Electronic ignition issue

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70Swinger340

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Hey guys need a little input here as to my issue on our 70 340. First of all I am not well versed in electrical issues (I believe the term is electrically challenged,snicker) nor do I have the proper tools to deal with these issues so trial by error and of course a few dollars to try and get things sorted out. But you only learn by trial and error so here I am. The car is running the electronic ignition upgrade and likely installed some years back. We parked the dart for the winter and prior the car ran good and strong. Brought it out of storage and put about a 100 miles on it without issue. Last week I fired it up took and fueled it up went for a rip and about 1/2 hour into it we felt a low idle miss. Seemed to smooth out once we got it into 2nd and 3rd gears 4th we couldn't feel much on the highway.Well the low idle miss got worse so I pulled the plugs and found that the gap was set at .40 not .35. We bought the car used and with a questionable checkered history on it so in the real world the history does not exist and was something we were prepared to deal with as we have other plans for it. I reset the plugs to .35 and made sure all was good. Fired it up and this seems to be where it has gone down hill. It appears that cylinders #2 and #5 are not firing.I used a water squirt bottle to determine this. I have done the cap and rotor(3 sets),new coil,new plugs and ECU,checked the reluctor gap and it is a tight .008 and and still #2 & #5 appear non firing.It has accell 8mm superstock plug wires that look to be in decent shape. I do believe this could be simple to remedy but not knowing 100% of what else to look for I guess I need a little help. So in advance I greatly appreciate any kind of input. Thanks in advance, Jeff
 
The thing to determine is.................

is the cylinder(s) not firing because of ignition,

or or some other reason?

First, "rig" the plug wires one of two ways

Pull the boots up at the cap and loosen the plug wires, so that you can pull them out

OR stick small brads/ nails gently down beside each plug wire in the cap.

Get the engine warm and idling at it's "normal" idle, then take a grounded probe and ground each cap tower one at a time. Listen carefully and look at the tach. The engine should drop the same RPM or "sound the same" for each cylinder as you short it.

When you find a cylinder which makes no difference, get your ground probe down there and short the tower for that plug, as you pull the wire up out of the cap. Then slowly pull the ground probe back to get a "feel" for the spark.

DO NOT let the gap become more than about 3/8" or a little more, as an "open" spark wire can DAMAGE (I.E. "kill") the ECU

If the spark looks OK on the "bad" cylinders, make DARN sure the plug wires and plugs are OK on those cylinders. Either substitute known good plugs/ wires, or swap them to another cylinder and verify whether the problem follows the wire or plug

After you have done all the above, you should have a REAL good idea as to whether this is actually ignition or not.
 
Plug wires that look good doesn't mean much. Pulling them off to access the plugs can do more harm than good
For the plug gap to grow wider over time is normal.
New plugs and wires may be all you need.
 
may sound dumb but, start the car in the dark of night and see if you can spot a broken plug wire grounding out somewhere
 
You can get an in-line spark tester for ~$5 at Harbor Freight. Stick it in-line w/ the plug wire and see if the bulb flashes. If so, it is firing. I keep one in all my cars. Also, get one of their multimeters (sometimes free). Throw in some alligator clip jumper wires and you have all the tools needed.

To add knowlege, search youtube and wikipedia. Simple DC electronics is trivial to learn. Most people understand current flow, but maybe 80% on FABO don't know what a voltage difference means, since they say nonsensical thing like "I have 12 V going into ...".
 
Thank you all for your input.Definitely need to learn more on the electrical. Since I posted a few days ago I was able to spend more time looking at things and decided that new wires were needed and got a set of msd 8.5 mm wires. Also I have been able to determine I think why # 5 was not firing. All the contacts in the cap had marks on them but #5 it was clean so I will assume that to indicate the contact in the cap was not made. I ended up reusing the old one just to get things fired up and for the 1st 30 seconds it sounded good and the 1-7 side seemed smooth but 2-8 is still ruff and then it started to pop again. The cap and rotors I got seem to be sloppy and not near the quality of the mopar cap so back to the dealership. Thanks
 
Just a thought you said popping noise could you have a valve that is sticking. Maybe a little trans fluid down the carb while running may help sense it sat. And i have had this problem once couple cylinders not firing. I had a valve job done and painted the heads when put back togather. I had the plugs out when painted and the spark plugs werent grounding. Maybe try cleaning spark plug holes on cylinders in question.
 
Yes dribble a little down the carb just a bit above idle it will smoke till its all burned out but will lube the top end and unstick a slightly stuck valve.
 
I have heard of the atf down the carb but never tried it. If I get things up and running I may just give it a shot. I got a inline spark tester today, thanks Bill for that tip,so I may go back out and kick the cat again here. Thanks Jeff
 
A little mr marvel mystery oil in the gas wont hurt you either. Dont go wild but you can dump it right in the gas and it makes for great lubercation.
 
