8N will not throttle up

powrguy · Jan 10, 2019

Well, my 8N (a 1951 model, SM distributor) all of a sudden has no throttle response. It will start, but barely runs, and does not increase speed when throttle is advanced. Yes, I checked all the linkages and fuel flow to the carb, and they are apparently normal.

I checked compression, and all cylinders are 90-95psi. My thought is that this indicates valves are closing okay, and no head gasket leak (no water in oil, oil is clean and normal level).

It almost acts as though it may be out of time, but it starts, and there's no back-firing.

Could it be a cam gear/governor gear problem? Don't know where to look next, so anyone that may have had similar problem could chime in?

I DO see that the governor linkage to the carb moves as the engine rpm changes slightly. It just seems to have NO throttle response at all, even though the throttle linkage opens the butterfly on the carb, but the engine remains at near-idle speed, regardless of throttle position, if that helps.

Tractor had been running fine, 2 weeks ago, and when it was started this past weekend, the above situation occurred.

OK, 8N Guru's, I put a new carb on, tried to start the tractor, and SOS; starts at idle and won't throttle up. I had COMPLETELY drained the fuel tank, put in fresh fuel, changed screen and gasket on the fuel tank shutoff bowl, removed air inlet pipe, cleaned air filter (wasn't sludged up at all, but changed the oil in it, anyway), cleaned and re-gapped plugs, etc.

Don't wanna pull the governor apart, as it was a SUDDEN problem, not a slow deterioration (like when the balls wear out).

Next move may be a bullet hole in the damned thing! LOL

ruffdog · Jan 10, 2019

You should be able to operate the throttle on the carb independent of the linkage coming from the governor. Then you would know if it is a engine problem or the governor.

mapper · Jan 11, 2019

Did you replace the little screen at the elbow that connects to the carburetor?

powrguy · Jan 11, 2019

mapper said:
Did you replace the little screen at the elbow that connects to the carburetor?

New elbow and screen at carb inlet were installed with the new carb.

powrguy · Jan 12, 2019

Okay....latest troubleshooting nightmares. After I lost spark for whatever reason, I put in a new points and condensor, disconnected the exaust pipe from the exhaust manifold, and then cranked the engine.....and, it started. Not only did it start, it actually responded to the throttle, for about 1 minute....small round carbonized balls came out of the exhaust manifold when it was first started, and then it quit running. I re-started it, but it would only run super-smoothly at idle, but NOT AT ALL when I advanced the throttle lever (it would sputter and die). I gathered up the carbonized balls that scattered all over the floor, and wound up with about a handful and a half of 1/4" to 3/8" balls and pieces, which were actually small baked acorns, I think. This indicated to me that some rodent crawled up the exhaust pipe, navigated through the muffler baffles and screens, and stored acorns in the exhaust manifold area in the engine, and probably also in the muffler. There's no sign that the debris would have entered the cylinders, as the exhaust pressure would have forced them out, AND, the engine compression test was good. I'll try to clear debris from the exhaust pipe and muffler, but may just replace the exahaust system and be done with that issue.

My other problem currently, along with the no-throttle-response issue, is that I have what appears to be coolant/oil mixture dripping from the oil filler neck breather cap. I have no idea how this coolant can be coming out the breather, since the oil in the crankcase is at proper level, and is clean as when the oil was changed about a month ago, and the tractor has had hardly any run-time since then. How can coolant come out of the breather cap, with NO COOLANT in the oil pan?

Thoughts?

powrguy · Jan 13, 2019

Problem apparently has been solved.

The burnt acorns finally were expelled from the exhaust manifold, and with the exhaust pipe disconnected, tractor is again running fine. If I connect the exhaust pipe, the tractor goes back to not throttling up, pressure builds and expels condensation out the oil fill breather, etc.

I'm ordering an new exhaust system and am runnning now with no exhaust to return the tractor to the barn, from my garage.

thanks for all the input here.

ruffdog · Jan 13, 2019

Ha! Years back I started a "barn find" 69 Corvette and blew out a 5 gal pail worth of burnt acorns out the exhaust. Revving up that Vette engine could really shoot them out too!

powrguy · Jan 13, 2019

ruffdog said:
Ha! Years back I started a "barn find" 69 Corvette and blew out a 5 gal pail worth of burnt acorns out the exhaust. Revving up that Vette engine could really shoot them out too!

I didn't know WHAT was happening when I dropped the exhaust and started it up......those acorns and debris bounced and blew all over my garage floor. Must have been building up in the exhaust for some time, and there's NO WAY to get the muffler cleared out, so I just ordered a new complete exhaust. I'm thinking maybe putting a screen over the pipe outlet, to keep rodents from doing it again.