92 low hour 742B mitsubishi motor wont stay running

[h-m]

Hello all you good people! i have a 92 742B with 1200 hours on it, and i just developed a problem with the motor, it won't stay running. it will start decent and run for a few minutes and then die out, can sorta limp it back to shop by running throttle back and forth, like pumping an accelarator on a car, it won't keep running though. it has gotten a lot worse now and will barely run now, i have fuel in the sight glass of the solex carb, so i don't think i have a fuel supply issue, where to next, spark seemed kinda erratic from coil lead while cranking, almost seemed like it wouldn't fire then it would fire for a while then nothing agian, spark at #1 cylinder seems to be very erratic also, fire occasionally then nothing then fire again. anyone got some voltage / ohm values so i can take a look at some of the components in the ignition system? maybe you guys know what parts are prone to failure? any help you guys can provide, will be much appreciated. maybe the carb needs a good going over???? let me know what you think. thank you. micheal

 

[OldMachinist]

I'd start with checking the points gap in the distributor. If that's good then with cap off crank the engine and watch the points to make sure they aren't sticking. Also watch the rotor to see if its going around smoothly or stuttering.

 

[h-m]

I'd start with checking the points gap in the distributor. If that's good then with cap off crank the engine and watch the points to make sure they aren't sticking. Also watch the rotor to see if its going around smoothly or stuttering.

gotcha' i will try that and start there! thanks very much. i pulled the points and filed them, but i never cranked it to watch them. i will give it a go. i am guessing points contact with a dull hazy look to them across the whole contact surface, is maybe a bad thing? i filed on them and they seem to be quite cratered, file hits the outer circumference but left the center 1/2 untouched, i am guessing maybe time for a replacement set????? maybe time for general tune up? cap rotor, points, condenser, etc etc.... thank you. micheal

 

[brdgbldr]

gotcha' i will try that and start there! thanks very much. i pulled the points and filed them, but i never cranked it to watch them. i will give it a go. i am guessing points contact with a dull hazy look to them across the whole contact surface, is maybe a bad thing? i filed on them and they seem to be quite cratered, file hits the outer circumference but left the center 1/2 untouched, i am guessing maybe time for a replacement set????? maybe time for general tune up? cap rotor, points, condenser, etc etc.... thank you. micheal

I bought a 742B about a year ago and while getting it running I noticed that the "anti-dieseling" solenoid was not connected. When I re-connected the hoses and wires I got the exact problem you are describing. When I disconnect it, it will run just fine but will of course diesel when I shut it down. If all else fails check the solenoid.

 

[h-m]

I bought a 742B about a year ago and while getting it running I noticed that the "anti-dieseling" solenoid was not connected. When I re-connected the hoses and wires I got the exact problem you are describing. When I disconnect it, it will run just fine but will of course diesel when I shut it down. If all else fails check the solenoid.

hey all, got my 742B running good again. trip to bobcat dealer and got the tuneup kit, points, condenser, rotor and plugs in one box and cap in another box and installed everything and gapped to specs in the manuel, retimed it just as manuel says and she runs fine now! thanks for all your help everyone! micheal