Home » Public Forums » GMCnet » Air Fuel Ratio
| Air Fuel Ratio [message #110509] |
Sat, 01 January 2011 13:25  |
Oldngray
Messages: 544
Registered: August 2009
Location: Punta Gorda Florida
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This is the third thread I stated as a result of yesterdays excursion.
When I first installed my Innovate wide band system I mentioned here that the readings were very good and some here suggested that I leave the Carb alone which I did.
Yesterday when I left the house I noticed the readings on hard Acceleration were 16 - 18, then in Cruise at about 50-55 the readings were above 15 nearer 16, when I coasted, at first the gauge would read 10-12 then go all the way to 20. The Engine backfired through the Carb once when I floored it to see if the Secondaries would open. It has never done that before. Have not heard any pinging, and other than what I mentioned here the engine runs really smooth.
While sitting in the Feed Store Parking lot yesterday, I removed the nbr 7 Plug while checking for spark. The first thing I noticed was how white the ground and element was.
Any thoughts would be appreciated.
Richard MacDonald
Punta Gorda, Florida
Sold our TZE April 2015
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| Re: [GMCnet] Air Fuel Ratio [message #110512 is a reply to message #110509] |
Sat, 01 January 2011 14:10  |
Douglas Norton
Messages: 191
Registered: April 2008
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An "any thought". I am probably like most responders, I know little, offer lots of little too. What I do know is that white plugs often get that way running lean, very lean. That also can mean at the same time they are running very hot (can also be caused by spark being too advanced). I have always feared running lean because I try to do that and worry about burning a valve or melting a piston (I have done both in the distant past). So I installed a pyrometer in my exhaust pipe near the manifold. [brown plugs are ok, black and sooty are too rich]. This is just a start of an analysis, someone who knows more than me can suggest vacuum leak, plugged fuel filter, etc. as the cause.
--- On Sat, 1/1/11, Richard MacDonald <rm1936@gmail.com> wrote:
From: Richard MacDonald <rm1936@gmail.com>
Subject: [GMCnet] Air Fuel Ratio
To: gmclist@temp.gmcnet.org
Date: Saturday, January 1, 2011, 11:25 AM
This is the third thread I stated as a result of yesterdays excursion.
When I first installed my Innovate wide band system I mentioned here that the readings were very good and some here suggested that I leave the Carb alone which I did.
Yesterday when I left the house I noticed the readings on hard Acceleration were 16 - 18, then in Cruise at about 50-55 the readings were above 15 nearer 16, when I coasted, at first the gauge would read 10-12 then go all the way to 20. The Engine backfired through the Carb once when I floored it to see if the Secondaries would open. It has never done that before. Have not heard any pinging, and other than what I mentioned here the engine runs really smooth.
While sitting in the Feed Store Parking lot yesterday, I removed the nbr 7 Plug while checking for spark. The first thing I noticed was how white the ground and element was.
Any thoughts would be appreciated.
--
Richard MacDonald
Punta Gorda, Florida
76 Edgemonte TZE 266V102313
Celebrating 50 years with my Wife and best friend Nancy
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| Re: [GMCnet] Air Fuel Ratio [message #110517 is a reply to message #110512] |
Sat, 01 January 2011 17:23 |
Hoosier
Messages: 20
Registered: May 2008
Location: Roxboro, NC
Karma: 0
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Richard
My first thoughts are how many miles on the plug and how does it compare with another plug? My next step would be to check compression on that cylinder and depending, compare with others.
Keep us posted!
RayBechtel
Roxboro, NC
1976 Royale
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| Re: Air Fuel Ratio [message #110519 is a reply to message #110509] |
Sat, 01 January 2011 17:26 |
Craig Lechowicz
Messages: 541
Registered: October 2006
Location: Waterford, MI
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Richard,
Lots of people will know more about this than I do, but 16-18 under hard acceleration is way too lean. That 12 or so from coast would be good here. The white plug and the backfiring also support being too lean. Probably the 1st question is, is the carb getting enough fuel? (air leaks in lines, bad fuel pump, clogged filters, etc.). If there is enough fuel in the carb, then, is there something keeping the secondaries from flowing proper amount of fuel, like broken parts not raising the metering rods properly with air valve opening, wrong jets, dirt in the carb, etc. Also, is the power enrichment valve working properly?
