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Re: Vibration at 2500 rpm
[Re: pjc360]
#2360905
08/27/17 11:57 PM
08/27/17 11:57 PM
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Joined: Nov 2011
Posts: 653
montana
pjc360
OP
mopar
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OP
mopar
Joined: Nov 2011
Posts: 653
montana
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It's most definelty a miss fire, I've confirmed that this evening.
When I hold the throttle at 2400-2600 rpm you can hear it in the exhaust.
I checked all my plugs, they appear to be ok, I've ohmed out all my spark plug wires, they check out.
Idk where to start, distributor is brand new firecore 50, I've verified timing, my balancer is correct, I've verified that with a piston stop.
The light on My crane cams hi-6 cd ignition box starts cutting in and out a little bit while the miss fire is happening.
Could it be a poor ground on the cd box? The rev limiter malfunctioning?
This is really bizzar, it idles smooth, but the second you start putting
A load on it it starts Miss firing and popping out the exhaust.
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Re: Vibration at 2500 rpm
[Re: pjc360]
#2360910
08/28/17 12:01 AM
08/28/17 12:01 AM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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Much better this than a balancing issue!. Check my baby (Rotor Phasing) as a potential. check dist reluctor gap & it might also be the box. EDIT & the plugs are good right? vac leak?
Last edited by RapidRobert; 08/28/17 12:03 AM.
live every 24 hour block of time like it's your last day on earth
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Re: Vibration at 2500 rpm
[Re: pjc360]
#2360948
08/28/17 01:25 AM
08/28/17 01:25 AM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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I've had this issue ever since I put this box in my truck and the entire time I thought it was drivetrain related.
It could also be the ignition coil it's self though right? I just don't understand how it could be the coil when it appears to ohm out just fine with my multimeter when I check the resistance.
Did it start right when the box was swapped in? & I'm assuming there were other changes done at the same time which would have kept a person from seeing the obvious, that it was the new device, the box. Usually a bad coil that will run, The eng starts to run miss or just dies after it gets warm.
live every 24 hour block of time like it's your last day on earth
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Re: Vibration at 2500 rpm
[Re: RapidRobert]
#2360980
08/28/17 02:29 AM
08/28/17 02:29 AM
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Joined: Nov 2011
Posts: 653
montana
pjc360
OP
mopar
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OP
mopar
Joined: Nov 2011
Posts: 653
montana
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I've had this issue ever since I put this box in my truck and the entire time I thought it was drivetrain related.
It could also be the ignition coil it's self though right? I just don't understand how it could be the coil when it appears to ohm out just fine with my multimeter when I check the resistance.
Did it start right when the box was swapped in? & I'm assuming there were other changes done at the same time which would have kept a person from seeing the obvious, that it was the new device, the box. Usually a bad coil that will run, The eng starts to run miss or just dies after it gets warm. This has been an issue for awhile, I can't exactly pin point if this happened imidiatley following the install of this crane ignition box, but the way it's feeling really warm to the touch especially when I'm holding the throttle at the rough spot where it's Miss firing just really makes me think whatever is causing the miss fire is inside the cd ignition box it's self. I wish I had a way of confirming it but the only thing I can really do is try grounding the ignition box directly to the negative post on the battery and seeing if it gets better, if it doesn't then I can try a different coil, if that doesn't work then I'll have to replace the cd ignition box with a different one and see what that does. I've ohmed all my spark plug wires, they all check out, plugs look good, distributor cap is brand new so is the rotor, distributor it's self is brand new, timing is correct, timing marks have been verified with Piston stop, pick up coil ohms out great. It's really gotta be in this crane cd ignition box, it seriously kind of seems like the rev limiter is glitching in and out, I'm going to dis-connect the rev limiter and see if the issue remains tomorrow along with grounding the cd ignition box directly to negative post on the battery.
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Re: Vibration at 2500 rpm
[Re: pjc360]
#2361055
08/28/17 11:15 AM
08/28/17 11:15 AM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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What I would do is sub back in the regular Mopar ign (dist if needed to be changed, a regular ECU/coil) & see if it straightens out. you could make up some jumpers with alligator clips on the ends for easy connections & you'll have an ans in no time.
live every 24 hour block of time like it's your last day on earth
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Re: Vibration at 2500 rpm
[Re: RapidRobert]
#2361209
08/28/17 04:31 PM
08/28/17 04:31 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,376
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Wow, I would have been wiling to bet quite a bit on crankshaft balance. All the classic symptoms were there.
