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No Spark or Fuel During Engine Crank

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No Spark or Fuel During Engine Crank
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thundley57

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Location
Bakersfield, CA
Vehicle(s)
1983 CJ7, 258 cu, Howell TBI upgrade
Recently installed the Howell TBI on my 83 CJ7 AMC 258 i6 / 4.2l liter and it ran fantastic for 2 months until today while I was out on a drive, the motor suddenly quit and would not re-start. After a little troubleshooting I discovered that when I turn the key on the check engine light comes on, the fuel pump comes on for a few seconds and pressures up to 12 psi but when I start cranking the engine the pump does not come on and there is no spark to any of the cylinders. The check engine light stay on steady while cranking and there are no codes registering in the ECM.

Any ideas on where to start looking?
 
you need to trouble shoot your ignition system, I dont think there is anything wrong with the efi based on what you are saying
 
Check the + side of the coil while cranking.
If under 7v check your primary wire to your ignition switch.
 
Thank you gentlemen for your responses. I will do some checking and let you know what I find. I know the ECM must see a tach signal before it will allow the fuel pump to run while cranking so I suspect it may have something to do with the coil. Is it possible that the Duraspark module went south on me since there is no spark either?
 
From what I have read through these Jeep forums over the years, an icm can fail in different ways. The cheap ones can fail even easier. Usually a failing icm will develop an ignition miss and progressively get worse. A good indicator is that it will get pretty warm to the touch. It will get hot enough that goopy stuff will start to leak out of it. If you have a spare one, a swap will be a good test. A poor icm ground wire, which is the black wire going into the distributor, will destroy an icm easily. This wire is better routed direct to the battery negative. The distributor pickup coil can fail also. There should be between 600-800 ohms between the orange and violet wires coming out of the distributor to test it. The best way to test this stuff is in the factory service manual.
 
Is there a way to test the distributor pick up coil? I actually just replaced mine thinking it was a good idea since I had the distributor torn apart to change the centrifugal weights. Wondering if I got a bad one or something?
 
So I have approximately 2 volts at the positive side of the coil with the key in the on position and basically 0 volts while cranking. Looking at the wiring diagram, the positive red wire splices and goes to what looks like a resistor (not labeled) and then the wire goes to blue on the other side, through a junction box and then to what I think is the ignition switch. The other end of the spliced red wire goes directly to the ignition switch (I think).

Any ideas on where I should look next? Is there supposed to be 12V delivered to the coil during cranking and then a lesser amount of voltage while in run?
 
thundley57 said:
So I have approximately 2 volts at the positive side of the coil with the key in the on position and basically 0 volts while cranking. Looking at the wiring diagram, the positive red wire splices and goes to what looks like a resistor (not labeled) and then the wire goes to blue on the other side, through a junction box and then to what I think is the ignition switch. The other end of the spliced red wire goes directly to the ignition switch (I think).



Any ideas on where I should look next? Is there supposed to be 12V delivered to the coil during cranking and then a lesser amount of voltage while in run?
Click to expand...



Check your ignition switch for 12 v in and 12v out


Sent from my iPhone using Tapatalk
 
I think you should inspect the fusible links located in two of the red wires going into the starter solenoid. When you start your CJ the primary ignition will send full battery voltage to the coil, after it starts there will be 6 volts.
 
Last edited:
thundley57 said:
Would either one of the fusible links being blown still allow the engine to crank over?
Click to expand...
Yes,

You checked the + cranking voltage at the coil as I suggested and found 0v
Now take the next step and test ohms between the coil + and dash connector. You should have 135 ohms, if you have 140 ohms or higher replace the resistor wire.
 
Had time for the first time today to troubleshoot this problem a bit. I don't think it's either one of the fusible links which I'm assuming are both connected directly to the starter solenoid. Is this true or should I be looking somewhere else?

I also replaced the ignition module with a spare I had on hand with no luck. My next stop is the ignition switch. There are two red connectors wired to the ignition switch. Does anybody know if one or both should have 12V to them. From what I can determine from the wiring diagram it looks like the red wire with a white stripe is the power to the coil. Can anybody confirm this? Is this the one I should check for 12V with the ignition switch turned on?

Also, does the manual Transmission have a neutral safety switch and if so could this possibly be the problem?

Thanks for all of your replies on this, I need to get my beloved Jeep running again!
 
Cranking with no spark or fuel is fairly easy thing to diagnose.
I always take it step by step similar to my previous post.
I refuse to throw parts at a problem, or skip over steps for this type of issue.
I understand it takes patience, and it's not for everyone.
However, it is what works for me.
 
Ok I discovered today that I somewhat mis-diagnosed my problem because I initially mistakenly checked voltage at the negative side of the coil instead of the positive because the coil pigtail that was supplied to me by CRT Performance had the wire colors swapped.

I have about 5.5V in run and about 8.5V while cranking (battery is definitely fully charged). I jumpered from the positive battery terminal to the ignition side of the starter solenoid and it still would not start. Swapped the coil with a backup I have and still no go. I have 12V going into the ignition switch and 12V leaving via the red w/tr wire leaving the ign swtch when in run and crank.

Can anybody tell me how much voltage I should have on the blue wire to the S side of the starter solenoid while cranking? Any other ideas...I'm dying here!

Posi said:
Yes,

You checked the + cranking voltage at the coil as I suggested and found 0v
Now take the next step and test ohms between the coil + and dash connector. You should have 135 ohms, if you have 140 ohms or higher replace the resistor wire.
Click to expand...

Shame on me, just went back and read the previous posts and must have skimmed through this one, will do this tomorrow. I still should be getting 12V to the coil during crank though right?
 
Looking at the wiring schematic for my '86, when you are in start position on the ignition switch, the light blue wire from the switch sends 12v to the ignition module, computer and starter solenoid. The light blue color will be used on this whole system so you can check the voltage from these. You really have to trace it down until you find the voltage loss.
 
Torxhead said:
Looking at the wiring schematic for my '86, when you are in start position on the ignition switch, the light blue wire from the switch sends 12v to the ignition module, computer and starter solenoid. The light blue color will be used on this whole system so you can check the voltage from these. You really have to trace it down until you find the voltage loss.
Click to expand...

Thanks Torxhead, will check. Sorry for prolonging this thread especially when possibly I am slow to perform the obvious steps but although I'm a very mechanical dude, I consider myself a little "slow" when it comes to electrical stuff. I'm confident that with your guys help I will eventually solve this problem and post the findings in the hopes of helping another electrical "short bus rider".
 
thundley57 said:
I have about 5.5V in run and about 8.5V while cranking (battery is definitely fully charged). I jumpered from the positive battery terminal to the ignition side of the starter solenoid and it still would not start. Swapped the coil with a backup I have and still no go. I have 12V going into the ignition switch and 12V leaving via the red w/tr wire leaving the ign swtch when in run and crank.
Click to expand...
If you have 5.5v at the + coil with key on your resistor wire is fine, no need to check that. You first said it had 0v that's why I ask you to check the terminal from the + side coil to dash connector.

You already ruled out the light blue wire, and starter solenoid. I believe you will find your problem in the red ignition wire running from the ignition side of the starter solenoid to where it splices into the red ignition wire running to the + coil. Sometimes that splice gets crusty. Make sure all your connections at the starter solenoid, and coil are clean as well.
 
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