Minor stumbling issue

[73F100Shortbed]

Vince would this happen in the matter of 2 years or so? I did replace the whole distributor around 2 years ago.

 

[blacksnapon]

Vince would this happen in the matter of 2 years or so? I did replace the whole distributor around 2 years ago.

Its entirely possible. A lot depends on the skill of the remanufacturer, and what they actually did to reman it. Pull the cap and manually move the plate to see if it will move in an unnatural way or sieze doing it.

 

[73F100Shortbed]

Ok thanks I will check that.

 

[73F100Shortbed]

so I checked more stuff today. I did find out the timing was off a few degrees. I have no idea why it moved. I re-adjusted it and it appears to rev up better than before. I even set off a car alarm nearby when revving lol. If you hold it around 1500rpms it has a slight stumble. I ordered a kit from NAPA and according to the numbers I was able to read it looks like I have a 1972 Motorcraft 2150 carb. Tonight when it gets a little cooler out I'm going to take it on a drive and see if moving the timing improved anything. I also checked the vacuum advance at the distributor and it advances the timing just fine. The carb pulls vacuum when you rev it up according to my vacuum gauge. If rebuilding the carb. doesn't fix my problem I'll be at a total loss since everything else seems to check out.

 

[LEB Ben]

Well I hope for your sake it is the carb. Dunno what else it could be, maybe a valve issue????? But didn't you just throw that engine in?

 

[73F100Shortbed]

Yeah it doesn't even have 10000 miles on it. Even for being an AZ engine I'm pretty sure it's not a valve. Hopefully the carb. just needs some attention. Looks like it's never been touched before. I'm a little annoyed that the timing moved, but it was only like a degree or two so I guess it is possible to happen.

 

[Alvin in AZ]

Your symptoms reminds me of a Pinto I had once that'd get black
rubber bits in the carburetor's fuel bowl. I never did figure out
-where- that dangged stuff was coming from but a new in-line
filter and a new hose from the filter to the carburetor stopped it,
if I remember it right.

Also had those symptoms one time on my '75 after I got water in
the fuel bowl and it formed clear-jelly-like pieces the size of peas
or beans. That drove me crazy for about two weeks. Got a cool
new hotter Standard Motor Products coil with threaded terminals
out of that deal tho. LOL So it wasn't a complete loss.

Funny thing was I didn't see it looking into the fuel bowl the first
time or two not until I took the float out and swished the fuel
around with a screwdriver did I see something that wasn't quite
right. Took it off and dumped it out on a rag and there they were.
Not quite as clear as the stuff in eyeballs, but similar, I remember
thinking how it reminded me of that stuff.

Got water in the fuel bowl lately? I'd washed my engine and when
pulling the plastic bag off the carburetor, water ran off it right into
the fuel bowl vent! I saw it happen but it was this time of year and
fiNgured it was so hot and dry here, it'd evaporate or get sucked
into the engine or something. Oops.

What about a vacuum leak?
Could a vacuum leak cause those symptoms too?
Course it'd have to be intermittent somehow. :/

--------------------------

Back to the '72 Pinto:
The gear shift lever had the plastic part that broke and I fixed
it without buying a new part. LOL Just ran across something
the other day about that problem being very common and how
Ford ran out of the part etc. Had forgot all about that problem.

Alvin in AZ

 

[73F100Shortbed]

My experience with vacuum leaks is that you notice them more at idle, fluctuation in idle ,etc. The engine also has steady vacuum. Of course anything is possible. That being said my engine has two vacuum lines. PCV (basically a calculated vacuum leak. The valve is new and you can hear it rattling so it works) hose which was just replaced and the line for the distributor which I verified was good today. I don't think the intake is leaking to cause a vacuum leak but I could spray it down just to see. No water in carb. that I know of. There could be dirt in there. I did just change the filters. I'm going to get my kit later or tomorrow and take the carb. apart and see if there is anything in there. I figure it can't hurt given a kit is under $20. It's not like I have to invest a ton of money to keep the truck going. And I figure I owe it to the truck for getting me safely out of the ghetto the other night even running bad.

 

[73F100Shortbed]

I forgot to add that the points plate moved fine. Checked that today like Vince suggested.

I got the carb. kit and will rebuild it tomorrow. I took it on the highway after picking up the kit. The truck ran a lot better after moving the timing. Had plenty of power and accelerate great. Only issue was the minor stumbling it has had for 4 years. Not a big deal, but I will just go ahead with the carb. rebuild.

