Joined: May 06, 2010 Posts: 32 Location: Wisconsin
Posted: Sat Jan 01, 2011 8:53 pm Post subject: M38A1 project update
I have finally gotten around to posting some pics of my ongoing M38A1 project (see previous posts, but sorry, the pics of the body no longer show). The engine and running gear are up and running and will start on the body this spring. The engine runs great as long as I keep the ventilation fording valve closed. If I open it up to the running position it runs too lean. I plugged all the vent lines and found the excessive air flow coming through the PVC valve from the crankcase. I dissembled the valve and checked its parts/function (ok) and double checked its installation (OK?). I thought it was supposed to restrict the flow at idle but seems to be letting to much air from the crankcase through. Any suggestions?
Are you sure all three valves are installed and oriented correctly and the spring poppet in the PCV valve is free to open and close? Have you done a propane enrichment check for other vacuum leaks at the intake and carb base? _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: May 06, 2010 Posts: 32 Location: Wisconsin
Posted: Sun Jan 02, 2011 9:34 am Post subject:
Thanks for your help. What three valves are you referring to? The PVC valve, fording valve and...? The PVC valve parts and assy are just as indicated in the manual; the cone is sucked against the spring closing off the larger space and only allows air through the small hole in the center during high vacuum idle. At least I think thats the way it should work.
I did do the propane test as well as spraying all the joints w/ wd40. No change noticed. If the engine runs too lean with the fording valve open, and I somehow fix that, wouldn't it then run to rich with it closed? How does your M38 react when you operate the valve?
BTW, why don't my pics show up? The links work if you try them.
For the photos it's just the way Flicker controls your property.
Click on share, click on "grab the HTML/BBCode", select the BBCode by clicking in the small circle.
You will see this in the drop down window:
Quote:
Copy and paste the code below:
Then copy the BBCode in that small drop down window.
then paste that code in between the [Img] blocks in your post or the BBCode by itself in your post.
This is all a lot easier with "Mypicgallery.com" or our willysmjeeps photo storage where you just right click on the image and select "copy image url" or "Copy image location" then past that between the two [Img] brackets. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
1-PCV Valve
2-Crankcase left hand fording valve. (adjacent to the PCV valve)
3-Crankcase upper vent fording valve. (at the carb to air cleaner crossover pipe.)
Normal operation is both fording valves open and the PCV valve allowing flow out of the crankcase and into the intake. The first troubleshooting step should be to confirm that the three valves are oriented correctly and allow flow in the correct direction. Check this physically by disconnecting the tubing and moving air through the valves. Or you can isolate the fording/PCV system by disconnecting the tube at the forward end of the PCV valve and plugging that elbow. Leave the oil filler cap loose and then run the engine. Any incorrect fuel/air mixture at this point has nothing to do with those three valves.
The two "AA" items are the two fording valves and the place to disconnect is tube "Z" at elbow "Y" and plug the opening left in elbo "Y".
If she still runs too lean and you can find no induction air leaks then check that the wiper "T" fitting item "CC" has the required restrictor installed in the side of the "T" that goes to the distributor. If that restrictor is missing that will account for the excessive air in the induction system. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: May 06, 2010 Posts: 32 Location: Wisconsin
Posted: Sun Jan 02, 2011 1:26 pm Post subject:
Thats a lot of useful info, thanks for taking the time to post it, Wes. The fording valve on the air cleaner crossover is not installed yet; the distributer vent restrictor is present. Isn't turning off AA valve connected to the Z PVC valve the same as plugging the Y elbow? It runs fine with that valve closed. At high vacuum idle the PVC valve is supposed to close down so that there is only flow through the small hole in the center of that cone piece in the valve. But that is still a significant vacuum leak. Is the carb supposed to be adjusted to compensate for that?
I've seen the fording valves installed backwards and handles not keyed correctly. I've seen broken internal springs on PVC valve, PVC valves assembled wrong and installed backwards. My suggestion was to separate the two valves entirely from the vacuum system for troubleshooting purposes. Plug that elbow and if she still runs lean you will now know what is not causing the issue.
Carb is always adjusted with those two calibrated vacuum (PVC and Wipers/distributor) leaks functioning.
Exactly how did you determine the fuel/air mixture was too lean? _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: May 06, 2010 Posts: 32 Location: Wisconsin
Posted: Mon Jan 03, 2011 9:07 pm Post subject:
As soon as I get back home I'll go and double check everything you mentioned. I must have overlooked something.
If the carb is adjusted to compensate for the calibrated vacuum leaks, wouldn't it run rich when you close the valves? How does your M38 respond?
I believe it is lean when I open the valve because the engine speeds up, the exhaust sound gets very harsh w/ occ miss (no muffler yet), and has poor throttle response (no smoke). With the valve closed it runs very smooth and quiet, and can be adj. for a very sloow idle speed.
Then my next question is what were the vacuum gage readings on your troubleshooting runs? _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: May 06, 2010 Posts: 32 Location: Wisconsin
Posted: Thu May 12, 2011 4:32 pm Post subject: Fording Valve
Wes,
With the fording valve closed, the vacuum gauge reads 16.5; when open, it speeds up and reads 14.5. Sorry for the delay in responding; just got back. The 16.5 reading area on the gauge is in the "late timing" area, so I checked the timing and it was at the 0 mark on the pulley so I retimed it to the 10 mark. No change in the vacuum reading but did run a little better. Also changed from the YS to a YF carb; not much difference.
Original problem: Engine idles real good and responds to throttle when the fording valve connected to the PVC valve is closed. When open, the engine speeds up; exhaust sounds harsh and stumbles when the throttle is opened. I've done all the checks for vacuum leaks and found none. Also checked PVC valve condition and installation.
Could the camshaft gear be out of timing by a tooth or so? Not sure what else would explain the low vacuum reading other then a leak.
The fording valves are normally left open. 95% or more of the M38's operations were with the valves open. The carb is adjusted with the valve open. If you set the carb and timing correctly with the fording valves open then as will be expected and is common the engine will not run as well with the valves closed.
If you cannot get her adjusted correctly with the valves open then you have other issues that need to be addressed. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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