Distributor issue (Jeep won't start)

[4BY4ADV]

TL : DR - Can where the disti and oil pump mate up get misaligned from the cam gear? I'm assuming yes....

New 4.0 installed by mechanic(had 227k miles and some issues that would only be resolved with a new motor). After a couple hundred miles during the break-in process, the CEL turns on. Scan codes and it's P1391. Mechanic says not a big issue, everything is running great, so bring it in next week and we'll get it figured out. He looked at it and determined that the distributor needed to be replaced as it's output was inconsistent. No big deal, order it, let's get this done, call me when you have the part and are ready to install it.

It's been a month without hearing from him and considering how busy his shop is and how long other things took, I got a bit frustrated and decided to swap it myself.

Did it the lazy man's way marking where the rotor was pointed. First thing I noticed was that the rotor was just *slightly off from the previous disti, but trying to adjust one tooth like what I had seen online meant that the flat key didn't fit into the oil pump. I chalked it up to maybe my vision... maybe that's where the rotor was supposed to be pointed. It took a couple tries but it started and ran fine. Only problem is it didn't fix the P1391.

Last night I decided to pull the disti and have a closer look at things and I noticed that my original disti had the alignment bolt "ears" ground off and had a different plate holding it down. It allowed for some adjustment, which I know is not needed. So that got me thinking, I wonder if it really was off by just one tooth and I need to swap back to the other disti that can rotate slightly. I swapped back and it ran rough this time. Great... I'm going backwards.

This morning I decided to go back to the new disti as it least it was running, even if it took a couple tries to start. But this morning it isn't starting at all. Turns over a few times but won't start. As if it's not firing at all and flooding. Installed a new ignition coil because I've replaced everything else on the engine and why not at this point try and have every damn part brand new. Didn't fix it. SO, I'm thinking somehow the slot in the oil pump got misaligned from the cam, and I'm off enough that none of the points are lining up with when the cylinders should be firing.

So, at this point, do I need to find cyl 1 TDC, manually rotate the oil pump "keyhole", then reinstall the disti so that it lines up with the 1 spark plug wire?

Really frustrated that what should have been a 30 minute job is now turning into a few hours.

 

[hear]

I'm a big fan of doing it the lazy way, but when in doubt, go back and find TDC and use the pin to align the dizzy with TDC. Now I believe there are actually 2 holes in the dizzy for TDC alignment, one for the 6cyl and one for the 4 cyl. Remember that it's the cap that actually determines how many sparks to give per revolution.

The diz itself does not allow for any adjustment, the computer will advance the spark on its own to get the required ignition timing. So gone are the days of loosening the bolt & rotating it while using a timing light. Sad, because that was fun and I had those tools, which are now useless to me. There are only 13 teeth on the diz gear, so being off by one results in a ~27* difference. So it's either really close or it's off by close to 30 degrees, which is obvious to the naked eye. If the oil pump slot is the reason it won't drop in just use a screwdriver to rotate the pump drive shaft, its position doesn't affect anything; it's not tied to the cam position in any way.

 

[4BY4ADV]

Yeah, thinking it's the pump drive that got slightly off.... then started causing the "fun". I'll try that this evening after I get off work.

 

[hear]

there is always the relatively remote possibility that your timing chain jumped a tooth and now your timing is all out of whack.

 

[GregBelleville]

What you're describing sounds very similar what I went through when I replaced my distributor earlier this year. I'm attaching a video that helped me as the fix described at the end resolved my problem with the distributor not aligning correctly. The helical gear on the new distributor was installed upside down by the manufacturer. Once I punched out the roll pin, removed the gear and flipped it right side up and reinstalled the roll pin, the distributor slid right in to the correct alignment position.

 

[JKP]

Yeah, thinking it's the pump drive that got slightly off.... then started causing the "fun". I'll try that this evening after I get off work.

You have to adjust the oil pump with a long screwdriver to get the distributor to drop into the correct spot. The oil pump slot should be at 11 o'clock.

If that fails to line it up, you may have to remove the distributor gear pin and rotate the gear 180 deg. I had to do this to a replacement distributor once.

 

[4BY4ADV]

Ok… so it looked like the gear was off. Punched the pin out and rotated 180 degrees. I left the old disti in while I found TDC and the rotor was pointing closer to cyl 5 spark plug on the cap. So it looks like I had two things going against me. Fingers crossed it fires up after all this!

