[Bobalong]

Quicksilver
"How much time are you talking about here? One second? One minute?"

Fires off and then just peters out in a couple of seconds.

[STEELCITYFIREBIRD]

The needle always unseats when the float drops running and off with the clip, that's what the clip was for I believe, modern needle and seats eliminated the sticking problem. By eliminating the clip you have made an anti drain back check valve while the engine is off, not allowing air IN, like a finger on the end of a straw.

Bobalong,Change your theory to a diagnosed casual problem by checking for an empty carb @ no start.( The pump may have a few squirts in it due to the fuel well it sits in.)


Filling the tank and parking with the nose down hill on a decent grade will diagnose a drain back issue after verifying a drainback empty carb.

A cranking test,pressure gauge deadhead mounted on the end of the fuel line,.... and purged of air will, give you what your pump(heart) is capable of producing, and if your holding pressure between the pump and carb engine off (Checks leaky 'heart' inlet valve), you have to cap the return line, or pinch off it off very well.

Intermittents can be a PITA, but an accurate diagnosis makes for a one shot, viable repair....and is rather satisfying!!

HTH

[Cliff R]

Modern fuels help with the needle sticking on the seat problem more than what they are made of.

This new fuel evaporates like alcohol and hardly leaves anything behind that would gum-up or stick the needle to the seat. Kind of interesting that it doesn't seem to matter whether folks are seeking out ethanol free or not in the hottest summer months we start having complaints coming into the shop and start seeing threads on the Websites from folks having issues with all current fuel formulations.

Older fuels left considerably more "varnish" behind and turned to "gum" in the bottom of the fuel bowl after long periods of drying up. That same residue would glue a needle into a seat so tight I've seen a few that were difficult to get out with pliers! This new fuel will leave what we call "apple jelly" behind when water is present in it. Doesn't seem to be much of a problem with larger automotive carburetors but your chain saw or weedeater is DOOMED if you don't keep fresh fuel mix in it and use it once a month or so to keep things in suspension.

Long periods of not using any type of power equipment will end up with the same result using any of this new fuel in it. I work on a LOT of small equipment here, and can drop the bowl on just about any Honda 4 stroke engine powering a generator, power washer, etc and clean the fuel bowl and push a precision drill bit or spring wire up thru the needle to clean things up, and have them back in service in less than 5 minutes.

Leaving the clip off the needle does stop any potential "drain back", but even with that said the seat is located pretty high in the fuel bowl on a Q-jet so the level it can drain back to is pretty limited right to start with.......Cliff

["QUICK-SILVER"]

Originally Posted by Cliff R

Modern fuels help with the needle sticking on the seat problem more than what they are made of.

What I'm seeing here looks like red oxide primer when it dries. Bit gummy when wet but fine powder when dry. It does coat parts and make needles sticky. Which makes using the hook somewhat mandatory.

Originally Posted by Cliff R

Leaving the clip off the needle does stop any potential "drain back", but even with that said the seat is located pretty high in the fuel bowl on a Q-jet so the level it can drain back to is pretty limited right to start with.......Cliff

And just for kicks...Popped the top on a 77 Q-jet. The lowest fuel could drain back was 1.2" deep. Which was really close to full fuel level with the float set at 3/8ths inch.

Clay

["QUICK-SILVER"]

Originally Posted by Bobalong

Fires off and then just peters out in a couple of seconds.

Seeing in black smoke when it does fire back up?

Clay

[STEELCITYFIREBIRD]

Good stuff.
Drain back seems an improbability from the carb bowl.
Drain down from a leaky well plug/etc, is what your hinting @ QS?


I see the "apple butter" all the time too on small engine power equipment.

I call it "man chowder" .
When it's been in there a while it sure is corrosive, takes the plating right out of a plated bowl where it lays and jams up the main jet solid.

