‘65 cold start with high idle problem

[Greaseball]

My ‘65 401 engine has a cold start problem that I cannot find a fix for.  Hoping you guys can help me out.

 

The problem is after the car has started, the carb will not stay on high idle.  The choke appears to be operating correctly, but the carb keeps coming off the high idle cam as if it’s already warmed up (which definitely it isn’t!).

 

When the engine is cold and before it’s started, the carb sets itself up correctly with a tap of the accelerator pedal: the choke blade covers the primaries and the idle cam sits up in the high idle position.  After the car starts, it drops off the high idle position of the cam.  I can’t figure out why it does this.  Any help?

 

 

Dan

[moran75]

BTW I’m by no means an expert, and I’m sure they will contribute …but in meantime …

 

Do you mean a) drops off immediately after starting car, choke plate uncovers primaries and car stalls immediately?

 

Or b) seems/appears to come off cam quicker than it should , and car eventually stalls?

 

If it’s a) maybe there’s something wrong with your choke coil as it’s that tension which keeps choke plate in position and over time relaxes and let’s  cam progressively drop off high idle ?

 

if b) I had that happen and I noticed my dash pot wasn’t engaging when idle cam came off high idle, and therefore put the issue down to some kind vacuum issue which dashpot prevents..:.so I adjusted dashpot position and all ok

 

now that I’m writing maybe my problem   was simply an idle speed issue ? Too low when high idle cam came off , hence stalling? Anyway, adjusting dashpot ‘worked’ 😀

 

 

Have you got a manual? when I got my 65 it had been sitting for years and choke didn’t work at all etc etc…and I was a novice to mechanics …I found this forum a great help but I also had the manual which explained the mysterious workings of a Carter AFB ….and between the two got it sorted….

 

good luck

kev (London, England )

[EmTee]

10 hours ago, Greaseball said:

When the engine is cold and before it’s started, the carb sets itself up correctly with a tap of the accelerator pedal...

Maybe there's a problem with your technique?  You say that you 'tap' the accelerator prior to starting.  It's possible that although this is sufficient for the choke to close, maybe the fast-idle linkage isn't fully set and therefore 'falls-off' too soon.  Rather than 'tapping' the accelerator, try pushing the accelerator fully to the floor and then release it before cranking.  With the engine cold and air cleaner removed, you should see the idle stop screw sitting completely on the highest fast-idle step.  After running for a minute, then a 'tap' of the accelerator should cause the idle stop to fall down to a lower step on the fast-idle cam.  Once warm, the idle stop should be at the lowest step, or on some carbs the fast-idle cam completely falls away.

[carbking]

A bit more information would have been useful, but in the absense of information, will use the "scattergun" approach:

 

The 1965 401 could have come from the factory with either a Rochester 4-G or a Carter AFB. Both came with hot air chokes, which were keyed to the operating temperature of the engine. The fast idle cam is connected to the choke arm, thus the position of the fast idle cam is proportional to the position of the choke butterfly. Since these chokes are keyed to the engine temperature, the choke butterfly should slowly open, and be fully opened in 5~8 minutes. However, if one has one's foot on the footfeed, thus removing the "drag" of the fast idle screw on the cam, it can open somewhat quicker.

 

If the carburetor is original, then possible concerns and fixes would be: (A) adjustment, (B) keeping one's foot on the footfeed, or (C) significant wear on the fast idle cam.

 

Some folks think they can circumvent factory engineering and install a cheap aftermarket carburetor. Most of these come with an electric choke, which is NOT keyed to engine temperature. Electric chokes which I have tested go completely off in 45 ~ 90 seconds. Since the fast idle cam is keyed to the choke, the fast idle cam will drop before the engine is ready for the cam to drop, and stalling often occurs.

 

If an aftermarket carb with electric choke or just an aftermarket electric choke has been installed, the "fix" is to return the engine to the way the engineers designed it.

 

More information on automatic chokes may be found here: AUTOMATIC CHOKES

 

Jon

[NTX5467]

I concur, more information might be needed.  As to if the carb is OEM, which one, or if it's a replacement of some sort.