 

[hear]

5 is roughly the rotor pointing 180 the wrong way I think, but since the rotor spins twice for every full turn of the engine that makes it only 90* out of phase...I would expect it to not start at all set like that.

 

[4BY4ADV]

180 the wrong way? Firing order is 1,5,3,6,2,4.

Wouldn’t it be 60 degrees off? Regardless, it was not pointed where it should be pointed.

Got it all buttoned up, but too late to fire it up. Figured it would be smarter taking one last look at everything in the daylight before starting it.

 

[JKP]

The crank turns twice for a single rotation of the rotor.

If the engine is at TDC, the trailing edge of the contact should be at the cyl 1 post on the distributor.

 

[4BY4ADV]

Thank you guys for the help. That video regarding the synchronization process filled in all the gaps and caught a stupid little defect.

It started with zero hesitation/as fast as a brand new 2023 vehicle. Now here’s hoping that P1391 is gone and I can get it smogged.

 

[GregBelleville]

Thank you guys for the help. That video regarding the synchronization process filled in all the gaps and caught a stupid little defect.

It started with zero hesitation/as fast as a brand new 2023 vehicle. Now here’s hoping that P1391 is gone and I can get it smogged.

Nice, glad that video helped, I'm just paying it forward as someone sent it to me when I was replacing my distributor as well. Kind of crazy that these distributors are all being assembled incorrectly from the factory.

 

[hear]

Nice, glad that video helped, I'm just paying it forward as someone sent it to me when I was replacing my distributor as well. Kind of crazy that these distributors are all being assembled incorrectly from the factory.

Put one in the win column for my Autozone Duralast distributor. Worked out of the box.

 

[GregBelleville]

Put one in the win column for my Autozone Duralast distributor. Worked out of the box.

Haha, that's a rare win for auto zone parts!

 

[4BY4ADV]

Nice, glad that video helped, I'm just paying it forward as someone sent it to me when I was replacing my distributor as well. Kind of crazy that these distributors are all being assembled incorrectly from the factory.

Yeah… Pretty dumb. I’d love to give them feedback but I know it would never make it to the correct person and actually get fixed. They’d just say, “wow, this is the first time we’ve heard of it, so it’s probably just you.”

 

[4BY4ADV]

Put one in the win column for my Autozone Duralast distributor. Worked out of the box.

Now I want to walk into an Autozone and have them pull the dizzy for me to check…. lol

 

[hear]

180 the wrong way? Firing order is 1,5,3,6,2,4.

Wouldn’t it be 60 degrees off? Regardless, it was not pointed where it should be pointed.

Got it all buttoned up, but too late to fire it up. Figured it would be smarter taking one last look at everything in the daylight before starting it.

my bad, I didn't even check the firing order. I was thinking 5 was directly across from 1 on the diz.

Now I want to walk into an Autozone and have them pull the dizzy for me to check…. lol

Although reading through this thread, it's not evident to me what the actual problem was. What would you be looking for?

 

[4BY4ADV]

Issue being the orientation of the helical gear on the dizzy shaft. The ones that Oreilly sells from HEI have the gear off by 180 degrees. If you advances the timing by about half a tooth. Punching the roll pin out, rotating the gear 180 degrees, and reinserting fixes the issue.

And my next tool purchase is a roll pin punch set. I spent too much time trying to get that thing out.

 

[GregBelleville]

my bad, I didn't even check the firing order. I was thinking 5 was directly across from 1 on the diz.




Although reading through this thread, it's not evident to me what the actual problem was. What would you be looking for?

Looking at the distributor you won't be able to tell anything. However when you try to install it you will find that you won't be able to get the rotor to align correctly toward the 5o clock position because the gear is off by like a half tooth. Once you remove the gear and flip it over it installs like it should.

 

[4BY4ADV]

Looking at the distributor you won't be able to tell anything. However when you try to install it you will find that you won't be able to get the rotor to align correctly toward the 5o clock position because the gear is off by like a half tooth. Once you remove the gear and flip it over it installs like it should.

That too. Comparing my old/new dizzys I could see the difference. But the first swap I did, I noticed that the rotor was just slightly off in position from where I had marked my original rotor as pointing. I thought maybe it was the old dizzy that was off and the new one would fix my problems. But no… it was definitely off.