Carburetor EGR port question

Does anyone have any idea how much vacuum should develop at an EGR port
on a carburetor with the engine revved to about 2000rpm?

I installed a brand spanking new Holley 2280 carburetor on my 87 Dodge
Dakota V6 engine and failed the NO part of the California smog test. The
HC and CO tests passed well below average. I came back home and
checked the action on the EGR valve. No movement on the visible piston
when the engine was revved.

The EGR valve checked out okay when tested. It opened with less than 10
inches of vacuum and stayed open indefinitely. The Coolant Vacuum Switch
Cold Closed (CVSCC) is operating correctly. The vacuum hoses involved
are all in good shape, no leaks.

I checked the vacuum at the EGR port on the brand spanking new
carburetor and only got about 1 or 2 inches of vacuum at about 2000 rpm.

Manifold vacuum is 19 inches at a 700rpm idle.

What gives?

"Simpson" wrote

> Does anyone have any idea how much vacuum should develop at an EGR port
> on a carburetor with the engine revved to about 2000rpm?
>
> I installed a brand spanking new Holley 2280 carburetor on my 87 Dodge
> Dakota V6 engine and failed the NO part of the California smog test. The
> HC and CO tests passed well below average. I came back home and
> checked the action on the EGR valve. No movement on the visible piston
> when the engine was revved.
>
> The EGR valve checked out okay when tested. It opened with less than 10
> inches of vacuum and stayed open indefinitely. The Coolant Vacuum Switch
> Cold Closed (CVSCC) is operating correctly. The vacuum hoses involved
> are all in good shape, no leaks.
>
> I checked the vacuum at the EGR port on the brand spanking new
> carburetor and only got about 1 or 2 inches of vacuum at about 2000 rpm.
>
> Manifold vacuum is 19 inches at a 700rpm idle.
>
> What gives?

You sure you're hooked up to the right port?

A few pages of 2280 info a quick search found.....
http://www.slantsix.org/articles/cho.../2280-info.jpg
http://www.slantsix.org/articles/cho...2280-info2.jpg
http://www.slantsix.org/articles/cho...2280-info3.jpg
http://www.slantsix.org/articles/cho...2280-info4.jpg

Simpson wrote:
> Does anyone have any idea how much vacuum should develop at an EGR port
> on a carburetor with the engine revved to about 2000rpm?
>
> I installed a brand spanking new Holley 2280 carburetor on my 87 Dodge
> Dakota V6 engine and failed the NO part of the California smog test. The
> HC and CO tests passed well below average. I came back home and checked
> the action on the EGR valve. No movement on the visible piston when the
> engine was revved.
>
> The EGR valve checked out okay when tested. It opened with less than 10
> inches of vacuum and stayed open indefinitely. The Coolant Vacuum Switch
> Cold Closed (CVSCC) is operating correctly. The vacuum hoses involved
> are all in good shape, no leaks.
>
> I checked the vacuum at the EGR port on the brand spanking new
> carburetor and only got about 1 or 2 inches of vacuum at about 2000 rpm.
>
> Manifold vacuum is 19 inches at a 700rpm idle.
>
> What gives?
>

I don't know that particular carb, but have seen that kind of failure
before. When I saw it it was a gasket in wrong or the wrong one in so a
notch in the base plate was covered when it was supposed to be open.

The other times I have seen the base plate in upside down. There are
notches in some that need to be on the carb side, not the manifold side
and if folks don't know this, the plate can be in wrong.

I would figure the port you are using was blocked or it would have one
or the other types of vacuum.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com

MasterBlaster wrote:
> "Simpson" wrote
>
>> Does anyone have any idea how much vacuum should develop at an EGR port
>> on a carburetor with the engine revved to about 2000rpm?
>>
>> I installed a brand spanking new Holley 2280 carburetor on my 87 Dodge
>> Dakota V6 engine and failed the NO part of the California smog test. The
>> HC and CO tests passed well below average. I came back home and
>> checked the action on the EGR valve. No movement on the visible piston
>> when the engine was revved.
>>
>> The EGR valve checked out okay when tested. It opened with less than 10
>> inches of vacuum and stayed open indefinitely. The Coolant Vacuum Switch
>> Cold Closed (CVSCC) is operating correctly. The vacuum hoses involved
>> are all in good shape, no leaks.
>>
>> I checked the vacuum at the EGR port on the brand spanking new
>> carburetor and only got about 1 or 2 inches of vacuum at about 2000 rpm.
>>
>> Manifold vacuum is 19 inches at a 700rpm idle.
>>
>> What gives?
>
> You sure you're hooked up to the right port?