 

In an OEM situation, once the choke "is set" prior to starting, the choke thermostat coil closes the choke valve and raises the linkage controlling the automatic choke fast idle cam.  Resulting a higher initial engine speed.  AND, as the engine sits there running with NO accel pedal intervention, the fast idle speed should stay where it is (or get higher as the engine and oil warm up).  

 

IF the accel pedal is tapped after the engine starts and runs a bit, by that time, the choke pull-off is working to open the choke plate to keep the engine from running too rich.  Tapping the accel pedal at THAT time should result in the new choke plate position (and related linkage) to move the fast idle cam to an intermediate position to a lower idle speed, but still faster than hot base idle.  Then, as the engine warms and the choke thermostat coil warms and allows the choke plate to progress toward hot base idle, the fast idle cam's linkage will also progress toward it being "off", with progressively lower intermediate idle speeds.

 

IF the thermostat has enough tension to close the choke plate initially, then why the sudden drop in fast idle speed presents a mystery, of sorts, as that should not be happening if everything is present and working decently well.  Far more possible for the choke to stick closed than to suddenly open, to me.  UNLESS, per chance, the plastic (generally) fast idle cam has fractured on the "lower section" and is laying on the intake manifold, meaning that after the choke is initially set, the car starts, then a second tap for an intermediate-level fast idle speed is supposed to happen, but the fractured fast idle cam's lower section is not there for the fast idle speed screw to contact?  So, the carb is at "hot base idle" when it should not be, with a cold motor.

 

That's my theory, absent any pictorial evidence,

NTX5467

[Greaseball]

1 hour ago, carbking said:

A bit more information would have been useful, but in the absense of information, will use the "scattergun" approach:

 

The 1965 401 could have come from the factory with either a Rochester 4-G or a Carter AFB. Both came with hot air chokes, which were keyed to the operating temperature of the engine. The fast idle cam is connected to the choke arm, thus the position of the fast idle cam is proportional to the position of the choke butterfly. Since these chokes are keyed to the engine temperature, the choke butterfly should slowly open, and be fully opened in 5~8 minutes. However, if one has one's foot on the footfeed, thus removing the "drag" of the fast idle screw on the cam, it can open somewhat quicker.

 

If the carburetor is original, then possible concerns and fixes would be: (A) adjustment, (B) keeping one's foot on the footfeed, or (C) significant wear on the fast idle cam.

 

Some folks think they can circumvent factory engineering and install a cheap aftermarket carburetor. Most of these come with an electric choke, which is NOT keyed to engine temperature. Electric chokes which I have tested go completely off in 45 ~ 90 seconds. Since the fast idle cam is keyed to the choke, the fast idle cam will drop before the engine is ready for the cam to drop, and stalling often occurs.

 

If an aftermarket carb with electric choke or just an aftermarket electric choke has been installed, the "fix" is to return the engine to the way the engineers designed it.

 

More information on automatic chokes may be found here: AUTOMATIC CHOKES

 

Jon

 

Hello Jon and everyone else who has chipped in with a reply to help me out.

 

The carb on this car is the Carter AFB.  Sorry about omitting that detail; I had forgotten that the 1965 models could have also come with the Rochester carb.

 

The carb and choke assembly is complete and as it came from the factory.  I’ve checked the vacuum in the choke control and it’s drawing heated air from the exhaust manifold through the stove pipe.  I’ve also checked the functioning of the choke coil; it appears to be operating ok.  The choke blades cover the primaries when the engine is cold.  Also, the choke blade fully opens over the primary barrels when the engine is warmed.

 

I’ve checked my initial accelerator pedal technique when setting the carb up before attempting to start the engine when it’s cold.  My technique is more than a tap, more like a stab of the accelerator pedal all the way down to the floorboard.  It’s sufficient to set the idle cam onto the high-idle position.  Also, I’ve verified that the accelerator pump on the carb is healthy.

 

When the engine starts, the cam gets pulled off of the high-idle position.  I can keep the engine from dying by manually manipulating the accelerator pedal, but I shouldn’t have to do that.

 

I’ll post picture below of before starting conditions and after starting conditions of the idle cam and the choke blade 

[Greaseball]

Before starting conditions (but after setting up the choke with a stab of the accelerator pedal) of choke blade and high-idle cam

[Greaseball]

After starting conditions of the choke blade and high-idle cam if the engine dies without manually manipulating the accelerator pedal.

