1994 Dodge Dakota Engine turns over, no spark

Tiny
TYGUY75
  • 1994 DODGE DAKOTA

Electrical problem
1994 Dodge Dakota 6 cyl Two Wheel Drive Manual

I have a 1994 dodge dakota slt with the 3.9 v6 magnum engine. I bought the truck off a guy who could not get the thing to start. We're getting no spark and I have replaced the spark plugs, plug wires, distributor cap and rotor, ignition coil, and I had the ECU rebuilt, and still no spark.
What's the next thing to look at? Have I skipped an important step? I'm pretty well out of ideas, so I'm pretty much just checking all my fuses, but so far, they're all still intact. Is there a switch I should check or any fuses/fusable links that are not in the fusebox?

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Sunday, August 15th, 2010 AT 3:16 PM

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Tiny
CARADIODOC
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Tyguy75. Welcome to the forum. Yes, you missed the most important step. Did you check for fuel pressure? If it is also missing, you have a problem that the two systems have in common.

Start by measuring the voltage on either of the two small terminals on the back of the alternator. You should see full battery voltage on one of them for one second after turning the ignition switch to "run", and again during engine cranking. If it is there for the first second but not during cranking, the automatic shutdown relay is not turning on due to missing pulses from the crankshaft position sensor or camshaft position sensor. The ASD relay also sends power to the fuel pump, alternator field, injectors, coil(s), and oxygen sensor heaters.

Caradiodoc

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Sunday, August 15th, 2010 AT 3:31 PM
Tiny
TYGUY75
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Greatly appreciated responce caradiodoc. So what's the correct way to test for fuel pressure? If the problem turns out to be exactly what you've described, what is the correct fix? Do I need a new ASD relay or a new crankshaft position sensor?
Sorry to sound so nooby about this. I'm 17 and constantly working on some project car or another, mostly playing out of Haynes manuals and the internet. I'm hoping to start my mechanic apprenticeship next year, but at this point I'm still getting comfortable with anything beyond oil changes and spark plugs.

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Sunday, August 15th, 2010 AT 10:35 PM
Tiny
CARADIODOC
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Nice to hear about your goals. I taught Engine Rebuilding, Electrical, Brakes, and Suspension and Alignment for nine years and have a lot of notes pages that I produced. Holler if you have other questions or would like copies.

The place to start with this vehicle is the system operation. Manufacturer's service manuals include these sections. They do a much better job than the aftermarket manuals.

When you turn on the ignition switch, the Engine Computer turns on the automatic shutdown (ASD) relay for one second. That is to insure fuel pressure is up and ready for starting in case the pressure dropped off overnight. You should be able to hear the pump run for that one-second burp. What's more important is what happens next. During engine rotation, cranking or running, pulses of voltage are generated by the camshaft position sensor and the crankshaft position sensor. When the Engine Computer sees those pulses, it turns the ASD relay on again. Voltage from the relay goes to the fuel pump, alternator field, ignition coil, injectors, and oxygen sensor heaters.

In the case of a crash that ruptures a fuel line, fuel won't spray from the injectors when there's no pressure so the engine stalls. When the engine stalls, there are no pulses from the cam and crank sensors so the computer turns the ASD relay off and that turns off the fuel pump to prevent dumping raw fuel onto the ground. The system is designed to prevent fires and is very effective and reliable.

There are really three circuits. The ignition coil circuit is the one you've been working in. The fuel pump is the second circuit. Both of them give very little trouble. The third circuit consists of those two sensors and causes the most trouble.

One advantage you have is Chrysler has a very user-friendly way of asking the Engine Computer to tell you what's wrong. Cycle the ignition switch from "off" to "run" to "off" to "run" to "off" to "run" three times within five seconds without cranking the engine. If the engine does crank, even for an instant, turn the switch off, wait a few seconds, then start over. After the third cycle, watch the Check Engine light. It will be on for a few seconds as a bulb check, then will go off, and after a few more seconds will start to flash out a series of two-digit fault codes. Most vehicles will start with code 12; that's one flash, a short pause, two flashes, then a longer pause before the next code starts. Code 12 just means the ignition switch was turned off recently. Write down the rest of the codes. The last one will be code 55 which just means "end of message". If you think you miscounted, cycle the ignition switch off and back on once and the sequence should repeat. On a few vehicles you will have to cycle the switch three times to view the codes again.

During the '80s and '90s Chrysler was very consistent with their codes. You can use almost any service manual for any Chrysler vehicle to find a description for each one. Let me know what you come up with for code numbers and I'll look up the descriptions. If we're lucky, one will have to do with one of the two sensors I mentioned.

The camshaft position sensor is in the distributor. The crankshaft position sensor is on the passenger side rear of the engine. I believe it actually sits in the transmission housing. It's a magnetic sensor that reads gaps in a metal ring attached to the flex plate to determine which cylinder is on top dead center. I never replaced a crank sensor on a truck, but on the front-wheel-drive vehicles, the air gap of the sensor is critical. A new sensor from Chrysler's supplier will have a thin cardboard spacer glued on the end to set the gap. Push the new sensor all the way in and tighten the bolt. That spacer will slide off when the engine is started. Some aftermarket sensors have a plastic rib molded onto the end to set the gap. It will partially wear away during engine operation. If that style sensor is removed, the rib must be cut off and a new paper spacer stuck on to reset the gap. The dealer's parts department has the spacers. Again, I don't know if that applies to the trucks, but on the fwd vehicles, if you push the sensor all the way in without a spacer, it will be broken the first time the engine is cranked.