I'm absolutely sure. I have a spare carb of the same design that is
disassembled. There are not many who are more familiar with the guts of
this carb than I am. I became knowledgeable about it through necessity.
The truck came stock with a Holley 6280, which is the electronic
feedback version of the 2280, the main difference being a fuel mixture
control solenoid. The solenoid is no longer available as a replacement
part and when it goes the only recourse is to locate a used one, which
in my experience is no better than the one that went south. So I decided
to replace the feedback 6280 with the non-feedback 2280. The problem
with the mixture control solenoid first surfaced about eight years ago.

After sleeping on it, I think the problem may be a leak in the purge
line to the charcoal canister. This purge line enters the carb through a
port in the exact same place as the EGR port, just above the closed
throttle plates. This would explain the low vacuum at the EGR port. The
lack of EGR function, plus the vacuum leak, which would cause a lean
condition, would combine to create a higher than normal temperature in
the combustion chamber resulting in the abnormally high NO readings. The
ceramic insulators on the plugs have that very white look caused by a
lean fuel mix. Soon as I finish my morning cup I'm going to warm up the
engine, disconnect the purge line, plug the purge line port in the carb
and test the EGR function again.


>
> A few pages of 2280 info a quick search found.....
> http://www.slantsix.org/articles/cho.../2280-info.jpg
> http://www.slantsix.org/articles/cho...2280-info2.jpg
> http://www.slantsix.org/articles/cho...2280-info3.jpg
> http://www.slantsix.org/articles/cho...2280-info4.jpg
>
>


--

Chuck Norris can fool all of the people all of the time and Chuck Norris
supports McCain.

McCain -- it rhymes with Hussein, Bahrain, cocaine, insane, wolfbane,
chest pain and chow mein.

Mike Romain wrote:
> Simpson wrote:
>> Does anyone have any idea how much vacuum should develop at an EGR port
>> on a carburetor with the engine revved to about 2000rpm?
>>
>> I installed a brand spanking new Holley 2280 carburetor on my 87 Dodge
>> Dakota V6 engine and failed the NO part of the California smog test. The
>> HC and CO tests passed well below average. I came back home and checked
>> the action on the EGR valve. No movement on the visible piston when the
>> engine was revved.
>>
>> The EGR valve checked out okay when tested. It opened with less than 10
>> inches of vacuum and stayed open indefinitely. The Coolant Vacuum Switch
>> Cold Closed (CVSCC) is operating correctly. The vacuum hoses involved
>> are all in good shape, no leaks.
>>
>> I checked the vacuum at the EGR port on the brand spanking new
>> carburetor and only got about 1 or 2 inches of vacuum at about 2000 rpm.
>>
>> Manifold vacuum is 19 inches at a 700rpm idle.
>>
>> What gives?
>>
>
> I don't know that particular carb, but have seen that kind of failure
> before. When I saw it it was a gasket in wrong or the wrong one in so a
> notch in the base plate was covered when it was supposed to be open.
>
> The other times I have seen the base plate in upside down. There are
> notches in some that need to be on the carb side, not the manifold side
> and if folks don't know this, the plate can be in wrong.

Could this 'base plate' be a one inch aluminum spacer with a single
manifold vacuum port? Or are you referring to the actual throttle
portion of the carb? That would be kind of hard to put in upside down.
In any case, as in my reply to MasterBlaster, I suspect a leak in the
canister purge line, which enters the carb just above the closed
throttle plates, same as the EGR port.

>
> I would figure the port you are using was blocked or it would have one
> or the other types of vacuum.

It's brand new, straight from the Holley factory, after sitting on some
shelf for about 20 years or more.

