Not getting enough fuel.

[MyOtherCarisaWheel Horse 10]

95 520h - when cold if you run it anymore than about 1/2 throttle, it will stall out every minute or so, once warmed up it’s not so bad and can be run faster. The filter usually has next to no gas in it but seems to have a bit more once tractor warms up. If you tilt the inlet side of the fuel filter upwards, the engine will noticeably speed up a bit.

Former owner replaced fuel pump with new one, replaced fuel filter and cleaned tank, then gave up and sold it off.

What can be done to increase fuel flow to the engine besides adding an electric fuel pump? TIA

[ineedanother 1,365]

That sounds to me like it is running lean, but first things first if you really suspect fuel supply, pull the fuel line at the carb to see if it is pumping fuel. If the PO suspected the pump and changed it but it didn't help, it sounds like the problem might not have been a bad fuel pump so changing it again would be a waste of time and $$. 

[MyOtherCarisaWheel Horse 10]

I’ll try pulling the plugs to see if I can get a read on if it’s lean or not, thanks for the idea.👍

[wallfish 15,946]

Have you tried adjusting the carb?

To find air leaks (which would cause a lean condition) you can spray carb cleaner around the carb body like the throttle shaft and the intake with the engine running. Any change in rpm would indicate a leak sucking in the spray. There have been some issues noted with the halves of the Onan intakes separating and leaking air. That certainly could be a PITA to find if not knowing about it. Check it with the spray when cold running. It could be swelling and seal some from the heat of warmed up?

If the fuel filter is horizontal it can appear like they don't have anything in there but fuel is passing. Is tilting the fuel filter adding fuel or choking it off? If it's running rich instead of lean, then choking off fuel would speed the rpm up.

[lynnmor 6,807]

Pull the carburetor and clean it properly.  Since you need to pull the intake, inspect it for leaks at the seam.  Having the intake off would be a good time to adjust the valves.

[MyOtherCarisaWheel Horse 10]

7 hours ago, wallfish said:

Have you tried adjusting the carb?

To find air leaks (which would cause a lean condition) you can spray carb cleaner around the carb body like the throttle shaft and the intake with the engine running. Any change in rpm would indicate a leak sucking in the spray. There have been some issues noted with the halves of the Onan intakes separating and leaking air. That certainly could be a PITA to find if not knowing about it. Check it with the spray when cold running. It could be swelling and seal some from the heat of warmed up?

If the fuel filter is horizontal it can appear like they don't have anything in there but fuel is passing. Is tilting the fuel filter adding fuel or choking it off? If it's running rich instead of lean, then choking off fuel would speed the rpm up.

Good suggestion. I’ll try that and report back. Thanks👍

[Pullstart 59,828]

Many times ethanol fuel swells fuel lines too.  It doesn’t take much to replace the lines, and I’ve made the switch to ethanol free and though it’s a bit more coin at the pump I haven’t missed a meal from it…

[lynnmor 6,807]

4 hours ago, MyOtherCarisaWheel Horse said:

Good suggestion. I’ll try that and report back. Thanks👍

The only adjustment is the idle mixture and that ain't the problem.

[953 nut 51,899]

13 hours ago, MyOtherCarisaWheel Horse said:

Former owner replaced fuel pump with new one, replaced fuel filter and cleaned tank, then gave up and sold it off.

 

13 hours ago, MyOtherCarisaWheel Horse said:

If you tilt the inlet side of the fuel filter upwards, the engine will noticeably speed up a bit

If the fuel hose wasn't replaced you should start there. Could have a slight leak that is allowing the pump to suck air rather than fuel.

2 hours ago, Pullstart said:

Many times ethanol fuel swells fuel lines too.  It doesn’t take much to replace the lines, and I’ve made the switch to ethanol free and though it’s a bit more coin at the pump I haven’t missed a meal from it…

https://www.pure-gas.org/

[MyOtherCarisaWheel Horse 10]

I replaced the fuel pump with a known good one from another 520h. May be a bit better, will not know for sure till I mow again.

 

checked plugs, running a bit rich but not excessively so.

 

sprayed all around carb with starting fluid, no change in engine speed, no vacuum leaks that I can detect.

 

put some Berreymans B-12 in gas tank and dumped some down the carb. No difference as of yet.

 

Still shuts off randomly from apparent lack of gas.

 

plan to replace all fuel lines but gas flowed freely out the line when I removed the the fuel pump so I don’t think that will make a difference.

 

any ideas?

Edited August 22, 2023 by MyOtherCarisaWheel Horse
Correct spelling

[Gasaholic 183]

5 minutes ago, MyOtherCarisaWheel Horse said:

 

 

plan to replace all fuel lines but gas flowed freely out the line when I removed the the fuel pump so I don’t think that will make a difference.

 

any ideas?

Fuel line under pressure, if it has internal cracking (common with today's modern fuels) fuel pressure can get past the inner sleeve of the line and swell it shut.. once pressure releases, fuel flows normally. When I had my own shop, it was a POLICY of mine that fuel lines were replaced every 2 or 3 years simply as a matter of maintenance, even if they "looked good" - 2-strokes got new fuel lines EVERY YEAR (along with all filters)  Fuel lines in bulk were (and still are) relatively cheap, and frequently solved or improved performance problems. 

 

I was going to say that should have been your FIRST step, but others have already pointed that out fuel lines are so often overlooked because they "look fine" on the outside - When you pull a line off a nipple however, inspect the line by looking at it end on and squeeze it flat, and chances are you'll notice the inner liner of the fuel line will have several cracks showing on the "end grain"... then think about what the rest of the fuel line may look like (especially areas where it is close to heat sources such as along transmission area, near the engine, etc.) 

[MyOtherCarisaWheel Horse 10]

Fuel lines are cheep enough that it is certainly worth a try. When I took the fuel pump off my old tractor the lines came off easily. When I took them off the one with the stalling out issue and the new fuel pump on it, I broke off one of the fittings on the “new” pump.

Edited August 22, 2023 by MyOtherCarisaWheel Horse
Correct spelling