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66 Chevy 250 dies at stop signs and red lights....help
#1366326 Thu Jun 25 2020 12:10 AM
Joined: Dec 2016
Posts: 14
L
Lawman Offline OP
New Guy
I have a 66 Chevy C10 with a 250 in line 6 engine with a 1 barrel rochchester carb. Recently it has started dying when approaching a red light or stop sign. She cranks easy, runs fine, accelerates fine, and will idle all day if you are not decelerating. It’s a 3speed manual transmission and pumping the gas to keep it running while stoping is not fun. When this started I noticed a small drip of fuel coming from the mechanical fuel pump, (it’s an airtex fuel pump). I tightened all the screws holding the thing together, stopped the little infrequent drip of fuel....still had the problem. So I replaced the fuel pump anyway.....still have the problem. I have set and rest the ignition timing, it was never off, 4 degrees before TDC. I have adjusted the mixture screw on the rochchester by small increments to no avail, it still dies when decelerating. So, I need some advice here....there must be something I am missing....I’ve owned the truck for 17 years and never had this problem before. Any help would be appreciated.

Re: 66 Chevy 250 dies at stop signs and red lights....help
Lawman #1366336 Thu Jun 25 2020 01:03 AM
Joined: May 2005
Posts: 7,347
B
General Purpose
After it dies at stop light, does it start right up?

How can it idle fine and not idle fine when stopping? So when does it "idle fine" ?

It seems like debris is moving forward as forward momentum stops, then floats back on acceleration. Fuel filter, tank pick up or tank debris? If it runs good in all other modes like you say. Idle, acceleration, it doesn't seem like carb or pump?

Not flooding right?

Plenty of gas in tank right?

I know this sounds silly but can you go from 30MPH to a gradual roll and let truck stop without brakes or trans and see what is does. In a large parking lot or something.


I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.


Re: 66 Chevy 250 dies at stop signs and red lights....help
Lawman #1366343 Thu Jun 25 2020 01:17 AM
Joined: Apr 2005
Posts: 8,909
Grease Monkey, Moderator General Truck Talk & Greasy Spoon
Note to all: This is not me using another sign in. Lawman, scroll down a few posts (20-25) and you will find a similar thread with some good answers. “Idles all day but dies when stopping “.


Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne 4dr 230 I-6 one owner (I’m #2)
‘39 Dodge Businessmans Coupe
USAF 1965-69 Weather Observation Tech (got paid to look at the clouds)


"I fought the law and the law won" now I are a retired one!
Support those brave men/women who stand the "Thin Blue Line"! Hug a cop!

Re: 66 Chevy 250 dies at stop signs and red lights....help
Lawman #1366344 Thu Jun 25 2020 01:30 AM
Joined: May 2005
Posts: 7,347
B
General Purpose
I just read that. I was thinking what could change in the carb to cause this. Jerry had a good point about leaky/soaked float which would raise the level in carb BUT:
1. Poster doesn't say anything about flooding? that's why I asked
2. Martin, in that post you did find the float drop was off 1/2 inch and that fixed it. CAN YOU PLEASE TELL US WHICH WAY THE DROP WAS OFF 1/2 inch? too much drop or not enough? I'm guessing too much. That would be the flooding direction. Like a sinking float. Not enough would be the starving direction.

Here is the thread.

I have to stick with debris now that I committed. We'll see.


I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.


Re: 66 Chevy 250 dies at stop signs and red lights....help
Lawman #1366348 Thu Jun 25 2020 01:58 AM
Joined: Apr 2005
Posts: 8,909
Grease Monkey, Moderator General Truck Talk & Greasy Spoon
Too much drop and yes the float adjustment fixed it.


Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne 4dr 230 I-6 one owner (I’m #2)
‘39 Dodge Businessmans Coupe
USAF 1965-69 Weather Observation Tech (got paid to look at the clouds)


"I fought the law and the law won" now I are a retired one!
Support those brave men/women who stand the "Thin Blue Line"! Hug a cop!

