Hey folks, I've consulted this site many times already for advice but thought now was the time to make a specific post.

I recently nabbed a '69 ranchero with a 250 cid inline 6 cylinder. 69000 miles on it. Autolite 1101 carb.
Car runs decent, but only with the choke half closed. Fires right up and idles on fast idle, but as the thermal choke works it's magic and begins to open the choke, it starts stumbling and eventually dies. So if I want to drive the car I have to over-torque the thermal choke spring so that when the spring is fully relaxed it's still holding the butterfly valve at about 50% open. This works but the performance is obviously not great.

Here's what I've done:
1.) Completely replaced the carburetor and gaskets and reset it to specification (float level, accelerator pump, idle mixture, etc etc.) This did nothing but hey at least I have a new clean carb.
2.) Sprayed wd-40 all around carb and intake spacer to search for leaks, didn't see anything...
3.) New fuel filter
4.) Replaced the fuel pump and pump-to-carb fuel line. The orignal fuel line was dented a little so I thought a full replacement would help. It didn't.
5.) New spark plugs - previous ones were pretty gnarly looking when I pulled them out.
6.) New PCV valve
7.) Plugged ALL VAC LINES off the carburetor to see if I could isolate some sort of vacuum leak, this did nothing.
8.) Compression Test - performed with all plugs in place, throttle not open. I figured out later I should remove plugs and hold open throttle, but here are the numbers nonetheless.......

#1: 140,
#2: 135,
#3: 100,
#4: 145,
#5: 145,
#6: 150

*It's obvious the compressoin of #3 is pretty low. But would this be enough to cause the problem I'm seeing with the choke?

My next steps are to replace the points breaker because it's looking a little worn, and the condensor while I'm in there. Also replacing the spark plug wires. Need to check double check timing, too, just haven't yet.
These are all relatively cheap fixes, that's why I'm doing it.
Trying to do everything I can within my ability before taking it back to the mechanic with my tail between my legs.

Does anyone else have any ideas why this may be happening?

THANKS!!!

 

Wow!!!!! Nice find!!!!! IMHO, definitely check point gap/dwell, typically set it to the largest gap setting and add a drop to teflon lube to the cam lobe (for the points to rub against to open/close).... also being in GA if you have "blended fuels like much of the country, check the carb fuel mix adjustment as it might need to be richened up a tad... and also check the initial distributor timing and advance, a couple of extra degrees (initial timing) is not a bad thing as long as it doesn't ping!

 

Thanks for the reply Beechkid! You mentioned setting the points gap to the largest setting....the manual calls for a 0.025 gap...you are saying to go larger? Just curious.
So far I've been putting only ethanol free gas in it....not sure the octane rating of the ethanol free stuff.
I'll definitely follow up with a post after I set the gap and get the timing right.
Any thoughts on that one cylinder with low compression?? That has me worried...

 

I would do a little digging deeper with regards to the point gap setting...as there is always a range..... With regards to the one cylinder that is low, yeah, it's a little low but not really enough to cause a stumble per sey.....

I did a little digging in my old Cylmer book as my dad use to have a 1969 F100 and sure enough i found it! You are right...the point gap for the 250 I6 is .025 but the dwell angle range is 37-42 degrees... the 240 CID gap is listed at .027.... so I would 1st make sure the gap is correctly set at .025... if that doesn't make any difference, then I would check the dwell or just adjust the gap out to .027... but my real instinct is the initial timing needs to be bumped up a bit and the fuel mixture needs to be adjusted (ie richened up a smidge)

 

Got it.....thanks! New breaker points are in the mail coming from Rock Auto so I hope to have those in place in a few days.
I'll report back with my findings! I know I always like to see the conclusion when people are describing these sort of issues.

 

Good move!!! Hope that include a new condensor as well... BTW...BlueStreak (which is mfg by Standard) are the best ignition points made out there!

 

Hey I just wanted to follow up on this issue for anyone that may come across this later.
Turns out the low compression on cylinder 3 was due to a leaking exhaust valve...Took her to the shop and they did a leakdown test which let them pinpoint the issue.

So they removed the cyclinder head and re-surfaced the valves and replaced valve seats, etc. Fresh coat of Ford "Corporate Blue" on the cylinder head and she's running so much better now with a lot of improvement in acceleration and idling.

Also the shop discovered that the "refurbished" AutoLite carburetor I installed was faulty. We weren't sure exactly why, but we ended up using the base of the refurbished carb and the top half of the original carb to get a good running condition! So beware when ordering rebuilt or refurbished carbs as they don't always work as expected - most of you folks probably already are weary of that.

Oh and now new problems arise of course....newish aluminum radiator loosing coolant somewhere which wasn't an issue before....gah! The shop installed a new thermostat which I may be removing....we'll see....

 

Congrats!!!! You are getting there!

 

Contact point ignition systems are pretty much stone knives and bearskins these days. They work fine when everything is setup according to Hoyle, but there are a lot of different things that can go wrong and cause trouble. The first thing is to use only what might be called "antique" points. Anything sold today over the counter today at a parts store is counterfeit junk, made with crappy materials and recycled beer cans. There are a gazillion leftover Autolite, Motorcraft, Blue Streak, Standard from back in the day, these are what you want to use. That famous auction site is the easiest way. Buy a handful and you're set for life. The condensers are a lot more problematic. There is no way to test them without equipment most people don't have. The condensers sold today are even worse than the points.

If you know someone who has an ignition oscilloscope they are really good at sniffing out defects in wiring, or distributor, bad condenser, all kinds of stuff. Deploying Ye Olde Parts Cannon is dangerous these days because the ignition parts are so crappy.

Don't worry too much about compression, get the shop manual and give it a good Tune-Up. You have a good baseline now, excessive cylinder or ring wear causes low compression but oftentimes it is due to stuck rings due to gum and varnish. A solvent can really help with this. Couple that with some highway runs, make sure it's got a good factory temp thermostat (Autolite surplus is your friend here too) installed and reaches normal factory temps and I bet the compression numbers will improve and/or equalize.