 

[73F100Shortbed]

Rebuilt the carb. It was relatively clean inside. It still has an issue, but I didn't test drive it yet. I think I still have to adjust the mixture screws a bit but it isn't looking hopeful that this will solve it.

 

[73F100Shortbed]

So driving it yielded better results, but not quite there yet. The kit came with carb. base gaskets. One for the pcv spacer to the intake and carb. to spacer. They are of the same thickness. My old gasket between carb. and spacer is a lot thicker....like the thickness of at least 2 cds. Is it possible that this is causing the carb. to be too high from the intake? I'm just reaching for ideas here. It is almost like it is a second spacer. But before swapping gaskets I figured I would see if it is worth the time to pull the carb. off again. I also will adjust the mixture screws more with a vacuum gauge tomorrow. The only difficult part of this is I removed the vacuum tree out of the intake because nothing was hooked up to it and replaced it with a plug. I hope I have something to thread into the intake and can hook up my gauge.

 

[Alvin in AZ]

Only issue was the minor stumbling it has had for 4 years.

4 years?

"...that's the sort of information a guy needs to know" -Jeff Foxworthy

Even with -no- accelerator pump a carburetor "should " be able to be
used and show -no- stumble -if- you take it slow and easy. No kidding.

Those things can mask a lot of faults but are good to have working right
-if- some sort of acceleration is planned.

Reaming out the low speed jets is the cure for a stumbling 2100/2150.
But first, what's the fuel level?

Measured it from the machined edge of the opened-up carburetor to the
top of the fuel.

About that back firing... was it into the carburetor or out the exhaust? :/

----------------------------

http://www.panix.com/~alvinj/file12/booster.jpg
The skinny tips (poking out of the fat emulsion-tubes) are pinched down
and serve as the low speed circuit's mixture limiting jets. First, know what
you've got so changes can be "measured" in a SWAG sort or way. LOL

Alvin in AZ
ps-
Are the little holes in your emulsion tubes all up around the top or down
along the sides? Up around the top (like the loose one) is the "good kind"!
http://www.panix.com/~alvinj/file12/booster.jpg

 

[73F100Shortbed]

The emulsion tubes have holes all the way down.

I didn't open the carb. with fuel in it. I just measured the float dry as per the instructions. I made sure all of the openings inside were clear. The jets were clear as well.

 

[Alvin in AZ]

The emulsion tubes have holes all the way down.
I didn't open the carb. with fuel in it. I just measured the float dry as
per the instructions. I made sure all of the openings inside were clear.
The jets were clear as well.

Since it's been stumbling/lean for 4 years trash in the carburetor
ain't it. LOL

IME, the dry measurement method ain't worth anything. :/

-------------------------

A local dyno-shop told me I had "figured out their secret to making
the Autolite/Motorcraft carburetors work real good! " No kidding.

But since they basically are-not-replaceable :/ (they get too loose)
what-they-do is solder up the holes they don't want and drill new
holes where they do want 'em.

But hold on!

I'm not sure if I haven't got it backwards and you got the good kind!. LOL

->let me look into it and get back with the best place for the holes<-

"the older I get, the dumber I get :/" -Alvin

Dumber than you thought in AZ

 

[73F100Shortbed]

There is no trash in the carb. It was completely taken apart today and only found a few specs of dirt. I wouldn't really say it is running lean either. I can floor it from a dead stop. No stumbling. If I hold at a certain rpm it'll stumble occasionally. It's not the worst thing in the world but I thought I might as well look into it after all this time lol. I'm going to mess with it some more tomorrow. Any advice about the gaskets issue I posted above?

 

[Alvin in AZ]

I wouldn't really say it is running lean either.

You wouldn't, but I would. (but it's just a guess so far)

Has it made a habit over the years of "backfiring" out the tailpipe or
out the carburetor?

That'll tell us if it was "way too lean".
way too lean = backfires through the carburetor
way too rich = backfires out the tailpipe

------------------------

Coming down off a steep mountain last week and having it in gear
and carburetor throttle plates in the idle position for several minutes
at a stretch and it didn't backfire once the whole time tells me I don't
have my idle set too rich.

