The Stovebolt Site Forums The Shop Area Engine Shop Engine sputters/coughs and dies after 15-20 mins of idle

1958 Chevrolet 235, newly rebuild. Stock intake with Carter YF 2100s carb. 1954 Corvette exhaust manifold(I think the heat riser spring is installed correctly from the pictures I could find.)

Engine starts and warms up great. After 15-20 mins the engine sputter/coughs and dies. It will restart if I can hold open the throttle enough. I have searched the forums and found some helpful info leading me to think it was flooding but, the engine still dies. First couple of tries I found the carb was dripping with fuel. So, I thought it was just flooding the carb. I checked the float height and corrected it. It still died. I then lowered it another 32nd or two and it died again, but I saw no fuel/moisture around the throttle body. I don't want to drop the float too much more and cause other issues. Can the heat riser, if not functioning correctly, cause this? Any ideas would be greatly appreciated.

Before this, I had issues with my pertronix not firing the #6 spark plug under compression, so I swapped the Dizzy for the HEI unit I had from Tom Langdon. That made the engine rev just fine. I don't know if that has anything to do with it. The coil shouldn't be the issue cause it wouldn't crank back up with more throttle if it was the coil, right?

Try it with gas cap off.

To expand on bartamos’ suggestion, if you have a non vented gas cap or the vent is plugged your gas tank will build vacuum and not allow fuel to get to the fuel pump. Setting for a few minutes will relieve the vacuum enough to restart. You failed to mention if upon restart the engine keeps running til you shut it down or if it dies again in 20 minutes.🛠

Put a T into the gas line between the fuel pump and the carb and monitor the fuel pressure with a 0-10 PSI gauge. It sounds like you have too much fuel pump pressure and the fuel is pushing the needle valve off its seat at idle and flooding the engine. If it were starving for gas you wouldn't have to hold the throttle wide open in the "clear flood" mode to restart. Are you running a mechanical or an electric fuel pump? Max fuel pressure for a carbureted engine should be around 4-5 PSI.
Jerry

Could be that, I just could not think of anything else that would take 15-20 minutes except pulling a vacuum on the tank. The dripping points to flooding. Wire the heat riser open to test if it's that.

How long have you had the YF2100? Not miles, but length of time.
The accelerator pump diaphragm does not get along at all with today's formula of gas. They develop pinholes and cause significant flooding just as you are describing. I get 1.5 to 3 years out of mine before I have to replace the diaphragm.
Pull your plugs and see if they are covered with black soot.
Perform the tests mentioned above.
If those tests don't indicate problems and the spark plugs are sooty and the carb has not been rebuilt for a long while, rebuild it.
Like I always say, "Its always the carburetor."
Actually I never say that, but it might be the problem in your case, since you are going to check out everything else first.
What I should always say is, "You should always check out everything else before you dig into the carburetor." But that takes too long to type.
Carl

The cap is self venting, but I will give this a try.



See above regarding the cap. I should have mentioned that I can restart the engine, but only if I give the throttle a good press, just like it was flooding. That is right after it dies and NOT waiting for minutes after. It dies almost immediately after I let off the throttle after it has warmed up and trying to restart it.


I will see if I can fix up a pressure gauge. I am leaning towards it still flooding from what I see and I have read. I am running a mechanical fuel pump. Same from before the rebuild.



I have had the carb for a long time, but I rebuilt it with a good kit prior to installing on the new rebuilt engine. I know about the pump diaphragm issues cause my 300 I6 in my 78' Ford has the newer/different YF carb and has issues with today's gas. What a pain!


It's not dripping now after I made some float corrections, but it's still sputtering and dying like it did before. As for the vacuum in the tank, I wouldn't be able to restart right after it died, right? I would have to wait? Cause, right now I can restart right after it dies, but I have to give it alot of throttle like it's flooded.


Thank you all for the advice! I will try these things this week end and report back! It's been 6+ years since the old girl has been on the road and I am dying to have it back and dependable!

It sounds like you have other issues,


But ill add this about the new vented gas caps.

Sometimes the new vented gas caps do not vent properly.

You'll know if its the gas cap, when you remove the gas cap after the truck starts bucking you'll hear air rush in at the filler neck.
When my truck started bucking after about 15 20 minutes it ended up being the new vented gas cap. The older N.O.S caps don't seem to have this issue

In my case I Modified the new cap.


