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Post by alaskanrocket on Apr 20, 2020 14:14:01 GMT -5
OK, Heres where I'll start. I did a rebuild on a L134 this winter it's .060 over and still within tolerances so I put new pistons, rings, bearings throughout, and new valve guides reamed to spec and lapped the valves the best I could. A back story, Ive been fighting this jeep power train for years, this is the third engine Ive put in it since I never want to spend the money to get one properly machined and rebuilt. Good blocks are hard to come by in Alaska, they have either mismatched bearing caps, bored out to .060 and clapped out, or cracked, etc, etc.
Ive only driven it once since the rebuild and it didn't go well, it ran fine for the first 5 minutes or so then just died, seemed electrical at the time, checked all the connections, jumped back in it and still wouldn't fire, gave it some choke and she fired up and would only run partially choked, barely made it home. Since then replaced the fuel tank with a new one and new fuel lines suspecting there was some junk in the tank. Ive been working on getting it adjusted properly since then and this is where im having my current issue.
The data I have.... Rebuilt carburetor with parts kit from one of the reputable jeep parts dealers after I completed the engine rebuild, Installed new base gasket with diffuser and torqued it down (did not use torque wrench but pretty good oomph on it all hundred times ive had it off and on) New points set to .020, new cap, rotor, condenser. The distributor bushing does have a bit of play, (its insane that I have 5 distributors and they all some issue or another). Static timed the engine and it fired right up with no issues (this was right after the rebuild and before the initial test drive). Oil pressure was around 40psi at idle when cold, then drops to around 10psi when hot. Timed by Vacuum from the intake manifold and vacuum was relatively steady at 20PSI. (Since then with all the fiddling with everything vacuum is now around 19psi). Checked compressions warm and dry and had 100,95,100,100 (with the intake closed)
Adjusting the carb. Initially on fire up I adjust the idle speed screw to open enough to run and the mixture screw to 1.5 turns open, it only idles smoothly at fairly high idle rpm. The engine has a miss at idle and seems to smoke a lot, I'd like to attribute this to a rich carb condition but Im not ruling out oil since I didn't do any real machine work to the engine and a lot of stuff was close to max tolerance. Pulled the plugs and after the 5 hours or so of troubleshooting run time they were pretty sooty (not oily), so cleaned and re-installed (autolite 295's). My dwell/tach meter isn't working so Ive not been able to check rpm/dwell yet. Checked for vacuum leaks all around the carb with propane and didn't find any. Ive attempted to run the idle speed screw down to where it barely runs and adjust the mixture screw but it never really smooths out. Once I increase the idle speed screw to where the miss goes away the idle mixture screw does nothing, I can screw it in all the way and it makes no change to idle speed and the carb is still very responsive, I should note that there is not fuel coming through the venturi at this point or anywhere else above the throttle plate as far as I can tell, the potential is there and I just cant see it but I don't think so. Ive tried to lower the idle down and apply choke and it immediately wants to die. Ive checked the plunger travel and it is at scout pilots recommended heights and adjusted the metering valve with the proper carter tool, I have also made sure the float setting is correct with the proper carter tool. Ive spent quite a few hours working on this, researching, and then messed with it all weekend and cant get rid of that miss and seemingly rich condition. Ive read tons of stuff in the forums and on this site and even discovered my distributor advance was seized up (now fixed, thanks to this website). Im not really sure what else to do from here. The carb is currently torn apart on the bench looking for a plugged jet or something else glaring and Im starting to think this may not be just a carb issue. I feel like I need to go back to square one and start all over in case ive missed something.
I'd appreciate any input on where to go from here. Thanks in advance and I'll be happy to answer any further questions, hopefully I answered most of them above. Thanks!! |
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Post by Scoutpilot on Apr 20, 2020 15:15:51 GMT -5
Okay. Won't run without choke applied. Indicates a vacuum leak. You can't determine the idle RPM. Guess. Anything above 800RPM won't allow for a standard leak test. It just won't show. Sooty, wet plugs tell me of a too-rich mixture which is the standard response. Eventually, this doesn't help. Bushings and a new shaft are getting to be pretty much standard requirements in what used to be a simple rebuild. Torsional forces on the shaft and bores cause wear that is approximately egg-shaped for each. As the gap widens, more air is allowed to leak in and screw up the air-fuel ratio.
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Post by alaskanrocket on Apr 20, 2020 16:17:17 GMT -5
Hey Scoutpilot! Thanks for the response. Im going to borrow my buddies dwell/tach meter tonight and try a leak test again with a lower rpm. I'll update you with my findings. Since I have it torn apart I may just chuck it up and re-bush it, I'll have to look at setup options. Thanks again, I'll keep you apprised of my findings.
