Oil & Fuel Too much fuel? PT422,120hrs

rmcconnell · Sep 4, 2007

I have a PT422 with a Robin Engine on it. It has approximately 120 hours on it. I've used it for mainly for mowing and some bucket work this year. About a week ago it started to run bad and stalled out. I've been troubleshooting it and have been unable to use it since.

Here is what it does:
It starts fine, but after a short period (<1-2 minutes) the exhaust turns black and it struggles to run. It will not idle on low. Choking it makes it worse.

Here is what I've tried:
1. changed spark plugs- new ones, hotter new ones, etc
2. disassembled and cleaned carborator- looked like new, paid particular attention to brass fuel parts, fuel solenoid, and float shut-off.
3. used different gas- ran well when the tank was near empty
4. checked compression- over 150psi each cylinder
5. drained oil- thought that I smelled gas in it, and thought that the level may have been too high
6. watched the rocker arms- look to move fine
7. air filter- it is a new one and it runs the same with it removed

Any suggestion? Should I pull the extaust off and take a look in the exhaust ports? Could the fuel pump be running too fast and need replaced/repaired? Could I look into the carborator and tell if the float is working?

J_J · Sep 4, 2007

You could put a pressure gage before the carb, and see if the pressure is correct. You can not see the float unless you remove the bowl, and then, you can lift the float to see if it will shut off the fuel. If the float is not set correctly, or is not seated, it will let extra fuel into the engine, running or not. You said you smelled the oil, and it had a gas smell, and you thought the oil level was high.

I had something similar happen on a Honda, I pulled the recoil rope, engine would not turn, engine appeared to be locked up, so I removed the oil fill plug and gas and oil poured out. That told me that the float seat was leaking. I added new oil, and started the engine. I now turn the fuel shut off valve to off to avoid this situation, and let the engine die from fuel starvation. This also prevents sludge and varnish buildup, by having no gas in the carb.

I would first install a new seat in the carb, and see if that fixes the problem.

J_J · Sep 4, 2007

Let me add something about the fuel solenoid. It is designed to shut off the fuel when you turn off the engine. , but what if there is trash under the seat of the fuel solenoid, then the fuel would enter the main jet and cause flooding. I believe this is how it is supposed to work. It is a spring loaded plunger that is supposed to seal the main jet when no power is applied. When you start the engine, 12 volts is applied to the solenoid to pull the plunger off the main jet, and the engine should start.

rmcconnell · Sep 4, 2007

Thanks for the reply.

8. tested fuel solenoid- turned the key and solenoid opened and closed moving the shutoff stem.

I'll see if I can add a fuel shut-off valve. If nothing else, I'd like to mostly close this valve and see if that doesn't make it run better by resticting fuel.

Next time I tear the carborator apart I'll check the float for a leak and test that it shuts off fuel when it reaches a certain level in the carborator. Perhaps I'll just order some float+seat parts to install after I have it apart.

scarg · Sep 4, 2007

I had problems 3 years ago with my 422 (now i have bigger problems!)

I found that the fuel line was kinked between the gas tank and the fuel pump. Very kinked although it would run good until it warmed up and then sputter and finally die.

Steve

Clarke · Sep 4, 2007

You could have a leaking needle and seat, float set to high or float not floating anymore. Just a thought

sg

rmcconnell · Sep 4, 2007

Yeah, I think that it has to do with the float and seat. I'm no engine expert but all the black smoke leads me to think that it is getting too much fuel. Most problems that people seem to have are fuel restriction which would cause a stall. I seem to have lots of fuel and fuel smell.

There doesn't appear to be a float height set in the diagram.

I'd also say that I have good fuel flow because when I open the carborator drain screw it pours out of there for a while.

Clarke · Sep 5, 2007

You can most likely download the engine manual on the Robin web site it should give you the float specs and height.

sg

rmcconnell · Sep 5, 2007

!!
I may have it. I give credit to my friend's farmer cousin who said that a weed eater did this to him. He said that there was a hole in his float.

I took the carborator apart today (for the 3rd time) and looked closer at the float. There was no visible hole. However, when I squeezed it gas came shooting out!

Now where can I get a replacement float ASAP? Anybody? I'll call Powertrac and Robin tomorrow.

I'll post if this solves the problem.