I can floor it from a dead stop. No stumbling.
If I hold at a certain rpm it'll stumble occasionally.
It's not the worst thing in the world but I thought
I might as well look into it after all this time lol.
I'm going to mess with it some more tomorrow.

From way over here across the the internet, sounds like it needs
the mixture set. While in the "stumbling mode" quickly move the
"gas" pedal down just a little bit and then hold it there.

How did it act?

Do the same but let off it -just a little bit- real quick like and again,
hold it there in the new spot.

How'd it act that direction?

If it's running lean and you add "air" by opening the throttle just a
little quickly it'll stumble right quick because the gasoline takes time
to increase its flow. ...air is what you add -real quick-.

If it's running rich, it'll respond quick-as-your-foot with more power
"when you add air" then, back off when the fuel again goes back to
"too rich" by catching up to its "normally too rich conditions".

Going the other way, by restricting the air flow right quick, does the
opposite but remember the air-change-responds-quicker than the fuel
can respond. So the fuel kinda flows at a certain rate despite what
your foot and throttle pates are saying they want/need, if you do it
quick enough.

Alvin in AZ
ps- The gasket situation is tough to diagnose without being there.
You are there, look at the situation with each gasket carefully and
put it together. No, it can't be "too high", the higher spacing won't
do anything but make it run -better-.
pps-
Oops see you mentioned the 4 years in the first post. I lost track,
that's why I was into reaming the low speed circuit jets so early.
Being a 2150 could use a metering rod change maybe?
Is the carburetor the original with that engine?
ppps-
You know, when they rebuild those things like for AutoZone, they
take 'em all apart then slap 'em back together and mix the dangged
parts up! :/ Been there and seen that with distributors and other
stuff, so no reason not to with carburetors too, I'd guess.

 

[73F100Shortbed]

The carb. was on the first engine which was from a 71 Mustang. It has acted the same with both engines. The only time it backfired was the other day and I found out the timing was a bit out. I fixed that. No more backfiring. It was out the exhaust though. I'm going to do the mixtures again. I tried those things you suggested with the pedal this afternoon (I guess I know a few things lol) and results varied with how I turned the mixture screws. I will adjust them with a vacuum gauge tomorrow and see how it goes from there. I will leave the gaskets alone since you say it doesn't matter if it higher up. I didn't think it would be an issue but it never hurts to ask...just in case.

Thanks for all the responses

 

[Alvin in AZ]

http://www.panix.com/~alvinj/file12/booster.jpg
Up around the top (like the loose one) is the "good kind"! <---{wrong!}

===============================

Ok, did my homework and found out I got it backwards up there. :/

The good ones are installed in the picture and have the holes going
down two sides.
http://www.panix.com/~alvinj/file12/booster.jpg
The crummy ones have holes on four sides and all the holes are up
near the top.

-------------------

What size engine have you got that little 1.08"(?) carburetor on now?
(the venturi size, in inches, is marked on the (throttle crank) side of
the fuel bowl)

1 bbl YF Carter
187-220 CFM

Autolite/Motorcraft 2100 2v
Venturi size in inches = CFM
0.98 = 190
1.01 = 240
1.02 = 245
1.08 = 287
1.14 = 300
1.21 = 351
1.23 = 356
1.33 = 424

Alvin in AZ

 

[73F100Shortbed]

Ok so I have the good ones then.

It is on a 302.

 

[73F100Shortbed]

Ok so I made it out to the truck to do a little more work with this. Still a little stumble but much better than before. I hooked up gauge to manifold and vacuum was around 18. I turned the screws out some and got around 20. To double check everything I turned them in almost shut and it was sputtering with about 10 on the gauge. Turned them back out and got 20 again and this seems to be where it ran best. I didn't to turn them out more because I would prefer them to not fall out. I did try for a second but it didn't move the gauge much so I'm assuming this is the best spot. I'm open to more suggestions if you guys have any. I'm probably not going to drive the truck until Sunday, but I will see then if it makes a difference driving. I'm sure it will because it runs noticably better now. I'm open to pulling the carb. back apart to re-drill the jets, but I'd like to see some pictures of that so I do it the right way. I don't want to ruin it and have to spend a bunch of money on a carb. The little stumble isn't worth forking out $300 because it really isn't that bad. Thanks for all of the help and today has yielded the best results so far using the vacuum gauge. i had to make up a little adapter to hook up the gauge to the manifold.