No spark

Tiny
JEEPSTER94
  • MEMBER
  • 1994 JEEP WRANGLER
  • 127,000 MILES
I have a 1994 jeep wrangler 2.5 liter that has no spark from the ignition coil. I have changed the coil and the crank positioning sensor. There is no to very little power going into the coil. I changed a fuse and it went from 0 volts to 2.3 volts. The jeep has been sitting for a few months so there may be some corrosion buildup. Thank you for your help I really need it
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Friday, August 23rd, 2013 AT 2:07 PM

18 Replies

Tiny
CARADIODOC
  • EXPERT
2.3 volts suggests the automatic shutdown (ASD) relay is turning on but that there's a high-resistance connection somewhere, so lets check that circuit first. Remove the ASD relay, jump terminals 30 and 87 together in the socket, then read the voltage at the ignition coil or any injector.
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Friday, August 23rd, 2013 AT 2:15 PM
Tiny
JEEPSTER94
  • MEMBER
It worked I now have power to the coil. How do I turn the auto shutdown off?
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Friday, August 23rd, 2013 AT 3:06 PM
Tiny
JEEPSTER94
  • MEMBER
How do I fix the problem with the auto shoutdown?
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Friday, August 23rd, 2013 AT 3:11 PM
Tiny
CARADIODOC
  • EXPERT
Rats. That is not what I expected you were going to find. If you have full battery voltage at the ignition coil when you jump the ASD relay, that proves that circuit is okay with no blown fuses and no corroded connectors or splices. What you should do now is verify the Engine Computer is turning on that relay during cranking. I overlooked that in my first reply. You will have 0 volts at the ignition coil and all injectors unless the engine is rotating, (cranking or running).

A test light works best but you can use a digital voltmeter. You'll just have to watch the voltmeter closely. Most do not respond real fast. The Engine Computer will turn on the ASD relay for one second after you turn on the ignition switch. You may hear the fuel pump run for that one second too. After that, what is important is if that voltage comes back during cranking. If it does, you have a spark problem or a fuel supply problem. If the voltage does not come back during cranking, you will have no spark and no fuel pump and no injector pulses. All of those things get their power through the ASD relay.

When the ASD relay turns on for that first second but not during cranking it is caused by a failure of the crankshaft position sensor or the camshaft position sensor or a problem with the wiring to them. The first thing to do is check the diagnostic fault codes. Chrysler made that real easy to do yourself but I am not sure if a 1994 Jeep has that ability yet. Cycle the ignition switch three times from "off" to "run" without cranking the engine, leave it in "run", then count the flashes of the Check Engine light. The first series is the first digit of the first code, followed by a pause, then the flashes for the second digit. After a longer pause the next code will flash the same way. The last code will be 55 which just means "end of message".

Those two sensors will not always set a code when they fail. If you disconnect the battery, those codes will be erased too and they may not set again from just cranking the engine.
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Friday, August 23rd, 2013 AT 6:55 PM
Tiny
JEEPSTER94
  • MEMBER
I have changed the crankshaft positioning sensor, the ASD relay does not come on at all. My fuel pump does turn on but I do not know how to test the injectors. I will check the codes and get back to you.
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Saturday, August 24th, 2013 AT 7:01 AM
Tiny
JEEPSTER94
  • MEMBER
The check engine light does not come on.
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Saturday, August 24th, 2013 AT 7:07 AM
Tiny
CARADIODOC
  • EXPERT
There is two parts to the circuit. Since you had 12 volts to the ignition coil when you jumped the ASD relay, we know the high-current half is working and the fuse is okay. If you do not even see that 12 volts switch on with the relay installed for that first one second, that points to an Engine Computer problem or a different blown fuse. Engine Computers do not fail on Chrysler products very often. If you have a service manual and know how to read the wiring diagrams, there will usually be three or four 12 volts supplies feeding the Engine Computer that you need to check. One will be there all the time; one will be switched on through the ignition switch, and one will come through the ASD relay.

