Small Engines (Lawn Mowers, etc.): Starter Motor will not spin engine fast enough to start, briggs stratton, mtd yard machine

Question
QUESTION: Briggs&Stratton 14.5 HP I/C Quiet 42" Cut
Model# 287707-1224-E1
This is installed on a MTD Yard Machine Model 13AM675G062

I've searched both the MTD and B&S website but can't find any good troubleshooting tips.  I suspect the starter motor may not be functioning correctly but I'm not sure how to test it.  

The air filter and oil are clean. Spark Plug and Battery are new.
Starting Condition: Clutch Brake pedal depressed,Speed Control in the Park/Brake position, Shift in Neutral, Lift Lever fully up and I'm Sitting on the Seat.

Engine will only rotate something less than 360 Degrees and then stop. In the start ignition switch position; I can't get it to continue to rotate to start.  If it rotated at sufficient speed that it should start then I could check elsewhere.  I'm looking for some guidance how I could test out the starter motor to make sure it is working correctly.  Is it receiving the correct voltage at it's terminal? How can I trace the voltage from the battery to the starter motor while it's cranking and what should I see along the way.  If I can prove it is the starter motor then I can take a look inside to see if it's the spring or brushes etc. If it can't be repaired then at least I'll know what I need to replace.  I would appreciate any other troubleshooting tips you could offer and I thank you in advance for your help.

Best regards, Anthony


ANSWER: The best method to verify starter condition is a current draw test.  You will need a DC shunt to check the current draw.

http://www.youtube.com/watch?v=65EiiE4NoDI

I rarely find bad starter.  Mainly poor electrical connections.  Have you disconnected the battery and cleaned the battery cable ends and battery terminal posts with a wirebrush?

Will the starter turn the engine with the spark plug removed?

How old is the engine?  When did the problem start?  Has the mower sat for a while?  Is there any compression issues?  Too much compression?

Let me know.
Eric

---------- FOLLOW-UP ----------

QUESTION: 1. Have you disconnected the battery and cleaned the battery cable ends and battery terminal posts with a wirebrush?
Yes, that was the first thing I did.  I cleaned the battery cables and battery terminals. I also cleaned the positive cable on the starter motor.

2. How old is the engine?       (10 years)

3. Has the mower sat for a while?   (18-24 months)

4. When did the problem start?     (When I tried to start the mower last week)

5. Is there any compression issues?  Too much compression?
(No known issues.  It was running correctly before being put into storage.)

6. Will the starter turn the engine with the spark plug removed?
  Yes!! I quess I should have thought it through first because I made quite a mess.
  It spit out gas and oil everywhere.  You were correct that it was not the starter motor.

  The starter motor could not turn the engine with the spark plug.  It had no trouble spinning up with the spark plug removed.  I then re-attached the spark plug and was able to get the mower to run for ~3 minutes.  It didn’t run smoothly but it did power up.
It then stalled out and I couldn’t get it started again.  Before I remove the plug and start this sequence over again I thought I better talk to you first before I damage the engine.

New Questions:
1.   Where do I go from here?  
2.   If the piston was partly frozen from being in storage; could I run the engine for 15 seconds at a time without the spark plug to sort of lubricant the piston?  Then try to start the engine again normally?  Need some more of your expertise Eric.
Thanks Anthony  

Answer
During storage or when you refueled the mower the carburetor inlet needle leaked gas into the engine crankcase oil.  Does the oil smell like gas and is it really thin?  I'm guessing the answer is yes.

You either need to rebuild the carb and replace the inlet needle or you can install an inline fuel shut-off valve and shut the fuel off when not using the mower.

Either way you go you must change the oil and get all the gassy/oil out of the engine.  Drain the oil, refill, run engine for a few minutes and repeat two to three times.  A few quarts of cheap Wal-mart SAE-30 oil is cheap compared to a new engine or mower.


http://www.briggsandstratton.com/maint_repair/routine_maintenance/changing_oil/


The engine oil capacity is 48 oz, about a quart and a half.  I usuall start with a quart and 6 ounces and check.  So, 5 quarts will do for a good engine flush.

Note: the engine will smoke for a while until all the oil in the muffler burns out.  You can remove the muffler and soak overnight in parts cleaner to help remove some of the excess oil but it will still smoke a little.

Ever rebuilt a carb?

Eric