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post #1 of (permalink) Old 08-25-2005, 11:54 AM Thread Starter
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Elec Starting Issue - The Lost Spark (UPDATED FIX

First let me say thanks for all the input and suggestions I received on my last to posts. I have learned a lot but the bottom line is my symptoms remain the same. However, I now have some definitive facts and stats.

Details: '84 CJ7, TR Upgrade, MC2100 carb, Nuttered,

1. The Jeep starts first crank every morning, runs awesome
2. After running, I can immediately shut down and restart on first crank as often as I want. If I do it immediately.
3. Let the jeep sit for about 15 minutes and now, no spark at plugs. It turns but no start.
4. Wait about two hours, and the Jeep will fire and start first crank. This entire cycle repeats predictably.
5. I can roll start it easily when it won't start by key and it runs, idles, accelerates perfectly. It is just and intermittent spark issue.

The above symptoms persist despite the following effort and changes.

A. 3 different ignition modules
B. 2 different coils
C. 2 different solenoids
D. 2 different ignition switchs
E. Complete retermination of critical wiring points with
new terminals, crimps, dielectric grease,
F. Complete cleaning of battery terminals, primary grounds everywhere, etc.
G. Ensure positive connection at plug wires, distributor.
H. Adding recommended ground between distributor and module.

I have a buddy that works for a parts store that 'loaned' me all the numerous parts during my ordeal and I am pretty sure that I did not try multiple bad parts. Even used different brands.

I have taken some volt readings during/before the problem and have the following to offer.

1. Battery 12.74
2. Coil + side is 8.2v when running
3. on 'I' side of solenoid I get 4.56v with key in the 'RUN' state (but not actually running). From what I have heard this is not correct and is supposed to be 0. But this situation also exists first thing in the morning when the Jeep will start...hmmmm. 'S' post is 0 volts in RUN state. I thought this points to a bad ignition switch but using two different switches it is the same reading. I am not really sure how to determine if the harness is bad.

Team Rush (aka Junk Yard Genius) has suggested that this is a heat (temp or electrically hot) based problem. I tend to agree that over night or after prolonged sitting around everything cools down or discharges any stored electrical current. Perhaps as simple as a wire expanding with heat, losing contact?

I can see the likely hood but have looked at everything repeatedly and cannot seem to find the missing piece of this puzzle. So I throw this out there hoping for some more suggestions on what else to look at.

I live about 24 miles from the summit of Pikes Peak and if I don't solve this soon I may push the Jeep off the top and buy a SCION. Help save this jeep from senseless abuse if you can.

Thanks again for all the emails suggesting various assistance.
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post #2 of (permalink) Old 08-25-2005, 12:58 PM
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Re: Elec Starting Issue - Chptr 3 - The Lost Spark

OK, what could possibly happen between Totally hot and cooled off... heat issue sounds like a possibilty, but I'm thinking that if you have been thru the electrical so thoroughly, maybe fuel? Vapor lock? Are you certain you don't have fire at the spark plugs when it's doing this?

just trying to think outside of electrical.... do you have any fule lines running near anything hot? If it runs good, you shut it off and immeadiatly restart, the fuel may not have time to heat up and vapor lock, but after 10-15 minutes of sitting in the same place near a heat source, it could. then you have to wait for it to totally cool off.

just a thought though.... good luck
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post #3 of (permalink) Old 08-25-2005, 02:42 PM Thread Starter
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Re: Elec Starting Issue - Chptr 3 - The Lost Spark

It does not appear to be vapor lock. I am getting fuel. The float is adjusted and the bowl is at the correct level. Two nice streams of fuel into the carb. I pull a spark plug and hold against the block, crank, no sparkie.
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post #4 of (permalink) Old 08-25-2005, 02:44 PM
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Re: Elec Starting Issue - Chptr 3 - The Lost Spark

[ QUOTE ]
It does not appear to be vapor lock. I am getting fuel. The float is adjusted and the bowl is at the correct level. Two nice streams of fuel into the carb. I pull a spark plug and hold against the block, crank, no sparkie.

[/ QUOTE ]

ok then... next? [img]/ubbthreads/images/graemlins/grin.gif[/img]
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post #5 of (permalink) Old 08-25-2005, 02:52 PM
 
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Re: Elec Starting Issue - Chptr 3 - The Lost Spark

[ QUOTE ]
First let me say thanks for all the input and suggestions I received on my last to posts. I have learned a lot but the bottom line is my symptoms remain the same. However, I now have some definitive facts and stats.

