2000 Dodge Dakota no spark

Tiny
DIRTRIDER501
  • MEMBER
  • 2000 DODGE DAKOTA
  • 6 CYL
  • 2WD
  • MANUAL
  • 261,000 MILES
I can't figure out why my dakota won't start. It has had a rough idle for about 2 months. Then for the last week it has started hard, by that I mean it cranked forever to start. Once started ran good, just the rough idle and every now and then bad misfire while driving would clear up after a couple seconds though. Just this morning went to start it and no start. I have gas, 47 lbs at the rail. No spark. No power to coil, crank sensor or the cam sensor ( pickup coil ). What next? When I unplug my crank sensor fuel pump does not work. Is it in asd mode? To my understanding if it is my fuel pump will also be shut off, is that true or can only my spark be stopped? THanks
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Monday, July 19th, 2010 AT 7:22 PM

8 Replies

Tiny
CARADIODOC
  • EXPERT
Hi dirtrider501. Welcome to the forum. First of all, understanding how the circuit works will help in diagnosing it. When you first turn on the ignition switch, the Engine Computer turns on the automatic shutdown relay (ASD) for one second to insure fuel pressure is up and ready for starting. Besides the fuel pump or pump relay, the ASD relay also sends voltage to the ignition coil, injectors, oxygen sensor heaters, and alternator field. If you hear the hum of the fuel pump for that first second, you know the ASD circuit is working.

The Engine Computer turns the ASD relay on again when it sees engine rotation, either cranking or running. It knows that by the pulses coming from the crankshaft position sensor and on some engines, the camshaft position sensor. Both of those sensors run on 5.0 volts or 8.0 volts supplied by the Engine Computer.

The fuel pressure you measured could be from the one second initial burst. The missing voltage at the coil can be explained if you measured it when the engine wasn't rotating. If the fuel pump is running and the coil has no voltage, there has to be a break in a wire or splice since both are on the same circuit. To double-check, measure the voltage to the coil for that first second and again during engine cranking. If it's there only for that first second, suspect the crankshaft position sensor.

The rest of the system operation has to do with a crash that ruptures a fuel line. The engine can't run without fuel pressure so it stalls. Loss of pulses from the crankshaft position sensor tells the Engine Computer to turn off the ASD relay. That removes voltage to the fuel pump so it also turns off to prevent dumping raw fuel onto the ground. The circuit is very reliable but often misunderstood. A lot of people try to diagnose the first thing they find missing, spark or fuel pressure, but it's important to check for both. The most common failure is the crankshaft position sensor. The individual coil and pump circuits account for very few problems.

Caradiodoc
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Tuesday, July 20th, 2010 AT 1:26 AM
Tiny
DIRTRIDER501
  • MEMBER
I understand all you said, but I do have fuel pressure the whole entire time. After I am done cranking on it for any amount of time the fuel pump still runs for a couple seconds after. Do you know what the ohms should be on the hall effect sensor? Or the crank sensor? I am pretty sure it is either of those, I just hate to throw parts at it. Also I have seen and heard of older dakotas having a wiring splice issue about 8 inches under the fuse box, do you know if that includes my year or if that is pre 97 ( the second generation of dakotas) thanks
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Tuesday, July 20th, 2010 AT 5:55 PM
Tiny
CARADIODOC
  • EXPERT
Dandy observation on the fuel pump. If it was running during cranking, the crankshaft position sensor is working. Check for voltage at the ignition coil. One wire, possibly a dark green with orange stripe, (that's from memory) should have battery voltage during cranking. It is on the same circuit as the fuel pump. If voltage is missing and you have no spark, that could be the splice you're referring to. In that case, I'll have to find a Chrysler service manual to determine where that splice is located.

Caradiodoc
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Tuesday, July 20th, 2010 AT 10:20 PM
Tiny
DIRTRIDER501
  • MEMBER
Correct I have no power while cranking to the coil off that wire. I have had on 2 occasions where the crank sensor was bad, even though the fuel pump was running properly. Really threw me for a loop. Let me know if that splice deal is accurate on this year truck or if possibly I may have my third crank sensor only working half properly! On a second note they were both Chrysler products that did that too!
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Wednesday, July 21st, 2010 AT 6:15 AM
Tiny
CARADIODOC
  • EXPERT
Well, if you read the system operation description in the service manual, they say one sensor turns on the ASD relay and the other one is for injector timing. All I've ever found is when either sensor is defective, the ASD relay doesn't turn on and there is no power to the coil(s) OR the fuel pump. Complicating the issue is some vehicles have a separate fuel pump relay that is in parallel with the ASD relay so they both turn on together but they feed different circuits. Complicating that even more, there are a few vehicles that use two different pins from the Engine Computer to run each relay.

If you have no voltage to the coil during cranking, the first thing to do is determine if the ASD relay is turning on. If you had Chrysler's DRB3 scanner, it will tell when the relay is commanded on. I don't know if aftermarket scanners will show that. An easier way is to pop the cover off the relay, reinstall it, and watch the flipper while a helper cranks the engine. If the contact flips on but there is no voltage to the coil, it becomes a simple matter of finding the break in the circuit. If the ASD relay is not turning on, head back to the cam and crank sensors.

As an alternative, you can try measuring for the same voltage on the two small nuts on the back of the alternator. One of them should also have battery voltage during cranking.

Caradiodoc
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Wednesday, July 21st, 2010 AT 3:26 PM
Tiny
DIRTRIDER501
  • MEMBER
I hope I am not stepping ahead of myself but I believe I figured it out tonight. After many hours of chasing wires and going through alldata schematics I found a oxygen sensor that was grounding itself out, and when I unplugged it I started receiving power and my pulsating ground. However my coil does not work, I believe my oxygen sensor shorted out and was sending feedback through the computer and lead to my coil being shorted out. I will find out for sure tomorrow when I order up a new coil and oxygen sensor. I will keep you posted. Thanks for the incite.
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Wednesday, July 21st, 2010 AT 9:10 PM
Tiny
CARADIODOC
  • EXPERT
Dandy. I always find it interesting how people track down problems and find them. Hope you've found the solution.

Caradiodoc
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Thursday, July 22nd, 2010 AT 3:33 AM
Tiny
DIRTRIDER501
  • MEMBER
Yup believe it or not that is what it was! I put a new coil on it and left the oxygen sensors unplugged fires right up! I plug the oxygen sensors in and no fire! Well shes running again without oxygen sensors but I will put those in tomorrow. Thanks for your answers.
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Thursday, July 22nd, 2010 AT 5:23 PM

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