Engine stalls

[Ferris95]

Have 68 with a 390 2 barrel and automatic trans that I am having a stalling issue. Starts and runs fine. But lately it will just all of a sudden die. It will start again, and then die again within a minute or 2. Seems to be at low speed or when stopped. Any leads on what it may be is appreciated before I take it to a shop and have it looked at.

[cep62]

Welcome to our site.
Carburetors can take a learning curve to understand.
What's it doing when it stalls ?
black smoke means it's rich , does it smell like gas ? choke could be stuck shut ,
Does it slowly die ? Only in gear? only when cold?
can you keep it running by pumping the gas pedal ?
That could all be some simple adjustments.
Do you have an "accurate" tachometer what's the idle speed?
points ignition?

[M-100]

Check for vacuum leaks . It's probably a big one like a lose carburetor base.

[Ferris95]

First, thanks for the replies! I will go out and look for some of what you all mentioned. I’ll spray some carb cleaner around the hoses and see if it revs up or bogs down. Something else I should do there? It dies in gear and in park. Just started doing it all of a sudden. It just stalls like you turned the key off. No smoke that I have seen. Will start right back up and sometimes stall again right away, and sometimes run for a minute or two and stall.
I have cleaned it a couple times with engine cleaner and a pressure washer. But it’s all dry.

Actually thinking of going to a Holley Sniper anyway. Anyone have thoughts on that vs the current 2 barrel carb or may switch to a 4 barrel intake and carb? Or is there already a good thread on here about all that? Also looking to convert to power steering and have a guy here in Summerville, SC that does that stuff and getting a quote. If not a daily driver, should I just go with the Bendix gear instead of the Saginaw so I don’t have to have the steering shaft shortened by cutting it and welding it back together? I hear if you use the bendix, it’s pretty much a bolt on thing an I can do it. Don’t have welding capability at home. Do have factory AC, so hope that doesn’t get in the way of the PS pump! A good thread on here about that too?

[zgerbic]

Sounds like an idle circuit problem. Could be something like you have trash/rust in the idle mixture passage or just before the idle mixture screw(s). Could try pulling out the screws, blow out the passage and put the screws in gently and back out a turn or a turn and a half and see if the engine will stay running. If so readjust the mixture screws to get the most RPM/mixture right.

If the truck still has points, it could be that they are burned enough to fail to open reliably, or have too big a gap. Also if the vacuum advance diaphram failed, the engine will be more retarded at idle than it was, causing a lower than normal idle or slightly less power at idle, needed for the automatic trans load.

Also, if you have an automatic. Check the vacuum line to the transmission at both ends for a vacuum leak. Also check around the power brake line at both ends.

You should figure out what is actually wrong before spending on a new carb/injection system. If the truck was running ok before, try to fix the existing carb first. It will be easier to put on a new 2 barrel carb, especially if it is the right linkage model for the truck. If you replace the 2 barrel, see what CFM carb you actually have now on the engine and if it is on the smaller side, like for a 302 instead of one for a 360 or 390, get one sized properly for the engine you have. Remember the industry rule on carbs, smaller is always better than too big.

Unless you put a more radical cam and headers on the engine, you probably will not get much/any more power out of a 4 barrel, just lower gas mileage. Besides having to change the intake manifold, you may have changes to the choke/wiring, fuel line, linkages for throttle and transmission and heater hose connections. Oil leaks can be a problem when you change the manifold unless you take a lot of care to seal the manifold to the engine. What you may find is a great deal of expense, work and time to get it running right again and it may not run any better than it did with the 2 barrel.

Judging from what I have seen lately, new carbs can be problematic due to poor quality design and manufacturing.

[Ferris95]

Thanks Zgerbic! I will check out those things tomorrow. I do have an automatic trans. Not sure on the Carb CFM as the tag isn’t on it, but will look at it closer tomorrow. Ya, I would rather stay with the 2 barrel than go to a 4 barrel. Will only change if I decide to go to the Holley Sniper (unless there is a better one) ???

[jzjames]

I’ve learned to always consider a going-out coil when the engine starts cutting out for no reason.
As for carb problems, my first check is a sticking float.

[Ferris95]

Ok, so I sprayed brake cleaner everywhere while the engine was actually running. No discernible engine change. It would keep stalling and then starting right back up and either die right away, or wait a minute or less and die. It didn’t seem to die if I kept the engine reved up high (as far as I remember). Will try that again. Trying to attach some pics that are within the size restrictions so y’all can see the layout and let me know any opinions on what may be happening and on what carb I have in case I need to get a rebuild kit. Maybe a Autolite 2100 or 2300 (Holley I think on the 2300). I used to be actually pretty good at this, but it’s been 30 years or so…

[Ferris95]

Three more pics it wouldn’t let me load all at once…

Also, why the spacer plate under the carb?

[Wes]

The glass fuel filter needs to be replaced with a disposable paper element filter. The screen in the glass filter is not fine enough to stop debris from entering the carb.
I forget what the spacer does haven't seen one since my dad's 72. Where do the hoses go?
If you put your hand over the air horn, blocking air flow into carb, does the engine stall or speed up.

Sometimes if a carb passage is blocked, if you rev the engine to @ 2k rpm and slam the choke closed, the high vacuum can suck the blockage out.
Try not to allow the engine to stall while doing this. If it does stall treat it like a flooded engine.
There may be no help, but to take it a part and clean it out. If you do put a kit in it, get an ethanol tolerant kit.

I see you have an hei distributor. One symptom of an ignition control module failing is an instant shut down. Test the feed wire by wigging it while engine is running. How is the dist powered?(where is the battery + voltage coming from)

[sparky72]

If it dies suddenly without stumbling or running rough before dying, I would suspect something electrical (coil, ignition module, power wire grounding out somewhere, etc.)