Stumbling dying engine under throttle 223

[ThinLizzy13]

My engine is dying under hard throttle. Sitting in neutral the engine idles totally fine. Slowly press the pedal and it will rev up fine. If sitting at idle and I punch it to the floor it instantly bogs down, misses, and then dies. If I quick give it half throttle, let off, and then punch it, it will rev right up. Trying to drive it from a stop it will start bucking and missing but eventually even out if I go easy on it.

A bit of recent engine history - I pulled the intake/exhaust and cleaned it up and reinstalled around the beginning of the year. New gaskets and bolts torqued to spec. Most recently I converted over to DSII.

So far I've been working my way through fuel, ignition, and air.

Fuel - pressure seems good. 5 psi before the fuel filter and 5 psi after.

Ignition - went through the wiring again to make sure all the DSII stuff was hooked up correctly. Swapped out the the module with an extra and it made no difference. Put a new coil in and wiring is set up for full 12v to coil. Pulled all plugs and gapped to DSII spec. Double checked all the sparkplug wires and looked for arcing, everything looked good. Found a crack in the dizzy cap - replaced and made no difference.

Air - ran without air filter (oil bath), made no difference lol.

I checked for vacuum leaks and the only place I could find one was the throttle shafts, which I already knew about. Vac advance was working correctly at the dizzy, and it pulled steady vac at the carb. I could find zero leaks by spraying around the base of the carb and around the intake.
I ended up pulling the carb and giving it a once over (I had recently rebuilt it). I installed throttle shaft bushings while it was out, which made no difference to the issue but did even out my idle.
Currently I'm running an autolite 1100 without SCV. Before that I was running a freshly rebuilt Carter YF which also experienced the issues.

I'm at a bit of a loss at this point. To me it seems like there must be a vac leak somewhere. I'm going to get more starting fluid and check again tomorrow. Maybe some more experienced members out there have some suggestions, I could use a "fresh set of eyes."
I'm beginning to think I should've just kept running load-o-matic!

[slick4x4]

Is the accelerator pump on your carb working good ?
You can look down the throat & move the linkage by hand
And you should see gas squirt down the opening
(Do it while not running)
Another problem with a bad accelerator pump
Is that they make for hard , cold starting
... usally have to choke them to get started

[ThinLizzy13]

Thanks slick 4x4. The accelerator pump is new and in good working order. The engine fires right up cold and it gives a strong squirt of gas...

[Mr. Jones]

One other thing the mechanic found on my 300 along with ACCEL coil problem was a broken valve spring...he used a lazer thermometer on each exhaust port and found one running cold,you might have a weak spring in there.....

[slick4x4]

hmmmm ....
Does it do fine pulling a load ?
If so .... fuel shouldn't be a problem....

Now I'm thinking weak spark....
Even new stuff can be faulty...

Hard to diagnose

[ThinLizzy13]

Hard to diagnose

It was confusing, but I seem to have solved the issue!

I checked for vacuum leaks again today and didn't find any. I noticed a carb whistle at a very specific idle RPM. I think it was just the way the air flowed through the carb with the cleaner off but to be safe I used some RTV sealant on the base in case it was warped. Probably not the smartest move, but oh well.
So with vacuum leaks firmly ruled out, all I could think about was the accelerator pump that Slick4x4 mentioned. So I pulled the carb again to check the inside. Turns out the autolite 1100 without the SCV has an internal check ball on the accelerator pump circuit. I placed a check ball in that passage ON TOP on the internal one. After removing the additional ball that I had incorrectly put in, the truck went down the road fine
After being warmed up it'll rev up when I punch it in neutral now too.

Mr. Jones - I am paranoid about this coil now though....

[slick4x4]

Ive ran a vehicle with a bad accelerator pump
And the way you described it , fit it to a tee.....
Glad you got it smoothed out

[ThinLizzy13]

I guess if it walks like a duck? Lol. Strange that my Carter YF’s accelerator pump is also out of adjustment. Maybe I’m just terrible at accelerator pumps?

[ThinLizzy13]

Well I spoke too soon. Must’ve just been a coincidence because the problem returned. Tried the carter out again and the problem went away. I guess at this point it’s something with that Autolite.
Anyway I got ‘er tuned in and went for a spin. Thing ran like a dream. Then half way through my loop the oil pressure light started coming on at idle. Hooked up a mechanical gauge and am getting 6-8psi at idle. If I hold it at 2k rpm the PSI will jump up to 14-16ish then drop to 8 and then jump back up and keep fluctuating.
It’s a 5/16 oil pump for a 223 that has never been used, just been sitting on the shelf for 15 or so years.

[slick4x4]

Id put a 1/2 can of sea foam in the oil
Drive it about 45 minutes
Drain the oil completely
Put in a quality filter & oil
......
And keep yer fingers crossed

[ThinLizzy13]

Got lucky, put a half quart of oil in and the oil pressure is 10psi hot at idle and 32psi hot at 2k rpm. Maybe the ‘64 oil pump sits slightly different than the ‘63 and before? Or maybe has a different flow? Either way, all seems good, for now.....

[FarmMotorSports]

Ok, it's been years since I had a 223 open, but I remember the pick up tube being a long bolt on affair.
call me the nervous sort but, you might have a leak where the pick up tube bolts to the oil pump, or a fracture in the long pick up tube.
The extra oil would cover the bottom of the pump, and mask the problem... Until the pick up falls off...


It's a pan gasket and a half day ??? to drop the pan, inspect and seal it up. Maybe a weekend if you do it in the driveway during miserable weather, and nothing cooperates during tear down or reassembly.

How many half days to rebuild a 223?

[ThinLizzy13]

Thanks farmmotorsports. I should probably check that, it’s making me a little nervous too. It’s not a bad job. It took me about 3 hours to drop the pan, switch the pump out, and reinstall - and that was being slow about it. Worst part was torqueing all the pan bolts to spec...

[ThinLizzy13]

Well this is embarrassing, but it appears I've been running my 223 a quart low forever. According to the shop manual it takes 6 quarts of oil with a filter change. My uncle always put 5 in so that's what I've been doing. Big Oops

[FarmMotorSports]

So does the dipstick read correctly when it's full?

[ThinLizzy13]

So does the dipstick read correctly when it's full?

I couldn't read the dipstick cause it was so warn when I got the truck. So I marked where 5 quarts was the first time I changed the oil.


Edit: I'm still going to drop the pan and check the oil pump.

[ThinLizzy13]

Well this thread has gotten a bit off topic, but I dropped my pan. Had a bolt back out of the pump and the other ones were finger tight.





The bolts don't have washers. I slathered them up with loctite and cranked 'em down. Hope it holds