 

Thanks for your help!

 

Dan

[1965rivgs]

  Tighten your choke adjustment. The choke blade should be completely closed and the adjustment should be a tad tighter than that. After a tighter adjustment the fast idle cam will be where it should be which is the highest step on the cam.

  After starting the incoming air will open the offset choke blade slightly and allow the first drop in cold start RPM at the fast idle cam. Just be sure the choke is not so tight that it doesn't allow enough incoming volume of air and cause the engine to "load up".

  Also, after the engine is up to temp, check the fast idle cam to be sure it falls free of the fast idle adjustment screw which will allow idle speed control to the base idle screw.

Tom Mooney

[Seafoam65]

Agreed......richen up the choke by loosening the screws on thechoke thrmostat and tightening it up a little.

[Greaseball]

Thanks guys,

 

Over the weekend I richened up the choke by turning the choke housing.  However, after doing that, the choke blades would not fully open when the engine was thoroughly warmed up.  I returned the choke housing to where it originally started; my thinking was that I definitely do not want the choke blades partially closing over the primaries on an running engine running at operating temperature.

 

Now what?  I can’t seem to find a happy medium with the choke and idle cam between between cold starting and hot running

 

 

Dan

Edited April 4, 2023 by Greaseball
added detail (see edit history)

[NTX5467]

Thanks for the additional information and pictures!

 

Choke thermostats can tighten with age, which can make setting them to a factory spec not be where it needs to be.  The choke plate should just close fully about 70 degrees F AMBIENT for the engine and carb, not just the air around them.  Not a "snap" closed, but an easy, just enough tension to close, which is usually where the factory spec is for when the car was new.

 

With a non-running engine, manually move the choke blade to full-closed after the throttle is opened a bit.  See what it does and then release the throttle, letting the fast idle screw and cam do their interface activity.  Once that has been done, manually click the fast idle cam open and check for interface with the fast idle speed screw.  How many steps before the throttle is back at hot base idle location, with the fast idle speed screw not touching the fast idle cam?  Of course, as you move the fast idle cam manually, the choke plate will incrementally open more, too.

 

Side issue . . . how long has this been going on?

 

Take care,

NTX5467

[1965rivgs]

44 minutes ago, Greaseball said:

Thanks guys,

 

Over the weekend I richened up the choke by turning the choke housing.  However, after doing that, the choke blades would not fully open when the engine was thoroughly warmed up.  I returned the choke housing to where it originally started; my thinking was that I definitely do not want the choke blades partially closing over the primaries on an running engine running at operating temperature.

 

Now what?  I can’t seem to find a happy medium with the choke and idle cam between between cold starting and hot running

 

 

Dan

  Make sure you have a gasket on the choke housing cover.

  Remove the hot air tube from the choke housing nipple and be sure you have vacuum at the nipple when the engine is running. If not, the passage which originates between the primary bores in the base of the carb and runs to the choke housing is blocked- very common....or, the o ring which seals this passage between the carb body and choke housing may be leaking or missing.

  If all of the above checks out the tube which runs through the exhaust manifold may be blocked.

  That choke hot air tube should be very hot to the touch if the system is working correctly. There should also be an insulating sleeve along the length of the tube but if the tube is uncovered it should still operate properly.

Tom Mooney

Edited April 4, 2023 by 1965rivgs (see edit history)

[carbking]

Willis and Tom type faster than I

 

Take a look at the link I posted earlier on automatic chokes. Scroll close to the end to the paragraph on testing. Perform these tests on your choke.

 

Jon.

[Greaseball]

59 minutes ago, 1965rivgs said:

  Make sure you have a gasket on the choke housing cover.

  Remove the hot air tube from the choke housing nipple and be sure you have vacuum at the nipple when the engine is running. If not, the passage which originates between the primary bores in the base of the carb and runs to the choke housing is blocked- very common....or, the o ring which seals this passage between the carb body and choke housing may be leaking or missing.

  If all of the above checks out the tube which runs through the exhaust manifold may be blocked.

  That choke hot air tube should be very hot to the touch if the system is working correctly. There should also be an insulating sleeve along the length of the tube but if the tube is uncovered it should still operate properly.

