Old Tecumseh dies after running a minute or two

T

Tdj2591

Member
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
 
First, HM 80-100 is an engine range, not model number. If it is a 10 hp engine I’m assuming you may have a HM100, unless it is an overhead valve engine. Engine numbers will be stamped on the shroud, please take another look for them.
 
If I had to put the computer screen to my forehead and guess, bad fuel was put into it, or the exhaust is plugged with a mouse nest.
 
Sorry, I forgot to include that. Yes, it is a 10hp. I’ve looked everywhere and cannot find an engine serial number. Pretty certain there’s been no mouse. It started and ran constantly without problem for over 24 hours. This problem only began after the low oil sensor shut it down.

I wonder if the oil sensor could be bad?
 
Trying adding some choke as it's dieing or if running rough start adding little bit of choke to see if it gets worse or slightly better.

Did you remove the carb fixed low speed jet jet that is under the plastic cap and clean it?

Might even try using a gravity fed external tank to the carb.
Their is a fine screen on the end of the gas petcock that is at the tank.
Blow air back through the petcock with the gas cap off to temporary unclog the screen. If that helps remove the petcock and clean the screen and tank again.
You can disconnect the oil sensors for now.

Install another spark plug.
 
Tdj2591 said:
Sorry, I forgot to include that. Yes, it is a 10hp. I’ve looked everywhere and cannot find an engine serial number. Pretty certain there’s been no mouse. It started and ran constantly without problem for over 24 hours. This problem only began after the low oil sensor shut it down.

I wonder if the oil sensor could be bad?
Click to expand...
disconnect the oil sensor and try again. I would wonder why it used so much oil. It should be checked each time before starting, and changed periodically.
 
Hello T.,

These are fairly simple to work on if you have some basic tools, common sense and a camara phone. A few internet videos would also help.

This problem could have been easily interpreted as a low oil shutdown, but a tiny piece of trash stuck in the carburetor main jet could also be an issue. The fuel tank shutoff and float needle valve could also have some trash caught inside them.

I have a Coleman 4000 watt with a B&S 8HP that typically sits for years with no fuel in it. Eventually. what little residual fuel left behind inside the tank mostly evaporates, but it leaves behind shellac like deposits and that eventually turns into a fine powder.

New fuel put in the tank begins to loosen this stuff over time and it eventually makes its way into the fuel needle valve and carburetor. Your son was lucky to get a 24-hour run time out of this before it shut down.

These older engines were known to use a little oil, especially at 3600 RPM for the generator head to function properly.

Also considering the age, the ignition coil may be breaking down internally after that 24-hour marathon run that it had. Even excess rust on the flywheel magnet can create this problem.

The engine information is normally stamped small numbers and letters on the pull starter housing. Being this is a generator; the numbers will be hard to see if it has the large nylon "extended run" fuel tank on it.
 
I've got that exact Colemate/Powermate with the 10HP HM100 Tecumseh plus some others.
The engine and gen all obsolete and in the category of dinosaur eggs, but it just keeps going like the energizer bunny.

What I do to long term store the gasoline gen's is first I never install ethanol gas then on the Coleman/Tecumseh plus others I do a strong mix of gasoline and ATF in the gas tank and remove the carb bowl drain plug and drain all gas then turn on the petcock and send ATF gas to the carb. Start the engine then let it run awhile and then kill and store. When ready to use just do a preliminary test run then fill the gas tank full and operate. The ATF keeps all lubed during storage and no dried trash and is not even noticeable to the engine operation.
The ATF also keeps metal tanks from rusting. I could do a strong mix of 2 cycle oil mix of around 35:1 but ATF is cheaper and always does good.
On the HM100 Tecumseh gen I can easily switch from propane to gas if desired.
You mentioned backfire when dying sometimes. Mine does the same thing, just the nature of the beast when killing the engine with it running at high rpm,s due to no gasoline ABS on the carb. (anti backfire solenoid)

You need to try to get a hint when troubleshooting if it's fuel related or ignition related.
Might be a magneto.
 
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