The Stovebolt Site Forums The Shop Area Engine Shop Backfiring, Leaking Carb, etc...

I'll give a recap of the situation since I've been sidetracked with a defective fuel tank for the last six weeks. I installed the new fuel tank today so I'm back on the hunt for the problem that started all this nonsense to begin with.

Truck backfired through the tailpipe on the interstate.

Many suggested that it was most likely an ignition problem rather than a fuel problem.

I bypassed the ignition switch by rigging a toggle between the starter and coil. The backfire didn't go away on a short test drive thereby removing a faulty ignition switch as the culprit. Points are new, cap and rotor are new, Goodman condenser has been installed for a couple years.

During testing in the garage, the engine backfired through the carb and the carb began leaking profusely. (rebuilt Carter YF)

Today, after getting the fuel tank installed and attempting to start the truck, it started briefly and ran for a few seconds before fuel began pouring from the carburetor.

Stuck float and/or needle valve?

Maybe a collapsed float. Sometimes a backfire puts enough pressure into the float bowl to damage or collapse a hollow brass float. How much effort would it be to pull the top off the carb and inspect the condition of the float?
Jerry

No problem at all. Can it be done in situ or should I pull the carb off the engine?

The Rochester B only has a fuel line and 4 screws to remove the top- - - -not sure about the Carter, since they need so little maintenance. The Rochesters need zippers instead of screws!
Jerry

The Carter has 7 screws, plus one has to remove a clip; no problem.

Another possibility since you replaced the tank, is a speck of dirt on the fuel valve seat.

What is sold as gasoline, ethanol or not, tends to leave a residue behind on fuel fittings, in the fuel line, etc. Removing or replacing any of the fuel system can result in some of the residue breaking loose, and traveling forward.

Jerry - I like the zipper analogy

Jon

Let me refresh peoples' memories. All this crap started before the fuel tank problem. I'm just now getting back to it since I got the fuel tank issue resolved.

The outlet flange broke while I was trying to drain the tank because I suspected that bad gas could have been causing my problems.

Shamelessly stolen from my grandmother, except she was talking about how many times she needed surgery- - - - -she told her doctor he should put in a zipper!
LOL!
Jerry

The Carter YF carbs have a flimsy diaphragm in the bottom of the fuel bowl. The backfire could have blown it out. Weather that would cause flooding I'm not so sure about.

George

A leaky accelerator pump diaphragm will definitely cause flooding, but will not cause profuse exterior gas leakage.

OK Gentlemen, here;s the latest.

Ol' Roy is back on the road and seems to be all squared away.

When I popped the top on the carburetor, this is what I saw at the bottom of the bowl. WTH??? I suppose that backfire coughing through the carb did that? No clue.

I'm sure you all remember when this all began back during the last week of November or first week of December that I thought the backfire was from a bad batch of gasoline.

The truck ran like its usual Swiss Watch self for 15 miles and then busted a grumpy on the interstate 5 miles after filling up with 87 unleaded at Sam's Club.

I immediately suspected bad gas but went through the tests of the ignition system since that's normally a likely cause. Bypassing the ignition switch proved that it was not the problem and the backfiring continued and progressed to coughing through the carb.

This then turned into fuel pouring out of the carburetor.

Since I wanted to start with a clean slate for my diagnostic tests, I attempted to drain the 15 gallons remaining in the tank and replace it with fresh fuel from a different station.

Well, you all know what happened. The fuel outlet broke off the bottom of the Spectra tank and 15 gallons of gas poured out into the cab and buckets and assorted containers, and the floor, etc.

I got the new Spectra replacement tank installed yesterday but stilll had the fuel leak trouble at the carb. I fixed that today without too much difficulty and took Ol' Roy for a 15 mile test drive/beer run.

I made every effort to induce a backfire but was unsuccessful in this pursuit. The truck starts immediately and runs smooth as silk like it has for the last 4000+ miles since I awakened it from its long slumber.

Anyway, I'm putting the problem down to bad gas. Take a look at that sample of the fuel that came out of the first tank. Does that look like any 87 unleaded you've ever seen lately?

On the plus side, I never would have discovered the faulty fuel tank outlet if I didn't have to drain the gas. It could have broken off while driving and/or broken off after the 36 month warranty had expired. I now have a new tank and a decent used tank that can likely be fixed if necessary.

If anyone has any other theories as to the cause of my problems, please let me know. There is no "smoking gun" that I can find. I'm just putting together a circumstantial case for bad gas. For the record, I've been buying gas at that same Sam's Club for over 2 years without any fuel related issues in any of my vehicles. They all fill up there.

It's been a while since I rebuilt my Carter carb, but something must have been amiss for the needle valve to fall out. I'm guessing it was just coincidental to you getting gas at Sam's Club.

That is some nasty gasoline, but I think you'll have trouble convincing Sam's Club to even reimburse you for the fillup you did before the issue occurred.

But the good news is you got it fixed.

Coincidentally, my mom told me today that she saw somebody on "Nextdoor" ranting about "bad gas" he got from Costco that did $700 damage to his vehicle. Costco told him to go pound sand.

I'll see what happens but it seems like everything is hunky dory.

That so-called gas doesn't even smell like gasoline. It smells like some sort of cleaning fluid.

Doesn't surprise me, don't know about Georgia but in Oregon all that the State checks is that a gallon is actually a gallon. In my prior life I saw lots of nasty "fuel" at the root of hard start / drivability issues.

Struggling to imagine how a needle falls plumb out of the seat.

Some YFs have a spring with their needle. Does yours?

