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Greetings:

I have a fairly old LT1046 that’s been dependable over the years; it could sit for months (with a float charger on the battery), and it usually would start right up. Last year, it started running rough and having some starting issues, which I solved by replacing the carb, filters, spark plugs, etc.

Recently, however, it will not start at all. (Using starting fluid will get it to run for a couple of seconds, so it’s getting spark.) Have replaced the fuel filter and fuel pump, and can see that when cranked, fuel is getting sucked into the filter. Have replaced the carb. Have removed the spring from the anti-backfire solenoid (just to see if that might be the issue). No dice — it seems like no gas is reaching the carb. Checked fuel line from fuel pump to carb — it’s clear but did not smell of gas. (I use ethanol free gas in it.)

ideas?

Further details: disconnected the fuel out line from fuel pump and cranked the engine. Fuel flowed to the fuel filter but not out of the fuel pump. Ergo, that’s the source of the problem.

Checked vacuum line from engine; it’s clear and sound.

ideas? I’ve seen some suggestions online to just replace the impulse pump with an electric one.

You say:
I’ve seen some suggestions online to just replace the impulse pump with an electric one.

You say it's been dependable for years.
Why not just replace the impulse pump and be done with it.
Impulse pumps are cheap and dependable.

A good electric pump is going to be costly and it HAS TO BE A VERY LOW PRESSURE type and the good ones are about $75. (low pressure - not over 2 lbs and 1/2 pound even better. Electric Ok on automotive but not small engines lawn tractor types)

Sure you can maybe find a $20 China type fuel pump but you are just asking for trouble.

Thanks. I’d replaced the old fuel pump (which clearly wasn’t working at all) with one that came with the carb/plugs/filter kit I bought from Amazon. Replacement pump was able to suck fuel into the filter, but apparently did not have enough oomph to suck it up another vertical foot to the pump body.

In doing some further research, apparently these “4 bolt” Chinesium fuel pumps are crap. I’ll try one from a reputable source before trying electric.

It would not hurt to check the fuel line coming from the fuel tank. In recent years I have seen several fuel line with inner liners coming apart and be blocking the fuel flow when a vacuum is applied to the line.

Also make sure no trash is blocking the fuel outlet of the tank.

Take the fuel cap off and blow back through the fuel line into the tank of use not over 5 psi air pressure. (be sure and remove the fuel cap because some cap do not vent pressure backwards, they only allow vent inward)
As star Tech says sometimes a restriction or blockage in the fuel supply will prevent the suction type pulse pump from pumping.
If it starts pumping gas after you do the back flush you need to remove the tank, (because you sent the trash back into the tank) clean the inside and replace the fuel lines. (not a fun job if the tank is the rear mount, but just have to get er dun.
Make sure the pulse hose is not cracked and if the type that fits into a OHV valve cover the hose can be pushed in to far and not get a pulse.
The fuel pump pulse hose has to also leave the pulse source going Up, if the pulse hose goes down too soon it will get full of oil and not get the crankcase pulse due to the oil block.

Can you hook up a temporary fuel tank with a new hose to the carburetor and gravity feed the gas to see if it starts? This will bypass the fuel tank, hoses, filter and pump to determine if you are looking in the right area.

Good ideas folks, thanks. Will try the compressed air trick and see how that works.

Unfortunately, blowing out the fuel line with compressed air didn’t solve the problem. Cranking the engine sucks fuel into the filter, but still not enough to reach the pump. But I have a sneaking suspicion that there’s some crap in the gas tank — I replaced the gas cap a few months ago because it had degraded, and some of it might well have dropped into the tank.

If I have to pull the gas tank, anyone know of a good YT video that walks you through the steps? Or is there a way to clean / flush the tank en situ?

You might post up the complete LT1046 model number.
Some LT tanks are behind the engine and in front of the dash and have to loosen/remove the upper dash. Little easier than the rear mounted tank under the fenders.

