Spirit R/T backfires, doesn't start

So I decided recently to replace the coi lpack in my Spirit with a unit from a Dodge Neon. I got an MSD unit, soldered in the Neon pigtail, and all was well. However, I didn't have a place to mount the coil pack, so I built a custom mount out of aluminum that bolts to the top of the valve covers. This required resoldering the pigtail, because the wires needed to be lengthened to reach to the middle of the valve covers. I redid the wires, bolted down the coil pack, plugged everything, tried to start it up, and... nothing. Turns out that I had attached the spark plug wires in reverse order (i.e. wire to 1 was on the terminal for 4, wire for 2 was on the terminal for 3, etc.). I fixed that, and now the wires look like this:

This is how I have the wires arranged:

http://www.turbo-mopar.com/forums/at...682211&thumb=1

Tried to start the car, still nothing. Engine sounded like it was getting stuck on something - it would go chug, chug, chug, ergh. Strangely, if I disconnected the wires to the coil pack, the engine would continue cranking without stopping. I suspected that I had flooded the engine, so I pulled a plug and, sure enough, it smelled like gas. I pulled the rest of the plugs and dried them out, and also allowed the cylinder bores to dry out. Reconnected everything, tried to start the car. Now the engine continues to crank - it doesn't stop like it did before - but it also backfires. It only backfires once per attempt to start, and the backfire is VERY loud.

Observations:
- I tested continuity between the relevant pins of the PCM connector (17 and 19 for the ignition coils, 57 for the power feed) and the coil pack pigtail. Zero resistance on each.
- I checked that each plug got spark; however, I'm not sure whether the spark is particularly strong.
- Each of the plugs had a noticeable layer of carbonized crud. I was able to clean them off pretty easily, but the crud was significant for plugs that were only installed about six weeks ago. (Side note: the car does emit a puff of blue smoke on startup; however, this has been going on for a while and the old plugs were not noticeably carbonized)
- I can hear the fuel pump pressurize the fuel
- I verified that the resistance between terminals 1 & 4 and 2 & 3 were within spec (between 11k and 14k ohms)
- I looked down at the intermediate shaft sprocket to see if any teeth had been sheared off. I wasn't able to see so well down there, but everything appeared okay. There were no bits of metal under the car, either.

I've read that backfiring is usually a timing issue. That leads me to several possible culprits:

- I was wrong to assume that the similarity between the colors of the wires to the ignition coils (db/yl and bk/gy on the stock harness and db/tn and bk/gy on the Neon) meant that similarly-colored wires should be connected. Perhaps db/yl goes to blk/gy and bk/gy goes to db/tn...
- Maybe the timing belt skipped some teeth?

Any ideas or suggestions would be greatly appreciated! Thanks in advance.

Well I'd check the belt first, or you'll be chasing your tail otherwise.

Quote:

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Originally Posted by RoadWarrior222

Well I'd check the belt first, or you'll be chasing your tail otherwise.

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You're right, of course... I was just hoping to avoid that as it seems like a pain in the keister. Do you happen to know whether I need to go through the whole cam timing procedure, or is there a more simplified procedure for verifying that the timing is correct (e.g., don't remove anything, get the motor to TDC, verify that the holes in the cam sprockets match up with the holes in the cylinder head?)

Also, just cause I'm getting anxious - is it possible that I completely f'd my motor up? Bent a rod, screwed up the cams, etc.?

---------- Post added at 06:45 PM ---------- Previous post was at 06:37 PM ----------

Also, forgot to mention: no codes.

I think you may have wired it wrong. Try swapping wires on the coil, 2/3 for 1/4.

What you describe when cranking is you wired the new coil incorrectly. You won't have done any damage so don't worry. Maybe try moving the plug wires as suggested, if not, you'll need to rewire it.

Quote:

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Originally Posted by turbovanman

What you describe when cranking is you wired the new coil incorrectly. You won't have done any damage so don't worry. Maybe try moving the plug wires as suggested, if not, you'll need to rewire it.

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Are you saying that I connected the leads wrong? That seems implausible, since the arrangement is exactly the same as when I was initially using the MSD unit, which worked perfectly. All that's changed, as far as the pigtail is concerned, is the length of the wires. It's still bk/gy -> bk/gy, db/yl -> db/tn, and dg/or -> dg/or, just as specified in this thread:

Quote:

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Originally Posted by glhs0426

It's really an easy conversion. Answers found with a combination of paper and digital maps :)

R/T = Neon
DG/OR=DGOR
BK/GY=BK/GY
BL/YL=DB/TN

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If what you're saying is that the spark plug wires are misarranged, that seems more likely. I had been assuming that the plug wires on the R/T should be arranged as the plug wires are on the Neon:

Attachment 42029

However, it's possible that the wires should say the same as they are on the stock R/T coil pack:

Attachment 42030

Because it's possible that, for instance, the bk/gy triggers the 2-3 pair in the R/T coil and the 1-4 pair in the Neon. Annoying, but possible, and I will verify in the morning. Of course, if it works, it means that, if I had actually paid attention when initially installing the MSD unit, I would have bungled the job!

This would also explain why my mistake in installing the wires exactly in reverse still ended up in a no-start condition: each of the pairs of plug wires were still on the wrong side of the coil pack.

Well, swapped the 1-4 and 2-3 wire pairs, and it fires right up! Guess the Neon coil pack is so plug-and-play that you can (er, must?) keep the stock R/T wire layout - except that, as I found out in trying to fix the problem, it's a wasted spark system, so it doesn't matter whether you've got 1-4 or 4-1, or 2-3 or 3-2.

Thanks for your help, Ian and Simon. :thumb:

Glad you got her running and this is a good thread for anyone in the future, :thumb: