Flooding problems on 83 5.0

[Dave9052]

++Ok here goes, This is my 83 that I had raw gas smell that really would stink up the garage. You guys had lots of great advice and stink got a lot better. I bought a rebuilt carb, same one 4180C last year it ran fine. Now the stink came back, now for the strange part. The smell is for sure from the carb. So gas smell is bad most of the time after car is off. So I take off air cleaner and rear throttle plates are soaked with fuel so I think float is set to high or dirt in needle seat. I open fuel site screw gas is perfect, right at bottom of hole. Front fuel hole also perfect. So I am standing there scratching my head and all of a sudden about 10 large drops of gas drop into rear barrels on both sides Car is not running. What the heck so I remove site screw fuel is still at bottom of hole. So I restart car it cranks for 10 seconds and starts but runs rough until raw gas in intake burns off and then runs great revs up and the idle is perfect. It sits there running great and all of a sudden the front barrels spit out a bunch of gas and car stalls out. I check both site holes again fuel level perfect. I think maybe dirt in carb, which does not make sense to me but I take off fuel line and filter could not be any cleaner. I connect a clear plastic tube to fuel line where I removed it from carb, I put the end into a cup and crank engine with ign. off, it seems like I get a little gas and more air than gas out. I raise the open end of tube to remove cup and the clear tube is still about half full of gas as you would expect. This is the part that is strange. The gas is full of bubbles they keep coming up thru the gas like something is blowing air from fuel pump. Not just a few they are constant and large. I put my thumb over the end of the hose and it builds up a little pressure, this is all going on and no cranking. Could lots of air coming from fuel pump cause fuel to run into carb like I have described? and how would air get into fuel pump. The pump is bone dry no gas leak. Could air get in and fuel not leak out? There is no pressure in fuel tank I had the cap off. Thanks for any help. Sorry for long post.

[Walking-Tall]

All factory stuff in place? The first part sounds like percolation, lotsa heat (even previously normal amounts of heat) getting at fuel inside the carburetor that then leads to and then out of the secondary boosters, and in the primary metering block main wells and to and then out of the primary boosters... such is the idiocy of whoever decided that ethanol and it's lower boiling point should be added to gasoline, and where and how such problems arise. If the EGR spacer is under it and functional... do you have the tin heat shield thinga-ma-bob under the carburetor? How hot is the thermostat? If it's hotter than a 180-degree, I'd be putting a 180-degree in it for an attempt to cool the under-hood temperatures some, but a phenolic spacer under the carburetor, above the heat shield, would probably help the situation most.

The second part sounds like a hole or pinhole in the pickup tube in the gas tank, or somewhere along the fuel line, picking up and drawing forward some air...

Could more air than fuel going into the carburetor cause the runs from the boosters like that? No. Matter of fact, depending on how much air, and it sounds like you're getting a fair bit, it'd be a hard time keeping enough fuel in the float bowls... though not noticeable no doubt because you're observing the float/fuel levels in the bowls at idle or when it's shut off, when little to no fuel is being consumed.

[Dave9052]

Yes Mike all factory stuff is in place including all smog stuff. EGR valve is under it but not functional, vacuum line is blocked off to EGR. The heat shield is on as is phenolic spacer. I am not sure about thermostat as it was in when I bought the car. After I posted this and thought more about the fuel pump air problem I went out and jacked the car up and checked the fuel line from the fuel pump all along the underside to the tank. The rubber hoses all looked good as well as the metal lines, I would think if they were sucking air when pumping that when it was not pumping there would be at least be a fuel damp spot but all looks bone dry. I guess there could be a leak on top of tank as I can not check there. Tomorrow I will recheck gas line at carb and put end of gas tube under gas in container in order to confirm if it is pumping that much air out. Is it possible that fuel in pump is also so hot to cause percolation and causing the bubbles of air? The car does not seem to run real hot and has never overheated and today it only got up to 70. I think you are on to something about the percolation how else could that gas while car is just sitting, spit out that much gas? While car is running carb would be much cooler until shut off then carb would get very hot from engine. Is premium gas better? Thanks Mike for your help Dave

[Walking-Tall]

Unless and until EGR passages in the intake are blocked off, extra heat will always be present down there. If the EGR is actually functional, you might be better off allowing it to do it's thing so that maybe less heat builds up. Did I just say that? lol... scratch that, and fully ditch EGR, LOL!

On the pump getting hot enough to boil the fuel... not usual or likely... not at all the same as the heat from the exhaust that migrates up through the intake casting, the EGR spacer, and up into the carburetor's castings....

Yes, only 70 degrees today where you are... just imagine, and wait until it gets REAL hot outside. You're in MI... I used to live in Windsor over the bridge from you, where I got exposed to a whole new kind of smokin' hot in the summer. Fuel out of the boosters when there's not to be any sounds like percolation for sure. If you're not going to use EGR, it really would be a good idea to at least block the passage that's underneath the EGR spacer in the intake's carburetor flange, with a 1/4" or 1/2" aluminum spacer (whatever you can squeeze under there and still be able to close the hood) that actually reaches over there far enough on the passenger side where the EGR passage is, to block it off, to reduce the heat allowed to travel up presently...

