cj3A engine problems

restorationman · Post by **restorationman** » Wed Jul 06, 2011 9:47 pm

need help in troubleshooting 1950 cj3a engine problem. Starts and idles fine, but has slow throttle response time and no power to go up even slight inclines in the 25-38 mph range. Did not tear into engine or distributor, but did play with the carb. and switch it out with another W-O model. only 15 inches of fairly steady vaccum at the manifold port. I'm starting to think distributor? There is no vaccum advance on the distributor, not sure if it's supposed to have one? Just restored this jeep into a M38 look-a-like,Anyone with any tips? Thanks

artificer · Post by **artificer** » Thu Jul 07, 2011 4:19 pm

15 steady indicates ignition timing is out [generally] you can adjust using the gauge till the best reading is obtained then turn distributor back a little.
At the same time check cam dwell for closed up points which changes timing.

Post by **wesk** » Thu Jul 07, 2011 9:25 pm

If you don't have a dwell meter then just check the point gap with a feeler gage. 0.020 Also make sure you check the centrifugal advance for free movement. Vacuum advance units were not common on the CJ3A but were used on them for special purposes. If you wish to set the timing to the listed spec use 5 BTDC but up to 8 BTDC will work at most altitudes and with most fuel available.

restorationman · Post by **restorationman** » Thu Jul 07, 2011 9:28 pm

point gap checks fine, I'll check for vacuum leaks around intake and carb. next.

restorationman · Post by **restorationman** » Thu Jul 07, 2011 9:33 pm

I do have a dwell meter, what should the dwell be? How to check for free movement on the centrifigul advance? Aren't they mounted under the breaker plate?

artificer · Post by **artificer** » Thu Jul 07, 2011 10:05 pm

Dwell is 41* or 0.020" remove distributor cap & you should be able to move the rotor about 1/4"+ with your fingers....if there is no movement the mechanical advance is likely seized.
Remove rotor & put in a few drops of anti seize type stuff, come back awhile later & therotor should be moveable.

Post by **wesk** » Thu Jul 07, 2011 10:40 pm

If you had a timing light you would be finished with the project.

Just kidding. But you can check timing and centrifugal advance very quickly with the timing light.

Centrifugal advance mechanism is the springs and flyweights under the breaker mounting plate. If they have been ignored for years or left exposed to the elements you will need to do more than add a drop of oil to the felt under the rotor. If when you grasp the rotor and cannot move it at all then you will have to open the distributor up. Then you can inspect and see just how bad the corrosion is. If she moves just barely (real stiff) then try the drops of oil and work it by hand but if it doesn't free up then the best course of action is to remove the distributor and open it up.

While you have your sleeves rolled up and are talking timing this is a good time to see what you have for timing marks. If you only have the flywheel marks it would be a good time to align them and transfer the marks to your front pulley to make this an easier task in the future.

restorationman · Post by **restorationman** » Fri Jul 08, 2011 8:46 am

Checked the dwell ( a long time since I had to do that on a car) was at 35* Adjusted them and checked dwell again-- now at 40* figured it was close enough! Test drove-- A lot better! Checked for vacuum leaks, found none. Still only around 15 inches of vacuum- maybe these little 4 cyl. don't get much vacuum then that --I'm not sure. Carb. likes to run with a slight amount of choke. Checked for free movement of the rotor/ advance-- moves freely with about 1/4 inch movement like you stated, Sprayed a little lubricant with a small needle type nozzle to make sure they're lubricated ( under the point plate) jeep runs better, Still not 100% not sure where else to check.

Post by **wesk** » Fri Jul 08, 2011 9:33 am

Needing to use a wee bit of choke to keep her running smooth means one of two things.

1 - Too much air (too lean)
Check for induction air leaks. Common points are the manifold to carb
gasket, Intake to block gaskets, throttle shaft wear, and vacuum
plumbing.

2 - Not enough gas (too lean)
Check fuel pump output pressure and flow rate. Check carb float
level. Check all jets for cleanliness (unplug if needed). Check
condition of gaskets and mating surfaces of throttle body, bowl assy
and air horn.

Also make sure you have the correct thick gasket insulator between the carb and the manifold and that it has a thin gasket installed above and below it.

This is used on the MB, and CJ L134's as well.

restorationman · Post by **restorationman** » Sun Jul 10, 2011 9:11 pm

I need to check timing, but can't budge the distributor. Loosend collar clamp, and small bolt underneath-- but nothing. No power going up inclines- I would like to advance timing a little and see if it helps.

Post by **wesk** » Mon Jul 11, 2011 8:29 am

Strap wrench, lot's of PB blaster and slowly work it loose back and forth. Once she turns you should be able to lift it out. Then clean the hole and the friction surfaces and add some anti-seize before re-assembly.