Well the I kicked the cat here. Pulled the valve covers and had the wife turn it over and all seems to be working so I don't think we have a valve issue. Well it still won't start (run on it's own) but we appear to have spark with smooth turn over as it did want to fire and carried on for a few seconds. I pulled #1 plug and got tdc by using a dial indicator. The rotor lined up with #1. So I feel at least we are reasonably close in timing. Wanted to go a few more rounds but the battery was telling me otherwise. Is there something else now that I can look for as to why it doesn't want to do a total fire and run. Thanks
 
I'm having the same exact problem with my '71 Duster. I have checked nearly everything. Changed distributor, cap, rotor. Switched spark plugs and cables around to no avail. I even did a compression check. All is well. The last thing I checked that got my attention was the voltage output of my alternator. Turns out that it is going from 12.3 at idle to over 16 volts. Tells me that the voltage regulator is shot. I am assuming that the ecu is shot now because of overcharging. I still need to get a regulator and then test everything again.
 
Mr2.4 said:
I'm having the same exact problem with my '71 Duster. I have checked nearly everything. Changed distributor, cap, rotor. Switched spark plugs and cables around to no avail. I even did a compression check. All is well. The last thing I checked that got my attention was the voltage output of my alternator. Turns out that it is going from 12.3 at idle to over 16 volts. Tells me that the voltage regulator is shot. I am assuming that the ecu is shot now because of overcharging. I still need to get a regulator and then test everything again.
Click to expand...

You need to start your own thread to avoid confusion. Another member recently had the same problem, and it appears (at this point) NOT to be the VR
 
I'm not trying to confuse anybody by no means. I just saw that he has the exact same problem as me. Just giving him something to check. Heck even the same plus not firing.
 
Got the car fired up this morning. I had to advance the distributor a fair ways to get it to fire.My vacuum advance seems to be in a different position than my original mark and my visual recollection. It was lining up with the #8 cylinder visually now to get it to run it is between #6 - #8 which I think is probably too much. I don't have access to a timing light today so I am a little reluctant to go on a test run. If I do a short run is there a chance of damage to the engine with it advanced in this state. Also did a quick check on the alternator and it seems to be charging the battery back up to 14.0 after a few hard starting sessions this morning. Thanks Jeff
 
Go for the rip,if it is starting up fine with no kick back, and once your out turn down the stereo and be sure she is not pinging,you wont hurt nothing.Let us know
 
Went for a 2 km run and it seems to be fine,throttle response seems a little weak as it does seem a tad on the sluggish side and no ping. Heck I can live with this for a day or so. I had had it booked into the shop to rebuild the front end last week so if all goes good will have that rebuilt by the end of this week instead. While it is in there I can likely get the timing dialed in a little better.
 
Ok guys I am a little uneasy with the way this distributor is sitting and I played a little more to see how the engine would respond. As i brought forward above in this post I had to advance the distributor more than it was prior to my issue. I had advanced things to where the vacuum advance was tight against the #8 intake runner. Sounded not to bad and throttle response a tad perkier. But I shut it down and it ran on so I think to much advance. So now I am thinking maybe the springs for vacuum advance are weak and or broken. Or the pickup is not set to correspond with the reluctor. After playing with the open distributor and going tdc the pick up was not on the set point of the reluctor. Rather it was between 2 points. Now I visualize where the pickup is and the relationship to how much I had to rotate the distributor and feel the reluctor and pickup need to correspond with tdc and #1.Therefore the pickup may have to be reset to mach #1..I have got the pdf file on how to install this electronic distributor and looking at the diagram seem to see a difference in how mine is now. Could I be on the right track with one or both of my thoughts. Thanks Jeff
 
How do you feel about your cam drive? Any chance the top sprocket is plastic?

The reluctor should NOT be aligned with the pickup at TDC, but rather "where you set" initial timing. I run lots of lead, around 15* or so, and that is where the two should line up

You should be able to "set" your timing close enough to run in that manner. Bring the engine up towards TDC, but set the marks at wherever you want initial time. Then move the dist. to align the reluctor in the center of the pickup.

You should be able to get a "rough idea" of the condition of the advance by moving the rotor CW and then let it spring back. You should be able to move it against the advance springs freely, and it should snap back against the springs.

Take a good look and feel the shaft for sideplay and wear, and look at the cap and rotor for damage, which could indicate severe dist. bushing wear.
 
Thanks 67 for this info I will give things a good look tomorrow. Not sure about the cam sprocket as the history on this car is zero . This is one of those cars you likely were told to run from and fast...haha.This engine has been apart and back together.Thought about a chain slip but when I got tdc and rotor looking correct I kind of tossed that aside but now maybe we need to revisit that thought. I was hoping to just keep the car running for the summer and try to figure out whether or not I need to rebuild the engine.Seeing now maybe we need to really look at the power plant harder than just saying it runs and we don't require a rebuild ....Yet. Pretty much now thinking I may need to do a power train rebuild front to back and then we will know we have a dependable runner. Our plan is to hopefully blow it apart this October and rebuild the car over the 18 month period. Thanks again for the info,Jeff
 
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