I've found videos for such, but sometimes had to watch several because none was exact.
You say it will suck fuel to the filter but not past the filter into the pump.
I would think about checking for a vacuum leak past the fuel filter.
I have a vacuum pump and could crimp off the line on the tank side of the filter then either pressure test or vac test.
Or maybe run another fuel line from the pulse pump to a cannister setting on the floor below the pump and see if the pump will pump fuel from the low test tank supply. (you are using another fuel supply source and another fuel line.
Do not use your fuel filter. I've seen cracks in top of fuel filters, cracks in fuel lines and fuel lines that collasp inside and get all sorts of weird results and no external signs of gas leakage.

I like the idea of just running a temp fuel line from the pump to a gas can on the ground — simple and allows me to start eliminating variables one by one. Will try that when I have time to work on it again.

I also used a cheap bulb type siphon to remove the small amount (about 2 liters) of gas in the tank — gas was in good condition, but at the end it also sucked out some bits of what look like parts of a bug and misc crud, some of which clogged the check valve on the inlet side of the siphon pump. I suspect once I solve the fuel pump issue I’m going to have to replace the fuel lines (and probably tear down the tractor to remove and clean out the gas tank ).

You say you had to replace the gas cap
I've seen pieces of old gas cap o rings bits get into fuel lines.

Keep in mind that testing from a milk jug or gas can on the floor is starting with the fuel line dry and will take longer to get fuel to the pump vs from the LT 1046 tank has gravity fed fuel in the fuel line already. Will take somewhat longer to get fuel to the pump. If you do not have a bottom feed tank to test from You might have to gravity flow at first to get a fuel pump flow then move the test container lower. You have already determined that you need to clean the tank. You have to be careful with the PLASTIC nipple on the bottom of the existing tank. They will break off easily trying to remove the old hard fuel line from the old plastic nipple and replacement tanks are costly. I drain the tank of fuel first and cut the old fuel line and carefully remove the old fuel line from the nipple AFTER the tank is removed.

Move the tractor outside when testing.
AND
Be careful and keep YOURSELF safe.

Well, nuts!
Put a fuel supply line to the pump into a small container of gas sitting on the front wheel (such that it only would have to pump the gas up about 8” to get to the pump). Cranked the motor but the fuel out side of the pump remained dry as a bone. Will try a new/different impulse pump next.

Anyone have a Q&D way of testing whether an impulse pump is good or not? And if the impulse pump is good but won’t work the the vac line is connected, what are the likely suspects there? (Already checked the vac hose — it’s not cracked or anything.)

You asked this:
Anyone have a Q&D way of testing whether an impulse pump is good or not?

Try searching on-line for
How to test a small engine impulse type fuel pump?
Is it a Briggs OHV twin or maybe a Kohler engine????????????
I previously asked the Model, code and type of the engine that is in your LT1046? If it's a Briggs twin this info is on the top of the valve cover.
The reason I asked is I have had experience with some engines that have those same symptoms.
The LT1046 tractors did not all use the same make of engines is another reason I asked.

It’s an older LT1046, with a Koehler Command 23 engine.

SUCCESS!

Got an impulse pump from Amazon that is supposed to be a compatible replacement part for a Kohler Command 23 engine. Hooked it up to a temp gas container and vacuum line, and it drew / pumped gas just fine. Mounted it and hooked it up to the existing fuel in/out lines, and viola, it started right up!

So all that was wrong was the old fuel pump bit the dust (although the crud in the gas tank probably didn't help). Had I known what I was doing, I could have fixed it in five minutes.

Lesson learned: just because you replace a part with a "new" one, don't blindly assume the new part works (especially if it's Chinesium). Had I just tested the first "new" fuel pump and discovered it didn't work, I would have saved myself a bunch of time and aggravation.

So, while best practices means I probably do need to break down the tractor, remove / clean the gas tank and replace the very old fuel line, I can probably get through the rest of the season and wait to do so until this winter.

Now I just need for things to dry out a bit . . . after the driest summer in generations, we've had three days of rain. Between the tractor being out of condition for a few weeks and the recent rain, the grass / weeds I need to cut will be 18" high (fortunately, less than 0.4 ac.)!