Re: 66 Chevy 250 dies at stop signs and red lights....help
Lawman #1366353 Thu Jun 25 2020 02:55 AM
Joined: Dec 2016
Posts: 14
L
Lawman Offline OP
New Guy
Ok, it always starts right up when it dies at a stop light or sign. It cranks easy either cold or after warmed up. It accelerates just fine. Doesn’t appear to have a flooding problem. Tank is new (5 years) all lines replaced in last year, fuel pump replaced after this issue started. Plenty of gas in tank. I have a glass in line filter installed on the intake side of the fuel pump, gas looks clean, but the level of gas visible in the filter does fluctuate, but the filter has been installed here for several years.

I’ll try the coasting stop tomorrow, but that is basically what I’m doing anticipating stops now, pressing in the clutch shifting to neutral and hoping the engine doesn’t die and staying ready to tap the gas if it seems like it will die. Some time it does even this way. If you just crank it in the driveway, it will idle just fine for as long as you want. If you decelerate (with coasting) and stop and it doesn’t die, it idles fine too.

Re: 66 Chevy 250 dies at stop signs and red lights....help
Lawman #1366357 Thu Jun 25 2020 03:24 AM
Joined: Dec 2016
Posts: 14
L
Lawman Offline OP
New Guy
Ok, I read the entire earlier thread offered. Seems this best fits my issue, so I’m thinking carb, it’s a rochcehsrer B, maybe the float level. I’ll wait a bit to see what other input I get before getting into the carb. I’ll have to order a rebuild kit anyway.

I can’t explain the fact it idles perfectly EXCEPT when slowing for a stop. Thought maybe the vacuum advance might be sticking, but it seems to work fine revving the engine in the driveway. Mixture richness may be an issue, but I have adjusted that screw in quarter turn increments with little to no effect on the engine dieing issue. APPRECIATE YOUR HELP AND ADVICE.

Re: 66 Chevy 250 dies at stop signs and red lights....help
Lawman #1366462 Thu Jun 25 2020 11:11 PM
Joined: Dec 2016
Posts: 14
L
Lawman Offline OP
New Guy
I’ve tried to post replies answering some of thes questions twice, but they don’t show up.

After it dies at a stop, it always cranks easily.

It idles fine when you crank it, cold or warm. Sitting in the driveway it will idle all day, after it dies at a light and you crank it it-idles fine until the next stop.

To try and keep it going I am shifting to neutral and coasting gently to a stop using brakes lightly and keeping a foot on the gas in case it stumbles and dies.....some times it doesn’t die, but more than half the time it dies. It’s an aggravating way to drive.

It doesn’t appear to flood. There is plenty of gas in the tank. The tank is new, 5 years ago, gas lines were replaced in the last year.

There is a glass fuel filter before the fuel pump intake, fuel looks clean although the level of fuel in the filter fluctuates between 30% to almost full routinely. Been like that for years.

Read through the suggested thread and it may be a carburetor issue, float level maybe, but as I said it doesn’t appear flooded, cranks right back up and no excessive gas smells.

Lawman

Re: 66 Chevy 250 dies at stop signs and red lights....help
Lawman #1366465 Thu Jun 25 2020 11:45 PM
Joined: May 2005
Posts: 7,347
B
General Purpose
Your reply is showing up now.

Something easy and free to try, take filter out of the system for a test drive or two.


I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.


Re: 66 Chevy 250 dies at stop signs and red lights....help
Lawman #1366473 Fri Jun 26 2020 01:05 AM
Joined: Feb 2001
Posts: 1,339
T
Shop Shark
Lawman,

I am just going to throw this out there, Have you checked for a vacuum leak? The intake manifold at the cylinder head, Base of carb at the manifold? I would be reluctant to say, since it is a rochestor B carb, there are two screws that hold the base of the carb(where the throttle shaft is) to the fuel bowl part of the carb where the float is, that could be loose causing a vacuum leak. What is the idle set at? Where is the timing set, you can advance the timing a little bit and see if it makes a difference. Check for vacuum leaks with the engine running and some spray carb cleaner or a unlit propane torch around the intake manifold and the carb base.

Good luck. Some people will say I am off base with my thinking, But I have learned over the years to always check the easy things first.


Tommy
59 apache 1/2t
261 short stepside
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