Tom Mooney

Thanks, Tom.  I’ve already verified all that you mentioned and everything checks out, including the insulating sleeve around the tube between the exhaust manifold and the choke housing.  The housing does have the gaskets in place and the vacuum is present.

 

Dan

[Greaseball]

1 hour ago, NTX5467 said:

Thanks for the additional information and pictures!

 

Choke thermostats can tighten with age, which can make setting them to a factory spec not be where it needs to be.  The choke plate should just close fully about 70 degrees F AMBIENT for the engine and carb, not just the air around them.  Not a "snap" closed, but an easy, just enough tension to close, which is usually where the factory spec is for when the car was new.

 

With a non-running engine, manually move the choke blade to full-closed after the throttle is opened a bit.  See what it does and then release the throttle, letting the fast idle screw and cam do their interface activity.  Once that has been done, manually click the fast idle cam open and check for interface with the fast idle speed screw.  How many steps before the throttle is back at hot base idle location, with the fast idle speed screw not touching the fast idle cam?  Of course, as you move the fast idle cam manually, the choke plate will incrementally open more, too.

 

Side issue . . . how long has this been going on?

 

Take care,

NTX5467

Thanks for the information, Willis.  The garage temperature is around 60degF and I’ve even left the car outside when the temperature ranged between 45 to 50degF.  I’m going to have to play around with the choke housing adjustment some more and verify that the choke coil is expanding and contracting in a wide enough range.

 

I don’t know how long the car has been plagued by this issue.  I acquired the car a couple of months ago and the issue was already present. 

Edited April 4, 2023 by Greaseball
add detail (see edit history)

[Greaseball]

57 minutes ago, carbking said:

Willis and Tom type faster than I

 

Take a look at the link I posted earlier on automatic chokes. Scroll close to the end to the paragraph on testing. Perform these tests on your choke.

 

Jon.

Thank you for that link, Jon.  I have checked everything else out except for testing the choke coil (step 1 in the testing section within the link you provided) to see if it is expanding/contracting in a wide enough range to be effective.  I have a hunch the answers lies within this test; everything else seems to check out fine.

 

 

Dan

Edited April 4, 2023 by Greaseball
Add detail (see edit history)

[EmTee]

Sounds like the bimetal spring is worn-out.  As you said, the test result will confirm or refute that assumption.

[Greaseball]

12 minutes ago, EmTee said:

Sounds like the bimetal spring is worn-out.  As you said, the test result will confirm or refute that assumption.

I agree.  There’s not much left to verify other than the bimetal spring.  I’ll report back with my findings.

[1965rivgs]

11 minutes ago, Greaseball said:

I agree.  There’s not much left to verify other than the bimetal spring.  I’ll report back with my findings.

  Are you sure the tube in the exhaust manifold is clear? Did you try blowing compressed air through it? Your symptoms sound just like a lack of heated air flow through the choke housing.

Good luck!

Tom

[NTX5467]

OK, IF there is too much heat getting to the choke thermostat, is there not a related vacuum passage into the primary throttle bore and a drilled restriction within that passage (or the size of the passage itself) which limits the amount of heat and how soon it gets there?  Whether for these particular AFBs or the other carbs which use an internal choke pull-off (via a small piston connected to a rod)?  Will not those passages not clog with time, restricting the amount of heat being pulled in?

 

Seems that if that internal passage (in the carb) has become clogged, or restricted more than normal, any heat getting to the pipe connection/choke thermostat housing would be more "migratory" than not.  In other words, no hot exhaust gasses going somewhere they have no place to go after they get there.  Looking at the dynamics of the situation, basically.

 

Take care,

NTX5467

[Wayne R]

The previous owner may have put up with this and drove it like that for years, This may help you as well,

take a look a t   these photos, also a can of  carb cleaner can do wonders  working on carbs.  especially the inside of the

choke housing where the  piston adjustment is.

[Jim Cannon]

Dan-

I have seen this before. It is very subtle and easy to miss. The way the fast idle cam is setup, the choke pulling open is not supposed to pull the fast idle cam down. I have circled in your photo where the problem is. I suspect it has been assembled incorrectly, or you have some parts that are binding. The two need to rotate freely from each other.

