Marv 894 #1 Posted September 8, 2012 I have a Briggs 18hp IC engine on an MTD Lawn Machine that is giving me problems. I do not have a previous history for the engine. During start attempt the engine will begin to rotate but when it comes up on compression it will stall. Oddly, it can be started with the aid of a jumper battery and then runs decently. The battery is new. On the off chance the battery was defective I substituted a known good battery but it did not correct the problem. Jumping direct to the starter from the battery makes no difference. This engine is a 1997 model. Did this model have a known problem. Share this post Link to post Share on other sites
TT-(Moderator) 1,131 #2 Posted September 8, 2012 It's probably time for a new starter, but check all electrical connections first - including ground cables/wires. Share this post Link to post Share on other sites
Don1977 604 #3 Posted September 8, 2012 Also check the battery and starter cables for corrosion. I had one corroded inside the insulation bad enough that I had to replace it before I never got it to start. Share this post Link to post Share on other sites
Save Old Iron 1,565 #4 Posted September 8, 2012 Don't overlook valve adjustment being too tight Share this post Link to post Share on other sites
Marv 894 #5 Posted September 26, 2012 Hi SOI, Not sure how valve clearance being too tight would cause this problem. Could you explain the theory for me? I have already checked cables and installed another starter. Really didn't want to tear into the engine but may have to. Marv Share this post Link to post Share on other sites
Fordiesel69 258 #6 Posted October 1, 2012 I was just going to start a thread on this. I JUST went thru this with mine. I put a spare 1970's starter on it and the difference was night and day. The newer late 90's and 2000's starters were really chapened up and don't last as long. 1 Share this post Link to post Share on other sites
Save Old Iron 1,565 #7 Posted October 1, 2012 Hi SOI, Not sure how valve clearance being too tight would cause this problem. Could you explain the theory for me? I have already checked cables and installed another starter. Really didn't want to tear into the engine but may have to. Marv Marv, check out the following video. I should have said too loose. Brain was thinking loose, fingers where typing tight. The exhaust valve(s) will fail to open properly and cause excessive compression on the exhaust cycle. If you remove the spark plugs and the starter spins the engine MUCH faster, this could be your issue. Of course removing the spark plugs will allow any engine to crank faster, so this is not necessarily the most conclusive test you can perform. If you remove the spark plugs and the engine still cranks slowly,. then we have to revist the starting circuit. Keep in touch. Chuck Share this post Link to post Share on other sites
Fordiesel69 258 #8 Posted October 1, 2012 If he has the 18 hp twin I/C and it is the opposed and not the V twin, then the valves are not adjustable short of grinding the stems or the valve seats. The starter is almost always to blame aside from wiring or a worn out solenoid. In fact MTD has the smallest possible guage wire (for cost cutting) to support the current draw. If one size larger wire was used, im sure you could tell the difference in cranking speed. Over time this smaller wire cuases heat ans wear on the starter & solenoid. Ever notice why MTD units eat up starter solenoids more than non MTD brands. It is not just becuase they use cheaper / poorer solenoids. Wire size also plays a factor in this. Share this post Link to post Share on other sites
Save Old Iron 1,565 #9 Posted October 1, 2012 we can also try a voltage drop measurement - battery to starter. that one measurement will tell if wiring is the issue. Share this post Link to post Share on other sites
Rooster 191 #10 Posted October 2, 2012 The starter is almost always to blame aside from wiring or a worn out solenoid. Ever notice why MTD units eat up starter solenoids more than non MTD brands. It is not just becuase they use cheaper / poorer solenoids. Wire size also plays a factor in this. Yep and Yep! Wire size is a common problem on Briggs Opposed twins. Maybe everything worked great brand new, but over time the light gauge wire hurts the starter, battery, etc etc... Try this... Completely unhook your mowers eletrical system from the starter (that 1 wire). Use your "jumper battery" to start the engine...... How did it start? If the problem got better, the problem is in the mower electrical system, if it did not get better, the problem is in the engine. As for internal engine problems, hard starting can be a sign of a rod failure about to happen. You can check this without "going in" to the engine, several ways. Most of the time I would NOT think this to be your problem, however the Briggs Opposed twins are notorious for top rod failures. I have had more than one that did not want to crank over end up having a seizing top rod. some quick easy checks. Remove the engines rear cover, look at the top rod...many times they will show signs of heat problems...if the rod cap and main journal area of the rod are "Blue"....you have an issue! Pull the plugs, hit the starter...does it spin easy now? As I said, this is probably not your issue, but I have seen it. The "Oppy's" can be tough on starters, that lil starter is cranking over quite a bit of mass. One final issue you could have, though you don't see it often in an engine that has not been worked on. A sheared flywheel key, or partially sheared allowing advanced timing will make the Oppy's VERY hard starters! Share this post Link to post Share on other sites
Marv 894 #11 Posted October 24, 2012 Update. Well I finally got back to this problem. I did replace the starter with a good used one. Didn't cure the problem. Using a new battery, cables, and solenoid I completely bypassed the electrical system on the machine. The engine cranked very much better and started ok. So, the final fix was replaced the ground cable and starter solenoid. The engine cranks good now. I want to thank you all for your recommendations. This thing had me scratching my head including the one I sit on. Thanks so much Marv Share this post Link to post Share on other sites
