Engine only runs with full choke

[Welder Dave]

So much for my good luck. I have a Miller Big 40 welder with a Continental F163 engine I got for cheap a few years ago from a trailer shop that rarely used it. The trailer shop wanted to rent/borrow it for a small job so I got it running and welding great. I burned a couple rods and made sure everything worked properly. Went to pick it up Monday and made sure it started right up. Trailer shop tried it out before they headed out and everything was good. Got to the job and it worked great at first but then had no weld output. They called me and had tried everything I could think of. I drove to their shop and they brought the welder back. It had started to rain a bit anyway. We started the welder and saw it had no arc but also would only run on full choke. One of the hoses on an inline fuel filter had come loose and/or cracked. Not enough to drip but loose enough you could turn the hose. Couldn't tighten the clamp anymore. I read online that that can cause a lean condition and require full choke to compensate. Just wondering if anyone on here has had a similar issue or could confirm a loose fuel hose could cause an engine to need full choke to run? I'm going to take it to a welder repair shop but hoping I can fix the engine issue myself and save a little money.

 

[JaredV]

Probably just some crud in the main jet which needs choke to increase vacuum to help pull fuel past it.

 

[Truck Shop]

F163 Conti should be a flathead with updraft carb. Use a can of carb cleaner and spray
manifold and carb, looking for vacuum leaks. 14 to 1 fuel ratio, using the choke richens
mixture. So either the carb has a issue or it's sucking air else wear.
*
The old ford 8N tractors was a prime example of a lean condition involving valve guides.
Ford years ago used a removeable two piece valve guide. Those were known to wear
the valve stems at point of the guide half's mating area. The indication was to run, the
choke had to be pulled about half way out to compensate for crankcase air being pulled
past valve guides. Ford later used one piece guides.

 

[LCA078]

It's easy to break vacuum and suck air instead of fuel with old fuel lines. You'll never see a drip but it will suck air instead of fuel. Not sure if the fuel tank is above the carb or not or if there is a lift pump but agree will all the above. Clean out the jets and replace hoses is a good first start.

Good news is the engine runs on full choke so it's pointing pretty hard to a fuel delivery issue...not spark or air.

 

[ThatGuysFarm]

I have a Hobart portable welder that when it gets hot it loses fuel pressure and will die unless at full choke. I put a little clickity clackity 12v fuel pump in line that the rancher had in his shop, in a hurry to finish a job in the middle of BFE. Been working great like that for 17 years now.

 

[Truck Shop]

Carbs only operate on pressurized fuel delivery controlled by needle/seat & float in first phase.
Idle and part throttle are vacuum controlled second phase. Vacuum has no effect on first phase,
dealing with carb by it's self. If pump is sucking air it's running out of fuel.

I have a Hobart portable welder that when it gets hot it loses fuel pressure and will die unless at full choke.

That is known as "vapor lock", common with poor fuel line routing, and diaphragm pumps
of years past. Hence the Y block Ford with a fuel line looking like a porcupine with all the
clothes pins attached.

 

[LCA078]

Thinking more about it, I'm leaning on Truck Shop's analysis. Maybe you have multiple things going on but follow Truck Shop on this one...

 

[Welder Dave]

Update. I put a new inline filter on with tight connections. Still would only run with choke on but would run at a little over half choke after warmed up. I took the drain plug out of the carb to see if any crap came out. Looked like clear gas so put it back in. Started it back up and it would run without the choke but coughed a little when revving up. I flipped the idler off a few times to let it rev up and it's running like it should now without choke. Yeah, one problem fixed! I think a little dirt may have dislodged when I took the drain plug out. Taking it to a welder repair shop to get the no weld problem figured out. Hopefully it's something simple. Once I get it back I'm going to put a new fuel line on with a shut off valve. It's a pain just changing the filter with the gas flowing. You need 3 hands. One just to block the fuel line.

 

[Truck Shop]

Draining let needle/seat drop/open and let what ever tiny particle through that might
have been blocking seat.

 

[willie59]

It sounds to me like you need to break down the carb and clean it. Fact, in order to make a carb engine run by applying choke means the main jet is clogged, plain and simple. Could be from debris, could also be ethanol poisoning, at least that's what I call it, ethanol murders small engine carburetors. As for the weld output, I don't know much about the big 40, but for years Miller has used a rotating field design for their machines. A field winding has to be excited to create a magnetic field, and since it's rotating, this requires using carbon brushes at a slip ring mounted on the shaft of the rotating field. My point, whenever a Miller doesn't have weld or generator output, the first thing to look at is the brush holder at the slip ring of the rotating field. If those carbon brushes are worn out, no exciting the field, no output.