>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 'New' frame in the works for '08. Some Canadian Bush Trip and Build
> Photos: http://mikeromainjeeptrips.shutterfly.com

Simpson wrote:
> Mike Romain wrote:
>> Simpson wrote:
>>> Does anyone have any idea how much vacuum should develop at an EGR
>>> port on a carburetor with the engine revved to about 2000rpm?
>>>
>>> I installed a brand spanking new Holley 2280 carburetor on my 87
>>> Dodge Dakota V6 engine and failed the NO part of the California smog
>>> test. The HC and CO tests passed well below average. I came back
>>> home and checked the action on the EGR valve. No movement on the
>>> visible piston when the engine was revved.
>>>
>>> The EGR valve checked out okay when tested. It opened with less than
>>> 10 inches of vacuum and stayed open indefinitely. The Coolant Vacuum
>>> Switch Cold Closed (CVSCC) is operating correctly. The vacuum hoses
>>> involved are all in good shape, no leaks.
>>>
>>> I checked the vacuum at the EGR port on the brand spanking new
>>> carburetor and only got about 1 or 2 inches of vacuum at about 2000 rpm.
>>>
>>> Manifold vacuum is 19 inches at a 700rpm idle.
>>>
>>> What gives?
>>>
>>
>> I don't know that particular carb, but have seen that kind of failure
>> before. When I saw it it was a gasket in wrong or the wrong one in so
>> a notch in the base plate was covered when it was supposed to be open.
>>
>> The other times I have seen the base plate in upside down. There are
>> notches in some that need to be on the carb side, not the manifold
>> side and if folks don't know this, the plate can be in wrong.
>
> Could this 'base plate' be a one inch aluminum spacer with a single
> manifold vacuum port?

Yes it could. Sometimes the kits come with multiple types of base
gaskets with different holes or slots.

Or are you referring to the actual throttle
> portion of the carb? That would be kind of hard to put in upside down.
> In any case, as in my reply to MasterBlaster, I suspect a leak in the
> canister purge line, which enters the carb just above the closed
> throttle plates, same as the EGR port.

There is an easy test for that though I don't think it can be the
trouble unless you were measuring the vacuum downstream vs at the carb
nipple, just pinch the line closed.

>
>>
>> I would figure the port you are using was blocked or it would have one
>> or the other types of vacuum.
>
> It's brand new, straight from the Holley factory, after sitting on some
> shelf for about 20 years or more.
>
>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 'New' frame in the works for '08. Some Canadian Bush Trip and Build
>> Photos: http://mikeromainjeeptrips.shutterfly.com

"Simpson" > wrote in message
. net...
> MasterBlaster wrote:
>> "Simpson" wrote
>>
>>> Does anyone have any idea how much vacuum should develop at an EGR port
>>> on a carburetor with the engine revved to about 2000rpm?
>>>
>>> I installed a brand spanking new Holley 2280 carburetor on my 87 Dodge
>>> Dakota V6 engine and failed the NO part of the California smog test. The
>>> HC and CO tests passed well below average. I came back home and
>>> checked the action on the EGR valve. No movement on the visible piston
>>> when the engine was revved.
>>>
>>> The EGR valve checked out okay when tested. It opened with less than 10
>>> inches of vacuum and stayed open indefinitely. The Coolant Vacuum Switch
>>> Cold Closed (CVSCC) is operating correctly. The vacuum hoses involved
>>> are all in good shape, no leaks.
>>>
>>> I checked the vacuum at the EGR port on the brand spanking new
>>> carburetor and only got about 1 or 2 inches of vacuum at about 2000 rpm.
>>>
>>> Manifold vacuum is 19 inches at a 700rpm idle.
>>>
>>> What gives?
>>
>> You sure you're hooked up to the right port?
>
> I'm absolutely sure. I have a spare carb of the same design that is
> disassembled. There are not many who are more familiar with the guts of
> this carb than I am. I became knowledgeable about it through necessity.
> The truck came stock with a Holley 6280, which is the electronic feedback
> version of the 2280, the main difference being a fuel mixture control
> solenoid. The solenoid is no longer available as a replacement part and
> when it goes the only recourse is to locate a used one, which in my
> experience is no better than the one that went south. So I decided to
> replace the feedback 6280 with the non-feedback 2280. The problem with the
> mixture control solenoid first surfaced about eight years ago.
>
> After sleeping on it, I think the problem may be a leak in the purge line
> to the charcoal canister. This purge line enters the carb through a port
> in the exact same place as the EGR port, just above the closed throttle
> plates. This would explain the low vacuum at the EGR port. The lack of EGR
> function, plus the vacuum leak, which would cause a lean condition, would
> combine to create a higher than normal temperature in the combustion
> chamber resulting in the abnormally high NO readings. The ceramic
> insulators on the plugs have that very white look caused by a lean fuel
> mix. Soon as I finish my morning cup I'm going to warm up the engine,
> disconnect the purge line, plug the purge line port in the carb and test
> the EGR function again.
>
>
>>
>> A few pages of 2280 info a quick search found.....
>> http://www.slantsix.org/articles/cho.../2280-info.jpg
>> http://www.slantsix.org/articles/cho...2280-info2.jpg
>> http://www.slantsix.org/articles/cho...2280-info3.jpg
>> http://www.slantsix.org/articles/cho...2280-info4.jpg


Are you absolutely certain you haven't bypassed the vacuum amplifier? As I
recall, venturi vacuum only generates around two inches vacuum max and thus
needs the vacuum amplifier to operate the EGR valve. Again, if I recall
correctly, the amplifier will boost it to around 8 inches.