Details: '84 CJ7, TR Upgrade, MC2100 carb, Nuttered,

1. The Jeep starts first crank every morning, runs awesome
2. After running, I can immediately shut down and restart on first crank as often as I want. If I do it immediately.
3. Let the jeep sit for about 15 minutes and now, no spark at plugs. It turns but no start.
4. Wait about two hours, and the Jeep will fire and start first crank. This entire cycle repeats predictably.
5. I can roll start it easily when it won't start by key and it runs, idles, accelerates perfectly. It is just and intermittent spark issue.

[/ QUOTE ]

Damn, I had an idea up until #5.....

[ QUOTE ]

The above symptoms persist despite the following effort and changes.

A. 3 different ignition modules
B. 2 different coils
C. 2 different solenoids
D. 2 different ignition switchs
E. Complete retermination of critical wiring points with
new terminals, crimps, dielectric grease,
F. Complete cleaning of battery terminals, primary grounds everywhere, etc
G. Ensure positive connection at plug wires, distributor.
H. Adding recommended ground between distributor and module.

I have a buddy that works for a parts store that 'loaned' me all the numerous parts during my ordeal and I am pretty sure that I did not try multiple bad parts. Even used different brands.

I have taken some volt readings during/before the problem and have the following to offer.

1. Battery 12.74
2. Coil + side is 8.2v when running
3. on 'I' side of solenoid I get 4.56v with key in the 'RUN' state (but not actually running). From what I have heard this is not correct and is supposed to be 0. But this situation also exists first thing in the morning when the Jeep will start...hmmmm. 'S' post is 0 volts in RUN state. I thought this points to a bad ignition switch but using two different switches it is the same reading. I am not really sure how to determine if the harness is bad.

[/ QUOTE ]

I think you missed my correction in that the voltage here should be the same as the voltage on the (+) side of the coil because there is a wire that runs from the (+) side of the coil to this terminal.!!!
4.5 volts still seems a little low even with the lower resistance of the TFI coil. I'll have to check mine.

[ QUOTE ]
Team Rush (aka Junk Yard Genius) has suggested that this is a heat (temp or electrically hot) based problem. I tend to agree that over night or after prolonged sitting around everything cools down or discharges any stored electrical current. Perhaps as simple as a wire expanding with heat, losing contact?

[/ QUOTE ]

I would agree with JYG except for #5 above in that you can push start it. ???? What is the battery voltage when it's hot?? Maybe the battery cannot supply enough current when hot. Just a weirrd quess. Have another battery to try? And I think that he means TEMP related not electrically hot. I had one DUraSpark box that wouldn't fire if the battery voltage dropped to low during cranking and one that whent in ocillation and fired continously, just at the wrong moments. Cheap imitations.

[ QUOTE ]
I can see the likely hood but have looked at everything repeatedly and cannot seem to find the missing piece of this puzzle. So I throw this out there hoping for some more suggestions on what else to look at.

I live about 24 miles from the summit of Pikes Peak and if I don't solve this soon I may push the Jeep off the top and buy a SCION. Help save this jeep from senseless abuse if you can.

Thanks again for all the emails suggesting various assistance.

[/ QUOTE ]

Without re-reading all your posts, Is the problem just on trying to restart it or does it die when running.

If the problem is when it's cranking then I would pull check the voltage on the (+) terminal on the coil when cranking to see if it drops to low. Maybe checking the voltage at the IGN Module plugs also.

Here is a paper on how to a quick test the DuraSpark module. Don't know were this came from but looks like something that came out of a DuraSpark box.

Don't know about tapping on the side of the distributor is suppose to do....

I notice you didn't replace the spark plug wires. If a wire developes a break inside it can start to arc. at first this is not a problem but as it continues to arc it eats away at the conductor inside the wire making the break bigger and bigger until you need a big spark to jump the gap. When your cranking a hot engine, the voltage drops and may not be able to produce enough voltage to jump the gap.
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post #6 of (permalink) Old 08-25-2005, 03:46 PM Thread Starter
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Re: Elec Starting Issue - Chptr 3 - The Lost Spark

When hot the Battery voltage is 12.88

Voltage on coil + side does match that of 'I' terminal on solenoid.

This is just a cranking problem, never dies once running, idles great, good overall engine performance.

