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No start, backfire thru carb

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cpt logger View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr. 2023 at 6:28pm
A freshly overhauled L-134 with a high compression head will produce 125 PSI of compression.

I should ask Mark W. what the compression is on Chug a lug. I have not had the time to keep up on his thread about Chug, my fault.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SeeJayTwo Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr. 2023 at 7:37pm
Compression retest. Took two more tests. Took off an adapter on gauge hose that was not necessary.
Test 1:
1-110
2-115
3-100
4-110

Test 2
1-116
2-120
3-95
4-120

4/5 strokes each cylinder
Throttle open, choke open
All gauges will have a tolerance


Edited by SeeJayTwo - 17 Apr. 2023 at 7:39pm
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Oldpappy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr. 2023 at 8:41pm
Sounds like a freshly built engine. As already said, there is no reason to start taking it apart with compression that good. 

You must have another problem, and it it likely ignition timing. 

Many times I have encountered Jeeps where the flywheel timing marks cannot be used either because the flywheel was mounted incorrectly, or the marks are just not visible.

Here is what I do.

1) Bring the number one piston up to TDC on Compression Stroke, be sure it is on compression stroke. 
2) Check position of the rotor and make sure that it is pointing to the wire going to the number one cylinder. If not, just move the wires around counter clockwise to make sure the firing order is correct. 
3) This should get you to where the engine will start, and if you were truly at TDC the timing may need to be advanced a little.

Note: The cam gear is on the oil pump, and if the oil pump was installed without being "clocked" to the expected position the #1 terminal on the distributor can be anywhere in the circle. It does not matter, so long as you identify the terminal being fired when number one piston is in firing position.  

 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SeeJayTwo Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr. 2023 at 9:00pm
Did your 1,2,3 several times and moved dizzy CW and CCW as per my previous posts. Checked all that several different ways. Checked 1342 CCW many times. Moved plug wires around to detect anything.  I'm going to wait for the tune up stuff to arrive. If you guys say leave valves alone I will switch back to spark/timing. 
Side note. I took out that metal disc "cover" over points. Is that essential? 

I think I read somewhere that there can be a set of anomlies that you can have compression with sticky, burnt valves? But of course the internet has a lot BS from time to time. 


Edited by SeeJayTwo - 17 Apr. 2023 at 9:19pm
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Lee MN View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lee MN Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr. 2023 at 9:59pm
The disc is the dust cover, it will run fine without it you can leave it out while troubleshooting if you like.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote SeeJayTwo Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr. 2023 at 10:01pm
Thanks Lee.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr. 2023 at 10:59pm
"I think I read somewhere that there can be a set of anomlies that you can have compression with sticky, burnt valves?"

Nope, if you have stuck or burnt valves you will not have the kind of compression readings you reported.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SeeJayTwo Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr. 2023 at 11:03pm
I think that is good news. thanks Pap.
My poor old starter is hanging in there so far. 


Edited by SeeJayTwo - 17 Apr. 2023 at 11:05pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr. 2023 at 2:54am
I have a suggestion, replace the plug wires first, then try to start it. If it fires with no "backfire". Then they were the issue. If not, next I would rinse & repeat with the spark plugs. If no joy, then the capacitor. Etc, etc.

Yes this takes some time, but it does two things. First, this way we find out what the issue(s) was/were. Second, if all the ignition parts are replaced at one time & the issue either persists, or gets worse, we have no idea as to which +/or how many of the new part was/were bad. Yes, these days they are often junk straight out of the box! AMHIK. I get to clear up someone else's ignition problems at least once a month. They always have replaced everything at once. What a PITAxle. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SeeJayTwo Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr. 2023 at 3:21am
I believe the only new part that could be "bad" enough to keep it from starting would be the condenser.