_______________________________________

You mentioned the heat riser spring
Heres the spring position

...link...

...link...

...fig 3....
________________________________________


I once had an issue of random flooding of the carb. Ended up being debris in the carb and at the fuel inlet port. I installed one of those inline filters at the carb.

...carb filter at beginning of video...


Good luck on your troubleshooting

I once had a new vented fuel cap that didn't vent. It caused the same symptoms as you are describing. Run it with the cap off or just slightly tightened. It was one of the easiest fixes possible.

Here's a thread on my lessons learned. I actually found that a 'new vented' gas cap didn't vent properly and the heat riser was stuck in the hot position.

(CLICK)

Keep us posted on your issue. Good luck!

The fix is to drill a 1/16 hole in cap.

I had a little time before going to work today( I'm a cop and work evenings). I started the engine and took the gas cap off. Engine died at 12min and 5 secs. Today was warmer day then last test. I'll try the heat riser next and then find a fuel pressure gauge.

We troubleshootin now

So, I want to make sure I have this right. It dies after 12-20 minutes. You can get it to restart but it won’t stay running. When it cools down you can start the process over with the same results. Am I right?
Just throwing this out there..... debris in the tank floating around until it blocks the fuel pickup. Went it sets for a few seconds the debris releases until sucked back up to the pickup.🛠

i recently fixed my GMC won't start hot because the coil was on the edge of going bad, it wouldn't spark good enough to hot start, but cold it would
these engines get hot fast, maybe your coil is warming up and can't spark no more

but do as other suggested, check fuel delivery first
A / B testing a new coil isn't too difficult after than
it's probably not the carburetor if it can run for 12 minutes
-s

Getting close. Don't do several things at once. One at a time and test.
1. Tie up the riser. Make sure you have it open. Test run.
No result,
2. Get a new coil, they are cheap. Test run.
No result
3. If I and 2 don't do it, and not condenser, we have to go with gas flow. Fuel delivery problem.
Pump, tank residue, fuel filter, carb. Be sure you have gas in the tank.

He’s running a Langdon’s HEI.

Thanks Martin. That eliminates a condenser failing and probably eliminates a coil. ApacheFeind, Sorry. I have edited to exclude coil and condenser.

Do a full test on the fuel pump. I'm wasting billions of electrons here, because NOBODY ever does that. With the fuel line disconnected at the carburetor, idle the engine for 30 seconds. Use a piece of rubber fuel line to route the gas into a catch container. A good fuel pump will flow a pint of fuel (16 ounces) or more into the catch can. Test the fuel pressure- - - -for a carbureted engine normal pressure will be around 3-5 PSI and the pressure will stay there for a short time after the engine is stopped. Now go to the input side of the pump with a vacuum gauge. There should be 12 inches of vacuum or more and it should also stay there for a few seconds on engine shutdown. If the pump passes all these tests, then go looking for a restriction in the tank or the tank to pump fuel line.

Now, do like everybody else does, make a SWAG, and throw a wheelbarrow full of parts at the problem.
Jerry

Yes, if you have access to those gauges or want to spend a wheelbarrow full of money on gauges you won't use again, that may identify the problem.

If you want to use logic with less work and no money, this is the case for that.

Next step after riser test. Disconnect fuel line at pump inlet and attach a hose down to a gas can sitting in the ground. The pump will suck the gas into carb as you run the motor. See if it runs longer than 15 min. This will bypass the tank and show if trouble is upstream of pump and it will help verify if pump is good or bad also. Report results.

If it still dies:
Disconnect fuel line at carb and attach hose to carb inlet and feed carb from a container using gravity. This, of course, eliminates the pump. Report.

Don't know your expertise on these things so don't mean to talk down to you, but if you need help with how to do this hose plumbing, post some pics of how your carb and pump are plumbed. You may or may not need to get a hose barb fitting or two.

A vacuum/fuel pressure gauge costs less than a good hamburger and fries at a casual dining restaurant, and the vacuum gauge needs to be used every time the idle mixture is adjusted on a carbureted engine. Every FLAPS has one on the shelf with the rest of the basic tuneup tools like feeler gauges and compression testers. I guess it's simpler to make wild-donkey guesses and then bloviate about them.

https://www.harborfreight.com/fuel-pump-and-vacuum-tester-62637.html

Jerry

Where I have I mentioned or typed that I have thrown any parts at MY engine problem or made any SWAGs? I'll wait...

