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Engine won’t start

Tridiumeor

Tridiumeor

Basic User
City
Bozeman
State
MT
My stock 4.2 will not start. It all started a couple years ago when I went over a small bump and it died. It had been doing it recently, but it always restarted right away. It will try to start but never fully turns over to run.

I have checked the battery, which is good.
I have checked for spark, which is good.
I have checked that the fuel pump works.
I have checked for obvious grounding issues and see none, the main ground is tight.

Does anyone have any troubleshooting tips before I just tow it in somewhere?

Thanks!

-Blake
 
The simple stuff. Spray some starting fluid in the carb and try it. If you have spark at the plugs, then if the starter is good it should start. If it starts and doesn't keep running after a few tries, then you aren't getting fuel.
 
I can turn the key and as long as I continue turning the key it sounds like it is on. As soon as I stop turning the key, it dies and will not remain on.
I have sprayed starting fluid into the carb. In the past I have bypass the fuel tank and has the fuel line in a cup full of fuel and as I tried starting the Jeep it would drain the cup of fuel.
 
Sounds like a wiring issue. When cranking the coil is fed full 12v power to provide a stronger spark. When the key is released the voltage to the coil is provided via a different power source that reduces voltage. It sounds like the run side wiring has an open or intermittent connection. Have you tried a different ignition box? The silver box on the fender with 2 sets of wire coming out of it? (This is a stock ford part)

1714320246223.jpeg
 
Ok, I replaced the ignition module with a new one. A Duralast from AutoZone. Inspecting all of the wires coming from it they appear to be ok, they have splices in them, but appear to be solidly in place. I am still not getting the Jeep to stay on after I release the key from start.
This is frustrating because I’m sure any of you guys could have this diagnosed and fixed in 15 minutes…
 
Could be something with the coil being bad, too, just speculating. Maybe when you hit the bump it broke internally and so when voltage drops from 12 when key goes from Start to Run it won't fire. Just a guess? Coil is cheap and easy to change. You could have a damaged wire somewhere, maybe ignition switch issue??
 
Tridiumeor said:
I can turn the key and as long as I continue turning the key it sounds like it is on. As soon as I stop turning the key, it dies and will not remain on.
I have sprayed starting fluid into the carb. In the past I have bypass the fuel tank and has the fuel line in a cup full of fuel and as I tried starting the Jeep it would drain the cup of fuel.
Click to expand...
Check voltage at the coil when in the "start" position and "run" position.
Voltage when cranking should be ~ battery voltage. Voltage in run position should be reduced to ~8-9 volts. Lack of voltage at coil can be either bad ignition switch, switch wiring, resistor wire to coil, etc.

Check and report back.

Also, have you confirmed the ground strap (jumping across motor mount) from the frame to the engine block is good?
 
Red wire from Ignition module splits and feeds the ignition coil and the starter solenoid. It gets Very hot and after keeping ignition key on accessory mode begins to smoke. The wire jacket is very gummy and very hot to touch. I will plan to replace this wire, do you think this could be causing the intermittent connection?
 
Tridiumeor said:
Red wire from Ignition module splits and feeds the ignition coil and the starter solenoid. It gets Very hot and after keeping ignition key on accessory mode begins to smoke. The wire jacket is very gummy and very hot to touch. I will plan to replace this wire, do you think this could be causing the intermittent connection?
Click to expand...
This wire?

Resistance wire.png

If so, that is the resistance wire that reduces the 12v battery voltage down to the lower "run" voltage for the coil.
It could be an issue with the connections to the wire or a problem with the coil.
Try the volage tests again with the wire disconnected from the coil to see if the wire acts the same without the load of the coil.
 
Sounds like it is not the ignition module, but just be aware that it is very common for them to be bad right out of the box with the ones sold today. Low quality imported stuff.

I have stacks of spare parts, so I generally do part swapping to isolate the problem. I would try a known good coil to see if the current one might have a short causing the excess load issue.

The fact your wire gets extremely hot to the point of smoking indicates it has too large of an electrical load on it. (Easy for large current to flow) This is usually caused by a short in the wire or the part it is connected to having a short in it. Carefully inspect the wire‘s full length looking for signs of cracked insulation.

Trying to run the Jeep in the current condition without fixing the root problem exposes you to dealing with an engine fire, so be cautious with your testing.
 
FLCJ8 said:
This wire?