 

[Tenwheeler]

It sounds to me like you need to break down the carb and clean it. Fact, in order to make a carb engine run by applying choke means the main jet is clogged, plain and simple. Could be from debris, could also be ethanol poisoning, at least that's what I call it, ethanol murders small engine carburetors. As for the weld output, I don't know much about the big 40, but for years Miller has used a rotating field design for their machines. A field winding has to be excited to create a magnetic field, and since it's rotating, this requires using carbon brushes at a slip ring mounted on the shaft of the rotating field. My point, whenever a Miller doesn't have weld or generator output, the first thing to look at is the brush holder at the slip ring of the rotating field. If those carbon brushes are worn out, no exciting the field, no output.

Ethanol Poisoning! I like that terminology and hate that stuff! Do not know much about the Big 40 as well but I thought they had a Pinto engine in them.
As far as the brush area maybe similar to a SA200. Take the brush cover off. lift the brushes a bit and work some emery cloth in there. Old machine that has been in the barn for 15 years will lay a 1/4 - 7018 like glass.

 

[Truck Shop]

Just varnished, main jet is removeable without disassembly, typical of down drafts.
*
https://www.gtgravelyparts.com/aluminum-carburetors

 

[willie59]

Just varnished, main jet is removeable without disassembly, typical of down drafts.
*
https://www.gtgravelyparts.com/aluminum-carburetors

Just varnished? I would say yes, if it's only seen 100% gas. But ethanol, that's not varnish. I'm not a scientist, but I think, and it's just my wild arse opinion, ethanol gas in a carb engine, unless it's used daily and replenished frequently, I think the ethanol sugars break down and become solids again, which clogs the fine passages in a carb jet that even solvents can break loose. I've yet to find a solvent that can clean ethanol residue.

 

[Truck Shop]

Being that this a old welder and has had a lifetime of setting, and more than likely sat
with regular gas years back, it's probably varnished. It's a model that dates back to 1971.

 

[Welder Dave]

It was welding so don't think it lost residual magnetism. I'm taking it to a shop that is pretty much the go to shop for engine drive welders especially SA200's but there are a lot of Big 40's out there too.
As far as the engine we don't have a lot of ethanol in the gas in Alberta. The machine sat for a long time only used occasionally as a powerplant when the power went out. Before I agreed to buy it I made sure it ran and worked. The gas
tank was bone dry which I think was a good thing. Put some fresh gas in and it started right up and ran like it been running the day before. Had to tighten a screw on the idler but it welded and idled up like it's supposed to. I did put some Seafoam in the gas tank. That was 2 or 3 years ago.

I got a battery and put some fresh gas in last Friday. It would only run for several seconds on starting fluid so I figured it wasn't getting fuel. I got a bigger Jerry can of gas but first I blew through the fuel line at the inline filter. After that it started right up and ran and welded great. I brought it to the trailer shop. They even tried it out before heading to the job. It quit welding during a weld. They brought it back to the shop and that's when I discovered it would only run with the choke on and one of rubber fuel lines on the filter was loose. I picked up a new inline filter and got all the hoses tight. I started it and could get it to run at about 5/8 choke. Then I took the drain bolt out for a couple seconds to look for crap in the float bowl. Looked pretty clear so put the bolt back in. Then after running it and playing around with the choke and letting it rev up several times with the idler switch I got it to run good without the choke. I'm thinking Truck Shop is correct the needle dropped and what ever tiny bit of crap was plugging the jet came out. I can ask them at the repair shop to look at the carb but if it doesn't act up might not need anything else done. I'm hoping the welding issue isn't anything too serious or expensive to fix.

 

[Tinkerer]

If the motor has flexible fuel lines here is an example of what gas with ethanol can do to them. This is what I dealt with recently. The line is completely plugged with a disintegrated liner of supposedly ethanol resistant hose.

 

[LCA078]

Whether we like it or not, pretty much all plastic and rubber based products will change over time due to material degradation. Adding in exposure to heat, oils, fuels, solvents, UV, or constant flexing/vibration just greatly accelerates the degradation.

Anytime I hear something is "resistant" to something, I just hear "it's a temporary solution".

@Tinkerer Great pics showing how a hose can be fubar'd internally when the exterior still looks good.

 

[HarleyHappy]

What are you guys using for clear fuel line, that’s diesel rated?
I have clear fuel line, for testing but haven’t found any that will hold up for more than a few months.
Would mind putting in some clear line permanently.

 

[Truck Shop]

The line is completely plugged with a disintegrated liner of supposedly ethanol resistant hose.

What brand of hose? and how long had it set or was it used regularly? How old?
Many variables--so best solution if a going to set for extended period of time
run the system dry or drain it.

 

[LCA078]

Would mind putting in some clear line permanently.

I gotta ask why? Would an inline glass indicator fit the need instead?