The single most important test is to determine if the ASD relay is being turned on during cranking. You most likely will not be able to hear the fuel pump running so the easiest way is to use an inexpensive digital voltmeter or a test light on any of the points that get their voltage from that relay. The ignition coil is usually fairly easy to reach, and the 12 volt feed wire is typically dark green with an orange stripe. That same wire feeds the field winding in the alternator. It's impossible to tell which terminal is which on the back of the alternator because the two wires disappear into a black plastic block. It doesn't matter though. When the ASD relay turns on, one of the two small nuts holding that block on will have full battery voltage and the other one will have less, but not zero volts. Both will have zero volts if the ASD relay did not turn on.

A more involved method of determining if the ASD relay is turning on is to remove its cover, then watch the movable contact while a helper cranks the engine. You should see it flip for that first one second, then it should flip again during cranking. If it does flip for that first second but not during cranking, suspect the cam or crank sensor. That's where the diagnostic fault codes will come in handy. Any stored codes will be erased from memory if the battery was disconnected or run dead so you might have to crank the engine for a while for the problem to be detected and the code recorded again.

Another way to read the codes is with a scanner. If you plan on working on cars professionally, I strongly recommend you buy a scanner of your own so you don't have to wait in line to use the shop's equipment. I'm driving around right now with my Chrysler DRB2 connected to my minivan. It will do everything necessary while aftermarket scanners never do all the things the manufacturer's stuff will do. The DRB2 works on all Chrysler products from 1983 through 1995 but it requires various plug-in cartridges. I also have the newer DRB3 which works on 1998 through most 2004 or 2005 models. With a plug-in cartridge, it will work on '94 - '97 Chryslers as well as any brand and model of car sold in the U.S. After 1996. A different cartridge lets it work back to the 1983 models.

If you want to invest in an aftermarket scanner, the best one, I've heard, for the money is the Genysis version 3.0. I never used it but I heard it can be updated over the internet. Snap-on has a number of scanners too but everything they sell including updates is expensive. You can find good used equipment from the guys who drive the tool trucks around to the shops. They will trade in stuff from people who are upgrading or leaving the industry. Other times they will know someone who has a scanner they're trying to sell so they can buy a newer one. The common vendors are Mac, Matco, Cornwell, and Snap-on. If you can't find them in the phone book, stop in at any new car dealership and ask the mechanics when the guys show up. It's usually once a week or once every other week.

If you really want to have fun, I sell the DRB3 at old car show swap meets. You can buy them over the internet right from the manufacturer, (OTC), but the kit is very expensive, around $6200.00. I get them for less through the parts department of the dealership I used to work for. You can find a good used DRB2 on eBay for less than $200.00 which would be fine for your truck but be sure it comes with the proper cartridge. The last one had a yellow sticker matching the yellow service manuals for 1994. It is an updated version of all the other cartridges that came before it. The cost is reasonable for someone starting out, but the vehicles it covers are disappearing fast.

Both the DRB 2 and DRB3 include an "actuator" test that allows you to run stuff that is controlled by the various computers. In the case of your Engine Computer, with the press of a button, you can fire the ignition coil to see if it's working, fire the injectors, turn on the radiator fan, tun on the ASD relay, and turn on the fuel pump relay if the vehicle uses one separate from the ASD relay. I've never seen an aftermarket scanner that can do actuator tests, but that could have changed within the past few years.

Caradiodoc

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Monday, August 16th, 2010 AT 5:19 AM
Tiny
MIKE91GA
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Love how everywhere I go, everyone wants help with their problem but NO ONE will post what fixed it. Its not all about you. You find the problem, POST IT you lazy sum B*.

On my dodge I found that the hall effect sensor/ distributor pickup magnet had a bunch of crud on it. So sometimes it put out a signal which resulted in intermittent engine failure.
Cost $40 to replace and has been cranking great since.

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Thursday, October 2nd, 2014 AT 8:02 AM
Tiny
DAVID SPONSEL
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Hey just to let know, my 95 dodge Dakota had same issue with no. Spark, end up being crankshaft sensor. Replaced and now back on the road

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Sunday, February 19th, 2017 AT 4:15 PM
Tiny
2CARPROS KEN
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Hey,

Great addition to this thread! Please feel free to help out on the site whenever it can add information that will help people.

Best, Ken

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Wednesday, February 22nd, 2017 AT 2:06 PM
Tiny
TERRICORDONI
  • 1994 DODGE DAKOTA
  • MERGED

Electrical problem
1994 Dodge Dakota V8 Four Wheel Drive Automatic

no spark to the coil. Please help

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Wednesday, February 22nd, 2017 AT 2:07 PM
Tiny
WRENCHTECH
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Spark doesn't go to the coil, it comes from the coil. You have to test for power at one terminal and ground pulse on the other terminal.

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Wednesday, February 22nd, 2017 AT 2:07 PM
Tiny
TERRICORDONI
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There is no power going to the coil at all

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Wednesday, February 22nd, 2017 AT 2:07 PM
Tiny
WRENCHTECH
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Did you realize that it's only supposed to be powered for the first 2 seconds of "key on" and then again when the PCM see a tach signal from cranking?

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Wednesday, February 22nd, 2017 AT 2:07 PM

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