1994 Jeep Wrangler Jeep Wrangler with 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
Do you
have the same problem?
Yes
No
Friday, August 23rd, 2013 AT 2:07 PM

14 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.
Was this
answer
helpful?
Yes
No
+3
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?
Was this
answer
helpful?
Yes
No
+2
Friday, August 23rd, 2013 AT 3:06 PM
Tiny
JEEPSTER94
  • MEMBER
How do I fix the problem with the auto shoutdown?
Was this
answer
helpful?
Yes
No
Friday, August 23rd, 2013 AT 3:11 PM
Tiny
CARADIODOC
  • EXPERT
Rats. That's 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 don't 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'm not sure if a '94 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 won't 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.
Was this
answer
helpful?
Yes
No
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
Was this
answer
helpful?
Yes
No
-2
Saturday, August 24th, 2013 AT 7:01 AM
Tiny
JEEPSTER94
  • MEMBER
The check engine light does not come on
Was this
answer
helpful?
Yes
No
Saturday, August 24th, 2013 AT 7:07 AM
Tiny
CARADIODOC
  • EXPERT
There's 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 don't 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 don't 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 didn't see 12 volts for one second after turning on the ignition switch, check it again with a test light. Most voltmeters don't respond fast enough to catch that one-second blip.
Was this
answer
helpful?
Yes
No
-1
Saturday, August 24th, 2013 AT 1:52 PM
Tiny
JEEPSTER94
  • MEMBER
I used a voltometer 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.
Was this
answer
helpful?
Yes
No
-2
Saturday, August 24th, 2013 AT 2:34 PM
Tiny
CARADIODOC
  • EXPERT
Don't worry about the injectors. What's of most importance is does that relay click on for one second when the ignition switch is turned on. If it does not, there's a problem in the circuit that controls it. If it does, there's a problem with the cam or crank sensor.
Was this
answer
helpful?
Yes
No
+2
Saturday, August 24th, 2013 AT 2:51 PM
Tiny
JEEPSTER94
  • MEMBER
It does not click
Was this
answer
helpful?
Yes
No
-1
Saturday, August 24th, 2013 AT 3:01 PM
Tiny
JEEPSTER94
  • MEMBER
I have checked all my fuses I have power to all but the acc lps fuse. I changed it but still no power.
Was this
answer
helpful?
Yes
No
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 '93 Grand Cherokee, and that didn't 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 don't 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's 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.
Was this
answer
helpful?
Yes
No
Sunday, August 25th, 2013 AT 1:32 AM
Tiny
JEEPSTER94
  • MEMBER
There is no power to the other 2 terminals.
Was this
answer
helpful?
Yes
No
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 don't know what they used for an ignition switch but if it's the same one Chrysler used in the early '90s, 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.
Was this
answer
helpful?
Yes
No
Monday, August 26th, 2013 AT 1:50 AM

Please login or register to post a reply.

Recommended Guides