Engine stalling

[Kip7143]

Hi all!

I have two vehicles, one with a 350 Chevy 73 motor and the second with a 4.2L 81 chev straight 6. Both motors are acting very similarly except the 350 is running a little more consistently. I’ll walk through everything I’ve done on both.. but I’m kind of at a dead end here.

1981 C10. Truck dies at idle in gear. Usually I can have it running in park but the idle is high and the truck sputters a lot, and is very rough. I can throttle the truck and it continues to run. I can even drive it down the road.. but once I let off the throttle it will die. Usually pretty suddenly.

So far on the truck I’ve replaced all vacuum hoses. The dist cap, pick up, coil, rotor, plugs and wires. I’ve timed it in park, idle a little higher then normal. I have taken the carb off the truck and done a visual but nothing seems incorrect. Still the truck is stalling as soon as I go drop it into drive. The carb is a Rochester verajett II. The idle mixture screw was sealed but appears to be uncovered. I have not done anything else to the carb. I’m thinking rebuild the carb?

The second is the 350. The vehicle was parked for close to 10 years and I’m slowly waking it up. The carb was freshly rebuilt, then cleaned the points, set timing, and finished the final tuning of the carb. I drove the car for about 2 weeks when the fuel tank dislodged everything that had rusted in there and clogged the system. Almost a year later I have a new tank in, new sending unit, in-line filter and inlet screen.

I filled it up with fuel and it started quite easy. Ran pretty decently. After my 20 ish minute drive yesterday it started to bog while in drive. You could hear the rpm changing as I was holding the throttle still. When I got home and put it in reverse it stalled. I had to two foot it back In the garage. As I was looking under the hood and doing minor carb adjustments I noticed the fuel in the Inline filter was going back down to the pump. So I ordered a new pump and put it in today.

I took it for another drive, this time only about 5-6 minutes and it was really strong off the bat but as it warmed up it started to have the same symptoms. I should mention- no choke on this motor. Carb is a edlebrock 1405

This vehicle is still on points. Question though: would poor timing stall the vehicle, but let it throttle up nicely? I’m going to check timing again tomorrow but I don’t think timing is causing the bog issues.

Any ideas or Input is greatly appreciated. I am considering changing from points to EI. I just want to drive my summer toys!!

Thanks in advance.

[Rickysnickers]

Have you tried replacing the fuel filters on both vehicles, recently? I see where the 2nd one has an inline filter, but when was that one installed?

[Kip7143]

On the C10 I replaced the inline filter maybe 2 years ago, the 350 is a fresh filter.

Thanks for the input! Keep it coming. I have a video of the 350 running but I don’t know how to post videos.

[kglowacky]

long shot. check the vac advance unit in the dist. Maybe they are stuck open or closed from sitting. Get one of those small hand vac pumps and see if it moves when you pull a vacuum. Again, long shot but you asked for ideas.

[Dead Parrot]

For the Eddy 1405, the power pistons are sensitive about gum, like might happen when the gas evaporated after a year. Symptoms include a bog on acceleration. Simple to clean. Loosen(not remove) the small hex/torx screw for each piston cover plate and rotate the plate to the side. The piston and rod should pop up. Spray both piston and bore with carb cleaner. Repeat for other piston. Putting piston back in often takes a couple gentle tries to get the rod to find the jet. Rotate cover plate back and snug up the screws. This same procedure lets you change the rods and springs without opening up the carb.

Once a motor is warm, especially in the summer, lack of a choke should not be an issue as it would be full open anyway.

If either/both have vacuum assist power brakes, the booster can leak enough to cause a lean condition while still providing some brake assist.

Check any hoses that run to automatic transmissions. Even if replaced a year or two ago, mice sometimes chew on hoses. Same for any suction hoses on top of fuel tanks.

For both, what is your initial timing with no vacuum pot connected? Too retarded on the initial can cause idle/low speed issues.

[Kip7143]

Originally Posted by Dead Parrot

For the Eddy 1405, the power pistons are sensitive about gum, like might happen when the gas evaporated after a year. Symptoms include a bog on acceleration. Simple to clean. Loosen(not remove) the small hex/torx screw for each piston cover plate and rotate the plate to the side. The piston and rod should pop up. Spray both piston and bore with carb cleaner. Repeat for other piston. Putting piston back in often takes a couple gentle tries to get the rod to find the jet. Rotate cover plate back and snug up the screws. This same procedure lets you change the rods and springs without opening up the carb.

