17.5hp OHV Briggs-Turns over slow

fpappal

Member
I have a 17.5 hp OHV Briggs (model 313707) on an older MTD mower. Years ago the starter was having a hard time turning the engine over to start it. I did some research and discovered the valve clearance needed to be adjusted. After I adjusted the clearance it started like it should. The mower has sat for the last two years and when I tried to start it today it was doing the same thing. The starter will turn it over for one revolution then stop. Turn the key again and it will turn it over for one revolution and stop. I have tried two different batteries, both fully charged and both work fine in other mowers. I have removed the battery cable at the starter and cleaned the connection. I have rechecked the valves and the clearance is what it should be. The oil level is where it should be, no gas is in the oil. If I remove the spark plug the starter spins the engine over like it should. There is some sort of compression issue preventing the starter from being able turn it over. Any suggestions?
 
It is not unheard of for the compression release mechamism to break. The only way to tell is to remove the sump and inspect the camshaft. The compression release is on the camshaft.

If you were certain it was working o.k. before you stored it, I would check for corroded terminals on the battery cables at the battery (And check the battery cables themselves, if they have green corrosion on them that would cause resistance to flow of current to the starter). MTD battery cables are barely large enough to do the job when they are new. Check and clean the battery cable ground connection, I think its near the battery or at the starter solenoid and it would not hurt to remove the positive battery cables from the starter solenoid and clean the posts and battery cable terminal ends as well. Any corrosion anywhere in the circuit will reduce the current to the starter.

It might not be a bad idea to try a jumper cable connection (Just the negative jumper cable, not both) from the battery negative post to the engine block, to eliminate the possibility there is high resistance where the engine is bolted to the frame, or in any of the other frame connections between where the negative cable fastens on the frame and the starter.
 
Thanks,
I tried everything you suggested and nothing has changed. I decided to see how much electricity I had going to the starter when I turned the key. Using a multi meter I have around 12.5V at the battery. At the starter the multi meter is only showing around 4V while it is spinning. Should I expect to see that closer to 12V? Either way 4V seems very low to me which may explain why it is having such a hard time turning the engine over. If that is indeed to low then were am I losing it to? I have removed every single connection and cleaned them whether they needed it or not.
 
Take a jumper cable directly from battery pos(+)to pos(+ terminial on starter & see if starter cranks eng,if it does,measure voltage at battery(+)terminal of starter sol when cranking eng using ign sw,voltage should be same as at battery pos(+) terminal when cranking,if lower then you may have a loose/dirty cable connection between battery/starter sol or a bad cable(acid may have gotten into cable connectors eating away wire inside insulation.

If voltage ok to starter sol from battery,check voltage on opposite side of sol at terminal for starter motor while cranking eng with ign sw,if voltage lower than battery side of sol then contacts burned/bad or you have a mech problem inside sol,replace starter sol,if voltage ok at starter side of sol but low at starter,then clean/tighten cable connections at sol/starter or replace cable if that doesn't cure low voltage at starter.
 
I was going to suggest the solinoid has a bad contact ring inside. You can put a regular auto motive start solinoid on there if you want. It will never wear out. Did that on my Troy Horse tiller. Made a BIG differance. At car show flea markets i have gotten them as cheap as 9 bucks brand new. Store cost will be a lot more. Look through Ebay.
 
That voltage should be up around 9 volts or higher. Cable problems. Follow how the other guys are telling you what to do.
 
Just for the heck of it I decided to see how the voltage dropped at the battery while cranking. I hooked my meter directly up to battery and turned the key. The voltage dropped from 12.5 to 3V. I did same thing to a different mower and it dropped to about 10v. I then put the battery in a different mower and it also only dropped to 10v. What would cause such a huge drop in voltage? From what I can tell the solenoid is ok. Could the problem be with the starter? Thanks
 
Best thing to do is goto ebay & buy a new/used starter,from what you say about voltage drop indicates a major problem inside starter,one/more of the following could be the cause of your problem.

1-magnets broke/broken loose damageing armature windings.
2-armature winding(s)grounded.
3-commutator bars shorted due to carbon buildup from brush wear in slots.
4-worn brushes.
5-brush holders/brush leads shorted to case by carbon from brush wear.
6-worn/bad bearings in starter motor.
7-grease/oil on brushes/commutator bars & brush holder.
 
Hi, I had the same trouble with a 4 cyl diesel. I found that if I plugged the air intake with my hand, it would stop the compression issue and spin over good. I removed my hand and it would fire right up. Ed Will Oliver BC
 
I fixed the problem without having to replace a single part. I took the starter off with the plan of buying a new one. I noticed a very small amount of rust where the starter mounts to the engine. I used a little emery cloth to remove the rust and put it back on the tractor. Turned the key and it started right up. I spent a lot of time on this darn thing and it was a tiny amount of rust causing all the problems. The tractor has never sat outside a day of its life. So it ended up being an easy fix after a few hours of headaches.
 

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