Edited by SeeJayTwo - 18 Apr. 2023 at 7:00am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oilleaker1 Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr. 2023 at 7:30am
Put your finger over the number one spark plug hole and feel for compression coming up. Then check where the rotor in the distributor is pointing. That will tell you if you are 180 out as Lee suggested. Your 1342 wire orientation going CCW starts where the rotor is pointing. Check the cap for cracks . To back fire it needs to be way out of time. You have no stuck valves and spark, so that would be first on the list to check. When the compression stops pushing on your finger, you are at TDC. 5 degrees before TDC,  back it off a touch and then set the distributor to be just cracking open the points. That should get you close. Too bad you can't get the cover over the hole open and look. Maybe a hammer screwdriver impact could break loose the flat bladed screw on the cover.? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom in RI Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr. 2023 at 7:51am
Agreed, this is sounding like a close check of where #1 is located is needed.  Timing seems to be off. It is way too easy and common for a distributor to be installed with odd oil pump clocking.  
Any chance you cee timing marks on your crankshaft pully?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr. 2023 at 9:48am
Follow the above suggestions first, most of the time it will be something simple. So, make absolutely sure which terminal on the distributor is number one, starting from there install the new wires in correct order CCW. 

I suggest buying a known good quality tune up set. I buy "Blue Steak" brand from CMV, but Napa also carries good sets. Don't use the imported crap some of the big suppliers sell. If what they sell is good quality they will state the brand of the part. If they don't look elsewhere. 

If all of this advice is followed and you still get backfire, the only other thing I can think of is the cam timing might be off. 

If it sat for that long it is possible there was enough resistance in the valve train on initial turn to have broken teeth on the cam timing gear, causing it to jump time.


Edited by Oldpappy - 18 Apr. 2023 at 9:49am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SeeJayTwo Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr. 2023 at 4:39pm
Points, condenser, plugs, wires, cap, rotor, coil coming about Sunday 23 April. Will report result. I hope I was just fooled by not seeing that spark was weak and intermittent. Wanted to hear it run a few seconds before new parts. The condition of all the parts is awful.... 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lee MN Quote  Post ReplyReply Direct Link To This Post Posted: 19 Apr. 2023 at 7:36am
Originally posted by SeeJayTwo SeeJayTwo wrote:

Points, condenser, plugs, wires, cap, rotor, coil coming about Sunday 23 April. Will report result. I hope I was just fooled by not seeing that spark was weak and intermittent. Wanted to hear it run a few seconds before new parts. The condition of all the parts is awful.... 


I’d start with the condenser, for future reference napa, and orileys have quality ignition parts for our old Jeeps in most cases in stock or the next day at the latest.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote cpt logger Quote  Post ReplyReply Direct Link To This Post Posted: 19 Apr. 2023 at 5:19pm
Originally posted by SeeJayTwo SeeJayTwo wrote:

I believe the only new part that could be "bad" enough to keep it from starting would be the condenser.


While I would hate to shake your belief system, I have had at least two coils be bad straight out of the box. They were made in India & China.

On my motorcycle I had two point sets that failed to have a ground. It was one of the few times I replaced points just because "it was time" according to Honda. Now this bike has two sets of points on it. One for #1 & #3 and one for #2 & #4. Imagine my frustration when I replaced the points & condensers with new & now had no spark at all on any of the cylinders! I reinstalled the old condensers with no change. Next, I reinstalled the old points. She fired right up & ran great! Those old points & condensers were still on the bike 20+ years & 35,000+ miles later. Still working fine. 

At the Honda shop they tested the points & condensers. They found the grounding problem & gave me some new ones. I insisted that they test the new ones for the grounding issue. Four boxes of eight points later, I had two known good sets of points. They had zero known good sets of points. Those points came directly from Honda in a Honda box. The replacement "New from Honda" points & condensers were In the boxes in a Zip-Lock bag in the fairing when the bike burned up in a barn fire. I now rarely change points & condensers just because.

While the Honda points were from Japan, which is in Asia, this was a long time ago. I still use Japanese electrical parts on Japanese machines.

Again, I do not want to shake your faith. These are some of my experiences. As usual, YMMV.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote SeeJayTwo Quote  Post ReplyReply Direct Link To This Post Posted: 19 Apr. 2023 at 6:32pm
Yes I am aware of all that. 

My issue was my impatience..... this forum straightened me out quick about thinking it was valves. That's when I really examined the condition of the ignition, even though I had spark.
I have to put all the new parts on at once because of the condition of the old parts.



Edited by SeeJayTwo - 20 Apr. 2023 at 12:07am
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Oldpappy Quote  Post ReplyReply Direct Link To This Post Posted: 19 Apr. 2023 at 9:17pm
I'm out.
If you can't get there in a Jeep you don't need to be there!
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