Or as my dad used to say when things got that bad, "you're gonna be baling hay!"

You might want to consider placing the gas filter BEFORE the pulse pump to trap the gas tank trash before it enter the pump, if it's not already located as such.
Tall grass if you do not get er bailed also makes the snow look deeper.
At least cut a trail to the door step, redneck style.

What's this "snow" you speak of? (Writing from Central Texas, where we've had more than 2" of snow maybe half a dozen times in the past 15 years!)

Fuel filter is just upstream of the pump, so all's good there.

Cutting grass of that height . . . I usually run over it with the deck all the way up, wait a couple of days (so that the grass clippings dry up), and then hit it again at the normal height. (The area is mostly native prairie grasses, although Bermuda grass is starting to colonize.)

I had the same issue with a Kohler CV25S. Started right up and ran for a couple seconds. It turned out to be the fuel shutoff solenoid. The wire going to it broke somewhere(couldn’t find where) I ended up running it disconnected and seems to be fine.

StarTech said:

It would not hurt to check the fuel line coming from the fuel tank. In recent years I have seen several fuel line with inner liners coming apart and be blocking the fuel flow when a vacuum is applied to the line.

Also make sure no trash is blocking the fuel outlet of the tank.

Click to expand...

STARTECH. I had the same problem a couple times with the fuel line from the tank collapsing and stopping the fuel flow. It's a heck of a lot cheaper than putting a electric fuel pump on just to find out it's the fuel line.

LKB said:

What's this "snow" you speak of? (Writing from Central Texas, where we've had more than 2" of snow maybe half a dozen times in the past 15 years!)

Fuel filter is just upstream of the pump, so all's good there.

Cutting grass of that height . . . I usually run over it with the deck all the way up, wait a couple of days (so that the grass clippings dry up), and then hit it again at the normal height. (The area is mostly native prairie grasses, although Bermuda grass is starting to colonize.)

Click to expand...

Glad you got it fixed - some good advice. Central Texas... I'm in N. MN and my mowing is done for the year. It's 27F right now - supposed to be 19 and 17 the next two nights. Our 'Confinement' begins. I wish I could complain about having to cut the grass.

Remove hose that is attached to valve cover and fuel pump.

Remove the end that is attached to the fuel pump itself. Let the other end connected to valve cover.

See if you can feel a pulse while cranking the engine. Put your finger at open end of hose that goes to fuel pump.

I would do what Tilngot said about using an external tank with gravity feed to carb. All new hoses and not yours. If all works good then you are right and it is probably a gas tank/gas line issue.
This is easy to do if you have an extra gas tank or can.

I would recommend getting the factory service repiar manual from here......
https://cubcadetmanual.com/store/pr...n-and-garden-tractor-service-manual-download/

Gearheadred: good call; will get that.

FYI, the first 14 pages of the LT1046 service manual (which includes the steps for removing the fenders so that you can access the gas tank) can be found here:

Law57 said:

Glad you got it fixed - some good advice. Central Texas... I'm in N. MN and my mowing is done for the year. It's 27F right now - supposed to be 19 and 17 the next two nights. Our 'Confinement' begins. I wish I could complain about having to cut the grass.

Click to expand...

Currently 83F here in Central Texas; should be high 80’s later today. Will be lounging in the pool later.
First major cold front of the season to hit us Monday, which will drop the daily low temps to the 40’s.

LKB said:

Thanks. I’d replaced the old fuel pump (which clearly wasn’t working at all) with one that came with the carb/plugs/filter kit I bought from Amazon. Replacement pump was able to suck fuel into the filter, but apparently did not have enough oomph to suck it up another vertical foot to the pump body.

In doing some further research, apparently these “4 bolt” Chinesium fuel pumps are crap. I’ll try one from a reputable source before trying electric.

Click to expand...

