roughrider

[roughrider]

Ok,I had a carburetor butterfly bolt head break off and fall into my number six cylinder. that led to installing a new carburetor and a oil pump. Absolutely no touching distributor and its position.
When I went to crank it, it was backfiring through carburetor. found rotor button 180* off. why?
1979 cj5 4.2 258

 

[greg92jeepxj]

To be clear , you've had the head of a screw from the choke valve fall into the intake ? While destructive enough to an intake valve facing and small enough to get caught in a piston ring ( possibly) , I don't see how the ignition timing would have jumped 180 degrees out. Did you pull the distributor to verify if any gear drive teeth are stripped or broken ( the cam too ) or at least that the distributor rotates a full 360 degrees and hasn't jumped timing again ? For now , get the distributor back in at TDC #1 and reset the base timing and see what that does for you . Run the engine and recheck that initial timing is still correct . This is just too strange . But do you think it's just coincidental ? I mean , the screw head dropping and not the actual cause but another fault to cause the distributor timing to walk ? I just bought a cj5 , a 1973 ( I'm supposed to post it up but still in the diagnosing stage ) with a 258 one barrel. I installed the replacement distributor the PO gave me after verifying to the best of my knowledge the cam gear isn't Shreded as was the distributor drve gear was. Got it running ( have other issues to sort out ) and will check the cam and drive gear soon again. The replacement distributor shaft is nice and tight , not any play laterally , just the correct up and down play it should have . The old one had lots of play laterally and may have caused the gear to skip . Never seen this happen but won't rule it out. Then again , an owner before the guy I got it from tried to get it running and failed so he sold it. Maybe the diagnosing got too hectic and someone didn't tighten the distributor hold down clamp and the distributor hopped out of the block and Shreded the gear ? I'll never know. I mention all this because your distributor should be checked . You don't want to damage a cam gear , have to pull the oil pan ( as I did ) to look for broken teeth and all that this entails , just for a worn distributor. Please do this inspection . Better safe than sorry . Now is the time , before destruction may have you tearing down the engine . BTW , it can't hurt to check compression and a vacuum reading too to see if the reading is steady and not wandering indication a valve may not be sealing if not a vacuum leak or idle mixture out of sync for example.
P.S. - you made sure the oil pump shaft was properly engaged or the bolt won't seat the pump to the main cap , right ? I know it's not likely but your stumped and thought I'd throw that out there. Didn't mean to insult your capabilities in the least. Just scratching my head and seeing what falls out ,

 

[69jeepcj]

When he put the oil pump in. could the oil pump shaft some how turned the rotor? kinda how you can walk a rotor around by lifting the distributer turning one tooth and dropping it back in.. as Greg has said, I would put it back to TDC lift the distributer up turn the rotor back to TDC and drop it back it and see what happens.

 

[roughrider]

No insult taken. Performed all but vacuum test. All checks out. Removed all parts again reinstalled and now the engine is running properly. As you are still stumped and will always be stumped about rotor being 180 out. As for now its running and has 60 lbs oil pressure whereas it was below 20 before at idle.

 

[roughrider]

Installed new distributor right after purchase 6 yrs ago. Sure of proper installation. With all the other errors I found to have been performed on this vehicle, I would not have been surprised of that though.

 

[greg92jeepxj]

In my last post , I said the oil pump is bolted to the main cap . That is incorrect . On an in-line engine , it's bolted to the block where it accesses the oil gallery . Must have had a V8 on my mind. Sorry for the wrong info. Recently , I just installed a rear main seal in my 258 and found it necessary to rotate the engine before I loosened the main caps to make room to work . That causes the oil pump to pump out oil into the oil gallery and suck air. That would result in a loss of oil pressure at start up. At that piont it is necessary to pack the oil pump with petroleum jelly to help the pump prime on first start up. There are timing marks on the oil pump gears on all engines that will connect a distributor or cam sensor . When these marks are aligned , that will put the oil pump shaft in the correct phase to set the distributor at TDC so the ignition will be in time . It is possible to be 180 degrees out , but will be noticed immediately . I reinstalled the oil pump gears after priming pump and noticed after starting that I had a back fire as well. I reset the initial timing at TDC again also verifying #1 compression stroke and all was well after. I cannot say for sure and didn't much care since the initial timing was now correct but was wondering if the timing marks on the oil pump gears were off ? I quickly decided not to explore that thought and left well enough alone since I was not in the engineering state of mind with enough to do . The point is , somehow the ignition timing was thrown off and I HAD removed my distributor knowing I would be priming the oil pump after I turned the engine . Since the engine was now disturbed as the book calls it , the initial timing must be reset . It didn't make sense how this occurred but I remedied it and called it good. All that matters is to start from TDC #1 compression stroke and align the oil pump shaft and set the distributor in so the rotor is at the #1 cap terminal . That is all we need to know. I know you've already done this or your engine would still be a no start . Glad you've got it running and all is well. We'll leave the unexplainable to those who care . For right now , our timing , dwell and rpm takes precedence.