Stumped! FH680V problem

shane772

LawnSite Member
Location
BROKEN ARROW, OK
Motor is running good for 20-30 minutes then starts searching for rpm's. No change when I put on choke. Compression is 90psi in both cylinders (cold), bumps 3-5 psi with a squirt of oil in the cylinder. With this, I assumed it was electric since it didn't change with choke on and compression is well within range. Put 2 new coils and plugs, no change. Cleaned fins etc under shroud, no change. Beginning of the season I put on a new carb, maybe I should put the old one back on and see if it changes??? Any ideas as to what to check next?
 
Last edited:

fatboynormmie

LawnSite Bronze Member
Location
balto md
Try loosening the gas cap when it starts acting up. If it straightens out you have a clogged breather on the cap . Could also be the pick up tube inside the tank could be sucking air or is damaged due the ethanol. My .02
 

Ridin' Green

LawnSite Fanatic
Location
Michigan
Could be a coil going bad and as it heats up it starts acting up, which would explain why you can run for a while before it acts up.
 
OP
S

shane772

LawnSite Member
Location
BROKEN ARROW, OK
Ridin' Green, put 2 new coils on yesterday. Coils that were on it are only 2 months old too. Plugs look good and was getting spark from both.

Got up early and changed the carb. No change. This morning it was dark so mower was sitting still with blades on and had exact same problem. Once engine gets hot, starts searching and rpm's going up then down, repeat until it dies.
 

hal

LawnSite Fanatic
Location
Georgia
How old is this engine? Your governor spring may be getting weak. Also your oil may be too thin.
 
OP
S

shane772

LawnSite Member
Location
BROKEN ARROW, OK
1000 hrs on engine .Tried changing fuel filter, drain fuel and checked for water and also ran off a sepersepfuel source all with no change. Now I have to go get my route done with 1 mower, gonna be a long day! Lol
 

hal

LawnSite Fanatic
Location
Georgia
Check your governor linkage or other electrical components, it is heat related, baffles clean, valves correct... What unit is it on?
 
Top