Noob with a challenge! can you figure this one out?

Noob with a challenge! can you figure this one out?
I would like to get an answer to the question of how long it runs before it dies
I would also like to see pics of the voltage test results with exact settings of the switch posted with each picture.

I find it funny that the voltage can change, and wonder if it can be fuel starvation. However, having been an electrician for 30 some years I have seen funny stuff happen

tracing a wiring diagram is not hard, you just need to isolate what you want and not let the rest confuse you.
 
The reason for the voltage change in solid-state ignition is exactly the same as the reason for the same voltage change in point-type ignition - when the points (or ignition module) are "open" (module turned off), you'll read 12V at the coil because the circuit back to ground isn't complete. When the points (or module) are "closed" (module turned on, triggered by the Hall effect sensor), the circuit is complete so you see 12V divided by the coil and the ballast resistor (the module has an internal ballast), so you see 6V at the coil.
 
I have never had that problem with my cj but i have had that exact problem in a couple of old 70's dodge powerwagons ive owned. they would start in start position but die in run. what i found out is the ignition switch was going bad. i temporarilly installed a push button at the starter relay so when i wanted to start the truck i just turned the key to run and pushed the button and the truck started and ran until i shut it off. the only reason i did it that way is cuz it is a real pain to replace a ignition switch in that year of dodge, i had to remove the steering wheel, steering wheel lock,turn signal switch, and key cylinder just to get the old switch out. but in your jeep the switch is at the bottom of the steering column if i remember correctly but dont quote me on that. So i would try a new ignition switch and go from there.
 
had a similar issue with an 85 i used to own, wound up being the carburetor. i had the carter bbd. swapped out the carb and it ran like a dream, also could check your ignition switch? my 79 was doing the same thing (starting every other day) and i replaced the ignition switch runs tight
 
There are not a lot of things that will make an engine backfire through the carb, or backfire at all for that matter and as far as I know they are all timing/ignition related.
Check for slop in the chain the hall effects sensor in the distributer and the wires to the distributer.
 
IOPort51 said:
There are not a lot of things that will make an engine backfire through the carb, or backfire at all for that matter and as far as I know they are all timing/ignition related.
Check for slop in the chain the hall effects sensor in the distributer and the wires to the distributer.
Click to expand...

I'd put money on that his dizzy is two far advanced or retarded sounds like he needs to get a timing light on that
 
There is a saying,"When something is broken it is relatively easy to fix, it is when something doesn't work quite right that it becomes a real PITA."
This problem is not consistent, It is for a while and it isn't for a while, thats what is going to make this interesting.
All I will say at this point is that it is electrical and it has not yet completely failed. :cool:
 
After reading these post I would bet my bottom dollar that it is electrical 100%. It seems that there is a chafed wire somewhere in the ignition system being that it runs some time and others it dont. or a break down somewhere. personaly i would by-pass the switch and everything just to see if i can get it to start and run, then work out the problem. Timing also seems like an issue for the back firing. But it is very hard to find a problem with wiring when the problem is not ALWAYS there...GOOD LUCK!:)
 
Still problematic. It fires/combusts in the 'Start" mode and as soon as i let off the key it stops/dies/kills. I have probed the + terminal at the new MSD coil in start and the light is bright in start and slightly dimmer in "run" ( i have 12v at the +coil terminal in start and 6v in run).
I probed the - terminal at the coil and it flashes in start and is lit in run.
I have 12 v at the + terminal at the ICM. I have great spark from the coil wire to ground and a snappy spark at the plug.

Starting to think it's fuel related? New fuel pump. Gas shoots across the driveway with the fuel line removed at the filter. New clear view filter (return line plugged). Filter is clean and full. Gas shoots into carb when the linkaged is engaged. Removed stepper motor to clean stepper pins. From what i've read, the pins slide into a slots on a plate that is attached to an actuator rod in the motor and they are constantly moving in and out to adjust fuel/air mixture. Mine was frozen solid but the pins were about 3/16" into the carb throat.
I pulled and pulled and finally got the plate beyond the end of the stepper motor, removed the pins and soaked the stepper in WD-40 and after sitting i got the actuator to move in and out fairly easily. in order to reinstall i had to have the pins in more of an "out" position.
The stepper is reinstalled and when I start the Jeep it still fires/combusts in start but dies in run. The spepper pins are in the carb throat 3/8" and are not moving. Should they move by now or won't they electronically be moved until the motor is acually running?
I'll pull the top off the carb and check the float? But could the float really be a problem? I have gushes of gas when I work the linkage.
 
If it dies instantly when you release the key from start to run, then there's NO WAY that's a fuel-related problem. If it runs on for a short while after you release the key to run, then it COULD be fuel-related.

When the key is on to the "run" position, you may be able to crank over the motor by hand (with a wrench, or just using the fan belts) and watch the voltage on the (-) side of the coil go from +V to 0V to +V to 0V. Don't do that with the coil wire (the one that goes to the distributor) in place, or you may wind up with major manglement... because the engine COULD FIRE while you're manually cranking. Take that wire off and put it BEHIND THE SEAT while you're cranking.

I'm lookin' pretty hard at the ignition module right now.
 
TDHofstetter said:
If it dies instantly when you release the key from start to run, then there's NO WAY that's a fuel-related problem. If it runs on for a short while after you release the key to run, then it COULD be fuel-related.

When the key is on to the "run" position, you may be able to crank over the motor by hand (with a wrench, or just using the fan belts) and watch the voltage on the (-) side of the coil go from +V to 0V to +V to 0V. Don't do that with the coil wire (the one that goes to the distributor) in place, or you may wind up with major manglement... because the engine COULD FIRE while you're manually cranking. Take that wire off and put it BEHIND THE SEAT while you're cranking.