 

When you step on the throttle with the engine not running, the choke snaps shut and the fast idle cam moves up.

 

After you start the engine, as the choke opens and the linkage down to the fast idle cam moves, it is not supposed to be able to pull on the idle cam hard enough to move it. The linkage is connected to one piece that turns, which is connected to the fast idle cam by a hair spring that should absorb all of the movement.  This is what you need to look at.  It is supposed to be that when you tap the gas pedal (engine running) the carb fast idle cam falls away, but not before.

 

I hope this makes sense. Let us know what you find.

 

Oh, and when you start the cold engine, do not stab the throttle all the way to the floor. Go down slowly only about 1/2 way down, 2 or 3 times. Then turn key to start.  When you floor the gas pedal, you actuate the "choke unloader" linkage that is designed to start a flooded engine. It pushes the choke open.

[Greaseball]

3 hours ago, 1965rivgs said:

  Are you sure the tube in the exhaust manifold is clear? Did you try blowing compressed air through it? Your symptoms sound just like a lack of heated air flow through the choke housing.

Good luck!

Tom

Hi Tom.  Yes, I thought the same, the tube was probably clogged.  I pulled the tube out of the car and it was clear and unobstructed. 

[Greaseball]

51 minutes ago, Jim Cannon said:

Dan-

I have seen this before. It is very subtle and easy to miss. The way the fast idle cam is setup, the choke pulling open is not supposed to pull the fast idle cam down. I have circled in your photo where the problem is. I suspect it has been assembled incorrectly, or you have some parts that are binding. The two need to rotate freely from each other.

 

When you step on the throttle with the engine not running, the choke snaps shut and the fast idle cam moves up.

 

After you start the engine, as the choke opens and the linkage down to the fast idle cam moves, it is not supposed to be able to pull on the idle cam hard enough to move it. The linkage is connected to one piece that turns, which is connected to the fast idle cam by a hair spring that should absorb all of the movement.  This is what you need to look at.  It is supposed to be that when you tap the gas pedal (engine running) the carb fast idle cam falls away, but not before.

 

I hope this makes sense. Let us know what you find.

 

Oh, and when you start the cold engine, do not stab the throttle all the way to the floor. Go down slowly only about 1/2 way down, 2 or 3 times. Then turn key to start.  When you floor the gas pedal, you actuate the "choke unloader" linkage that is designed to start a flooded engine. It pushes the choke open.

Thank you for chiming in, Jim.  I’ve started to wonder if the cam and the linkage assembly (the parts that.you circled in red) are put together correctly.  I can’t locate a clear drawing or picture of how the pieces should go together.  I’ll get a better picture posted tomorrow of how things are currently assembled.

 

Also, thank you for suggesting a better starting procedure.  These old cars really have their idiosyncrasies, don’t they!  It’s like an unintentional security system so others can’t start the car and steal it!  I’ll give your suggestion a try. 

[Greaseball]

1 hour ago, Wayne R said:

The previous owner may have put up with this and drove it like that for years, This may help you as well,

take a look a t   these photos, also a can of  carb cleaner can do wonders  working on carbs.  especially the inside of the

choke housing where the  piston adjustment is.

Hello Wayne.  Thank you for the information.  I haven’t broken out the measuring devices yet, just a visual check to confirm that everything is in the correct position initially.  The instructions you provided will be helpful if I need to dig in deep to resolve this problem.

 

Dan

 

[1965rivgs]

8 hours ago, Greaseball said:

Hi Tom.  Yes, I thought the same, the tube was probably clogged.  I pulled the tube out of the car and it was clear and unobstructed. 

  I'm referring to the tube in the exhaust manifold, not the tube that extends from the manifold to the carb.

  Inside the manifold tube is what amounts to a "twisted dipstick" which enables more thorough heat transfer to the air which is being drawn in by the vacuum signal from the carb because it "twirles" the air. So you can't run a rod or something similar through the tube to check that the tube is clear...but at least you can blow through it with compressed air to check that it is clear or obstructed.

  If that tube is obstructed it will initially allow warm air to be drawn into the choke housing but the lack of constant and increasingly warmer air flow will not heat the choke spring enough to allow it to fully retract the choke blade.

