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Problem, fuel filter keeps draining leaving air bubble then engine will not run properly . It will run but the filter will not get full having a good supply for the pump. Fill the filter and motor runs as it should. New pump, fuel hoses, filter. Engine can set with a full filter as soon as you start it fuel in the filter disappears engine will run until you speed up. Tank is less then half full. Suction from the top of tank. All lines clear. Put pressure on the tank to get a full filter runs great. Anyone have a couple ideas? Good compression, 149 and 150 psi

Any time the filter is on the inlet side of the fuel pump. It will never stay full. Doesn't matter what it is on. Lawnmower, tractor, car etc. The filter acts like an expansion tank and the air space is filled with gas vapor. So unless you have an air leak between the filter, and the end of the fuel pickup your problem is not the filter staying full.

So what is the engine doing. Surging, running a period and stalling out and dying,

If you really still feel that the filter is a cause remove it and use a piece of fuel line in its place and see how it runs without the filter. I have a Craftsman tractor and my filter does this sometimes as well but still starts and runs fine. If I didn't have a clear filter, I would never know this was happening.

ILENGINE said:

Any time the filter is on the inlet side of the fuel pump. It will never stay full. Doesn't matter what it is on. Lawnmower, tractor, car etc. The filter acts like an expansion tank and the air space is filled with gas vapor. So unless you have an air leak between the filter, and the end of the fuel pickup your problem is not the filter staying full.

So what is the engine doing. Surging, running a period and stalling out and dying,

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Engine stops running after the filter drains. As long as the filter has fuel engine will run. Nothing wrong with the filter. For some reason the pump does not pump fuel . I am asking more about the impulse pressure. Would there be a reason the impulse is weak, coming off the valve cover. The fuel pick-up comes from top of tank. Thank you

OldDiyer said:

If you really still feel that the filter is a cause remove it and use a piece of fuel line in its place and see how it runs without the filter. I have a Craftsman tractor and my filter does this sometimes as well but still starts and runs fine. If I didn't have a clear filter, I would never know this was happening.

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Nothing wrong with the filter, Purchased a new pump incase the new one installed is a dud. Think I will pull the metal pick-up tube and inspect that. Just might have a crack at the very top where connected.
Thank you.

Johner said:

Engine stops running after the filter drains. As long as the filter has fuel engine will run. Nothing wrong with the filter. For some reason the pump does not pump fuel . I am asking more about the impulse pressure. Would there be a reason the impulse is weak, coming off the valve cover. The fuel pick-up comes from top of tank. Thank you

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If the filter is below the pump/carb and is being drained I would suspect that the pump is working but the issue is between the tank and the filter providing no air leak at the hose to filter fitting.

Something to consider....

On several mowers I've worked on -- all MTD products, including my own Cub RZT50 -- a bit of debris in the fuel tank has stopped the engine randomly. This happens because the fuel pick-up is unfiltered and the fuel has to pass through a narrow 90-degree brass elbow fitting at the top of the tank. Something as inconsequential as a dead fly can stop the fuel from reaching the filter. It's a difficult problem to diagnose because it's completely random, and after the mower sits for a few minutes, the debris will drift down out of the pick-up tube and back into the bottom of the fuel tank. The mower will start right up and run fine... for a while... until that same bit of junk gets slurped into the pick-up tube.

My fix for this problem has been to replace the factory pick-up tube -- a rigid plastic thing that resembles a heavy drinking straw -- with a length of standard 1/4" flexible rubber fuel line with a weighted filter installed at the bottom. This fix has never failed.

Tbone0106 said:

Something to consider....

On several mowers I've worked on -- all MTD products, including my own Cub RZT50 -- a bit of debris in the fuel tank has stopped the engine randomly. This happens because the fuel pick-up is unfiltered and the fuel has to pass through a narrow 90-degree brass elbow fitting at the top of the tank. Something as inconsequential as a dead fly can stop the fuel from reaching the filter. It's a difficult problem to diagnose because it's completely random, and after the mower sits for a few minutes, the debris will drift down out of the pick-up tube and back into the bottom of the fuel tank. The mower will start right up and run fine... for a while... until that same bit of junk gets slurped into the pick-up tube.

My fix for this problem has been to replace the factory pick-up tube -- a rigid plastic thing that resembles a heavy drinking straw -- with a length of standard 1/4" flexible rubber fuel line with a weighted filter installed at the bottom. This fix has never failed.

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Surprising what will be in fuel tanks and cause issues. Had a JD a couple weeks ago that was having run issues. Found one of those white bottle seals like from a bottle of sta-bil, a stink bug, a tent caterpillar, and a tree frog in the fuel tank next to the fuel pickup tube

ILENGINE said:

Surprising what will be in fuel tanks and cause issues. Had a JD a couple weeks ago that was having run issues. Found one of those white bottle seals like from a bottle of sta-bil, a stink bug, a tent caterpillar, and a tree frog in the fuel tank next to the fuel pickup tube

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A tree frog? An entire tree frog? There had to be a good story behind that one. Either that or somebody just left the thing parked for a very long time with the fuel cap off.

I concur, it happened to my JD130 pickup tube partly plugged. Very expensive repair they had to remove the whole back end to remove the tank. I thought I was careful fueling but much more now.

Tbone0106 said:

A tree frog? An entire tree frog? There had to be a good story behind that one. Either that or somebody just left the thing parked for a very long time with the fuel cap off.

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Farmer with on farm fuel storage, I suspect the frog had crawled into the fuel nozzle at some point and then when the fuel was pumped he was forced out of the nozzle into the tank

Yes as the others have said
Very common for debris , just plain old clippings to clog the fuel outlet so you are using fuel faster than it is being supplied thus the fuel filter draining is a symptom not the problem.
Another one that seems to pop up more & more these days is the fuel live delaminating
Modern fuel lines are now 3 individual tubes one inside another
The inner most one is bout 0.005" thick and designed to stop the fuel vapour diffusing through the hose & escaping into the atmosphere .
EPA strikes again
When you pull off & replace a fuel line over a barbed nipple it can rupture this thin membrane so it acts like one of those self filling rubber bladder dams
Been caught out twice with this happening so now I always cut 1/4" to 1/2" of the end of any suspect looking hose .

So the first "trick" is to put a NEW filter on backwards .
Problem goes away = air lock in the exit end of the filter

Next get a bucket and pull the fuel line off the carb , remove the spark plugs ( remember to ground them ) , crank the engine to get a flow started then watch the bucket to see if the flow peters out .
If the end of the hose is lower then the tank outlet then you should get a syphon happening and a steady flow ( remove the fuel cap )

As soon as the machine comes back will be taking the tank off incase there is gel in the bottom that is hard to see looking in and if there is a leak in the siphon pipe. I will post the results. The posts led me to a conclusion that is very viable. Thank you everyone for the input.

You might think about getting some fuel hose and rig it from your fuel pump into a fuel supply setting on the floor, like for example a milk jug and test. You can later rig your old fuel filter into the test hose fuel supply.

From post #2 copy and paste.
Lots of people are not aware of this statement below and think the clear filter should be full of fuel.

Any time the fuel filter is on the inlet side of the fuel pump. It will never stay full. Doesn't matter what it is on.