I'm lookin' pretty hard at the ignition module right now.
Click to expand...

And it runs sweet when it starts!
But yes, I get what you are saying about the fuel vs electrical but all the tests electrically prove out/test OK. I think I follow your thought of the probe to the - side. I did it with a bulbed test light though. In start it flashes and in run it is a solid light.
Great thought of the ICM. Not knowing if the original was bad, I bought a new $35 ICM. Yes, I've been told that the cheap one could be junk so I took one out of my running 85, still no go.
 
im still learning myself so im reading all the post i can.....last night i came across this "81 CJ8 AMC 258 i6 / 4.2l randomly dies" its from last november not sure if this will work. But it seems close. and it ended with a HEI being bad


but try...... turn the key and instead of letting go of it try to keep pressure on it and slowly take it back to the run position......does it stay running until the "rest" position of run? and or take the "rod" out of the ignition switch and manually push it down to see what it does from start to run .........checking on the "rack" of the steering column by bypassing the whole key switch and column part.....
 
Yes, the switch at the base of the column. I know what you are saying. When the Jeep came to us it was not running. Got it started on the original switch but it would start intermitently so I figured for $12 what could it hurt. Followed the instructions and guess I have it adjusted correctly as is works in all 5 positions, start, run, off/unlocked, off/locked and accessory. in "run" it still shows voltages like 12v at the ICM + or 6 v at the coil in run. Would it be a fair asessment that it is good? I thought since I broke a small piece of plastic off the replacement, I'd replace it again just to take it out of the loop. Still no go.
 
So, it started right off today but was quite rough. Could be the stepper pins too far into the throat but it ran but rough. kept it at higher rpms (1200 or so). after a minute or so I felt it stumble and then died. would not restart. Fires but won't run.

Ok, just wanted to take fuel out of the equation as has been considered by some to be a possibility. I did not do a whole rebuild but took the air horn off. The accelerator pump liiks fairly new. Took the venturi cluster out and checked the tubes which were clean. The whole bowl was clean. The float floats and is adjusted properly. I moved the stepper pins so they are in the bowl about 1/4". Reassembled and it fires but will not run.
 
IOPort51 said:
There is a saying,"When something is broken it is relatively easy to fix, it is when something doesn't work quite right that it becomes a real PITA."
This problem is not consistent, It is for a while and it isn't for a while, thats what is going to make this interesting.
All I will say at this point is that it is electrical and it has not yet completely failed. :cool:
Click to expand...

I hear you. Just not sure what I'm missing. I think every electrical item that has an influence has been replaced (and I would have anyway because it was all fairly old.). Just to reiterate, the ignition switch, the ICM, battery cables, solenoid, coil, cap, rotor wires and plugs. Dedicated grounds to the starter, dist/ICM, solenoid have been ran. I did the test light tests at the coil and it passed. Have plenty of spark at the coil wire and plugs in "start". Every Make-able connector has been cleaned and re-greased including the bulkead connector twice. Some folks have thought the $35 ICM could be bad out of the box so I swapped a know good on from my 85, no difference.
 
Is the emission system still intact? When I bought my 83 it would not idle. I tried replacing the carb and it still did not help. When I did the nutter by pass it idled like a champ. It turns out that some vacume lines were missing and the emission module would not let it idle.
 
manowar88 said:
I have never had that problem with my cj but i have had that exact problem in a couple of old 70's dodge powerwagons ive owned. they would start in start position but die in run. what i found out is the ignition switch was going bad. i temporarilly installed a push button at the starter relay so when i wanted to start the truck i just turned the key to run and pushed the button and the truck started and ran until i shut it off. the only reason i did it that way is cuz it is a real pain to replace a ignition switch in that year of dodge, i had to remove the steering wheel, steering wheel lock,turn signal switch, and key cylinder just to get the old switch out. but in your jeep the switch is at the bottom of the steering column if i remember correctly but dont quote me on that. So i would try a new ignition switch and go from there.
Click to expand...

Thanks. It would not start with the ignition switch it came with so I replaced it. I paid attention to the directions and set it to the proper detent. It works in all 5 positions; start (combustion takes place), run (6 v at the coil, volt meter registers, other things electrical work) off/ unlocked, off locked and accsy. I broke a piece of plastic in replacing it so put a second replacement in. Same deal.
 
62galaxie said:
Is the emission system still intact? When I bought my 83 it would not idle. I tried replacing the carb and it still did not help. When I did the nutter by pass it idled like a champ. It turns out that some vacume lines were missing and the emission module would not let it idle.
Click to expand...

Thanks. JeepHammer/Junk Yard Genius (Team Rush) had me try a "Nutter Bypass" test. By splicing into the connector out of the ICM and into the coil connection via the orange and violet wires it would effectively omit the computer. But alas, it did not start with this bypass test.
 
62galaxie said:
Is the emission system still intact? When I bought my 83 it would not idle. I tried replacing the carb and it still did not help. When I did the nutter by pass it idled like a champ. It turns out that some vacume lines were missing and the emission module would not let it idle.
Click to expand...

The emission system is still intact. I have checked many of the vacuum lines. There is no "shrieking" sound like a vac leak makes sometimes, when it has run. the only two disconnected lines are the two that go into the air cleaner. I plugged one but I guess i did not plug the other. But it did not start when they were in place.
 
did you try just jumping out the ignition system? take a pair of pliers and jump them across your solenoid, see if you can get it to turn over that way. had a similar issue w my 79 and i did that and it wound up being the ignition switch, not saying thats it but its worth a shot, good luck.
 
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