My Willys 3A and 3B Community
TECH FAQ SECTIONS => Electrical Systems => Topic started by: PercyUK on November 06, 2021, 04:04:19 AM
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So I have been chasing a misfire on my cj3a for sometime now and have now found the problem to be with the electronic crown distributor I purchased a while back.
Low speed it's fine but at high revs it misses.
There is nothing I can fix in it and am now looking for a decent replacement.
Is there a commonly agreed quality replacement out there and what is it.?
I am happy to return to points and condenser given the limited miles the Jeep gets each year.
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Do you have the stock coil, or the recommended higher output coil?
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Hi, I have a stock coil as there was no mention of a high output one in the instructions that came with it.
Sadly I have lost faith in it and would always be worried. I don't think I want a modern electronic unit that in theory couldn't rev as high as the old points system simply because it needed a high output coil.
I think I will replace it just so I can be confident that it won't randomly fail when I am far from home. At least with points and condenser I can fix it by the roadside.
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Are you looking for a new distributor? Do you still have the L134 engine?
With parts from Willys Distributors I rebuilt an Autolite IAT-4402. It was already installed on my L134 when I bought the jeep. It is a vacuum advance style but the previous owner did not connect the vacuum line. After the rebuild and installing the vacuum line, which has a dedicated port on the intake manifold, I have been very pleased with its performance.
The Autolite IAD-4008 w/ dust shield would be the original distributor. I think it also is a good distributor.
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I can understand your logic. However, electronic ignition is said to prevent "point bounce" among other issues. One problem with electronics and replacement parts is... GIGO (garbage in garbage out)... if the input is not adequate, the output can not be... as well as there has been lots of discussions about the "lack of standards" of "replacement parts" these days, both electronic and/or mechanical. It seems to be the luck of the draw of what one gets compared to another using the same manufacturer. A main reason why old NOS mechanical parts are preferred.
Maybe one of the members here that still has access to the CJ3BInfo site can provide a link to some of the high output coil/electronic system discussions there. My Petronix digital conversion kit came with the instructions/warnings of the need for a "high output coil". That is why I asked about your coil. BTW... I have the original distributor plate stored onboard set up with new condenser and points in case of an emergency need. Two screws hold the plates in position for an easy swap out on my original distributor. That's my Plan B.
I found the following infor useful from Hot spark .com...
Measuring Coil Primary Resistance: 4-Cylinder: Coil must have a minimum of 3 Ohms primary resistance. 8-Cylinder: Coil must have between 1.5 Ohms and 2.0 Ohms primary resistance. To measure primary resistance: Label and remove all wires to coil ( + or - ). Using a common digital multimeter in the 200 Ω mode, cross the red and black leads of the Ohmmeter. Allow a few seconds for the reading to settle and write down the reading.
Still in the 200 Ohm mode, measure between coil’s + and - terminals. Allow a few seconds for the reading to settle, until it stabilizes. Subtract the previous reading, taken with the leads crossed, to compensate for multimeter’s inherent resistance. Do not use a low-resistance coil, such as the MSD or Accel coil; they don’t have enough primary resistance for this application. Using a coil with too little primary resistance can cause the ignition module to overheat and misfire until it cools down again or fails, voiding the warranty.
Ohmmeter Calibration: When the Ohmmeter’s red and black leads are connected to each other, the reading should be 0.00 or very close to zero. If, though, for example, with both Ohmmeter leads shorted together, the reading is 0.5 Ω, you’ll need to subtract 0.5 Ω from the reading you get when measuring the coil’s primary resistance. For example, if the coil’s primary resistance reading is 3.5 Ω, but when the Ohmmeter leads are shorted together the reading is 0.5 Ω, then the coil’s primary resistance is 3.0 Ω: 3.5 Ω - 0.5 Ω = 3.0 Ω. This calibration procedure applies only to resistance measurements made in the 200 Ω mode of a digital Ohmmeter.
The inherent resistance of the leads is negligible in higher Ω modes of the Ohmmeter. If you’re using an analog Ohmmeter, touch the leads together while setting the needle on zero before measuring resistance.
Measuring Coil Secondary Resistance: For best performance, coil should have 7K Ohms or more secondary resistance. To measure secondary resistance: Label and remove all wires to coil ( + or - ). Using a common digital multimeter in the 20K Ω mode, place one Ohmmeter lead on the coil's + or - terminal and the other Ohmmeter lead in the coil's center high-tension wire socket, the socket that holds the lead from the center of the coil to the center of distributor cap.
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Wow Steve you certainly know your stuff.
I used to have a TVR Vixen which I retro fitted, 30 years ago, with electronic ignition and it never gave me a moments problems. Trouble is this Crown unit has failed my "circle of trust" and I fear that even if I fixed it I would always worry about it.
If it was a converted manual distributor, for want of a better phrase, I would change it back to points but this unit came already converted and cannot be changed.
Just for peace of mind I am going to go back to stock and perhaps retro fit electronics at some point in the future.
I do appreciate your comments though, its great to see the depth of knowledge thats available on this forum whenever you need it.
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Hi Bill, yes I have the original go devil engine fitted but sadly no old dizzy to rebuild. I am looking for ideas regarding a quality replacement as there are a lot of poor repos out there. Any views about who are making good replacements would be appreciated.
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Percy,
I have two customers who have been running new-made replacement distributors, one for 4-5 years, the other for 2-3. Both seem to be running fine up to this point. I got them from Walck's 4WD.