BigIronRam wrote:
> "Simpson" > wrote in message
> . net...
>> MasterBlaster wrote:
>>> "Simpson" wrote
>>>
>>>> Does anyone have any idea how much vacuum should develop at an EGR port
>>>> on a carburetor with the engine revved to about 2000rpm?
>>>>
>>>> I installed a brand spanking new Holley 2280 carburetor on my 87 Dodge
>>>> Dakota V6 engine and failed the NO part of the California smog test. The
>>>> HC and CO tests passed well below average. I came back home and
>>>> checked the action on the EGR valve. No movement on the visible piston
>>>> when the engine was revved.
>>>>
>>>> The EGR valve checked out okay when tested. It opened with less than 10
>>>> inches of vacuum and stayed open indefinitely. The Coolant Vacuum Switch
>>>> Cold Closed (CVSCC) is operating correctly. The vacuum hoses involved
>>>> are all in good shape, no leaks.
>>>>
>>>> I checked the vacuum at the EGR port on the brand spanking new
>>>> carburetor and only got about 1 or 2 inches of vacuum at about 2000 rpm.
>>>>
>>>> Manifold vacuum is 19 inches at a 700rpm idle.
>>>>
>>>> What gives?
>>> You sure you're hooked up to the right port?
>> I'm absolutely sure. I have a spare carb of the same design that is
>> disassembled. There are not many who are more familiar with the guts of
>> this carb than I am. I became knowledgeable about it through necessity.
>> The truck came stock with a Holley 6280, which is the electronic feedback
>> version of the 2280, the main difference being a fuel mixture control
>> solenoid. The solenoid is no longer available as a replacement part and
>> when it goes the only recourse is to locate a used one, which in my
>> experience is no better than the one that went south. So I decided to
>> replace the feedback 6280 with the non-feedback 2280. The problem with the
>> mixture control solenoid first surfaced about eight years ago.
>>
>> After sleeping on it, I think the problem may be a leak in the purge line
>> to the charcoal canister. This purge line enters the carb through a port
>> in the exact same place as the EGR port, just above the closed throttle
>> plates. This would explain the low vacuum at the EGR port. The lack of EGR
>> function, plus the vacuum leak, which would cause a lean condition, would
>> combine to create a higher than normal temperature in the combustion
>> chamber resulting in the abnormally high NO readings. The ceramic
>> insulators on the plugs have that very white look caused by a lean fuel
>> mix. Soon as I finish my morning cup I'm going to warm up the engine,
>> disconnect the purge line, plug the purge line port in the carb and test
>> the EGR function again.
>>
>>
>>> A few pages of 2280 info a quick search found.....
>>> http://www.slantsix.org/articles/cho.../2280-info.jpg
>>> http://www.slantsix.org/articles/cho...2280-info2.jpg
>>> http://www.slantsix.org/articles/cho...2280-info3.jpg
>>> http://www.slantsix.org/articles/cho...2280-info4.jpg
>
>
> Are you absolutely certain you haven't bypassed the vacuum amplifier? As I
> recall, venturi vacuum only generates around two inches vacuum max and thus
> needs the vacuum amplifier to operate the EGR valve. Again, if I recall
> correctly, the amplifier will boost it to around 8 inches.
>
>

I found the problem. There are two available ports that tap into the
carb just below the closed throttle plates. One develops vacuum and the
other doesn't. The one that doesn't develop vacuum is designated in the
installation sheet that came packed with this new carb as the 'EGR
vacuum line'. The one that does develop vacuum is designated as the
'spark vacuum line'.

On this version of the 2280, the designated EGR port is tied into
another port that is much higher up in the venturi via an external
vacuum hose with a tee fitting, and this tee fitting is then supposed to
connect to the EGR valve. However, the designated EGR port just doesn't
develop sufficient vacuum as measured directly with a vacuum meter. With
or without the connection to the higher port, the vacuum is the same,
less than two pounds at over 2000rpm. The EGR valve begins to open at
about 3 pounds and is fully opened at about 5 pounds.

