Air Fuel Ratio gauge and now have question?

[Gary Lewis]

You have either a carb problem or an AFR gauge problem.  There is no way that you should have that lean of a mix at WOT.  It really must be down around 11 - 12 to get good power.  And I can't believe that the vacuum advance hose could suck that much air to lean it that much.  However, it is something to check.

[ArdWrknTrk]

If you're using 'timed' vacuum the "leak".is above the throttle plate anyhow.

You can cap the hose with a piece of tape.
It's vacuum after all.

Yes. Your mains must be WAY too small if it just gets leaner and leaner as you increase speed (throttle opening)
And it sounds like you have no accelerator pump shot either....
The ratio should go rich when you step on it.

Sometimes you just have to accept that it is what it is.
Ford did it's damnedest to squeeze every mpg it could. And now you don't have any EGR to help under 'cruise'.

I wouldn't be surprised at all if you have a VERY hard time getting rid of the 'nibble' when on the highway and you start to tip into the throttle.

Remember, gasahol is going to return fewer mpg no matter what.
Maybe 10-15% less.....
The oil companies LOVE this.!
It just doesn't have the energy -gallon for gallon- that straight hydrocarbons do.

[FuzzFace2]

Well I backed the vacuum can way off and hooked the hose back up and got a hose plug just in case I had to disconnect it again.

Took truck to work again this morning.
No pinging but kind of lacking power on the high way. If I go WOT it doesn't really do much that you can feel.
The speed will get faster and the AFR is off the gage lean.

Also the AFR was between 14 & 15 and as said all I did was hook up the vacuum advance that I don't think is working because of how I have it adjusted.

After seeing this and how the AFR reacts I was thinking like Gary,  bad carb!
Other wise it works great.
Dave ----

[ArdWrknTrk]

Jonathan's knockoff YFA was $75, I think....

[Gary Lewis]

How 'bout $59.99 & free shipping: New/Repro YF Carb For The 300 Six.  But the price has gone up in the listing to a whopping $64.99.  

[FuzzFace2]

I think I can sneak $65+ by the banker LOL
I think Cory picked up a carb for his project 4x4 was going to check with him on where he got it.
Dave  ----

[ArdWrknTrk]

Thanks Gary.
Pretty sure I was thinking of this post by David.

Can't say I've ever had to purchase any YF replacement carb.

[Gary Lewis]

Not sure what David was referring to, but he'd probably seen several on ebay for sale.

Last I heard the carb Jonathan bought was going strong.

[FuzzFace2]

Carb has been ordered.
After knowing what shape it was in when I got the truck. Was lucky the carb worked as it had missing and wrong screws in it. Some parts were installed wrong or missing Thought it was fixed when I rebuilt it?

Then with the crazy AFR readings felt it best  to replace.
Dave. ----

[ArdWrknTrk]

I hope this works out for you, and you're able to tune out your knock.  

[Gary Lewis]

Yes, I hope it solves lots of problems.  MPG, AFR, etc.  

[ArdWrknTrk]

I was re-reading Dave's post here, and realized he has two fallacies.

A) Alcohol brings it's own oxygen.
Where Gary says stochiometric mixture for 10% is 14.04:1, that's chemistry. (by mass)
While what counts in an engine is heat and generated combustion byproduct (pushing on the piston.
Alcohol burns very cool.
Cool enough to light your hands on fire just for show.
You wouldn't do that with gasoline.  

The Oxygen sensor is reading residual oxygen in the exhaust.
The AFR is inferring a ratio based on combustion byproduct.
But this isn't accurate when you're getting a bunch of oxygen from your fuel, and not just the ~20% of our atmosphere.
While it is reflecting how complete the combustion is, it's not giving an accurate idea of how much fuel you're flowing.
.

[Gary Lewis]

That's a very good point, Jim.  I'd not thought about that.

So I Googled it and found this, which seems to make sense and fits with what you are saying.  Basically it says to monitor lambda instead of AFR since the meter is assuming gasoline because it doesn't know what is in the tank.

So if Dave is running 10% ethanol his reading of 17 is actually ~16.24.  (14.04/14.7*17 = 16.24)

[ArdWrknTrk]

Which gives us a more accurate picture of fuel consumption, but not power generated.

