Ford 860 Loping and Stalling when Hot and Under Load

[Shepfolly]

I would like to ask for any advice. I recently bought a Ford 860 and the seller said the engine had a professional engine rebuild. It started fine, and seemed to run good. At home when brush hogging twice now it tends to lope under load, and after about 20 minutes or so of mowing, when good and hot, it loses power and eventually stalls. It recovers some when I push the clutch in, then starts to stall again when I resume mowing. Choking it does not seem to help when it starts to lose power. Also, sometimes it seems to lope a little without the load on when just starting out and reving the engine. It always starts fine though fresh and seems to idle good. Can anyone help me know how to diagnose the problem? I appreciate any and all help.

Thanks! Rick

 

[Jimmyjack]

Check the archives. This model has an inherant problem with boiling gas or vapor locking because of the ethanol gas and the gas line running behind the manifold. This may or may not be your problem> I switched to regular gas not ethanol, and rerouted the gas line after I experimented with insulatiing it. Mine runs great. Might be something else, but if you have gas boiling problems when it gets hot, experiment.

 

[Ultradog MN]

Always, always - first thing out of the box - when it begins to run badly or quits, immediately pull a plug wire and VERIFY that you have a bright bluish white spark that will jump at least 3/8". Short or yellowish spark will not do. Requires no tools and will help a bunch in deciphering if the problem is spark or fuel.

 

[jeff pk]

I"m going through a similar problem. Just bought a 57 860 6v tractor that was recently rebuilt---has 130-135 compression in all cylinders. After about an hour of mowing it starts to stumble and surge between 900 & 1500 RPM. Thought it might be boiling gas as it had no shield---made a shield but it didn"t help. Fuel line runs next to manifold, so I may try to re-route it as Jimmyjack suggests. I found some spark at night (can see it in the dark) between secondary coil wire and Bat terminal on the coil, and Soundguy told me to check for cracks on the coil, and I may have found some around that connection. So I replaced the coil, and it seems to run better, but I haven"t taken it out yet to test it under load for an hour. I"ll post back and let you know if it"s fixed...

 

[BruceR TN]

Udog,
Thanks for the picture. I never really wanted to hold a plug wire to a ground (and haven't had to...yet) as I've been lit up a few times before (my dad was an electrical contractor). I always remember that copper tastes sweet and aluminum tastes bitter :^).

 

[Jerry/MT]

Surging can becaused by an overly lean mixture. What do you plugs look like? If thy look really white the mixture may be too lean. That can be caused by a leaky throttle shaft, cracked or rusted intake manifold, leaky manifold gasket or leaky carb gasket. These can cause air leaks around the carb metering section that lean the mixture. Another possibility is a restricted fuel supply

 

[john_Bud]

First things that came to mind were lean mixture and a weak coil.

 

[cheif]

Sounds like my 850 with a cracked intake manifold

 

[Shepfolly]

Thanks everyone for quick replies and some good ideas for me to check out. I will try these over the next few days and this coming weekend. Thanks again.

Rick

 

[Ultradog MN]

LOL.
You'll notice I have the plug wire kinda propped against that pipe and my hand is nowhere near it.

 

[jeff pk]

Post back if you find something.

 

[Doug (OH)]

That's a great shot! Doug

 

[Doug (OH)]

I'd check the coil also! Doug

 

[souNdguy]

ditto what's been said.

at moment of stall or weakness, check spark.. if it's good.. go on to fuel.. if it's bad, chase it down.

reason i say go to fuelif spark is good, is we can likely rule out governor as it runs normally before it starts loping. a bad gov would run bad all the time.

as was said. lean fuel needle or fuel obstruction, or a vacume leak causing a lean situation can do this.

read the plugs.. check carb, fuel flow.. etc.

post back.

 

[CAJM]

I had the same issue with my 861 with after heating up it would start to choke down. Never seemed to run hot on the gage but when i shut it down you could hear the boil. I change out the rdiator and switched over to a 6v electronic ignition and haven't had the issue since.