Tom Mooney

[NTX5467]

Thanks, y'all, for the additional, detailed information.

 

NTX5467

[Greaseball]

2 hours ago, 1965rivgs said:

  I'm referring to the tube in the exhaust manifold, not the tube that extends from the manifold to the carb.

  Inside the manifold tube is what amounts to a "twisted dipstick" which enables more thorough heat transfer to the air which is being drawn in by the vacuum signal from the carb because it "twirles" the air. So you can't run a rod or something similar through the tube to check that the tube is clear...but at least you can blow through it with compressed air to check that it is clear or obstructed.

  If that tube is obstructed it will initially allow warm air to be drawn into the choke housing but the lack of constant and increasingly warmer air flow will not heat the choke spring enough to allow it to fully retract the choke blade.

Tom Mooney

Thank you I for that explanation, Tom.  I did not know the inner construction of the exhaust manifold passage until your information.  This morning I verified that the passage through the manifold is unobstructed.  I think the problem is coming down to making smaller adjustments to the choke coil housing, possibly the choke coil itself not adequately expanding/contracting, and paying attention to my set-up technique when cold starting the engine

 

Thank you for all your suggestions!  They’ve been very helpful towards adding to my knowledge base.

 

Dan

[Greaseball]

12 hours ago, Jim Cannon said:

Dan-

I have seen this before. It is very subtle and easy to miss. The way the fast idle cam is setup, the choke pulling open is not supposed to pull the fast idle cam down. I have circled in your photo where the problem is. I suspect it has been assembled incorrectly, or you have some parts that are binding. The two need to rotate freely from each other.

 

When you step on the throttle with the engine not running, the choke snaps shut and the fast idle cam moves up.

 

After you start the engine, as the choke opens and the linkage down to the fast idle cam moves, it is not supposed to be able to pull on the idle cam hard enough to move it. The linkage is connected to one piece that turns, which is connected to the fast idle cam by a hair spring that should absorb all of the movement.  This is what you need to look at.  It is supposed to be that when you tap the gas pedal (engine running) the carb fast idle cam falls away, but not before.

 

I hope this makes sense. Let us know what you find.

 

Oh, and when you start the cold engine, do not stab the throttle all the way to the floor. Go down slowly only about 1/2 way down, 2 or 3 times. Then turn key to start.  When you floor the gas pedal, you actuate the "choke unloader" linkage that is designed to start a flooded engine. It pushes the choke open.

Thank you again, Jim, for this information.  I verified this morning that the idle cam, hair spring, and choke rod with lever are all intact and operating independently of each other.  This area of the carb (the area that you’ve circled in red) seems to check out just fine.

 

The other part of your information regarding proper set-up technique with the accelerator on a cold start is gold!  I think my technique was contributing to the problem.

 

 

Thank you for your help.

 

Dan

[Greaseball]

Thank you all for your help.  I’ve been able to narrow down the problem to a couple of issues.

 

The first problem is human error.  This morning I followed Jim Carrol’s suggestion on setting up the carb when the engine was cold.  Before I turned the key, I pushed the accelerator pedal half-way down 3 times.  Then I visually verified that the fast idle cam was in it’s proper position and the choke blade was closed.  I turned the key and the car fired right up and sat at fast idle!  Nice!!!!  

 

However, after I barely touched the accelerator pedal (maybe 15 to 20 seconds after the cold engine started) the cam came off of it’s fast idle position and the engine nearly died.  This is where the second phase of fixing the problem comes in.  I need to adjust the choke housing in smaller increments to dial it in better.  If that doesn’t quite get me to having this issue resolved, I’ll then look into the testing of the choke coil as outlined in the link that Jon (carbking) posted.  It’s possible that the choke coil isn’t articulating in a wide enough range to be completely effective.

 

I think I’m well on my way to having the problem resolved.  Thank you all who contributed to my request for help, you’ve been awesome.  This was my first posting for help on this site and it was a great experience.  Thank you again!  Now I’m on to my next problem with horns that are stuck honking….new post coming soon!  LOL

 

Dan

 

[Jim Cannon]

No, Dan. Don't adjust anything. Don't change anything. The carb and engine are performing exactly as designed.

