JD ZTR Surge and die

[kajnjim]

Got a tricky one. Need thoughts. Deere 375R. 25hp Briggs. Was surging and dying after ~ 1.5-2 hours of mowing. After carb work, ended up replacing with OEM carb. Removed and cleaned fuel tank. Blew out all fuel lines. Replaced fuel line from fuel tank to carb. Replaced fuel filter and fuel pump. Replaced both ignition coils. All to no avail. Brought to JD dealer and they ran it several times for extended amounts of time and tested under load in thick grass and it never missed a beat. Took it home and 20 minutes into mowing, started surging and dying again. Thought maybe bad gas, but I’m running our 355E on the same gas without issues. So both I and the mechanics at the JD dealer are stumped. Insight appreciated.

Jim

 

[StarTech]

Did you clean out the fuel tank? I had one earlier this year that was giving and between a honey and a yellow jacket that being suck up the fuel pickup the engine was dying. The pickup is large enough for these to get suck up but they couldn't get the restriction in the line. With engine off they just settle back out and had to be suck up again when they came close to the pickup tube. Timing was different depending on where they got washed to in the tank.

So you may trash in your tank too. Worth checking but getting the pickup out is a pain but that is about only to look inside the tank.

 

[kajnjim]

Did you clean out the fuel tank? I had one earlier this year that was giving and between a honey and a yellow jacket that being suck up the fuel pickup the engine was dying. The pickup is large enough for these to get suck up but they couldn't get the restriction in the line. With engine off they just settle back out and had to be suck up again when they came close to the pickup tube. Timing was different depending on where they got washed to in the tank.

So you may trash in your tank too. Worth checking but getting the pickup out is a pain but that is about only to look inside the tank.

Yessir. My next move was actually to pull tank and have another look at it.

 

[bertsmobile1]

Get your hands on another fuel tank , some 1/4" fuel line & 2 fuel taps
There are hundreds of old tanks out there from all the old gravity fed ride ones that died
Put a long fuel line on it with a tap and fit the other fuel tap on the existing fuel line between the tank & pump then 1/2 fill the spare tank and go mow
When your mower plays up slip the alternative tank directly onto your cab .
Expect the mower to run a tad slower but if the problem goes away you know it is the fuel supply
If not then you know it is in the engine .
IF it mows OK then shift the alternative tank to the fuel pump and see what happens.

Let us know how you go for further tests / instructions

 

[kajnjim]

Get your hands on another fuel tank , some 1/4" fuel line & 2 fuel taps
There are hundreds of old tanks out there from all the old gravity fed ride ones that died
Put a long fuel line on it with a tap and fit the other fuel tap on the existing fuel line between the tank & pump then 1/2 fill the spare tank and go mow
When your mower plays up slip the alternative tank directly onto your cab .
Expect the mower to run a tad slower but if the problem goes away you know it is the fuel supply
If not then you know it is in the engine .
IF it mows OK then shift the alternative tank to the fuel pump and see what happens.

Let us know how you go for further tests / instructions

Should “cab” say “carb”? Never thought of this to diagnose fuel delivery! Thanks.

 

[bertsmobile1]

Fat fingers, yes CARB .
Easiest way to rune some thing out is to replace or bypass it.
That is why you start with a direct connection to the carb then go back one element to the fuel pump
If it is a fuel supply problem you can go one step further back & hook the alternative tank to the fuel lines at the original tank
If all id good then it is the tank
Some JD tanks draw the fuel up using a standpipe hanging down from the top of the tank and these have been known to fracture or crack so once the fuel gets to a particular level then the mower starts to suck air .
PIA to get the tank out but easy to use an alternative tank
I use some from old 8 hp Tecumsehs that were engine mounted & came with an inbuilt tap .
Holds about 1/2 gallon.

 

[kajnjim]

Thanks!

 

[slomo]

Something like this can "slow down" trash getting into the tank. Simple fuel cap strainer.

 

[kajnjim]

Something like this can "slow down" trash getting into the tank. Simple fuel cap strainer.
View attachment 61577

I have a funnel with built-in screen. But this is also a good idea

 

[kajnjim]

I have a funnel with built-in screen. But this is also a good idea

Finally able to get back to mower. After much contemplation, I decided the problem must be fuel delivery pre-engine. I blew out all the lines again and replaced fuel tank. So far, so good. Time will tell. Thank y’all.

Jim