JD 345 random engine stalls

[oldnslo]

For reference this is a 94 0r 95 3445 with Kawasaki FD590V engine and 813 hrs on the clock.

This mower may run for 5 minutes or 1 1/2 hrs before it just randomly stumbles or just quits with no warning. Some times it will restart and other times it will not. First time it did this I saw inlet fuel filter was plumb empty so tried loosening (removed) the fuel cap. No change.

Hooked up my timing light and drove until it stalled. Showed like it was firing even when stalling so suspect fuel problem.

Triple checked for spark when warm and stalled and will jump an 1/8 gap with nice bright spark. Replaced plugs just to eliminate them being old and weak. No change.

Pulled the seat pan and replaced the fuel line to the tank. Also pulled the down tube in the tank and inspected for leaks, cracks, obstructions, etc.

Replaced all the fuel lines and filter since lines looked damaged in couple of spots. No change.

Pressure and flow tested the fuel pump both exceed minimum spec listed in service manual.

Mounted the filter so it is vertical - flow in the bottom. Filter starts out approx 1/3 full and over 20 minutes it is empty but the mower still runs.

My questions are:
On a mechanical fuel pump If the diaphragm is failing would the pump get weaker when warm Vs cold?
If the diaphragm has pin hole could gas be getting behind the diaphragm reducing the volume output over time? I see no external leaks and no evidence of gas getting in the oil. This pump does not have any drain line that I can see. (I believe the pump is original but not 100% sure)

Any other thoughts on what else to check?

TIA

 

[beenthere]

Some times it will restart and other times it will not.

But eventually it will restart? Does this happen regardless of whether you do something? Any clue as to what might change that would allow it to restart?

Hate it when these things happen...

 

[oldnslo]

Yes it will always restart. Sometimes right away , sometimes 5-10 minutes. My guess is the fuel pump gets weak / loses pump capacity for some reason. Tonight I ran it for above 45 minutes mowing lawn wit no problem pulled up in front of the garage and idled it down to blow the deck off and it just quit. I grabbed a screw driver and removed the drain from the carb and it was bone dry. Cranked it over for a few seconds and still dry. Let it sit while I retrieved my spark tester. Double checked spark was strong. Removed the spark tester & tried again. Nothing

During all of this the fuel filter was empty. Let it sit a couple minutes while I wiped the bottom of the fuel pump to see if it was damp, nothing appeared damp. Tried again fuel was pulled into the filter and it fired right up.

That is why I am questioning can a pump fail this way?

Yes I hate random failures.

 

[Amvcane]

Could there be something floating around in the fuel tank, getting sucked onto the pickup, stalling engine, eventually falling off when there is no suction?

 

[oldnslo]

You can see the down tube in the tank through the fill opening and I cannot see anything in the tank.

 

[tomplum]

Mechanical pumps do fail this way. Be it due to check valves sticking or, but it happens. I've only put a couple of these on , but I recall the vent being different on the replacement than the stock pump. One would think it would be way different say if the bowl vent was plugged off from the carb.

 

[oldnslo]

Does almost act like one of the check valves is not seating once it gets warm. Appreciate the help.

 

[oldnslo]

I pulled the fuel pump last night and found the mounting cavity had gas in it. Also noticed that when I pressed on the plunger gas was forced out both lines vs drawn in one and forced out the other. Installed new pump with drain hose and will hopefully get a dry day to run it around to confirm this solves the random stalling problem.

thanks everyone for your input.

 

[jenkinsph]

I had similar problems with my L130 mower and finally put a small electric fuel pump on it. Since then I can let it sit for a month or more and it starts up with a quick bump of the starter. I can turn the ignition on then wait a couple of seconds allowing it to pressure up then bump the starter and it fires right up. The pump was purchased from NAPA for about $30 and sure saves the starter and battery.

 

[Bass]

Is your problem solved with a new fuel pump? I'm having the exact same problem!!