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I need some help with this. Short history, I purchased this Scag mower brand new 5/07/2010 from our not so local scag dealer. She has been garaged, kept in the dry, never rained on or hosed down. She has been with me 10 years and well kept and only has 152 hours on the meter. It has been pretty reliable. 2012 replaced a relay in ignition box because of no start or no anything. Next issue was at about 100 hours replaced gearbox on top of blade deck. Next event was replace the gearbox again on top of blade deck. It was checked and full of oil when mounted and lasted around 20 hours. 3rd event was replacing it again. 3rd gearbox is still working. Now, for the last couple of months the engine, Kohler 31 hp EFI, almost dies going up a hill, going down a hill or making a left hand turn up or down a hill or just backing up to fast. Last Friday I had mowed 1-1/2 hours and it had been doing all that almost dieing stuff and when I went to back up the motor stumbled,(almost died) backfired and has never started since. I have worked on it for a week now and don't feel any closer to solving the problem.

Here is what I have done or checked; 1- Fuel, Tank is a little over 1/2 full. 2- Battery is fully charged at 12.4 volts. 3- checked 4 fuses, all look good. 4-Have checked every inch of wiring for shorts and cannot find one 5- pulled spark plugs, they are only a couple months old, they look, feel, smell wet with gasoline, crank engine with plugs out no gas blown out of spark plug holes. 6- reinstall with brand new spark plugs, engine is still cranking great but no start or signal that it might. Pulled new spark plugs back out, they appear dry. Placed a light meter probe into each spark plug wire end, lights up when switch is on and then fires rapidly as motor is being cranked. Grounded ,(clamped spark plugs to frame and both are firing great. 7- now seems like maybe its not getting gas. Electronic full pump starts up immediatly when switch is turned on and is plenty loud to be herd, (same sound as always). 8- Took end of gas line off of fuel filter to see if gas was coming from tank, (it wasn't pouring out but was dribbling out). Question, Can the fuel pump be making the normal electrict fuel pump sound but not be pumping gas? Forgot to mention that I had checked all the safety switches and they test good but if this was electrical would the fuel pump run and motor crank so well?

What do you think about this? I don't know what to look at, check next. My dealer went out of Scag business a few years back.

Thanks, Mike

Test the fuel pump output pressure. It is regulated at 39 PSI and it sounds like you have a lot less than that. Too low on line pressure and the injectors will not work.

It will cost you $5 to chat with SCAG TECH.

StarTech said:

Test the fuel pump output pressure. It is regulated at 39 PSI and it sounds like you have a lot less than that. Too low on line pressure and the injectors will not work.

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Thank You Star Tech. If I disconnect the outlet hose from fuel pump, (where the electrical fittings are) can I get an ideal of if the pump is squirting enough pressure? or will she blow from gasoline on the electrical terminals? Yea, probably sounds a little off but I don't have any kind of pressure gauge for that. Maybe there is a place more upwards on the hose where I can disconnect and read the squirt. I think I will have to take off the radiator resivoir- overflow bottle and the (computer modueal?) to gain access to a higher point for disconnecting the gas pressure line? Hey I am under a metal roof working on this thing, swet is running on everything. I'll get this done after daylight tomorrow morning and report back. I just went and took another look. When I remove the two before mentioned componets the gas line is crimped on the next devise where probably the fuel injectors is.

Just think I work out in the sun on over hot asphalt. Can't help any more as you do need a pressure gauge. This is something I had to get to work other fuel injected systems.

This is your engine Service Manual
see page 19 in troubleshooting section
You have a fuel problem. Drain all fuel from tanks, lines, check fuel & air filters for replacement & all fuel lines for being completely clear & open. Get rid of gas in your gas can legally, purchase a bottle of STAR TRON FUEL TREATMENT & add to empty gas can per instructions on bottle then fill gas can with 93 octane gasoline & give it a try. Let us know how it goes, thanks, Mark
Read this post & DO NOT USE STABIL FUEL TREATMENT.

Take the fuel line off after the shut off valve then get you a jar and open the shut off it should pour out the size of your hose or appear bigger than your hose. If not take off gas cap take a bright light look down inside for grass a other stuff if gas is not coming out take an air compressor and blow back Thur the line into the tank and recheck the fuel flow after you blow Thur it. The fuel pump can't deliver the fuel if it's not there to be delivered if line filter or tank has a block that slows the fuel down. Might have to repeat to get the fuel flow really moving. If it's not flowing like your pouring it Thur a funnel it's not a good flow and will not run correctly and might burn the 200 plus dollar fuel pump out. My thoughts is it is blocked in the line close to the tank or both

Ok, thanks for every ones help and advise. Here is where I am currently. I took off the fuel line just after fuel filter and the gas was coming out more of a heavy dribble than a flow. Had already been looking inside of gas tank. Tank inside is clean, very clean. So, ordered a new oem Bosch fuel filter. Just now received the fuel filter. Put it on and now have a good stream of gas flowing through it. So I'm thinking this is the trick and she will start now. Well, no she didn't. I pulled the plugs out several times to see if they were still firing and yes they are and have changed with new plugs. I also watched for gas on the plugs. #1 cylinder spark plug is wet and you can poor gas out of it. #2 cylinder spark plug has been dry every time that I have pulled them. I cranked it after pulling the plugs and #1 blows gas out the spark plug hole for 3-4 revolutions. #2 hole does not blow out gas. I'm thinking fuel injector might be bad on #2 cylinder. What are your thoughts. Do the fuel injectors have a part # stamped on them? I have looked all over Kohlers and Scags sites and they list three different injector #'s. My model # is STT61V-31EFI-SS, engine # is Kohler Aegis LH775 and engine serial # is 3802504701.
Thanks, Farmer Mike

You need to test the fuel pressure like StarTech said. Seeing a good flow means nothing if the pump can't sustain 39psi under line pressure.

slomo

If I am thinking correctly the fuel pressure should be 39 and can't be no more than 2 below or 2 above or the pump is bad.

Luffydog said:

If I am thinking correctly the fuel pressure should be 39 and can't be no more than 2 below or 2 above or the pump is bad.

Click to expand...

Is there a pressure regulator in that fuel system?

slomo