Once a motor is warm, especially in the summer, lack of a choke should not be an issue as it would be full open anyway.

If either/both have vacuum assist power brakes, the booster can leak enough to cause a lean condition while still providing some brake assist.

Check any hoses that run to automatic transmissions. Even if replaced a year or two ago, mice sometimes chew on hoses. Same for any suction hoses on top of fuel tanks.

For both, what is your initial timing with no vacuum pot connected? Too retarded on the initial can cause idle/low speed issues.

I will give the power pistons a clean tomorrow and update you. I was mentioned the lack of choke just so people know it’s not being choked out. The choke on the Rochester is functioning correctly. When the engine is warm the choke is off entirely. I will I spent all vacuum lines.

What’s the best way to check for a brake leak? The C10 doesn’t have power brakes but the other vehicle does.

Timing is slightly advanced on both. I doubled checked it this morning.

Thanks for all your input!

[dieseldawg142]

having a similar prob with my crew. at idle it surges and drops down to where it wants to die. runs great when off idle though.
after going over everything, started shooting starter fluid all over it. soon as i sprayed the throttle shaft bushing, it smoothed right out and ran great.
might be something to check out..

[Kip7143]

Quick update.. I removed the cleaned the idle and air mixture screw, checked the point gap and cleaned the power pistons. Car is running great. Drives great, idles pretty good. When I started adjusting the 2 screws I saw a change in the motor. 350 is running awesome. Thank you for your help!!

I think I’m going to order a carb kit for the C10 and give it a shot. I’ve never rebuilt a carb before so I’m a little nervous.

[jayoldschool]

On the 350... you need a longer brake vacuum hose. The one on there is too short, and will pull out of the booster on hard acceleration (and cause a vacuum leak). ;-)

[Dead Parrot]

Originally Posted by Kip7143

....

What’s the best way to check for a brake leak? The C10 doesn’t have power brakes but the other vehicle does.
....

If I read things correctly the vehicle with PB is running good now. But to answer the question: Simple way that doesn't involve leaning way into the engine area to pull a hose loose - Start and run the vehicle for a minute or two. Press the brake pedal several times with the motor running. Note the feel. Run motor for a minute after last press, then turn off. Let sit for a minute or so. Then press the brake pedal. You may hear a soft hiss as you press/release, this is good. If the feel is the same as when the motor was running, your booster is good or leaking slow enough to not cause an idle problem. You should get two or three presses before the vacuum is exhausted and the pedal gets stiff.

For the carb rebuild. Many kits cover multiple models of carbs and you may wind up with a few extra parts or gaskets. Just double check the pictures and instructions. A couple cans of cheap carb cleaner makes for a good first pass followed by better quality stuff for the final cleaning. Spray cleaner outside as it is noxious and flammable.

[Kip7143]

Hey! Yeah the 350 is running great. The vehicle is a Pontiac Parisienne, 71. I drove it today for about 40 minutes without issue. Very pleased.

Okay thanks for the Input. I’m trying with the C10 but just getting it to idle is a challenge right now. I’m looking for a carb kit and hopefully rebuild it soon. Summer time to drive these things!!

[Kip7143]

Hi. Further update with some questions.

For the 350, I’ve taken it out a few times now and it seems to be running well. I didn’t drive it for 2-3 days and when I did it was running sluggish again and eventually stalled in park. So I drove it home and removed the mixture screw and idle screw. They were visibly dirty. Keep in mind I just cleaned them last week. Once cleaned and re- installed the car ran great. Took it Into town and stopped for fuel. When I started the car again it was running a little rougher but didn’t stall. Stopped at the bank and started it with the same issue and it ran even worse. So am I going to need to remove the screws and wash the ports after every drive for it to run well? Do I need to run an additive in the gas? I’m running 91, in Canada. Once I got it home I cleaned them again and the car ran great.

Secondly I finally got around to the C10 with the Rochester. All the vacuum lines are solid so I tried spraying carb cleaner around the carb and I found a spot that if I sprayed, it idled up. So clearly it needs a carb kit. I’ll attach a picture where I sprayed.

Thanks again!!!

[Dead Parrot]

If the Pontiac has a fuel setup similar to Chevy, put an inline filter in the rubber hose where it jumps from the frame to the fuel pump. Fram G3 is the number for a 3/8 line. If your crud is coming from the gas tank, this filter will catch it before it gets to the pump and carb. Possible there is rust or other crud in the tank or even the filter sock on the sender coming apart.

