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| Here is a good one.... https://slantsix.org/forum/viewtopic.php?t=35407 |
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| Author: | THOR [ Mon May 18, 2009 9:07 pm ] |
| Post subject: | Here is a good one.... |
I have tried the search function on the board with so many different search titles that I have come to the conclusion that this particular problem has not been listed before, could be wrong, but what the heck. On Stephaniebrite77's Dart with EI, I am getting a loss of spark under load. I can start the car, and it will run fine in or out of gear, and when out of gear, I can usually rev the engine without much problem, occasionally I will get a little sputter. If it is in gear and I press on the accelerator like I would taking off from a stop, the car loses spark, and stalls. If I press the accelerator slowly (very slowly) I can usually get it up to about stall speed and then it has a consistent misfire that worsens as I continue to press the pedal. Eventually, I lose spark altogether, and the car will stall unless I take my foot off the pedal completely, it will then sputter slightly and then pick back up and be happy idling. It does this when warm or cold. How do I know it's losing spark you ask? I finally found my dial back timing gun, and with it equipped to the #1 plug wire, the light will flash normally when idling, and even sometimes when there is a light load on it, but if I mash the accelerator in gear, the light shuts off, or if I continue to apply load to the engine whilst in gear, it will go out. I have 5.5v to the coil, and the EI is hooked up properly. This seems to be a secondary ignition issue, so the EI unit, the pickup coil and associated wires should be ruled out. The coil is new, and does the same as the old coil, so that is not the issue either. Mechanical issues can also be ruled out, mostly because there are none. The car ran fine with the points ignition system. 4 wire ballast, and 5 pin EI box (Non-Mopar, but has worked fine before.) Timing at 10 BTDC, and it is rock-solid. I set the timing with the vacuum advance disconnected, so that's not an issue either. The car acts the same with the vacuum line hooked up as well as disconnected. Spark plugs are slightly dark, and are gapped at .040". Cap appears to be ok, no carbon traces where arcing would occur, and the rotor also appears to be fine, again, these were equipped on the points distributor (which now resides in my Valiant) and as such are ruled out. Coil to Distributor wire is not the problem (changed out with known good one, symptoms did not change), and neither are any of the other wires that I am aware of. I checked voltage supplied to the coil and to the ballast wires, and none are dropping voltage as load is applied. The ground wire from the block to the firewall is in good shape with good connections, and the connection from the battery (-) to the block is also good. I get battery voltage to the ballast when in "RUN" so that is not the issue either. The only thing I have not been able to try (and I am not sure if it would make a difference) is swapping the EI unit with another working one. The EI unit on the Dart seems to work fine in other cars, so that leads me to believe that the EI unit is not to blame here, although stranger things have infact, occurred. The EI unit is properly grounded to the firewall, and there is an infantescimal amount of resistance between the case of the EI unit and battery (-). Does anyone else have an idea? If I cannot figure it out by wednesday, I am taking it to class and putting a scope on it, and see what the pattern is. That should just about tell me what the problem is, I just don't want to fight the car to get it there.... Thanks in advance ~THOR~ |
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| Author: | Reed [ Mon May 18, 2009 9:29 pm ] |
| Post subject: | |
Faulty coil? |
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| Author: | Joshie225 [ Mon May 18, 2009 9:39 pm ] |
| Post subject: | |
What's the dwell? Have you tried temporarily bypassing the ballast resistor? |
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| Author: | emsvitil [ Tue May 19, 2009 12:51 am ] |
| Post subject: | |
5.5v at the coil seems low......... What happens if you bypass the ballast? (don't do this for very long............) |
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| Author: | ceej [ Tue May 19, 2009 6:48 am ] |
| Post subject: | |
Define infinitesimal. ≤ lead resistance? After subtracting lead resistance, how many Ω? What's the resistance from the firewall back to the negative terminal of the battery? I thought I had another EI module floating around the shop. I'll look for it tonight. It's somewhere in the building.  CJ |
