CH740 in new CC XT3 surging & dies (FIXED!)

[stembridge]

UPDATE: Mowed yesterday and not a single hiccup. Hopefully I've found the issue, but I won't be 100% convinced until it goes for several months without the problem recurring.

es

 

[stembridge]

I've run the tractor a couple more times, the last was plowing up my garden spot. As I started the first pass (putting the engine under load), it started spluttering again, so at the end of the row, I hopped off and jiggled both the engine-to-tractor harness connector as well as the rectifier connector (both of which I had squirted OxGard into previously). That seemed to do the trick, as it ran smooth the whole rest of the time I used it.

es

 

[stembridge]

Well, it's back to sputtering again. Disconnected both connectors mentioned above, cleaned and reconnected, with no improvement this time.

es

 

[stembridge]

Uploaded a short video taken while the engine was stumbling:

es

 

[slomo]

Remove the fuel line AT the carb or FI pump outlet. Drain into a glass jar. Look for water at the bottom. E-10 and water is a common thing. Like right now, 35 at night and 70 in the day, You get condensation in the bottom of the tank.

 

[Tiger Small Engine]

Remove the fuel line AT the carb or FI pump outlet. Drain into a glass jar. Look for water at the bottom. E-10 and water is a common thing. Like right now, 35 at night and 70 in the day, You get condensation in the bottom of the tank.

Install a temporary “nurse” fuel tank and see if it starts and runs for longer than 15 minutes.

 

[stembridge]

I’ll check the fuel, today hopefully, but keep in mind that this issue sometimes gets so bad that the engine dies and then will not turn over for a while (starter does not even click). Lights will come on and I can raise/lower the deck, so there’s power. That’s why I’m pretty sure this is an electrical issue, not fuel.

es

 

[stembridge]

Just attempted to start it to pull it out of the garden shed - cranked and immediately started cutting in and out, then died completely after ~10-15 seconds of semi-running. Will not restart (no click at starter), although other powered features work (headlights, etc.). This is consistent with what it's been doing off-and-on. I can't see how these symptoms line up with a fuel issue (but I'll still draw a fuel sample to check for water). Sure seems like an electrical gremlin!

Battery was showing 11.9 volts on the LCD display before I initially cranked, which is low. Battery had a good bit of crud on it, which I cleaned off - it's on the charger right now, which may or may not (based on previous experience) get it turning over again. (EDIT - charging the battery made no change - starter still won't click or turn).

EDIT #2: Disconnected the fuel line and got a good flow of gas, no evidence of water:



es

 

[stembridge]

I tested between the battery end of the ground (black) cable and a stud on the engine - zero resistance (well, 00.1), which should indicate the cable doesn't have an open in it (tested with cable end detached from battery). Also tested between the battery end of the red cable (while attached to battery so it was powered) to where it connects to the starter, and was getting full voltage there.

Cleaned (wire-brushed) the battery ends of the cables as well as the attachment bolts and nuts, and charged the battery up to 13.1 volts.

All fuses (in the fuse block behind the dash) are good.

Took the key switch out, disassembled and didn't see any signs of arcing - contacts looked clean. Reinstalled.

Earlier this year I had tested the stator output, and it passed all the tests in the Kohler manual - it's charging fine, or was at that particular point in time.

Lights and deck lift work fine, but still no start (no solenoid click, starter does not spin). I do hear a relay click when I turn the key to the "on" position, though...

I have the wiring schematic from the parts manual, but parts of it don't make sense to me (it's been 40+ years since I built any Heathkit projects). It seems to be incomplete. I'm also not sure which ignition system I have - I can post the model and serial number if needed to determine that.

I know I should start tracing circuits, but am unsure where to check next other than what's mentioned above.

Really appreciate y'all's suggestions...

es

 

[Tiger Small Engine]

I tested between the battery end of the ground (black) cable and a stud on the engine - zero resistance (well, 00.1), which should indicate the cable doesn't have an open in it (tested with cable end detached from battery). Also tested between the battery end of the red cable (while attached to battery so it was powered) to where it connects to the starter, and was getting full voltage there.

Cleaned (wire-brushed) the battery ends of the cables as well as the attachment bolts and nuts, and charged the battery up to 13.1 volts.

All fuses (in the fuse block behind the dash) are good.

Took the key switch out, disassembled and didn't see any signs of arcing - contacts looked clean. Reinstalled.

Earlier this year I had tested the stator output, and it passed all the tests in the Kohler manual - it's charging fine, or was at that particular point in time.

Lights and deck lift work fine, but still no start (no solenoid click, starter does not spin). I do hear a relay click when I turn the key to the "on" position, though...

I have the wiring schematic from the parts manual, but parts of it don't make sense to me (it's been 40+ years since I built any Heathkit projects). It seems to be incomplete. I'm also not sure which ignition system I have - I can post the model and serial number if needed to determine that.

I know I should start tracing circuits, but am unsure where to check next other than what's mentioned above.

Really appreciate y'all's suggestions...

es

So far you have done a thorough job diagnosing and eliminating possible problems. Have you load tested battery? When it dies, does it suddenly just quit, or slowly die?