One thing that recently happened to my friend Tim, is there are brass tubes that press into the carb top and allow it to pull fuel out of the bowl and into the jet system. One of those tubes came loose, and hence no fuel flow to one of the secondary jets. I can't take credit for that one, Steve at Cinnabar had us check that out. His backfired pretty severely at anything more than about 1/2 throttle though.
The change in ratio on coast might actually be "normal" I don't have any wideband experience (or at least not in 30 years or so). But, when the throttle 1st closes and intake vacuum goes up, puddled fuel in the manifold boils out, and sends the mixture rich. Once that is gone, it goes back lean as the engine is pulling more air through closed throttle plates on coast than the idle metering circuits are set up for.
Craig Lechowicz
'77 Kingsley, Waterford, MI
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| Re: [GMCnet] Air Fuel Ratio [message #110522 is a reply to message #110509] |
Sat, 01 January 2011 17:52 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Richard,
I agree the readings you getting on the wide band are lean, the backfiring
and white plug corroborate that.
I would suggest:
1) pull all eight plugs, check them for color - leave them out
2) pull t
As noted already I would start by pulling the carb filter as that's
relatively easy to do. If it's clean then it may be a good idea to
Regards,
Rob M.
USAussie - Downunder
AUS '75 Avion-The Blue StreakTZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Richard MacDonald
Sent: Sunday, January 02, 2011 6:26 AM
To: gmclist@temp.gmcnet.org
Subject: [GMCnet] Air Fuel Ratio
This is the third thread I stated as a result of yesterdays excursion.
When I first installed my Innovate wide band system I mentioned here that
the readings were very good and some here suggested that I leave the Carb
alone which I did.
Yesterday when I left the house I noticed the readings on hard Acceleration
were 16 - 18, then in Cruise at about 50-55 the readings were above 15
nearer 16, when I coasted, at first the gauge would read 10-12 then go all
the way to 20. The Engine backfired through the Carb once when I floored it
to see if the Secondaries would open. It has never done that before. Have
not heard any pinging, and other than what I mentioned here the engine runs
really smooth.
While sitting in the Feed Store Parking lot yesterday, I removed the nbr 7
Plug while checking for spark. The first thing I noticed was how white the
ground and element was.
Any thoughts would be appreciated.
--
Richard MacDonald
Punta Gorda, Florida
76 Edgemonte TZE 266V102313
Celebrating 50 years with my Wife and best friend Nancy
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: Air Fuel Ratio [message #110523 is a reply to message #110509] |
Sat, 01 January 2011 18:05 |
kingd
Messages: 592
Registered: June 2004
Karma: 2
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Senior Member |
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What I think I know. Lean under hard acceleration or pulling up a long hard grade is BAD !!! Can result in detonation which can break rings, eat sides off top of pistons and other bad things.
My brother-in-law owns and runs a nine bay repair shop and is himself a licenced mechanic in Ontario. He tells me that when they started changing plugs on engines after 10% Ethanol fuel started being widely used in Ontario, they were dismayed at the "whiteness" of the removed spark plugs from engines with 50K miles on the plugs. Either the Ethanol makes the mixture lean and causes white plugs but no engine damage or the mixture is OK and the Ethanol just causes white plugs. I was surprised at how white the plugs out of our 2004 Dodge 2.0SX(Neon) were at 100,000 KM(60,000Miles).
If I saw higher than 14.7 air/fuel(like 16 or higher) at something other than cruise, I'd be worried.
Others feel free to comment.