Not sure what you meant about checking voltage at MSD plugs ???

I have not replaced the spark plug wires, they are about two years old. The TFI cap and rotor are about 5 months old but I have not replaced them either.

Since I have tested two new modules as well as the one that was in there I have to believe that one of them would have been good. Thus is does not seem likely that the module is bad. All three units behaved identically.
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post #7 of (permalink) Old 08-25-2005, 06:30 PM
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Re: Elec Starting Issue - Chptr 3 - The Lost Spark

Toss my $.02 int the ring.
Focusing on:
1. Problems cranking, when cranking, no sparkie.
2. Can Push-start it.

I would guess:
1. The starter is somehow preventing the spark. The drag on the electrical system could do it.
2. The ignition components/connections involved only during cranking could be involved.

As a lark, I would try disconnecting the starter and push-starting it while the key is in the start position, then for a reality check, make sure it can be push-started in the run position again.

If it starts in the start position, look at the starter and it's connections. If it does not, it is the extra stuff in the ignition that only occurs during starting and the increased load of the starter is not the couse.
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post #8 of (permalink) Old 08-25-2005, 07:47 PM
 
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Re: Elec Starting Issue - Chptr 3 - The Lost Spark

[ QUOTE ]
When hot the Battery voltage is 12.88

[/ QUOTE ]
What is it when it's cranking hot?

[ QUOTE ]

Voltage on coil + side does match that of 'I' terminal on solenoid.

This is just a cranking problem, never dies once running, idles great, good overall engine performance.

Not sure what you meant about checking voltage at MSD plugs ???

[/ QUOTE ]

Sorry, I meant Ign Module Plugs
[ QUOTE ]

I have not replaced the spark plug wires, they are about two years old. The TFI cap and rotor are about 5 months old but I have not replaced them either.

Since I have tested two new modules as well as the one that was in there I have to believe that one of them would have been good. Thus is does not seem likely that the module is bad. All three units behaved identically.

[/ QUOTE ]

It would be nice to monitor the (-) terminal on the coil while it is cranking. If the voltage isn't switching off and on then the Module isn't working maybe because the pickup in the distributor isn't working.
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post #9 of (permalink) Old 08-25-2005, 09:23 PM
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Re: Elec Starting Issue - Chptr 3 - The Lost Spark

Strange, unusual problem.

But I think Scott has it.

During cranking something's dragging the voltage down - when hot.

Try disconnecting the 2 small wires on the solenoid. Find out which one gets hot (+) when the ign switch is in the crank position. Put it on the "S" terminal on the solenoid - the one that makes it crank.
Now the module is not being "helped" during cranking.

If it solves it, replace the solenoid - it's shorting inside during cranking.
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post #10 of (permalink) Old 08-26-2005, 07:28 AM
 
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Re: Elec Starting Issue - Chptr 3 - The Lost Spark

[ QUOTE ]
Strange, unusual problem.

But I think Scott has it.

During cranking something's dragging the voltage down - when hot.

Try disconnecting the 2 small wires on the solenoid. Find out which one gets hot (+) when the ign switch is in the crank position. Put it on the "S" terminal on the solenoid - the one that makes it crank.
Now the module is not being "helped" during cranking.

If it solves it, replace the solenoid - it's shorting inside during cranking.

[/ QUOTE ]

Well, he has allready replaced the starter solenoid twice.
I realy cant see that beuing a problem. But go ahead and check it anyway. It will be the one on the "I" terminal. If he did have it backwards it wouldn't crank.


Anyway here are some voltages on my TFI/DuraSpark system

(+) on the TFI coil with KEY in RUN position: 4.19 Volts
(+) on the TFI coil with KEY in START position: 9.98 Volts

(-) on the TFI coil with KEY in RUN position: 1.33 Volts
(-) on the TFI coil with KEY in START position: ~5.12 Volts *

(+) on the TFI coil with Engine Running: 6.89 Volts
(-) on the TFI coil with Engine Running: ~5.25 Volts*


(* This is taken with a Fluke 89 DVM. Your results may vary. What is actually going on here cannot be seen with a DVM.~is the tilde not negative and usually means approximate)
These voltages are refenced to (-) on the battery.
Ignition Resistance wire still in place.
Battery voltage @ 500 RPM =12.98 Volts
(-) Battery to block= 0.019 Volts
(-) Battery to Distributor Housing = 0.198 Volts !!!! (gotta do something about that)
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