Engine no start 1967 CJ-6 w/ Dauntless

[strayTexan]

Hey y'all I'm a big newbie to Jeeps... basically I am helping a friend get their 1967 CJ6 with the V6 started up again after four years of not running. He's pretty mechanically dis-inclined, so I've been trying to help him out and also learn something about carbureted engines. Here's what has happened so far...

Got a new battery, spark plugs, and spark plug wires, rebuilt the original Rochester two barrel carburetor.

Put a little motor oil in each cylinder. Drained the old gasoline and filled it with fresh gas. Put in a new-ish fuel filter and flushed the lines. The filter seemed all right so I tried cranking it several times and it would not start. Removed the motorcraft carb a previous owner installed, rebuilt the original carburetor and tired cranking again and it would not start. There was some back fire, some exhaust, but the engine would basically misfire once or twice and then die (I guess that's the odd-fire?). Here's more of a breakdown on the no start condition, as best as I can see it (I just work on cars for fun, there could be things I'm missing here).

Fuel: fresh gasoline; previous owner installed electronic fuel pump (that may be giving too much/too little pressure to the carb, I don't have any in-line pressure gauges); accelerator pumps on rebuilt carb are putting a strong stream of gas into the intake.

Air: the choke is completely manual, I have tried cranking with closed choke and open choke, we're in Santa Fe but the altitude shouldn't be that big deal.. right?

Spark: spark plug tester shows we're getting spark all the way to the plugs, also the exhaust and backfire would indicate to me the fuel is being ignited. I am lazy and didn't gap the plugs to spec, but would that really keep it from cranking? Am I missing something?

Timing: supposedly ran like a charm in 2022, haven't messed with it.

So... what do I do next? It was sitting for a long time in bad conditions (rodents took over, engine bay was not properly plugged up, some rodent droppings or sticks or things may have gotten into the intake). I did a dry compression test and the numbers were not encouraging. Pretty much 130 ish (adjusting for altitude) all around (is that normal for these engines?), except cylinder 1 was maybe 110~120 and cylinder 3 was only 100. (apologies for rough numbers, I wrote them down and can post them if they need to be exact). It seems to me that sitting for so long, the piston rings or something on one side of the engine went bad, now it won't start? How can I check that? Is it worth pulling off the intake and vacuuming some more? Wet compression test? I'm at the edge of my skills here.

Last, my friend is not excited about putting more money into it and we're really not on terms where I want to buy him a new engine lol. So if we can't get it running on bubble gum and elbow grease it's just going to sit.

 

[Jeep Soup]

You have spark.
You have Accelerator Squirt of Gas.
Should Cough Start or something.

My suggestion is.....
Get a Spray Can of Starting Fluid.
Open Choke, Have someone hold the Throttle pedal to Wide Open.
While this person Cranks the Engine, You Spray in short Spurts the starting fluid and see if it Catches. Try to keep it running on the Short Spurts of Starting Fluid until it can run on its own.

FYI, 130 psi compression is acceptable to get it running.
After you run it for some time, those will come back up as Everything Reseats, and gets Warm and Fuzzy again.

Good Luck

 

[TSB8C]

Barring an issue with engine internals, only three things needed to run:

1. Fuel - spurts in carb when accelerator is moved looks good. I do agree with "Jeep Soup" that a test would be using the starter fluid sprayed in the carb while cranking. You could also just dump a small amount of gas into the carb from a small squirt bottle or dribbler if you don't have starter fluid. But if you move the accelerator and see gas squirting in, this seems an unlikely issue.
2. Air - manual choke held open is definitely letting air in. And trying it closed or mostly closed when the engine is cold is a great test. A closed choke would cause a rich mixture and you said you're getting black smoke when trying.
3. Spark - tester showed spark and you're getting backfire; seems spark is also good. But did you check more than a single spark plug wire? I'd check each one (if your tester is one that connects to the end of the wires where they connect onto the plugs). Checking the contacts under the cap and the tip of the rotor should also be done to ensure each plug is getting the spark. However, backfire usually means timing is off (spark there, but at wrong time). You stated it supposedly ran good previously and you didn't mess with the distributor. But backfiring would point me in that direction. You asked about plug gaps. Should be done, but wouldn't stop engine from running unless some were WAY off altogether. Pop dizzy cap and check rotor position when engine moved to TDC. Have someone crank the engine while you move the dizzy a few degrees each way around TDC to see if the engine catches at some point.

Now I did have an old Plymouth Valiant years ago that wouldn't crank up. Checked all the three things above and all was good, but it just wouldn't fire up. Draining engine oil showed gas in the oil pan. Pulling the engine head I discovered 3 pistons with holes in the tops. You stated you did compression tests on all cylinders, so not likely the same issue. I just mention that as an example of an issue with the internals where the other three items still couldn't make it run.

 

[grimmjeeper]

One thing on an engine that has been sitting a long time.

Old gas can varnish and plug up the jets. That will block fuel from getting through the venturis. Best bet is to find a carburetor rebuild kit and recondition the carburetor. Spend time really cleaning each piece. It's a finicky job but it makes a difference.

The accelerator pump is a different circuit. So it can work but normal fuel flow can still be blocked.