Before we go looking for difficult stuff, did you check that voltage with a test light or a voltmeter? If you used a voltmeter and did not see 12 volts for one second after turning on the ignition switch, check it again with a test light. Most voltmeters do not respond fast enough to catch that one-second blip.
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Saturday, August 24th, 2013 AT 1:52 PM
Tiny
JEEPSTER94
  • MEMBER
I used a voltmeter but I do not have a 12 volt test light. I pulled the cap off of the relay and it does not move when the engine is cranked. I get fuel up to the fuel bar but I do not know how to test the injectors.
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Saturday, August 24th, 2013 AT 2:34 PM
Tiny
CARADIODOC
  • EXPERT
Do not worry about the injectors. What is of most importance is does that relay click on for one second when the ignition switch is turned on. If it does not, there is a problem in the circuit that controls it. If it does, there is a problem with the cam or crank sensor.
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Saturday, August 24th, 2013 AT 2:51 PM
Tiny
JEEPSTER94
  • MEMBER
It does not click.
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Saturday, August 24th, 2013 AT 3:01 PM
Tiny
JEEPSTER94
  • MEMBER
I have checked all my fuses I have power to all but the accessories LPS fuse. I changed it but still no power.
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Saturday, August 24th, 2013 AT 3:11 PM
Tiny
CARADIODOC
  • EXPERT
You need to check right at the Engine Computer. I have a real lot of Chrysler service manuals but the closest I can find for yours is for a 1993 Grand Cherokee, and that did not have the 2.5L engine. Chrysler was pretty consistent though with their wiring from year to year and with different engine sizes so let me see if this looks right.

They show terminal 3 as a pink/black wire with full battery voltage all the time for both the 4.0L and 5.2L engines. Terminal 9 is a light blue or a light blue/red wire that gets 12 volts from the ignition switch when it's in "run". You can remove the 60-pin connector and measure right on the terminals, but do not stick a meter probe in too far as that could stretch the terminals.

Next, there are multiple power ground wires to check. You can use an ohm meter to measure the continuity but a more accurate test is to remove the connector's rear cover, then back-probe the terminals through the rubber seal and measure voltage while the connector is plugged in and the ignition switch is on. Typically you can expect to find as much as 0.2 volts but more than that indicates a high-resistance connection. Terminals 5, 11, and 12 are all grounds and are all black/tan.

All of these wires are in one of the outer of the three rows of terminals, (assuming you have the common 60-pin connector, and not the newer style three smaller connectors). One row has terminals 1 - 20.

I should have you check something easier before I jump the gun and head to the computer. There is four terminals on the ASD relay socket. You already jumped the two high-current terminals. Look at the other two that are on the sides and parallel to each other. One of those should get 12 volts all the time the ignition switch is in "run". Make sure that is showing up.
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Sunday, August 25th, 2013 AT 1:32 AM
Tiny
JEEPSTER94
  • MEMBER
There is no power to the other two terminals.
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Sunday, August 25th, 2013 AT 2:40 PM
Tiny
CARADIODOC
  • EXPERT
Terminal 30 or 87 should have 12 volts all the time. We established he's there because you jumped those terminals and had 12 volts at the ignition coil. Of those two parallel terminals on the sides, one gets grounded by the computer to activate the relay and one gets 12 volts from the ignition switch.

I do not know what they used for an ignition switch but if it is the same one Chrysler used in the early 1990's, check that and its connector for signs of overheating and melting. Typically two terminals will be blackened and the connector body will be melted around them.
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Monday, August 26th, 2013 AT 1:50 AM
Tiny
JAYBOS10
  • MEMBER
What do you mean by ignition switch? On the steering wheel? I am at this point with no power at the other two points on the ASD. And stuck.
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Tuesday, September 25th, 2018 AT 1:28 PM
Tiny
CARADIODOC
  • EXPERT
The ignition switch is what you turn with the key. That supplies the 12 volts to one side of the coil in the ASD relay. The Engine Computer grounds the other terminal to turn the relay on, first for one second when the ignition switch is turned on, then again when the engine is rotating, (cranking or running), and it knows that by the signal pulses it receives from the crankshaft position sensor and the camshaft position sensor.

Two terminals on the ignition switch's connector and one set of contacts inside the switch commonly overheat and become burned and pitted, and the heat generated by one of them migrates out to the other part and causes the same damage. That part of the switch almost always is for the accessory circuit, so when it develops that problem, you will have no radio, power windows, and heater fan. The engine will still start and run normally. This happens most often to people who leave the fan set on the highest speed when they turn the ignition switch on and off. This switch problem rarely affects the low-current circuit that feeds the ASD relay, but it is one of the places we have to check for with this problem.

You should really start a new question specific to your vehicle so the other experts will see it and have a chance to reply. Here, only the two of us will be notified when an update has been posted. That may not get you the most help we can give you. Please be sure to list the engine size, mileage, and transmission type so our answers will be more relevant. List the diagnostic fault codes if you found any related to the problem, and include all the things you tested already, and the results.
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Tuesday, September 25th, 2018 AT 2:13 PM
Tiny
JAYBOS10
  • MEMBER
I would love to. How do I start a new question on this site?
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Wednesday, September 26th, 2018 AT 3:52 PM
Tiny
CARADIODOC
  • EXPERT
On the "Home" page, there is a large box at the top right that says, "Ask a question", and that will get you started with a series of drop-down menus. To save you some time, here is the link to take you directly to that page:

https://www.2carpros.com/questions/new
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Wednesday, September 26th, 2018 AT 5:25 PM

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