View attachment 113521

If so, that is the resistance wire that reduces the 12v battery voltage down to the lower "run" voltage for the coil.
It could be an issue with the connections to the wire or a problem with the coil.
Try the volage tests again with the wire disconnected from the coil to see if the wire acts the same without the load of the coil.
Click to expand...
For testing, you can disconnect the resistance wire and add a temporary wire direct from the + on the battery to the coil to see if it will run without the key in the crank position. Do not leave this wire on the coil for an extended period of time as it can burn up the windings in the coil. (You would be delivering full battery voltage and the coils like the lower voltage)

If you replace this wire you will either need a ballast resistor (like used in mopar vehicles of the 60’s & 70’s) or a resistor wire.
 
Ok I ordered a new ignition coil to be safe and a new resistor wire. It looks like the resistor wire comes with pre done bullet connectors, do I crimp a ring connector on it to connect to the ignition coil, or simply strip it down to the wire.
 
Still no start. I have now replaced the ignition coil with the original factory style coil instead of the e-coil I had previously installed. I have replaced the old resistor wire with new and spliced it into the same wires previously connected. I have added a ground strap from the motor/body mounting bracket to the motor mount bracket. I’m charging my battery to verify it is not simply low. Not sure where to go from here.
 
Tridiumeor said:
Still no start. I have now replaced the ignition coil with the original factory style coil instead of the e-coil I had previously installed. I have replaced the old resistor wire with new and spliced it into the same wires previously connected. I have added a ground strap from the motor/body mounting bracket to the motor mount bracket. I’m charging my battery to verify it is not simply low. Not sure where to go from here.
Click to expand...
Have you taken any voltage measurements?

From previous reply:
Check voltage at the coil when in the "start" position and "run" position.
Voltage when cranking should be ~ battery voltage. Voltage in run position should be reduced to ~8-9 volts. Lack of voltage at coil can be either bad ignition switch, switch wiring, resistor wire to coil, etc.

How do they look?
 
When I turn the key to start position I get around 8 volts, in run position the engine simply stops so I don’t get any voltage. I have tried putting the original AMC ignition control module back in and it does the same thing.
When I have the key in the accessory spot, without turning to start, I get around 12 at the splice where the Pink resistor wire, ignition module and harness block combine. But when I check at the ignition coil I get no volts. Is this normal and simply what’s happening because of the resistor wire?
 
Like spankrjs stated, did you check the coil, with a meter ? The primary and secondary for ohms ?
 
Testing with everything disconnected I am getting 1.3 testing on both points, 0.1 testing only on one point. Testing my previous e coil I get around the same.
 
Tridiumeor said:
When I turn the key to start position I get around 8 volts, in run position the engine simply stops so I don’t get any voltage. I have tried putting the original AMC ignition control module back in and it does the same thing.
When I have the key in the accessory spot, without turning to start, I get around 12 at the splice where the Pink resistor wire, ignition module and harness block combine. But when I check at the ignition coil I get no volts. Is this normal and simply what’s happening because of the resistor wire?
Click to expand...
In the "start" position you should get full (or close to full) battery voltage as this is coming straight from the "I" terminal at the starter solenoid bypassing the resistor wire. In the "run" position it runs through the resistor wire and is a reduced voltage (~8-9 volts)

Have you confirmed you have good battery voltage at the battery as well as the terminals at the starter solenoid?
You can temporarily disconnect the positive lead from the solenoid to the starter to do your testing without cranking the motor and running your battery down.

Also, there is a fuse that feeds the EEC module that should be checked.

Fuse.png
 
Suggest you take a look at all the wiring in the area of the coil and starter, Mine was wrapped with duct tape (factory) i.e. separate the wires, check their integrity and redo the insulation at the splices.
Do you still have this issue with the hot wire?
Tridiumeor said:
Red wire from Ignition module splits and feeds the ignition coil and the starter solenoid. It gets Very hot and after keeping ignition key on accessory mode begins to smoke. The wire jacket is very gummy and very hot to touch. I will plan to replace this wire, do you think this could be causing the intermittent connection?
Click to expand...


I don't see that you answered FLCJ8's questions:

It could be an issue with the connections to the wire or a problem with the coil.
Try the voltage tests again with the wire disconnected from the coil to see if the wire acts the same without the load of the coil.
 
I learned again the hard way this weekend, that the absolute littlest lack of contact or wiggle in the red or green wires to the coil (in the horseshoe-shaped connector) will cause a no-start condition. Those wires must make solid contact with the coil terminals, and that horseshoe connector can sometimes mess that up.
 
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