I have tested the fuel pump out put a couple of weeks ago and it was good. It pushed out a pint or more in less than a couple of seconds. I don't have a fuel pressure gauge, so i ordered one and it will be here on Monday. I'll hook it up and see if it's over pressured for my carb. This is the problem I am leaning towards being the culprit. I do have a vacuum gauge and will have to wait till my helper is here to assist in using it on the suction side of the pump.

Since I had a few minutes before going, in the rain, to my parents for lunch, I tried running the engine with the heat riser in the "off" position. The engine died after 16+ minutes.

From the tests thus far, and seeing fuel dripping from the carb before the float adjustments, I am thinking this will be a too much fuel/fuel pump issue. I'll report back when I have finished testing the pump since I'm NOT ignoring suggestions......

I don't think those comment were directed at you at all. Keep up the good work. If it is a stock pump, it will have correct pressure. The only problem I have is you are trickling in info about what you have already done and what components you may have that are not stock. Very hard to help with not knowing anything about history or efforts already addressed.

The pressure a mechanical fuel pump creates is a function of the diameter of the diaphragm and the tension of the spring that pushes it. All the camshaft does is lift the diaphragm and provide the vacuum to pull the fuel into the pump chamber through a one-way valve. Some rebuilders install any old spring that will fit, with little or no attention being paid to the output pressure. I've seen some "rebuilt" pumps produce 10 PSI or more and cause massive flooding problems when the needle valve can't shut off the flow at idle. Once the engine speeds up a little the excess fuel gets burned quickly enough to avoid flooding at cruise speed.
Jerry

The gas tank was pulled and taken to a radiator shop where they cleaned it and sealed it before I reinstalled for the engine start up. I also installed a new sending unit with the sock filter on it. I also have a glass bowl filter at the carb. So, there shouldn't be anything floating around in there unless it got in there when I filled up the tank at the gas station.


Not trying to make wild guesses. I just don't have all the tools easily accessible. I was able to locate a gauge like you linked. I got it hooked up with some brass fittings and started the engine. It showed the pump to have a steady 2.5 PSI.

After it died this time I restarted it with alot of throttle. I held the throttle for several seconds and let off. The engine then idled for several seconds before it tried to die again. If I rev'd the engine it would stay running.

OK, now we're making some progress. Do you have an inline fuel filter between the pump and the carburetor? A real filter- - -not one of those clear plastic things. It's beginning to sound like you're getting some sort of sediment into the needle valve assembly which is allowing the carb to flood periodically. Also shake the float to see if it's got some gasoline in it. Brass floats are soldered together, and they're notorious for springing leaks. A float partially filled with gas can't develop enough upward pressure to keep the needle valve closed properly when the float chamber fills. There has to be some reason for the flooding, which is obviously what's happening. You're having to rev the engine up enough to burn the extra gas and prevent the mixture from getting so rich the engine won't run. I'll also make a guess that the exhaust pipe(s) are black and sooty, and the spark plugs are black, as well. Find and fix the flooding problem, and you should be back in good shape.

What sort of "sealer" did the radiator shop use? It could be flaking off and contaminating the fuel.
Jerry

These are all good ideas. I just keep trying to think about the fact that is runs for so long. None of the suggestions, especially now that we know all the new and refreshed components, seem to pass the "runs for 12 minutes test". Something is developing. It develops in about the same time frame.
Does not fit most of our suggestions.

This is all brainstorming talk.
1. 2.5 psi is a little low. Your test did not show what may happen with pump after it sucks air for 12 minutes.
2. Leaking floats are hard to detect by shaking. Why would a leaky float last for 12 min?
3. The flooding theory is good especially if carb was leaking, BUT my brain says not enough gas. So maybe throw gobs of many at the fuel pump and buy one for $25.
4. Check for vacuum leaks
5. I don't know if an HEI coil acts this way when going out.
6. Does it have power for the 12 minutes? How quickly will it restart WITHOUT pumping?
7. You don't have the right to remain silent, anything you say will be held against you.

"I restarted it with a lot of throttle"- - - - - -to paraphrase, "I held the throttle wide open and cranked until it started". Is that correct? If so the engine is flooding. Find out why, and fix it.

Have you done the volume/pressure/vacuum test on the fuel pump yet? Didn't think so.
Jerry

It took me a while to find the cause of my flooding issue. Ended up being debris coming from the adapter fitting
...pic...
...cleaning...
...all cleaned up....