 

Once the engine starts, don't touch the gas pedal. Let it run on the fast idle to let the plugs get hot. Then when you touch the gas, it will fall off of the fast idle.

 

Your fast idle RPM may be set too high, but I doubt it. It is easy to check. With the engine at normal operating temperature (after driving around for 20 minutes or more) you put it in park, with the engine running, you set the fast idle cam up to the V that is stamped on the side of the cam, and in Park, you adjust the engine RPM to the fast idle RPM in the shop manual. I don't remember the exact number and I'm not at my shop today to look it up. There is a separate fast idle RPM screw that is different from the regular idle RPM adjust screw.

 

Starting an engine with a carb and an automatic choke is a bit of a learned experience. My daughter could never get my pickup truck to start cold. I would go out and it would start instantly when I turned the key. She insisted she was doing what I did, but obviously she was not. My wife wants a 1972 Ford Mustang. If I get her one, it will have EFI added because she has forgotten how to start a car with an automatic choke, after driving. cars with EFI for the past 30+ years.

 

Once you get the technique down, it will not be a problem.

 

 

[Greaseball]

48 minutes ago, Jim Cannon said:

No, Dan. Don't adjust anything. Don't change anything. The carb and engine are performing exactly as designed.

 

Once the engine starts, don't touch the gas pedal. Let it run on the fast idle to let the plugs get hot. Then when you touch the gas, it will fall off of the fast idle.

 

Your fast idle RPM may be set too high, but I doubt it. It is easy to check. With the engine at normal operating temperature (after driving around for 20 minutes or more) you put it in park, with the engine running, you set the fast idle cam up to the V that is stamped on the side of the cam, and in Park, you adjust the engine RPM to the fast idle RPM in the shop manual. I don't remember the exact number and I'm not at my shop today to look it up. There is a separate fast idle RPM screw that is different from the regular idle RPM adjust screw.

 

Starting an engine with a carb and an automatic choke is a bit of a learned experience. My daughter could never get my pickup truck to start cold. I would go out and it would start instantly when I turned the key. She insisted she was doing what I did, but obviously she was not. My wife wants a 1972 Ford Mustang. If I get her one, it will have EFI added because she has forgotten how to start a car with an automatic choke, after driving. cars with EFI for the past 30+ years.

 

Once you get the technique down, it will not be a problem.

 

 

Thank you for the additional information, Jim.  I’ve attached the shop specs for future reference to those who might refer to this thread I the future.  The fast-idle setting should be 600rpm.  I’ll verify mine the next time I have the opportunity to take it out on an extended drive.

 

Yup, starting these cars is nothing like and EFI system.  My other old car had a manual choke.  I guess I had forgotten some of the technique of cold-starting an automatic choke engine.

 

Dan

[1965rivgs]

3 hours ago, Jim Cannon said:

No, Dan. Don't adjust anything. Don't change anything. The carb and engine are performing exactly as designed.

 

Once the engine starts, don't touch the gas pedal. Let it run on the fast idle to let the plugs get hot. Then when you touch the gas, it will fall off of the fast idle.

 

Your fast idle RPM may be set too high, but I doubt it. It is easy to check. With the engine at normal operating temperature (after driving around for 20 minutes or more) you put it in park, with the engine running, you set the fast idle cam up to the V that is stamped on the side of the cam, and in Park, you adjust the engine RPM to the fast idle RPM in the shop manual. I don't remember the exact number and I'm not at my shop today to look it up. There is a separate fast idle RPM screw that is different from the regular idle RPM adjust screw.

 

Starting an engine with a carb and an automatic choke is a bit of a learned experience. My daughter could never get my pickup truck to start cold. I would go out and it would start instantly when I turned the key. She insisted she was doing what I did, but obviously she was not. My wife wants a 1972 Ford Mustang. If I get her one, it will have EFI added because she has forgotten how to start a car with an automatic choke, after driving. cars with EFI for the past 30+ years.

 

Once you get the technique down, it will not be a problem.