DAVE KING
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada
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| Re: [GMCnet] Air Fuel Ratio [message #110524 is a reply to message #110522] |
Sat, 01 January 2011 18:17 |
Oldngray
Messages: 544
Registered: August 2009
Location: Punta Gorda Florida
Karma: 0
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Senior Member |
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Rob, only received part of your reply. Please resend or edit.
Thanks
Richard MacDonald
Punta Gorda, Florida
Sold our TZE April 2015
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| Re: [GMCnet] Air Fuel Ratio [message #110525 is a reply to message #110522] |
Sat, 01 January 2011 18:19 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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OOPS!
Don't know what happened below!
One second the message was there then it was gone!
This notebook is doing some strange things!
I'll try again!
***************************************************************
Richard,
I agree the readings you getting on the wide band are lean, the backfiring
and the white plug corroborates that.
I would suggest:
1) Crank/start the engine for a minute so the fuel pump will fill the float
chamber.
2) Pull the carb fuel filter; if it is contaminated change it and go for a
test run.
3) If not contaminated remove the top of the carb and see what the fuel
level is in the float bowl and if there's anything else wrong (corrosion)
4) If the fuel level is correct (don't know what that is) put the carb top
back on
5) Test the fuel pump as per the Maintenance Manual
If all the steps above are OK I suspect you may have problems upstream of
the mechanical fuel pump.
Regards,
Rob M.
USAussie - Downunder
AUS '75 Avion-The Blue StreakTZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Rob Mueller
Sent: Sunday, January 02, 2011 10:53 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Air Fuel Ratio
Richard,
I agree the readings you getting on the wide band are lean, the backfiring
and white plug corroborate that.
I would suggest:
1) pull all eight plugs, check them for color - leave them out
2) pull t
As noted already I would start by pulling the carb filter as that's
relatively easy to do. If it's clean then it may be a good idea to
Regards,
Rob M.
USAussie - Downunder
AUS '75 Avion-The Blue StreakTZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Richard MacDonald
Sent: Sunday, January 02, 2011 6:26 AM
To: gmclist@temp.gmcnet.org
Subject: [GMCnet] Air Fuel Ratio
This is the third thread I stated as a result of yesterdays excursion.
When I first installed my Innovate wide band system I mentioned here that
the readings were very good and some here suggested that I leave the Carb
alone which I did.
Yesterday when I left the house I noticed the readings on hard Acceleration
were 16 - 18, then in Cruise at about 50-55 the readings were above 15
nearer 16, when I coasted, at first the gauge would read 10-12 then go all
the way to 20. The Engine backfired through the Carb once when I floored it
to see if the Secondaries would open. It has never done that before. Have
not heard any pinging, and other than what I mentioned here the engine runs
really smooth.
While sitting in the Feed Store Parking lot yesterday, I removed the nbr 7
Plug while checking for spark. The first thing I noticed was how white the
ground and element was.
Any thoughts would be appreciated.
--
Richard MacDonald
Punta Gorda, Florida
76 Edgemonte TZE 266V102313
Celebrating 50 years with my Wife and best friend Nancy
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: Air Fuel Ratio [message #110526 is a reply to message #110509] |
Sat, 01 January 2011 18:28 |
Oldngray
Messages: 544
Registered: August 2009
Location: Punta Gorda Florida
Karma: 0
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Senior Member |
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The Engine and the plugs have about 6500 miles on them. My Vacuum reads near 20 at idle, 10 while accelerating and 15-18 in cruise.
The Carb filter is clean, lots of fuel, at least when I depress the pedal I can see and hear fuel, when I crack the fuel line I get lots of fuel under pressure. I also have a Electric pump but do not use it unless needed.
I just ran the engine while parked. Brought it up to 185 degrees and it idled at 14-14.5. Vacuum was right at 20, acceleration was smooth, at first a/f went down to 12 then leveled out at 13.5-14.
Am going to drive it again on Monday to see if these numbers continue.
BTW, the Coil temp was cool to touch, no heat at all.
Richard MacDonald
Punta Gorda, Florida
Sold our TZE April 2015
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