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Post by Scoutpilot on Apr 20, 2020 17:36:38 GMT -5
If you are going to install bushings yourself, remember, DO NOT bore all the way through. Leave a narrow ledge inside for the bushing to butt up to. Measure the throttle shaft. If it's less than .010" OD at any point on its circumference, it's trash. Don't forget to ask questions about things with which you're unfamiliar.
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Post by alaskanrocket on Apr 21, 2020 12:06:37 GMT -5
Well I didn't get a chance to run by and grab that tach last night but I did take the time to measure OD of the shaft, and ID of the holes. The shaft to hole diameter difference was .006" -.007" so that must be my issue. Luckily the holes were pretty well centered in the casting so there's room to bush. After considering the time to build a jig to bore the housing for the bushings, even though I did have the right reamers and stock in the toolbox, I decided I had enough other stuff to do so I'll just send it to you to get re-bushed, in the meantime I ordered a "new housing" on ebay and I'll see how it does. At any rate, you should see a service request from me come through and I'll get it sent your way. Thanks a lot for the help so far. Jess
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Post by Scoutpilot on Apr 21, 2020 14:20:11 GMT -5
Good idea. When the shaft and bores wear they both wear into an egg shape which won't be easily discernible to the naked eye. I'll treat you right.
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Post by alaskanrocket on Apr 22, 2020 12:42:08 GMT -5
Update, Im an idiot.
That's not really an update but I feel like a big one right now. I decided to start at square one last night and begun with timing, and BAM! The timing was advanced a few degrees past TDC. I guess when I made my mark on the crank pulley with a sharpie its somewhat skewed while looking down at it once in the jeep. So I got my head down and lined up the ignition marks on the flywheel and she idled along with no miss. When initially trying to get the carb set I attempted to adjust the timing with far too high of an RPM which was probably why I was getting my highest vacuum at such an advanced setting. I now have it idling good at around 750 but its still doesn't want to idle great at 650, it stumbles a little but I'm fairly confident this is due to the vacuum leak in the throttle body. Anyhow, just wanted to provide you with an update and I have to say, I'm pretty embarrassed because the whole time there was something in the back of my mind telling me to check timing and I just wasn't listening because I was so confident in my initial settings. Now Dwell is at 41.5 degrees with a decent idle around 750.
After adjusting timing, I dropped the rpms down to ~600 with the idle stop screw, it was barely running at this point, and checked for leaks with propane and still found no rpm change. The only time it would start to smooth out was when the idle mixture screw was almost closed so I attempted to apply some choke and it died. I'm not giving this too much thought right now until I get the throttle body fixed. At least Im on the right track now. Thanks again for the help so far. Couldn't have done it without help from you and your website. Jess
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Post by Scoutpilot on Apr 22, 2020 14:03:15 GMT -5
Idiots don't learn lessons. You have advanced considerably. You gave me all I need to know about your situation.
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Post by alaskanrocket on May 5, 2020 12:30:41 GMT -5
Another update,
I was still having issues after getting the timing dialed in and replacing the throttle body with a new one. Idled great so I took it for a run around the block and about halfway through it would barely stay running and when I finally limped it back to the house my oil pressure had dropped of to almost nothing, I pulled the dipstick and it was overfilled and smelled heavily of gas. It only made sense to me at that point that it must be the fuel pump leaking into the crankcase since it was idling so well and didn't seem to be running rich at all, I pulled the fuel pump and sure enough it was wet with gas at the lever. I changed the oil, in which the old oil only took about 2 seconds to drain completely. Replaced the plugs, new oil in and replaced the fuel pump with a another newer one. So far the problem seems to be solved. I fired it back up and then it was idling great full oil pressure again, whew. But now there was a dead spot just after idle. So I adjusted the float which was a hair high and moved the metering rod up a bit (it was initially set with the carter tool) and finally let the accelerator pump soak in some vinegar then oiled it since it seemed to have a weak spray right off of idle. Dead spot gone, seems like it has good power and have driven it about 10 miles since with all of the original issues gone. Oddly though Im only ever able to get 40 deg of dwell but am attributing that to distributor bushings.
One new nuisance issue that I can't quite figure out is after coming down a hill and coming to a stop it dies, she fires right back up after hitting the starter and giving it a little throttle but doesn't seem to do it after long runs on flats just when Im coming down a hill in gear. So Im going to continue on troubleshooting that portion which may even be distributor related as the bushings in my distributor need to be replaced and makes troubleshooting the carb almost impossible until that gets sorted out.
Anyways, Just wanted to give an update on where Im at and say thanks again for the help. Jess
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Post by Scoutpilot on May 5, 2020 13:35:05 GMT -5
You are definitely making progress. The fullness of the fuel tank may have something to do with your down-hill issue. 40º of Dwell? I suspect a problem with the rubbing block on the points free arm. It may be worn short.
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