The Stovebolt Site Forums The Shop Area Engine Shop Bad gas?

I reciently bought a 54 gmc that had not been ran for over 2 years.i drained the old gas out [not much in it],and added fresh gas,cleaned the carb ,changed the fuel filter.I got it started and it runs poorly, pulled the top back off the carb and it still smells like it has bad gas in it, will it take awhile to clean up or is there any additives the I can use the speed up the process? Thanks in advance

Have you checked your points? Valves? Spark plugs?

Theres a few other things I would check before the tank so long as there isnt anything plugging the lines preventing gas from getting to the carb.

Yes I put new plugs in, points are good, has fire,set valves @12/20 .

oh.... I forgot to tell you I checked fuel psi it has 5lbs. I keep reading all this stuff about the carbs being warped? I was wondering is there was anybody that made replacements.

Speed up the process by eliminating doubt. Don't start out by thinking too deep. Start out by thinking it just needs some attention. From there discover what else needs attention. There will be plenty.
Start with a completely clean fuel supply. CAREFULLY take out the sending unit from the top of the fuel tank and look into the tank (hint:Don't use a lighter or match! Use a good Mag light or a flashlight that doesn't creat open sparks) to see if there is any corrosion in the bottom. If there is any, take the tank out the rest of the way and get it clean whatever means available whether you have to replace, profesionally clean or do it yourself. If you have to clean it try useing a pressure washer and then rinse it a few times with fresh gas.

Also replace any rubber fuel lines with new fuel lines (not just a rubber hose...Fuel line). Bad or brittle rubber lines can break up and end up in your fuel pump, fuel filter and/or carb. Any of this contamination can "take out" your fuel pump too.

Do a complete tuneup (plugs, points, filters, timing, etc.) before even messing with trying to start it.

Sometimes it just takes more work than you thought. That's just part of graduation from Stovebolt University.

Mixing old gas with fresh gas can cause more than a misfire. It can also stick intake valves shut & bend pushrods (don't ask me how I know this ) . Like Builder said cleaning the tank & lines is a must.

I completly drained out all the old gas. I was told there is a product named Sea Foam that would clean the system, anybody heard about it?

Tom, did you bother to collect a little of the "bad" gas in a glass mayo jar, spin it gently and check out whether there was water or solid crud at the bottom of the vertex? As was mentioned, the idea is a process of elimination without going too fast. Before I went tearing into the tank, I'd add a little gas, let it flush through the tank, drain and spin and check it for particles of crud. If none, move on..no sense in messing with the tank if it doesn't indicate solid contaminates.....run a point file through the existing points to knock off any oxidation (you've already checked the gap, but they could be oxidized) and then crank it up, burn out any cruddy fuel from the carb pot and pump/carb line. If it doesn't improve or there are crud particles present in the fresh fuel, then I would pop off the air horn, check the float level and make sure the little sliding power valve was not stuck. If the carb was crudded up it would be time for a good disassembly and soaking in carb cleaner, hi pressure blowout and finally a kit.

As Tiny pointed out, bad things CAN happen during a restart on an extended shutdown engine. I'd pop off the valve cover to verify it was oiling up on top (you've already done this) and then run it at the lowest idle possible until you either have it smooth out with the fresh fuel or elect to clean up the carb if there was crud present in the float bowl. Can't speak to Sea Foam as a fix.....I'd focus on getting new, clean fuel to the carb and then moving forward from there.

Dave

Old gas turns to varnish which mucks up smooth valve operation. If all else fails I'd check the valves for free motion.

Ok got the fuel system up to standards and got it to run somewhat, runs crappy still ,got idle screw all the way in and still wont idle, air fuel at 2 turns,runs only when you rev it up,acts like they do when you have a vacuum leak but I cover my hand over the carb and it will kill the motor, any more Ideas? thanks Tom

I like to positively eliminate gas/tank/rust/sediment as a suspect problem by disconnecting the fuel line from the gas tank to the fuel pump and blocking it off. A temporary fitting can be put into the fuel pump and a line run from it to a clean can of new gas. If it now runs good the fuel system is the problem and if it doesn't then it's something else. You're working with gasoline so precautions are essential.

Which carburetor do you have on the engine Tom???
Denny Graham

I've used sea foam on quite a few engines, it is a good product, but of course if there is too much crud in the system you'll have to do more than just use an additive.

It has the rochester carb on it Denny, it appears to be a rebulit motor from what I can see, it is clean inside and outside, has good compression, I took top off carb and float is good and carb does not appear to be gummed up.