are having fits with the aftermarket ones.

RwP
 

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Discussion Starter #5
All the voltages were right but my dad still insisted so we replaced the ignition switch and it did nothing (Other than costing $40). I did like you said with the ECU plug and still nothing. I measured everything with a multimeter and a 12v test light. I also put a mopar CPS and still got nothing. We think it might be a short somewhere.
 

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This may or may not apply---over the yrs I've run into repeatedly BAD GROUNDS where it sets up a parasitic circuit and drives electronics crazy---it's an intermittent condition/problem---another condition I've come across is wire breaks inside plug connector between the wire and the plug terminal---my last understanding is the electronics themselves operate on 5 volts and is isolated from the normal wiring ( the ECM/computer is fed 12 volts--after that the computer itself breaks it down to it's own 5 volts operating voltage for the electronics) this is independent from the vehicle's 12 volt system---example is the computer is the "CONDUCTOR" of an orchestra ( the engine) while the instruments/musicians are the sensors map--pickup--temp--tbs--etc etc-------MOST electronic/ECMs control 12volt items by grounding them to operate when needed to function------example: you coil is always hot--the computer controls the fluctuation of voltage to coil (on-off) to create spark------crank sensor tells it when to do it-------another issue is when the ECM goes bad you can't field test it properly to check---do you have access to another ECM to try or better yet another vehicle that is running and swap out your to it to see if it's functioning---these are thoughts
 

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We replaced the ECM after it first messed up and it didn't fix anything. We thought we may have just gotten a bad reman so we filed for warranty and got a new one and still the same thing. We think it is the bad ground issue you were talking about so I will check that in the morning. You wouldn't happen to know where the ground terminal for the ASD is would you? That seems to be where all our voltage issues are.
 

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We replaced the ECM after it first messed up and it didn't fix anything. We thought we may have just gotten a bad reman so we filed for warranty and got a new one and still the same thing. We think it is the bad ground issue you were talking about so I will check that in the morning. You wouldn't happen to know where the ground terminal for the ASD is would you? That seems to be where all our voltage issues are.
The ground for the ASD is the ECU. As is obvious from the wiring diagrams in the factory service manual.

Again, it seems like it's not seeing the crank position sensor pulses. Since it won't turn on the ASD or fuel pump relay until it SEES crank position sensor pulses.

Have you picked up the factory service manual (BIG hint - is it a Chilton Dakota or a Haynes Dakota? No?) and followed its troubleshooting charts?

RwP
 

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If you look under the fuse box, there is a factory splice. The splice breaks and there will be no power from the ASD for the injector and spark. pull the loom and tape off and it will be obvious. There is a you tube video on this. Its a common problem.
 
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