 

 

Jim,

  You may have missed it, or maybe I'm missing something, but Dan stated that if he adjusts the choke blade to fully close with a cold engine, then the choke blade will not fully open after the engine is hot... so he has adjusted the choke blade to be partially open with a cold engine. Obviously, a loose choke blade adjustment will not put the fast idle cam on the high step and results in the cold engine RPM to be too low. That was his original concern. He is chasing a choke issue

Tom

[Greaseball]

28 minutes ago, 1965rivgs said:

Jim,

  You may have missed it, or maybe I'm missing something, but Dan stated that if he adjusts the choke blade to fully close with a cold engine, then the choke blade will not fully open after the engine is hot... so he has adjusted the choke blade to be partially open with a cold engine. Obviously, a loose choke blade adjustment will not put the fast idle cam on the high step and results in the cold engine RPM to be too low. That was his original concern. He is chasing a choke issue

Tom

Thank you, Tom.  I think you’re correct, this will probably boil down to a choke issue.  I’ll probably find that the choke coil is not articulating enough to be fully effective.  However, Jim did help me solve a couple of issues that I was unaware of.  My cold starting procedure was causing some of my problems.  The other problem that I was unaware of was the proper rpm adjustment with the fast idle cam (this wouldn’t affect the initial problem that I described).  You’ve all chipped in to help me solve related issues.  I hope that I can make a few more checks and adjustments this coming weekend and get this issue resolved.

 

Thanks again!

Dan

[Jim Cannon]

5 hours ago, 1965rivgs said:

Jim,

  You may have missed it, or maybe I'm missing something, but Dan stated that if he adjusts the choke blade to fully close with a cold engine, then the choke blade will not fully open after the engine is hot... so he has adjusted the choke blade to be partially open with a cold engine. Obviously, a loose choke blade adjustment will not put the fast idle cam on the high step and results in the cold engine RPM to be too low. That was his original concern. He is chasing a choke issue

Tom

Tom-

It was a slight procedural error. Now that he is setting the automatic choke correctly, it IS closing all the way.

 

And it starts as it should.

 

And the choke pulling open is not taking it off of fast idle, like I thought it was. It was going off fast idle when he touched the gas pedal, so the fast idle cam falls away (as it is supposed to).  Dan did not understand that this was the correct behavior.

 

I think we are getting him all good.

[carbking]

One other possible issue that occurred to me after seeing the Buick specifications:

 

Here is an except from the Carter Service Manual:

 

"FAST IDLE LINKAGE ADJUSTMENT: With choke valve closed center index mark on cam should align with adjusting screw. To adjust, bend fast idle connector rod."

 

If this adjustment is not correct, then it is possible the  choke is correctly set, and operating correctly, but the cam is dropping to a step lower than it should.

 

Jon.

[1965rivgs]

11 minutes ago, carbking said:

One other possible issue that occurred to me after seeing the Buick specifications:

 

Here is an except from the Carter Service Manual:

 

"FAST IDLE LINKAGE ADJUSTMENT: With choke valve closed center index mark on cam should align with adjusting screw. To adjust, bend fast idle connector rod."

 

If this adjustment is not correct, then it is possible the  choke is correctly set, and operating correctly, but the cam is dropping to a step lower than it should.

 

Jon.

Hi Jon,

  That thought also came to mind for me but if you look at the pics which Dan posted after setting the choke, cold engine and before starting it looks like the fast idle cam would be in the proper position if the choke blade was completely closed...in the pic the choke blade is slightly open and the fast idle screw is barely off of the high step on the cam.

Tom

[carbking]

Tom - I thought as much, but it is an easy check. Definately worth checking.

 

Jon

[1965rivgs]

1 hour ago, carbking said:

Tom - I thought as much, but it is an easy check. Definately worth checking.

 

Jon

Hi Jon,

  I have a question for you which is relative to this discussion. Between owning quite a few Rivs and most being dual quad cars, serving other folks cars and rebuilding many, many I would guestimate I have probably worked on 100 to 200 AFB`s . In all the cases which involved choke system problems, which is certainly the majority of the cars/carbs, and disposing of choke springs which have been fouled by direct exhaust gas exposure, I have only found a handful of choke springs which no longer provide the necessary range of operation....maybe 5% ? And I most likely attributed the lack of range to be from installation of an improper choke assembly for the application. In my experience, the problem is almost always the hot air system, the particulars of which I mentioned above.

  What has been your experience?

Tom

Edited April 6, 2023 by 1965rivgs (see edit history)