G5200 staring issue

[cliffboyer]

Have had a problem recently whereby my G5200 mower requires a boost to battery to start it. Investigating things have shown starter solenoid terminal voltage drops to 10v when key is turned to start. Bypassing key with a push button from starter batt terminal to solenoid terminal, engine will crank and fire up. Battery is good and seems to be charging normally. No corroded connections or broken/shorted wires that I have found....not really that many to look for on this system....its pretty simple.

Turning attention to ignition switch has revealed the voltage drop happens because glow plugs are also being powered when in start position. That doesn't sound right, but perhaps it is.

My inclination is a faulty key switch. If not that, maybe plugs that are drawing more than their fair share of power. All other aspects of electrical system are in working order (lights, hour meter, etc).

Is there an ohm rating on a good plug that can be checked?

Your folks' thoughts?

 

[torch]

My first question is what leads you to believe that the battery is good? A battery can charge up to a reasonable voltage when connected to a high-impedance multi-meter, but have little current capacity under an actual load. I do not consider a starting battery to be good unless it passes a load test with a carbon pile tester that shows voltage while drawing hundreds of amps. Compare the results with the rated CCA (cold cranking amps) of the battery.

Since your starter cranks if either the battery is augmented with a boost or if the current draw is reduced when by-passing the glow plugs, this suggests to me that the battery is marginal. If you don't have access to a calibrated carbon pile tester, you can approximate the test by measuring the battery voltage while cranking the engine. If the battery voltage drops below about 9v when cranking, then you probably need a new battery.

The other possibility is that the starter is drawing excessive current. This commonly happens when the commutator becomes fouled with carbon/graphite dust. The dust comes from the brushes as they wear away over time, and fills the gaps between the contacts. Because the brushes are conductive, so is the dust and filling the spaces between the contacts with conductive dust allows current to by-pass the windings. Dissassembly and a good cleaning will often fix the problem, although if the brushes are worn that far it's usually a good idea to replace them at the same time. And while you are in there, check the bearings. If the armature is sloppy in the bearings it will run off-centre and draw huge amounts of current for little torque.

Now, on the other hand, if your cranking voltage test reveals that the battery voltage is staying up above, say, 11v or so that suggests a high resistance somewhere in the circuit. Probably corrosion, but possibly burnt solenoid contacts. Measure the voltage drop across the two big solenoid contacts when cranking. It should be very low -- less than 1 volt. You can do the same trick across any suspect connection or cable.

 

[Dave_eng]

Glow plugs should be ON in START. Ohm reading around 1.

Dave

 

[cliffboyer]

Thinking about it, that battery is probably going on 6+ years. And no, I did not check battery voltage while cranking....why I don't know.

Good to know on the ignition switch, too.

Appreciate the input and direction. Will continue again this evening.

 

[torch]

Good luck! Keep us posted.

 

[BruceP]

My G5200 started to 'CLICK' when I tried to start it. I troubleshot and determined that the series of safety-switches was dropping too much voltage so the starter-solenoid was only getting enough power to 'CLICK' and not engage the starter.

MY FIX: I wired in a relay to power the starter-solenoid using the original wire to the starter-solenoid to 'pick' that relay. This 'fix' took the load off of all the safety-switches so all they have to do is 'pick' the new relay.

I am not suggesting this is YOUR problem... but worth looking into.


As for basic troubleshooting YOUR problem. Here is how I would isolate the problem in under 4 minutes:
*) Assume battery is fully charged before you start troubleshooting

*) With voltmeter with black connected to battery minus terminal (NOT THE CONNECTOR)
1) probe battery plus TERMINAL and turn key to start
--if reading drops below 10v your battery is bad
2) probe engine-block (starter housing) and turn key to start.
-- if reading is over 50mV (0.050), you have ground problem to engine

*) Move meter black to battery PLUS terminal (NOT THE CONNECTOR)
1) probe LARGE red wire on starter and turn key to start
-- if reading is over 50mV, you have bad connection to starter
2) probe small wire on starter-solenoid and turn key to start
-- if reading is over 50mV, you have the same problem I had mentioned initially
(NOTE: this final measurement should be battery voltage until you turn key to START)

UPDATE: If all the above tests are within spec... it is pointing to bad starter.
Try 'jumpering' battery + to small wire on starter-solenoid if no crank problem is solenoid or starter.

Let us know the results.... I can help explain how to rebuild starter or solenoid.

 

[cliffboyer]

The verdict is.....tired old battery. I installed back in March 2012....man does time fly!

Voltage fluctuated between 7-8 volts when cranking.

Good call on checking starter interlock system. The wires to the PTO lever had 3" of the insulation chewed off them! Few pieces of heat shrink solved that.

Many thanks on the tips & advice. I was reading more potential issues into this than what in reality actually was. Lesson...keep it simple.

Thank you all again..Cheers!

 

[torch]

Good stuff.