Two things:
In the Carter YF there is a little "knob" like affair on the pin that holds in the float. If you have it installed backwards...meaning you have that little bump facing away from the carburetor body that is closest to the float mount, it will slide out toward the interior of the bowl, let your float drop down and you'll lose your needle every time. That pin must be installed so that the little bump is in the narrow part. If you install it incorrectly it may take a week or a month but it will always fall out. Hopefully the attached image will show you.

Number two: gasoline is only as good as it the storage facility that holds it. Ask RaceTrac. Around 2018 somebody decided to get gas from a holding facility outside Dallas and another somebody left the cap off or loose to the tanks. We got a lot of rain, water ran in...and water always runs to the bottom...and RaceTrac had to spend something like $400,000 repairing engines, cat converters...all sort of things. For that reason I never buy gas from (a) Sam's (b) Costco (c) RaceTrac or (d) QuikTrip. Only buy branded gasoline. The 4 I just mentioned will buy gas from anyone if they need it. About 5 years ago I poured gas into a small jar. Two or three months later I poured gas into another small jar and set it with the first one. Then about two or three months later I poured new gas into another and took a picture of all 3. The oldest gas looked just like what you have there. My guess is Sam's found somebody with some old gas and bought it. Remember Sams is not an oil company so they must buy junk from anyone who has it to sell. Good luck!

Here is another 2 images showing the way that little pin must be inserted. That bump keeps it from sliding off...that is sliding to the right side in the second image.

I’ll have to have a look see at mine. If it got it right, it was probably by accident. Makes sense now that I see your pictures.

I better pull my YF apart to look at that pin before I install it. It'll likely be so long that I do install it that I'll forget all about this issue.

Hi you guys. I'm not at home on my computer so looking at pictures is somewhat difficult on my shoe phone. However I did put the pin in correctly, I think. Looking at the carburetor from the driver's side, the pin went from left to right. With the bump on the left, toward the front of the vehicle. Looks right, right?

Of course, now I'm second-guessing myself because I'm trying to remember what orientation the parts were in when I reassembled it. I did it on the vehicle w with the top still connected to the linkage. So I think I was trying to keep it oriented in that position and the only way that I would have been able to get the pin in is from the front to the back. Of course I can't remember if I turned the top upside down enough where I would have stuck the pin in from the other side. I guess I'll find out if the pin falls out and things start going wonky again. Someone asked about the spring. Yes, if you look in the picture the spring and needle valve are sitting at the bottom of the bowl and I did install them together with the needle valve pointing up and the little spring with the rounded end on it rubbing the float Tang

Good luck! Once upon a time I found what was an NOS Carter YF that had been used for what appeared to be a very short while. The seller claimed the carburetor was defective and probably couldn't be made to work since the company was out of business. The minute I removed the top I saw that pin had been installed incorrectly and hadn't been caught by anyone. Maybe on a Friday...who knows but the needle, spring and pin were sitting right in the bottom of the float bowl. So for $30 I had a new one.

Interestingly, the pin and float were still in position , not hanging loose.

I had to remove the pin and float to re-install the valve and spring.

What happened inside the carburetor to cause the valve and spring to fall out is a mystery to me. Debris in the bad fuel? Backfire coughing through the carb? Pretty weird.

Drove Ol' Roy to work today and covered the same stretch of road where the backfire first manifested itself. I didn't lose power up the long grade and it didn't blow a stinker when I reached the top.

The carb float pin hasn't fallen out so I must have installed it in the right orientation.

Truck is getting its usual 12 mpg so it looks like everything is back to normal except for the following issue that didn't exist prior to all of this nonsense.

1. When I remove the gas cap, it is vacuum sucked to the filler neck. It is a one year old, vented Motorad cap - the same one sold by everybody, including under the Gates brand name. What happened? The tank is not pressurized. A vacuum is being created in the tank, I assume by the fuel pump. What should I do about it? Drill out the purge valve on the underside of the gas cap?

Your gas cap should be made so that it vents. I've seen one or two that weren't, but those are very rare and they don't make your pickup behave well. I bought a locking cap because gas theft is a problem here and is vented really nicely. I checked it by putting my mouth up against the rubber part and sucking air through. I'll let somebody else advise you on how to modify that cap...I'd be inclined to look for one that was vented from the start.

This cap is vented. It worked fine since I bought it a year or two ago. It's only now after all this stuff happened that it doesn't seem to be venting properly

Thanks...yes it is. Try pouring some solvent (naphtha would be good or also denatured alcohol) into the 5 holes there and see if that frees up the diaphragm inside. Maybe some of the ethanol gas got in there and caused it to stick? Also try blowing and sucking on the yellow part to see if you can tell if it is stuck.

I wonder if that crap Sam's Club gas that started this whole mess affected it somehow?

I'll do all that you suggest. For the time being, I put the 80 yr old Packard gas cap on the truck. No plastic or rubber to get messed up. Just a simple vented cap

Well, stories of people getting loads of bad gas all over Atlanta are in the news now. So far it's just CostCo but as Jon said, they all buy their cheap gas from the same places.

https://www.wsbradio.com/news/local...co-locations/NZUBWNGCRRCN3LRBBALVLICWQM/

Another problem that didn't exist prior to this fiasco is a non working fuel gauge. It registers full as soon as the key is switched on. The sending unit is new 2 years ago. It isn't one of the ones that Jon G recommends. Perhaps it's now the right time to buy one. What would cause the gauge to read full regardless of the float level?

A bad ground.

Jon

Thanks. I'll re-examine the connections.

The ground connection wire goes to one of the sending unit screws but that seems sort of inadequate considering the sending unit rests on a rubber seal so the only connection to the tank is the few threads of that screw in contact with the tank.

The tank rests on rubber pads in its cradle and the straps are cushioned where they contact the tank.

I'll run a dedicated ground wire from a known good ground to the same screw on the the gauge wire is grounded to on the sending unit.

... or an open between the sending unit and the gauge.