The coil - put the ohmmeter across the two input terminals, you say it is. Next put one ohmmeter in the plug wire hole and the other to a bare spot on the coil If you have continuity it's okay, too. I have never heard of coils cutting out at certain rpm levels.
You have checked continuity of all plug wires and they are all able to conduct electricity.
You have checked continuity of the pickup coil, and it's good.
Have you checked the spark plugs? Occasionally one is bad right out of the box.
You have wired the heavy red wire to battery positive post, connected ignition box to cab. So what connects the cab to the battery, ground-wise? Running a black wire all the way to battery negative is a good way to find out about the grounds. You have mounted the box in the cab. What kind of wire is the signal coming through from the distributor pickup coil? You have a moderately long pickup coil lead and it could be giving you troubles. For example, under certain conditions the pickup wire can act as an antenna and the voltage it gathers can fool the sensor circuit in the ignition box. Under other conditions the pickup coil lead may make a capacitor with the floor sheetmetal. This could be enough to send the system into oscillation.
I'd suggest a twisted shielded pair from distributor to ignition box.
There is a chance that the box has something wrong internally. I don't think there are any tests you can run unless you have an oscilloscope. You'd also need a signal source to drive the ignition box.
As this seems to be an rpm-related thing, have you tried setting it at different speeds and seeing what happened?
Good Luck!
R.
Last edited by dogdays; 08/28/17 04:52 PM.
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Re: Vibration at 2500 rpm
[Re: dogdays]
#2361438
08/28/17 11:13 PM
08/28/17 11:13 PM
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Joined: Nov 2011
Posts: 653
montana
pjc360
OP
mopar
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OP
mopar
Joined: Nov 2011
Posts: 653
montana
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Wow, I would have been wiling to bet quite a bit on crankshaft balance. All the classic symptoms were there.
The coil - put the ohmmeter across the two input terminals, you say it is. Next put one ohmmeter in the plug wire hole and the other to a bare spot on the coil If you have continuity it's okay, too. I have never heard of coils cutting out at certain rpm levels.
You have checked continuity of all plug wires and they are all able to conduct electricity.
You have checked continuity of the pickup coil, and it's good.
Have you checked the spark plugs? Occasionally one is bad right out of the box.
You have wired the heavy red wire to battery positive post, connected ignition box to cab. So what connects the cab to the battery, ground-wise? Running a black wire all the way to battery negative is a good way to find out about the grounds. You have mounted the box in the cab. What kind of wire is the signal coming through from the distributor pickup coil? You have a moderately long pickup coil lead and it could be giving you troubles. For example, under certain conditions the pickup wire can act as an antenna and the voltage it gathers can fool the sensor circuit in the ignition box. Under other conditions the pickup coil lead may make a capacitor with the floor sheetmetal. This could be enough to send the system into oscillation.
I'd suggest a twisted shielded pair from distributor to ignition box.
There is a chance that the box has something wrong internally. I don't think there are any tests you can run unless you have an oscilloscope. You'd also need a signal source to drive the ignition box.
As this seems to be an rpm-related thing, have you tried setting it at different speeds and seeing what happened?
Good Luck!
R. I have checked all the spark plugs, they are good. Pick up coil tests good, plug wires test good but they are a couple years old. 2-3 years old. The leads that run to the pick up coil are a twisted pair that came with the ignition box. And I added a twisted pair from a factory wiring harness off an older 72-74 w100 pick up to get a little more length out of them. I have routed the pick up coil wires away from the other wires as best as I could. The ground behind the seat of the truck probly isn't the best ground for the ignition box, but I have a heavy ground going from engine block to negative battery and from under hood on radiator core support to engine block and a heavy ground from frame to inner fender under the hood. I posted a thread exposing this issue with the crane box on another web site and a guy said he had a problem vet similiar to mine with the same ignition box and coil and it ended up being the coil, and that he sent it back to crane and they sent it back to him claiming it was fixed and it did fine for awhile and then the issue came back. He said when it came back he ditched that coil and bought an msd coil and it's been good ever since.
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Re: Vibration at 2500 rpm
[Re: pjc360]
#2361606
08/29/17 11:09 AM
08/29/17 11:09 AM
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Joined: Jan 2006
Posts: 8,162
USA
360view
Moparts resident spammer
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Moparts resident spammer
Joined: Jan 2006
Posts: 8,162
USA
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Sorry you are still having problems.