[Cliff R]

Yep, I left several things out including that all of this new fuel is really hard on rubber, neoprene, or nitrile. It will also eat up many types of coatings or delaminate some metals. It will also eat the solder out of the seams of these newer production brass floats. The failure rate we've seen here is 100 percent. Yes that's not a typo, purchased and installed quite a few brass floats in several different types of carburetors, and one by one they all came back with the float full of fuel on the bottom of the bowl!

For some types of carbs that don't have nitrophyl available we've had to dig out old brass floats from cores to get them back in service again!.....FWIW......Cliff

[dataway]

I have to say, unless you have the time and inclination to become a Q-jet expert ... just send the carb to Cliff and have him go through it, reasonable price and turn around ... mark the carb off the problem list and move on to something else.

Normally I'm a die hard DIY kind of guy, but sometimes the cost benefit analysis says let someone that does this everyday take care of and save yourself time and money.

[Cliff R]

Thanks. Biggest complaint we get is turn-around times. It seems like everyone waits till the body work is done, interior finished, and engine ready for the dyno or install to call the carb guy. I've learned to tell folks we're out many months when I'll most like get to it sooner. We are never looking for things to do in the shop and could probably work at least a year and never pick up the phone!.......Cliff

[Formulajones]

WOW! I've never had the new fuel eat the solder from the brass floats. I still run a brass float in the Q-jet of my bird that's been in place for 25 years.
Then put the original brass floats back in the Z carb 3 years ago when I refreshed that one. Daily drive both of them on pump gas. Pretty sure I have a pair of brass floats in the chevelle too. I built that carb at least 15 years ago and haven't opened it up since, but almost positive they are brass.

I wonder if it's newer brass floats with some other form of solder causing that issue??

[Cliff R]

Here's a little history and our experience with them.

We went full time with this business back in 2003. We started out using nitrophyl in the Q-jets but were using over the counter brass floats in various other models including some Ford carbs, AFB's, 2GC's, etc.

To date we have not had single nitrophyl float failure as the new material is closed-cell and not effected by any of this new fuel that we have experienced. Last time I checked the books we had over 12,900 work orders on file. That means that we have had our hands on that many carburetors (not all would have been full rebuilds), mostly Q-jets, and all of them got nitrophl floats with zero problems that we know of.

My own carb was set up in the late 1990's with a nitrophyl float and fine to this day, and I've used ran all sorts of different fuels thru it including some testing with E-85.

Early on in the business we did several beautiful Pontiac Tri-power's and a couple of Caddy's. Got ALL of them back with the floats sinking to the bottom of the bowl. Some were out there quite a while, the longest one I can remember was a mid-60's 2GC for an Olds or Buick smaller CID engine and it held up almost 2 years.

Sent one Tri-Power to Florida and one of the end carb floats failed in less than a week, quickly followed by one of the other ones.

Initially for the Rochester 2bbl's I started robbing OEM floats from cores, then was able to find a nitrophyl float for them and zero issues with them to date.

So my advice is to avoid any newer production brass floats for any of these carburetors and if yours hasn't failed consider yourself lucky....FWIW......Cliff

[Formulajones]

Sounds like the OEM brass or very old examples are fine. I'm guessing they are likely soldering these things with some new EPA friendly stuff, lol.

[tjs72lemans]

Not to mention bad brass floats for sending units. I has to go to the Ford (urgh)plastic black float in the sending unit for my 55 Chevy due to the same issue.

[Formulajones]

I haven't come across a brass float used in any new fuel tank sending unit in many years. Did a new tank and sending unit in our 56 Nomad year before last. Bought from Danchuck. Plastic float.

Just received a new complete Tanks Inc setup for a Firebird I'm doing, again, plastic float.

[Schurkey]

Be sure your fuel tank plastic float will float in gasoline. We had some discussion on another forum about sending unit floats (foam, I think) that would float in water, but sink in gasoline.

Cheap-junk reproduction parts, sourced from you-know-where.

[pontiac1981]

sounds like good old vapor lock.