Whether you want to measure in joules, BTU, Calories, watts or whatever.

[FuzzFace2]

New carb showed up yesterday bit did not open the box yet. No time before bed time.

I am thinking of digging into the old carb a little for 2 reasons.
Just to see if the avcel pump tube is still in place and working. Same with the high speed rid & jet.

And last time I had the carb top off to adjust the rod & jet I found the bowl floor covered is rust. I would need to address this issue before the new carb goes on.

Got to work part of Saturday so see if I have time over the weekend.
Dave  ----

[ArdWrknTrk]

Are your tanks rusty Dave?

It certainly can't hurt to have an easily changed filter up near the carb.
And thanks for the reminder. I found that my filter coupler was looking a little frayed yesterday.

[FuzzFace2]

ArdWrknTrk wrote

Are your tanks rusty Dave?

It certainly can't hurt to have an easily changed filter up near the carb.
And thanks for the reminder. I found that my filter coupler was looking a little frayed yesterday.

When installed they looked good from what I could see but with rust in the carb it has to be coming from some where?

I pulled the carb off motor and pulled it apart for a look-see.
It did have a little rust but not really bad.
The accel pump did not work when on the motor, 1 reason it was pulled other the rust.
On the bench it worked?
I also pulled out my Motor's book for professional that gave a better write up of the YF carb than the rebuild kit sheet.

The carb is missing a spring for the rod / jet but seams to be ok with out it. Made adjustments as per the book and carb went back on.
I did install a see through filter and will keep an eye on it when running off each tank to see what one has the rust issue.

I also adjusted the vacuum can on the dist. So it pulls in at a higher vacuum. I also bumped the timing up to 16 BTDC, total is about 48 BTDC now.

Took truck to work this morning and it ran great. My gage was 14.5 to 15.5 but most of the time 14.7 to 15.3.
WOT I did not see it drop leaner than 16.7.
So the old carb is working again and will run it till I am sure no rust will hurt the new carb.
Dave  ----

[ArdWrknTrk]

Wow, 16 seems a lot of initial timing.
If you had spark knock before I don't understand how that would help.
But, it certainly has to help with power.

Do you find it cranks slow or kicks back when starting?
Is the timing retard while cranking functional on your truck?

[FuzzFace2]

ArdWrknTrk wrote

Wow, 16 seems a lot of initial timing.
If you had spark knock before I don't understand how that would help.
But, it certainly has to help with power.

Do you find it cranks slow or kicks back when starting?
Is the timing retard while cranking functional on your truck?

Normally I would say the same thing at 16* BTDC.
When I had it set to 10*-12* it would crank a long time before starting.
Now some of that could be the accel pump may have stopped work at the same time I don't know?

I get no kick back when starting, 1 pump and it lights off with a tap of the key. Real close to what my 02 Durango EFI 5.9 dose on starting.

I don't know if the timing retard works or not?
How would one go about checking if it did or not?
Guessing check timing at idle and say its 16* BTDC.
Then with a helper have them start the motor and when checking with the light see if it starts at say 8* BTDC?
Oh I also did not have any pinging and that was a vary good thing!

With the run to work yesterday morning (1am) it was about 45*f out and the AFR was high 14's to low 15's at 65 - 70 MPH and was happy with that readings and the truck ran great.

On the way home (4pm) it was about 70*f out and the AFR was high 13's to low/mid 14's at 45 - 55 MPH (back roads) wish the readings were like on the morning run but the truck still ran great.

Right now I am keeping an eye on the see through filter to see what tank may have rust issues before doing much more with tuning for MPG and a carb swap.
Dave ----

oh wait to reading are off because of the 10% gas I run so it is running richer right?
Darn it

[Gary Lewis]

Yes, running ethanol means your true AFR is richer than what you are seeing on the gauge.  But you aren't too far off now.

On the retard, you can test it by starting the engine and then pulling the R/LB wire from the starter relay/solenoid and turning the key to Start.  As seen below that will send 12v to the ignition module telling it to retard.  If you have a timing light on it you should see the timing retard, or at least hear the RPM drop.