I have never had a problem with any of these cheap little round plastic three port pulsator pumps.
Whether you buy them from eBay / Amazon or go to the dealer and get a Briggs & Stratton when it makes no difference to me.
My thought is you have a restriction somewhere else..
I have seen a number of tractors and zero turns where the fuel wasn't coming out of the gas tank Port nearly fast enough or there were strands of grass, usually multiple, insects, ladybugs etc in there blocking stuff off.
Take the fuel line off at the fuel pump and with even a fairly small amount of fuel the gas is still come out via gravity on its own.
Also check your gas cap vent and make sure it isn't pulling a vacuum because this happens often.
Sometimes protest purposes all you have to do is crack the fuel cap a little bit loose and it will continue to run no problem.
Most running issues like this though and no start issues end up being clogged yet or jets in the carburetor and not fuel delivery to the carb.

TobyU said:

I have never had a problem with any of these cheap little round plastic three port pulsator pumps.
Whether you buy them from eBay / Amazon or go to the dealer and get a Briggs & Stratton when it makes no difference to me.
My thought is you have a restriction somewhere else..

Click to expand...

As you’ll down further in the thread, that was my original thought. But after ruling out everything else, I isolated and tested the “four bolt” new pump I had installed, and it plainly was not working. (There are a number of YT videos out there that report the same thing.)
When I installed another cheap ($15) impulse pump from Amazon (slightly different design, and supposedly a comparable replacement for the Kohler part), it fired right up.

LKB said:

As you’ll down further in the thread, that was my original thought. But after ruling out everything else, I isolated and tested the “four bolt” new pump I had installed, and it plainly was not working. (There are a number of YT videos out there that report the same thing.)
When I installed another cheap ($15) impulse pump from Amazon (slightly different design, and supposedly a comparable replacement for the Kohler part), it fired right up.

Click to expand...

That's good. While as I said I've never had a problem with any of them, it doesn't change my basic troubleshooting.
As I mentioned in my other post one of the first things I do after I give the carburetor an external fuel source in the throat of the intake to see if it is mechanically sound is to take the fuel line off at the carburetor to see if it has proper fuel flow to it.

This is where you would be able to see if a replacement or even original pulsator pump isn't really pulse pulsing like it should when you crank the engine over or better yet, give it another shot of carb cleaner or spray of gas in the intake and let it run for four or five seconds to really see how the fuel is pulsing out of the fuel lines of the carb.
So even though I've never had a problem with one of those parts I have the exact same mindset for any new part that NEW DOES NOT EQUAL GOOD OR WORKING.
LOL
Kind of like a trust but verify thing.

LKB said:

Unfortunately, blowing out the fuel line with compressed air didn’t solve the problem. Cranking the engine sucks fuel into the filter, but still not enough to reach the pump. But I have a sneaking suspicion that there’s some crap in the gas tank — I replaced the gas cap a few months ago because it had degraded, and some of it might well have dropped into the tank.

If I have to pull the gas tank, anyone know of a good YT video that walks you through the steps? Or is there a way to clean / flush the tank en situ?

Click to expand...

I had that problem with my Sabre earlier this season. Clean the tank, replace the filters and at least check the float bowl. I used clear line so I could see the fuel.

LKB said:

Greetings:

I have a fairly old LT1046 that’s been dependable over the years; it could sit for months (with a float charger on the battery), and it usually would start right up. Last year, it started running rough and having some starting issues, which I solved by replacing the carb, filters, spark plugs, etc.

Recently, however, it will not start at all. (Using starting fluid will get it to run for a couple of seconds, so it’s getting spark.) Have replaced the fuel filter and fuel pump, and can see that when cranked, fuel is getting sucked into the filter. Have replaced the carb. Have removed the spring from the anti-backfire solenoid (just to see if that might be the issue). No dice — it seems like no gas is reaching the carb. Checked fuel line from fuel pump to carb — it’s clear but did not smell of gas. (I use ethanol free gas in it.)

ideas?

Click to expand...

it dosen't take much to plug the main fuet jet. if that has happened, you will hae to take the carb apart and clean the main jet and imulsion tube.