For the C10, try snugging down all of the visible screws on the carb. Some carbs have screws that are only accessible while the carb is off but if one you can touch is loose, might get lucky and fix or slow the leak.

[Pontiac1976]

If the Pontiac has a fuel setup similar to Chevy, put an inline filter in the rubber hose where it jumps from the frame to the fuel pump. Fram G3 is the number for a 3/8 line. If your crud is coming from the gas tank, this filter will catch it before it gets to the pump and carb

I agree 110% with this. Very easy to see it there and change it when getting to dirty. And it stay cooler in that location.

[Kip7143]

Hi all,
Sorry for the delay, I was away on vacation! I have since returned and cleaned out the carb. I replaced all 3 gaskets, needle and seat and some clips on the choke and throttle assembly to ensure they were tight. The carb was full of black little gunk pieces. I’ll post pictures. Re-installed on the truck and cranked it over. It started quite easily and ran pretty well. In drive it ran smooth. I was pleased.

Until I noticed it was blowing black smoke with a liquid coming from the exhaust (I thought it was water condensation). Then I proceeded to the front and saw the charcoal canister was OVERFLOWING with gas.

I immediately shut the truck off. I went to the exhaust and found that the liquor coming from the pipe was indeed fuel, not water.

So, where did I go wrong?

[hatzie]

Have you mixed up the vapor, return, and supply connections at the tank?

[Kip7143]

No, the needle was cock-eyed so it just flooded the carb and that was the easiest part for the fuel to go. I fixed the issue and the truck is still running like garbage.

Who wants to buy a C10?!

[truckin 79]

Your charcoal cannister needs to be changed. Those pellets are charcoal pieces getting sucked into carb from hose that runs to cannister. Plug that line running into carb for now and when you get a chance change out cannister. You will want to clean and rebuild carb again.

[Dead Parrot]

I have seen other threads about the black grains. They are from a failed charcoal canister. Also tracks with the canister full of gas. Best is to replace with a good one. If you opt for deleting the canister, you have to allow for venting for your gas tank(s). If you just plug all the hoses, your gas tank won't flow fuel.

[jayoldschool]

Originally Posted by hatzie

Have you mixed up the vapor, return, and supply connections at the tank?

Very interesting point. I would have never thought of this one. Looking at the pellets, the charcoal canister has been having issues for awhile.

[Kip7143]

So, there’s a line from the canister right above the fuel inlet. Is it safe to say that line is a line that runs air into the carb? Because the float bowl is right below it and that’s where I found the majority of the pieces. I did remove the carb and clean it again when adjusting the needle and seat.

Plugging all the hoses won’t allow the tank to breath, but would unplugging them all have a negative affect as well? Once I cleaned the needle and seat and installed the carb I did not hook up the canister. All the vacuum lines are unplugged. Could that cause ****ty idle and stalling?

[Kip7143]

Originally Posted by jayoldschool

Very interesting point. I would have never thought of this one. Looking at the pellets, the charcoal canister has been having issues for awhile.

I will need to check the vacuum diagram. I’m searching for a new canister so once I find one and replace it I will double check these lines.

[Dead Parrot]

Originally Posted by Kip7143

......
Plugging all the hoses won’t allow the tank to breath, but would unplugging them all have a negative affect as well? Once I cleaned the needle and seat and installed the carb I did not hook up the canister. All the vacuum lines are unplugged. Could that cause ****ty idle and stalling?

Plug the one(s) that go to the carb. Leave any that go to the tank unplugged.

Open hoses that lead to the carb can cause crap idle and stalling.

Early pre-emission fuel tanks either had a short hose that ended in a vent or had a vented gas cap. Later ones use the charcoal canister as the vent.

[Kip7143]

Well I plugged the lines going to the carb and double checked my return lines. Everything is set up as it should be. Truck is still running like garbage and stalling. The only time it ran well was when the needle was stuck and flooded it with gas.

There’s a shop outside of town that deals with old cars… it’s going there.

[hatzie]

The vapor purge hose should tee into the PCV hose so the engine will suck the gasoline vapor out of the charcoal with the purge valve actuated.

You should have a vacuum line from the purge valve vacuum actuator to ported vacuum on the carburetor.

And the vapor recovery line to the tank(s) vent line(s)

The vapor port on the sender is the shortest of the three lines inside the tank.
You're getting charcoal in the float bowl. This means your EVAP cannister is soaked in liquid fuel. Leading to my question about whether the vapor line is attached to the vapor port and not the return line on the tank(s).

If you overfilled the tank it would do this too.