Old Tecumseh dies after running a minute or two

[grumpyunk]

I'd check the fuel flow at the carburetor float bowl inlet. Disconnect and collect the flow in a glass jar so you can check for water pearls. The flow should be full diameter with the shutoff valve wide open. If the flow is more of a trickle or slow, the interior of the fuel line could be coming apart. They can look perfect on the outside and be crumbling on the inside. You could also have a clogged filter or the outlet screen in the tank could have found some more plastic bits and gotten clogged a bit.
If you have full flow from the fuel line, then I would remove the float bowl and check that the float can move the needle freely to allow filling the bowl from the inlet. Gummy deposits or corrosion can cause the needle to bind, or the float may bind on the float pin or the two supports.
tom

 

[Gord Baker]

Have you tried checking the Valve Lash? 0.004-6". New Cap and New Low Oil Swtich would be next on my list after cleaning screen on carb inlet.

 

[rhkraft]

The pieces falling out of the gas cap bother me. Could be the cap is not venting properly. Did putting on the new cap help? Mixing oil with the gas is not something I would do. It is the same as storing 2 cycle engines without putting Stabil in the fuel to prevent varnish. The gasoline evaporates leaving the oil behind to become varnish. I don't understand why everyone is so obsessed the ethanol. Alcohol absorbs water just like Stabil and gas line anti-freeze and prevents rusting and other water borne debris. Newer engines are designed to run on ethanol and I have been using it in old engines for many years without problems. I have a 1991 MTD Briggs engine push mower and switched to ethanol when it came out. It starts on one to two pulls every time, even first start in the spring. It has always been kept inside, serviced once each fall with Stabil, oil change, and an air filter. Put in a few new sparkplugs over the years, rebuilt the rope starter, and replaced the two rear wheels that wore down and started falling apart. It doesn't use oil and runs great after 35 years of service. Leaving equipment outside that allows water in the fuel is the biggest problem. Tarps don't work, it gets damp under there and doesn't dry. Stabil and ethanol solve most water issues. I even used 90 Octane unleaded auto fuel in my airplane. I reason I didn't use ethanol is because the alcohol deteriorates the carb gaskets on some airplane engines, but I had to drain water from the fuel tanks during every pre-flight.

 

[Auto Doc's]

FWIW...

I have an old Craftsman 10HP generator.
Changed the oil a couple years ago and it wouldn't start afterwards. I never use ethanol gas, fuel tank is plastic so no rust, etc etc

It also has an oil level sensor switch. The sensor ohm'd out OK. Sensor connects to a little diode/relay box, which in turn has a lead to the three wire on/off toggle switch.
Disconnected that wire from the on/off switch and it fired right up.
Been running without it ever since...not worried about it bc I check the oil before firing it up anyway.

Maybe one day I'll replace the diode/relay. Maybe not!

Hello T.,

Those oil sensor "magic boxes" were not designed for long life or reliability and most are no longer available for older generators.

The oil in any portable generator has to be checked and topped off on a regular basis, but people were annoyed by this, so engineers came up with this convenient little "fix". At least they prevented many people from blowing their generators up due to neglect.

Most portable generators have to run at a constant 3600 RPM to produce a constant 60 cycles of usable electric power. Any engine running at that RPM will use a minor amount of oil after hours of use.

 

[outdoorpowermike]

When engine stalls, try to restart soon as possible with starter fluid or something 2t2. If engine returns and continues to run then the ign coil is most likely good. If it starts to crap out when engine is up to temp then you have a fuel related problem. Check fuel flow into carb, Tecumseh motors this old will have valve lash problems. Exhaust Valve not seating when hot and losing compression. If engine starts cools down and restarts maybe your problem. Please inform use of your repair fix.

 

[sgkent]

I'd check the fuel flow at the carburetor float bowl inlet. Disconnect and collect the flow in a glass jar so you can check for water pearls. The flow should be full diameter with the shutoff valve wide open. If the flow is more of a trickle or slow, the interior of the fuel line could be coming apart. They can look perfect on the outside and be crumbling on the inside. You could also have a clogged filter or the outlet screen in the tank could have found some more plastic bits and gotten clogged a bit.
If you have full flow from the fuel line, then I would remove the float bowl and check that the float can move the needle freely to allow filling the bowl from the inlet. Gummy deposits or corrosion can cause the needle to bind, or the float may bind on the float pin or the two supports.
tom

The OP wrote several posts back that was fixed:

Thanks to everyone who commented and gave me welcomed and helpful advice. I am pleased to say IT’S RUNNING! And, it’s running smoothly. I reattached the low oil sensor wire after installing a new needle seat and valve and ran it again. Turned off fuel and ran it until dry, then drained the tank and removed any residual fuel. It’s now back under my workbench until the next long power outage. Thanks again!

 

[M42duster]

Coleman Powermate 5000 Maxa ER Plus generator with a 10 hp Tecumseh bought new in 2005, Used 3 times, running only non-ethanol fuel, about 10 years apart. Turned off gas and ran engine until it died each time, then drained tank. Always stored inside and never exposed to weather. During recent ice storm my son borrowed it. I replaced the spark plug and added an in-line fuel filter and it started and ran smoothly for at least 24 hours. It died about 4am due to low oil shut down by oil sensor. He added oil and restarted it, but it ran rough and died after a minute or two. He may have added a little too much oil. He had to have power and bought a new generator when the stores opened and returned mine.

I removed and cleaned the carb, which appeared to be very clean. Needle and seat showed no wear or build up. No trash in the carb. Easily blew air thru fuel lines. Gas filter had plenty of fuel visible in it when I refueled it. Spark plug appeared okay and gap was correct. Changed oil, filled to correct level and changed air filter.

It started on first pull but ran rough even after turning off choke. Plugged in a 500 watt light and it smoothed out slightly, then died. Backfired when it shut down. Easily restarted but again died within a minute or two. It acts like it might be fuel starved. I verified that the fuel line was not collapsing, the fuel valve was completely open and not blocked and the filter had fuel in it.

The gas cap had an inner plastic disk that had deteriorated with lots of small to tiny pieces of plastic falling into the tank. The tank’s filter screen kept the plastic particles from the engine (unless smaller than the holes in the screen, and some were minute). I removed the tank, cleaned out all the debris and installed a new gas cap.

I’m not a mechanic. Any idea what might be causing this? Should I dismantle the carb and make sure that all passages are open? I didn’t change any carb screw settings.

Tecumseh HM80-100 (no serial number) L head
Coleman PM0525312, serial 94520848

I know you put a new gas cap on. Just confirm it's venting.