[erratic50]

I’d run it off a fuel bag or jug and see if it acts the same. Excess pressure like thecreturn line has a kink is a guess

[Dave9052]

Mike, I just remembered when I had the carb off the PO had filled in the EGR spacer completely with what looks like JB weld. Could I add another phenolic spacer, would that help? Can the carb hold down studs be screwed out of intake for more length as I have no extra stud length for another spacer. I will change the unknown thermostat out to a 180 just to be sure. Sorry for all the questions. Thanks Mike

[Dave9052]

I’d run it off a fuel bag or jug and see if it acts the same. Excess pressure like thecreturn line has a kink is a guess

Yes I will try that, I did not see any kink in return line. But there are some places in the lines that are hard to see. That is the smaller line right? Thanks for tip.

[Walking-Tall]

Wouldn't hurt, even a thin spacer like mentioned above, down on the intake, and a taller phenolic spacer if you can fit one... you can likely wind out the carburetor studs a bit if needed... but if there's an auto supply store near you with a HELP section, sometimes longer carburetor studs and nuts can be gotten there... or there's always just buying a length of threaded rod (5/16-18 down into the intake, I believe) and nuts and making your own longer studs...

Pretty sure a kink or blockage of some kind in a fuel return line, that you'd have no problem etching your initials in a brick wall with the output pressure, LOL! Seriously though, surely you wouldn't have the questionable weak fuel (+ air bubbles) flow that you're getting...

[Dave9052]

Thanks for all your help. I will let you know how it plays out

[Walking-Tall]

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[Dave9052]

Well today I removed carb added longer studs and another 3/8" spacer that makes total of 3 spacers. I can't add more spacers or hood will hit air cleaner. I ran the car and drove car for over 1 hour, it was plenty warmed up. About 10 minutes after shutdown the fuel again percolated out of secondary boosters, but not as much as before. I did check the temp on the outside of thermostat cover with infrared thermometer and it was 190 degrees so I need to change out thermostat. That should help with percolation. I have to figure out how to remove that one bolt in the thermostat cover. I also found out while removing carb, a PO blocked off the 1/2 inch emission tube that exits the top of both bowls . I removed the blockage (they used wire nuts lol). Is it possible removing blockage will help or will raw gas go into emission tube and cause other problems? Thanks

[Walking-Tall]

Okay, some progress.

The one thermostat housing bolt... takes a wrench and reach in from the side, 1/8 of turn or something at a time... yes, a slight PITA I was looking forward to not having to deal with that bolt if I could have went forward with the 351W... though my 302 isn't going to be crowding that area with anything a factory setup probably has...

Those big tubes are only "auxiliary" float bowl vents, that would have went originally through tubing to the carbon canister. You still have the steel tube bowl vents inside the air cleaner. Removing the blockage will vent float bowl fuel vapor, to atmosphere (and your nose and other people's noses), or to your carbon canister if that's connected. Not the problem you're having. Percolation is fuel boiling, down in the liquid fuel, creating enough vapor in primary metering block main wells and the passages to the primary boosters, and/or secondary metering plate passages that lead to the boosters, vapor that then at some point re-condenses and drips out of boosters, when there ain't supposed to be fuel exiting boosters.

There's something to be said about an aftermarket free-flowing exhaust system and no EGR or passages anywhere in sight... where there's much less chance of any sort of problem like this. What's your initial ignition timing set at? Not enough degrees BTDC can elevate engine temperatures, specifically exhaust temperatures... and we all know that the E in EGR stands for exhaust... lingering (more corked up exhaust system, more lingering) around causing havoc right there beneath the carburetor...

Best of luck with it. A 180-degree thermostat should help some... anybody sell ethanol-free gasoline around there?...

[Dave9052]

Hi Mike, My next step will be the thermostat, and I will check the timing and check into ethanol- free gas. I have been told that aviation fuel is ethanol free. Thanks again for all your help Mike, I love your thread on your vert! Dave

[Dave9052]

I’d run it off a fuel bag or jug and see if it acts the same. Excess pressure like thecreturn line has a kink is a guess

Return line seems fine I could force gas back to tank I will also check fuel line pressure. Thanks for tip.

[Dave9052]

Sorry 1 more question, should I get a 180 or 160 degree thermostat? I did not know they even had a 160 degree. Thanks

[Walking-Tall]

At least one gas station around here sells "ethanol-free". Dunno where your initial timing is right now, but see (unplug and block the vacuum advance hose) that it's at least at 10-degrees BTDC... shoot for more, as much as it will stand without pinging, later on when not having problems.

Quit apologizing, Dave. Nobody learns anything if nobody asks questions. Personally, I think 160's are a waste of time and money, and are hard on engines in other ways. I think it's pretty difficult to actually keep an engine down at 160-degrees operating temperature, unless it's in the middle of the cold dead of winter. Plus, the thermostat degree numbers are really just minimum temperatures... what the cooling system averages at has to do with all of it's components also like the radiator. A 180-degree thermostat is your friend during the warm months, giving the system a head start to be cooler, opening that 15 or so degrees sooner than a 195. Thanks for checking out my thread

[Dave9052]

Mike you are right about asking questions. My dad used to say "Nobody ever learned anything by talking, only by listening" I installed a 180 thermostat much cooler now. The one I took out was 195. What a pain that one bolt is. There is a gas station that sells no ethanol only 6 miles from me I will switch to that also. I will let you know how it works. Thanks Dave

[Walking-Tall]

Yes, that bolt... and yes, using the ethanol-free should help... and yes again, please keep us posted. Quite welcome.

[Dave9052]

Update; almost out of gas so I figure good time to change to no ethanol gas went to station only 6 miles from my house and got what they call "recreational gas" = no ethanol it is about 30 cents more a gallon. Anyway between new thermostat, carb spacers, and ethanol free gas no more percolation Thanks Mike

[Walking-Tall]

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