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| Author: | bigslant6fan [ Tue May 19, 2009 8:37 am ] |
| Post subject: | miss |
Have you checked the dist rotor phasing? some aftermarket dist. pickup coils are junk,and throw the phasing off 20-30o . |
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| Author: | THOR [ Tue May 19, 2009 8:39 am ] |
| Post subject: | |
I don't want to swap another coil on to see if it makes a difference, since 2 of them have done it, I doubt another would make a difference. I can try and run 12v to the coil and see where it gets me. Infantescimal as in slightly more than lead resistance, .05 ohms to be exact. I do not have a meter to check the dwell so I cannot say, but I can say that when it was installed before, the car ran fine. Then the points were installed, and then the EI was re-installed, and now we have this issue. I'll do some more looking when I get home. ~THOR~ |
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| Author: | SlantSixDan [ Tue May 19, 2009 8:46 am ] |
| Post subject: | |
Could be a faulty ECU, but first replace the cap and rotor, even though they look okeh. Use the good ones — Standard BlueStreak CH410X cap and NAPA Echlin MO-3000 rotor. |
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| Author: | Dart270 [ Tue May 19, 2009 9:17 am ] |
| Post subject: | |
Is it possible the leads to the dist got reversed? Lou |
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| Author: | THOR [ Tue May 19, 2009 4:26 pm ] |
| Post subject: | |
Quote: Is it possible the leads to the dist got reversed?
What difference would that make? Far as I have always known all the distributor does is change resistance value based on reluctor wheel position. I can definitely try them the other way around and see if that makes a difference.Lou Swapped cap and rotor over from the Duster yesterday to see if that changed anything (It has Bluestreak cap and rotor) and it made no difference, so the ones equipped are probably ok. I did not put the ones in her Dart on the Duster to verify, figured the swap from the Duster would be enough. I did find a broken #3 plug, and they are autolite plugs, but again, seeing as how they worked ok when the points were installed, I doubt that is the issue... now to go get another plug... ~THOR~ |
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| Author: | Joshie225 [ Tue May 19, 2009 4:33 pm ] |
| Post subject: | |
The distributor puts out an AC waveform. If the polarity is reversed it will affect the timing, but not the ignition system output. But if the spark is happening at the wrong time and the rotor is not near the correct terminal on the cap you can get cross firing in the distributor. |
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| Author: | coconuteater64 [ Tue May 19, 2009 4:35 pm ] |
| Post subject: | |
actually, coil polarity DOES make a difference. It'll run backwards, but it'll run crappy in comparison. Reversed polarity cuts coil output by about 20% (due to the theory of thermionic emission). |
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| Author: | SlantSixDan [ Tue May 19, 2009 4:57 pm ] |
| Post subject: | |
Yes, that's right, distributor pickup coil to module wire polarity is critical. Make sure it's correct. If you're not sure, swap the wires and try again. |
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| Author: | THOR [ Tue May 19, 2009 5:53 pm ] |
| Post subject: | |
Quote: Yes, that's right, distributor pickup coil to module wire polarity is critical. Make sure it's correct. If you're not sure, swap the wires and try again.
The wiring we have was cut from the the car we yanked it off of in the wrecking yard, so the actual wire end that was installed originally has long since been gone. I checked the wires again, and they are installed the way we had it before (I used Red/Yellow wires all the way down to the distributor)... Soon as I find my box 'o connectors, I will swap them and see what happens. ~THOR~ |
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| Author: | Aggressive Ted [ Wed May 20, 2009 12:58 pm ] |
| Post subject: | |
Thor, On my 74 Dart...... One thing I had happen a few years back when I bought my car was the ground on the ECU was bad, so added another ground wire. Also a good braided ground wire from the chassis to the block. I also grounded the battery to the chassis with a grounding stud. At one time I had that low of voltage at the coil, even after rewiring the engine harness and using new connectors. I changed the resistor over to the fully potted 1 ohm racing style. I now get 10 volts at the coil. You can also use the .85 ohm MSD Blaster 2 resistor. It has been working well the last 3 or 4 years. Take a look at how my NGK UR4 plugs are running with a .045 gap. Just click on the red link below. |
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