Now I always check all the fuel system connections male and female.
I use a under tank filter, mechanical fuel pump has glass bowl filter, and I added the filter at the carb after my flooding issue


Just one more thing to check next time your 10-10

I have to hold open the throttle, but not WOT and it starts right up. I believe it flooding too and I have been trying to figure out why. I have checked the float and adjusted it twice. Lowered it below spec by 2/32". Needle and seat are clear.

You're NOT reading my responses then cause I have done the volume and pressure tests. I will do the vacuum tomorrow when I have daylight. Geez. Take a breath already.

I have a glass bowl filter with a wix filter at the carb. I checked the float and the needle and seat both times I took the air horn off to adjust the float. The float had no fuel in it either time I checked, I shook it both times. I guess I'll take it out and submerge it in water to see if it take on anything. The needle and seat were clear. I even blew air through it the second time to be sure.

I'm not sure on the sealer used by the shop. They did another tank for me for my 78' Ford and I had no problems with it. That has been several years now.

DADS50-

I'll double check all my connections, maybe I got something flapping around that is causing an issue. Thanks for the pics.

I'm not being obstinate about testing procedures, just sharing your frustration. Chronic flooding can be an extremely aggravating problem and I've been in your situation numerous times. Occasionally it's just a poor fit between the needle valve and the seat and no amount of adjusting and tinkering would solve the problem. As long as the engine is running above idle, the liquid level in the float chamber doesn't rise above the level of the venturi, which allows fuel to spill over into the air stream and cause the flooding. The next time it starts to stumble and run rough, shine a bright light down the carb throat and see if there's gas dribbling out of the venturi. If so, that's a confirmation of a flood. There should be NO liquid gas visible in the carb bore. We used to be able to buy just the needle/seat assembly without purchasing a whole rebuild kit, but those days are long past. Does your needle valve have a rubber tip. or is it just a tapered metal to metal seal?
Jerry

I was thinking this has all the signs of a flooding condition too, especially since I can open the throttle and clear the issue. I was also thinking of doing as you suggest and looking down the throat of the carb as it begins to stumble and see what I see. It cuts out quick though so I may have to perch like a gargoyle in the engine compartment to see it in time. I will check and see if I can get just a needle and seat. The current needle does have a rubber tip.

There is a new old stock Rochester B needle and seat on Ebay right now, part number 7002359 for $14.95 with free shipping. search "Rochester needle and seat" and it's about 20 items down from the top of the listing. It's an original equipment metal to metal type.
Jerry

Will that work in a Carter YF 2100s?

I found that Mike's Carburators sells just the needle and seat.

No it will not. What has happened is the thread has gotten so lengthy that folks are forgetting what you have and what you’ve done. Sometimes that’s just how the site works and it is for sure not your fault.
My vote now is for a separate fuel source (outboard motor tank) or a gas can to eliminate the possibility of the fuel tank and lines. If it stays running then you can repair/replace from there. If it dies then dig into the carburetor further. If it still dies then you’ve got and ignition problem ie; bad coil for the HEI. Keep on plugging away eventually it will give up and you’ll whip its butt.

BTW, I have nowhere the experience that Jerry has but I did stay at a Holiday Inn once.

OOPS! I forgot we're dealing with a Carter! I seem to remember Jon (Carbking) mentioning that some Carter rebuild kits have the wrong needle and seat assembly- - - - -and it can cause flooding problems. Jon doesn't accept PM's, but he does answer his phone and he shares his encyclopedic knowledge of Carter carbs willingly. Google "The Carburetor Shop" or look up some of the tech tips Jon has posted for his phone number. Just be specific with your requests- - - -Jon is a busy guy and doesn't have a lot of time to chitchat!
Jerry

A member here had the same symptoms, spent a lot of time on issues we have discussed in this post. Finally it was the ignition switch.

Also read on Stovebolt: Coil, float hanging up on carb sides, vapor lock, winter blend fuel, water in fuel....

To expand on Bartamos' comment, I had a '72 Chevy PU that would cut out on the road at random times. I wound up replacing the resistance wire from the ignition switch to the coil and it STILL did it. The fix was (eventually) taking the terminals out of the clip that connects the wires to the coil and squeezing them a bit more shut with a pair of pliers. It was losing continuity because the connection was loose. Worked just fine after that till I sold that truck. Sometimes the easy fix is hard to find.