The port designated as the spark vacuum line *does* develop the proper
vacuum to operate the EGR valve. The spark vacuum on this truck is
supplied directly from the manifold vacuum. I've got the factory manual
which shows this in the same vacuum hose routing diagram that is pasted
to the underside of the hood.

So whatever the problem is with the designated EGR port on this carb,
the designated spark vacuum port has the proper vacuum characteristics
to operate the EGR valve: no vacuum at idle, increasing vacuum as the
throttle is opened. If I connect the EGR valve directly to the
designated spark vacuum port the EGR valve responds to the throttle as
it is supposed to. However, if I connect the designated spark vacuum
port to the higher port via the tee fitting, the response is sluggish to
non-existent. Therefore, in the interest of proper EGR operation and
passing the smog test, I am chucking what's in the instructions and
going with my gut on this one.

Mike Romain wrote:
> Simpson wrote:
>> Mike Romain wrote:
>>> Simpson wrote:
>>>> Does anyone have any idea how much vacuum should develop at an EGR
>>>> port on a carburetor with the engine revved to about 2000rpm?
>>>>
>>>> I installed a brand spanking new Holley 2280 carburetor on my 87
>>>> Dodge Dakota V6 engine and failed the NO part of the California smog
>>>> test. The HC and CO tests passed well below average. I came back
>>>> home and checked the action on the EGR valve. No movement on the
>>>> visible piston when the engine was revved.
>>>>
>>>> The EGR valve checked out okay when tested. It opened with less than
>>>> 10 inches of vacuum and stayed open indefinitely. The Coolant Vacuum
>>>> Switch Cold Closed (CVSCC) is operating correctly. The vacuum hoses
>>>> involved are all in good shape, no leaks.
>>>>
>>>> I checked the vacuum at the EGR port on the brand spanking new
>>>> carburetor and only got about 1 or 2 inches of vacuum at about 2000 rpm.
>>>>
>>>> Manifold vacuum is 19 inches at a 700rpm idle.
>>>>
>>>> What gives?
>>>>
>>> I don't know that particular carb, but have seen that kind of failure
>>> before. When I saw it it was a gasket in wrong or the wrong one in so
>>> a notch in the base plate was covered when it was supposed to be open.
>>>
>>> The other times I have seen the base plate in upside down. There are
>>> notches in some that need to be on the carb side, not the manifold
>>> side and if folks don't know this, the plate can be in wrong.
>> Could this 'base plate' be a one inch aluminum spacer with a single
>> manifold vacuum port?
>
> Yes it could. Sometimes the kits come with multiple types of base
> gaskets with different holes or slots.
>
> Or are you referring to the actual throttle
>> portion of the carb? That would be kind of hard to put in upside down.
>> In any case, as in my reply to MasterBlaster, I suspect a leak in the
>> canister purge line, which enters the carb just above the closed
>> throttle plates, same as the EGR port.
>
> There is an easy test for that though I don't think it can be the
> trouble unless you were measuring the vacuum downstream vs at the carb
> nipple, just pinch the line closed.
>
>>> I would figure the port you are using was blocked or it would have one
>>> or the other types of vacuum.
>> It's brand new, straight from the Holley factory, after sitting on some
>> shelf for about 20 years or more.
>>
>>> Mike
>>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>>> 'New' frame in the works for '08. Some Canadian Bush Trip and Build
>>> Photos: http://mikeromainjeeptrips.shutterfly.com


Mike, I solved the problem. See my detailed reply to BigIronRam in this
thread.

Thanks, for the help. You were on the right track as far as the port
probably being blocked goes. Whatever the reason, it just wasn't
developing EGR vacuum characteristics and would not even make it to 2
pounds at 2,000rpm.

In article > ,
Simpson > wrote:

> This would explain the low vacuum at the EGR port. The
> lack of EGR function, plus the vacuum leak, which would cause a lean
> condition, would combine to create a higher than normal temperature in
> the combustion chamber resulting in the abnormally high NO readings.

Not to nit pick but lean air fuel mixtures don't burn hotter.
They burn slower which causes associated component temperatures
to rise. Lean doesn't cause higher NOx, the extra O2 in the
exhaust from a lean mixture makes the reduction bed of a 3 way
catalyst less efficient resulting in higher NOx at the tail pipe.