Mower question - Page 3 - PeachParts Mercedes-Benz Forum

Dudesky · #31 05-29-2012, 06:41 PM

Quote:

Originally Posted by cmbdiesel

Finally got the mower dug out.

It has a Briggs 400 IC engine.

Doing the same thing as at the end of last year, runs great for about 15 minutes, then tries to die under load. During the 15 minutes, it went up hill, blades engaged, through thick grass with no problem. Once the problems started, it will go uphill without blades, or run with blades, but not through thick grass.
Was able to verify that it is not the gas cap, as I was able to remove the cap during the sputter with no change.
Would a governor issue kick in after the 15 minute period, or would it be constant?
Could a partial blockage either in the main jet or elsewhere in the carb only show up after the engine gets warm?

Check your compression to determine internal engine condition,something north of 50 psi give or take would be ok.

Like was said, that gizmo is the fuel pump, it has several diaphrams and springs, the diaphrams stretch where the spring rests causing a belly in the diaphram and loss of pump power.

If it shows up when the engine is warmed up, I'd check those fuel lines and the line from the engine to the fuel pump and see maybe if there is an internal line blockage. Sometimes those lines swell up inside and block flow.

BTW- that fuel pump looks like it has been worked on before as the hardware just didn't have that 'never been touched look'.There's a remote possibility if someone monkeyed with the pump, they could have it together wrong. They go together in a very particular order as for gasket and diaphram position.

It sounds like fuel to me....if the carb bowl has corrosion inside, the carb is scrap. You can pull the main jet and pilot jet and blow out the passages
with gumout and then hi press air. Still that shiny new hardware on that fuel pump is saying something.
I found this:

http://www.walkermowers.com/manuals/mowers/model-ms-manuals/5895-1.pdf

Governor is engaged from start up and would only change idle rpm.Most run around 2800-3000 rpm but you go by manufacturer spec.

Is the choke totally open after warm up?

Dubyagee · #32 05-29-2012, 07:51 PM

Has the spark plug been changed? Sounds like spark quench from a weak plug to me. If so, I would get a spark tester and verify spark output at the lead.

rscurtis · #33 05-29-2012, 08:25 PM

The FloJet carb. used on that engine is fully adjustable and fully repairable unless it has been physically damaged. Briggs and Stratton does not publish compression pressures. If the engine bounces back against compression when turned backwards (to disable the compression release) it has enough compression to run. I would check the valve clearance to eliminate it as a possibility. Intake- .007, exhaust, .011. Check it just past TDC on the power stroke to make sure the intake cam is not on the CR.

Dudesky · #34 05-29-2012, 08:46 PM

Quote:

Originally Posted by rscurtis

The FloJet carb. used on that engine is fully adjustable and fully repairable unless it has been physically damaged. Briggs and Stratton does not publish compression pressures. If the engine bounces back against compression when turned backwards (to disable the compression release) it has enough compression to run. I would check the valve clearance to eliminate it as a possibility. Intake- .007, exhaust, .011. Check it just past TDC on the power stroke to make sure the intake cam is not on the CR.

I'd check comp first. Less BS to do that.
I've seen them run like bears at 30 psi, anything north of 50 is usually good .
Briggs was pushing differential compression tests last tech vid I saw.