Chrysler dealerships used to have a special "black box" that could ride in the vehicle and record the frequency and amplitude of a shake, which is very valuable in narrowing the source down to wheel, diff, u joint, shaft, trans, engine, etc.
If it were my vehicle I would next do a
"Percent Power Drop" test at 2500 rpm
on each of the eight cylinders
by shorting each cylinder's spark plug in turn and
recording the rpm drop
to see if the miss is one one cylinder all the time,
or a wandering ignition problem that affects all 8 at random.
If its a wandering miss, substitute in known good ignition pieces one at a time.
If you find a bad cylinder, swap known good ignition pieces in one at a time, and carefully examine the distributor electrical path for that cylinder.
If the ignition pieces swap have no effect,
do a 'Dynamic compression test' and then a
'cylinder percent leakage ' test.
An ignition oscilloscope that shows all 8 cylinders "traces" on the screen can be very helpful.
More modern diagnostic scopes can also record 8 cylinder instantaneous pressures and temperatures picked up from special washers under spark plugs.
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Re: Vibration at 2500 rpm
[Re: pjc360]
#2361644
08/29/17 12:16 PM
08/29/17 12:16 PM
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Joined: May 2015
Posts: 1,134
Lost in Time
Iowan
super stock
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super stock
Joined: May 2015
Posts: 1,134
Lost in Time
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This probably is not the problem because I've only seen it once. But I had a BB with a miss at about 2500 rpm that turned out to be a gide and spring issue. We replaced the springs and did a valve job on the new Edelbrock heads. Problems solved.
This was shortly after the heads came out.
Have a great day
Iowan
"obsolete is neat"
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Re: Vibration at 2500 rpm
[Re: pjc360]
#2361788
08/29/17 04:19 PM
08/29/17 04:19 PM
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Joined: Jan 2006
Posts: 8,162
USA
360view
Moparts resident spammer
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Moparts resident spammer
Joined: Jan 2006
Posts: 8,162
USA
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A special meter is useful to track down ignition faults. I now have two of these Actron KAL Equip 2969 three way ignition testers http://www.ebay.com/itm/Kal-Equip-Spark-...509&vxp=mtrI bought the first one used for about $60 and after using it a few times decided that a second one to compare two cylinders simultaneously, or to compare an all cylinders average to one suspect cylinder would be helpful. The second cost about $40. These give you: peak Kilo Volts to initiate the spark, average milliseconds of spark duration also called "burn time" and the lower "burn" level KV after the spark starts If you hook the pickup clamp around the coil wire it gives you the average of all 8 cylinders. The length of burn time gives a hint about the air fuel ratio mixture in the cylinder. I believe this A/F ratio effect can be compared more dependably if you swap in the same special long ignition wire and iridium tip spark plug to the cylinder you are measuring. I would rather own one of the Sun Machines with the big 8 cylinder at once screen like I had in the 1980s but these KAL Equip units are a cheaper and more portable alternative.
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Re: Vibration at 2500 rpm
[Re: dogdays]
#2362265
08/30/17 12:18 PM
08/30/17 12:18 PM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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Do you have a stock ign (& coil) that you can toss in for a test?
live every 24 hour block of time like it's your last day on earth
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Re: Vibration at 2500 rpm
[Re: dynorad]
#2362321
08/30/17 02:13 PM
08/30/17 02:13 PM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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^^^ Excellent! he did try the light & it was showing a miss but not sure what wire he had it on & agreed I would do all 8 EDIT If there is an open at the plug (not likely/I cant see how) or its plug wire (very possible) there would be no flash (no ground path) & if the plug is fouled to the point where there was no spark cuz the current dead shorted in the carbon to ground thru the plug base it would flash but the cyl would not fire. We need closure here!
Last edited by RapidRobert; 08/30/17 05:09 PM.
live every 24 hour block of time like it's your last day on earth
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Re: Vibration at 2500 rpm
[Re: RapidRobert]
#2362589
08/30/17 11:03 PM
08/30/17 11:03 PM
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Joined: Jan 2008
Posts: 3,886
Lost and Spaced
bboogieart
master
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master
Joined: Jan 2008
Posts: 3,886
Lost and Spaced
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if the plug is fouled to the point where there was no spark Just wondering, wouldn't it make sense to pull and clean the plugs to address this issue? plug wire (very possible) there would be no flash (no ground path) Screw driver inserted in plug wire and held near ground to see spark? Am I missing something?
I have mechanical Aptitude.
I can screw up anything.
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