Wisconsin VG4D runs perfect until warmed up, then dies.

Hi,

I have a VG4D in an old New Holland L775 skidsteer that runs great until warmed up and then it just falls flat on its face... It's weird. It fires right up and runs perfectly plenty of power until it's run for about 10-15 minutes (depends on the ambient temperature and/or how hard you happen to be using it) and then the rpm starts going all fluttery and it starts missing and backfiring and losing power before it basically refuses to run any more. After things cool down, it runs great until some critical temp is reached and it craps out again.

Here are my theories and what I have done so far trying to figure this out...

1. Ignition system component getting warm /losing sparkiness?

* Replaced basically the entire system (Coil, wires, points, condenser, plugs, cap and rotor).

2. Engine getting too hot? Vapor locking?

*Pulled the tin to look for mouse nests...clean as a whistle in there.

* Made cuts between exhaust/intake manifolds like it shows in the manual. (I left about 3/16ths of an inch connecting them.)

*Wrapped fuel line in insulating tape between fuel bowl and carburetor. Also tried to shield the intake manifold from the exhaust manifold a bit using more insulating tape.

*I've got a new pancake muffler coming off eBay. (I've read that the wrong muffler can lead to overheating.) I don't really have high hopes for this fixing my problem though...

This thing has run fine with this engine for years (on its third engine...) until it started doing this this past winter. I plow snow with it all winter (Northern MN), so it has never sat for very long. Hard to pinpoint when exactly this started happening because on a cold morning I could do the entire driveway before it dies, but now that spring is here, the problem is definitely exacerbated by the warmer weather.

Thanks so much for any and all advice you can offer me on this...I am at my wits end and have been banging my head against the wall on this for months. I'm ready to pull the whole thing and just run the hydro pump with an electric motor from a Nissan Leaf or something...

Sincerely,
Jake

The first thing I would do is attach a spark tester and verify whether or not it loses spark when it quits.

Also, connect a non-powered 12 Volt test light to the terminal on the coil where the wire from the ignition switch connects (+ terminal if the coil is connected properly and this is a (-) ground system).

If it DOES lose spark note whether power is lost to the coil at the same time.

It wouldn't be the first time an ignition switch has acted up and cut power to the coil after it warms up.

If no loss of power to the coil primary another thing to look at would be where the wire or terminal stud passes though the distributor body to connect to the points and condenser, something could be shorting in that area when the engine heats up.

If it quits WITHOUT losing spark you've got some oddball thing going on with the fuel system. Is the tank vented, probably through a vented gas cap?

Did you get this solved? Ignition coil and condenser are possibilities. Sounds temperature-related; look for electrical connections and parts that may lose continuity due to thermal expansion also.

(quoted from post at 13:47:56 11/29/21)
Did you get this solved? Ignition coil and condenser are possibilities. Sounds temperature-related; look for electrical connections and parts that may lose continuity due to thermal expansion also.

Click to expand...

Also, some Wisconsins used a temperature safety shutdown switch attached to one of the headbolts.

The switch could be failing, or, for that matter, have you checked that the cooling fins on the cylinder heads and blocks and other cooling air passages are clear of debris and mouse nests?