I get a kick out of all those who change to electronic ignition "for reliability" but carry the points and condenser along "just in case". I don't know anyone who is running the original points distributor who carries an extra set of points or condenser. Or who has ever needed same.
BW
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Cheers Bruce, I will check it out and see if I can source one over here in the UK
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Well I'm stumped. I fitted a nice new distributor with new points and condenser and still have the misfire. New coil, new leads, new spark plugs and now a new dizzy. 12v input to the coil checked OK and I even provided a supply direct from the battery to remove the wiring harness from the equation but still without result. I even suspected that the alternator fitted might have been sending a spike or signal that interfered with the ignition so I removed the fan belt so it didn't spin and ran it but still no change. I am royalty confused and have run out of ideas. Bty I suspect that it is electrical because when a timing light is attached to the coils output I see the strobe light faltering and from experience it just feels electrical. Any ideas would be gratefully received.
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You haven't mentioned the "cap/rotor" condition yet. A crack or corrosion can cause an arc misfire. After checking that, I would suggest checking your 'grounds". Engine to frame strap corroded or loose? Too much paint on mounting threads and/or surfaces for proper grounds? That is how "I" would start to look elsewhere now after all of your "voltage input checks". I'm sure the "experts" will have more detailed suggestions. I hope it turns out to be something easy to fix for you. Good Luck!
Here's what google said about the cap and rotor and arcing...
How can you tell if distributor cap is bad?
Usually a faulty distributor rotor and cap will produce a few symptoms that alert the driver that service may be required.
Engine misfires. Engine misfires can occur for a number of reasons. ...
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Hi Steve, thanks for the reply.
I also have a new cap, points and rotor which came with the dizzy.
I think my earth's are good as everything else works fine but will check anyway just in case. I consider myself to be reasonably competent and experienced with motors but I must admit to being stumped at this point.!!!!
I may revisit the carb, even though it "feels" electrical, further updates to follow.
Cheers
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Percy, I wasn't trying to challenge your "competence", just going over my typical list of events I would follow, not knowing exactly what all you have already done and have there to work with. Electrical can be tricky, and especially hard to diagnose intermittent issues. My thinking was... a weak ground may "work" under low load and linear conditions, but under the demand of high speed RPM spark voltage demand, and/or vibrations, continuity issues may show up. I'm sure you'll find the problem. Keep us posted. Thanks.
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Hey Steve, I didn't think you were challenging at all, no worries there.
Sorry if my message conveyed that, it wasn't intentional just poorly written in haste.
Thanks for your help, and when I find out what's happening you will be the first to know.
Cheers
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Percy,
I have two customers who have been running new-made replacement distributors, one for 4-5 years, the other for 2-3. Both seem to be running fine up to this point. I got them from Walck's 4WD.
I get a kick out of all those who change to electronic ignition "for reliability" but carry the points and condenser along "just in case". I don't know anyone who is running the original points distributor who carries an extra set of points or condenser. Or who has ever needed same.
BW
Currently me. As I was unable to adapt the Petronix unit to my IAT-4405 I went back to points. I am currently carrying a spare coil, cap, rotor, points, two condensers one old one new Accel, A coil wire and a plug wire as well as 4 plugs.
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Hi Steve and everyone else.
Well I revisited my earth's as suggested , cleaned and replaced the cables, fitting two instead of one and no change. I am truely baffled at this point.
The next step is to use another strobe light to confirm my suspicions that it is electrical and then work from there.?
When I finally discover the problem you will all be the first to know!
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OK Percy, I didn't want to go in this direction from "my unique experience", but it seems you have covered all electrical bases. When I got my DJ, it had a strange miss and pop no matter what I did for tuning. When I removed the engine and took it apart, I found "open cracks" at the flanges of the intake mounts, letting in air to the shared cylinder out of sync. PO not only cracked the flanges, but did a 'bubba weld attempt' that was not solving anything. Maybe that 'crack potential' is something to check for on yours? Good Luck.
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Hiya, having just done a top end build I am keeping my fingers crossed that I don't have to revisit it again. I will carry on and keep you updated with any progress.
Sods law it will be something simple that I have overlooked....... Hopefully!!!!
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So I just broke down in my jeep and Im getting zero spark. I think its a bad ignition module because everything else checks out. I have an omix-ada electronic dist from Walcks. I found a replacement module on eBay which I will try but I have read that omix are pretty iffy on reliability. I don't have the old distributor. Does anyone know if the Pertronix module can be put into the omix distributor case? I did notice there are more wires on the omix module. I keep seeing that the pertronix is basically bullet proof with no issues. I am going to add a ground wire from coil to block just in case.
thoughts?
Thanks,
Nate
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Hi Nate, I can't help you I'm afraid. I was chasing a misfire at the time and was concerned that it may have been the electronic dizzy. I didn't think that I could diagnose the problem so I replaced it with a new mechanical one as I was more comfortable with the tech.
I'm sure one of the other guys will have the answer.
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So I just broke down in my jeep and Im getting zero spark. I think its a bad ignition module because everything else checks out. I have an omix-ada electronic dist from Walcks. I found a replacement module on eBay which I will try but I have read that omix are pretty iffy on reliability. I don't have the old distributor. Does anyone know if the Pertronix module can be put into the omix distributor case? I did notice there are more wires on the omix module. I keep seeing that the pertronix is basically bullet proof with no issues. I am going to add a ground wire from coil to block just in case.
thoughts?
Thanks,
Nate
This should be a new post started by you. It's easier to find and follow along vs. embedded in PercyUK's thread. I do have some thoughts.