Need Help with Robin Engine

[pairodime]

I'm having a problem with my 425 Robin engine-- she starts and runs for 3 to 15 seconds and then stops. I suspect it is starved for fuel but hate to randomly try solutions.

Here is some background-
-My 425 is the newest model with 50 hours on it.
-I've been having a minor problem with fuel hose. The engine would stall due to too much vapor in the fuel line. Terry had me reroute the fuel line so it wasn't in contact with the hydraulic lines and it seemed to make a difference, but it would still happen to stall after running for a long time.
-I ran the engine 10 hours over the past 2 days with my only problem being the fuel line. You can tell this was the problem because the fuel filter bulb had no fuel, only vapor. Once it cooled for a 15-20 minutes, the bulb would have fuel in it again and she would run fine.

So today, I was planning to do my 50 hour service, when I can't get it to run longer than 15 seconds. There is fuel in the line, filter bulb, all the way to the fuel pump. A review of the Robin service manual shows the carburetor has a float chamber that holds fuel. My suspicion is that my fuel problems have cause this chamber to not be refilled adequately and the PT dies when its contents have been exhausted? After a few minutes the PT will start again and run again' but once stalled will not start until some time has lapsed. Or, could there be some other problem with the carburetor? No matter how I adjust the choke or throttle, I cannot keep the engine running.

Any help would be appreciated. Thanks

 

[Egon]

Have you tried changing the filter?

Egon

 

[reb]

I'm not familiar with that particular engine, but I have had similar problems with carbureted engines where a screen at the carburetor inlet got clogged.

 

[pairodime]

Egon,
I haven't replaced the filter, but it is visible and has only minor deposits in it.

Reb,
There is no screen shown in the service manual, but I do believe there is a partial block somewhere or poor fuel pump performance. This problem is occuring when the tank is half full. On a whim, I topped the tank off and the problem goes away. Seems the the extra 8" of head pressure on the fuel system is able to keep the fuel flowing to the engine.

Anyone else have a suggestion? I think I'd like to call the Robins rep, does someone have the phone number of Jack?

Thanks.

 

[J_J]

You might try and add some extra fuel hose to the output of the fuel pump, and see if the fuel pump is pumping like it should. Disconnect the spark plug wires and crank the engine over several times. If you have good pressure, the fuel pump is good. If not, the diaphragm on the fuel pump could be bad. A diaphragm with a hole in it will let gas seep down to the engine and let you start and run for a little bit . If the carb has a solenoid in the float bowl, it might be sticking.

 

[pajoube]

Is this the first run 425 with the Robing Engine?
PJ

 

[toolz_not_toyz]

This sounds like vapor lock. You need to route the fuel line away from any heat source. That's probably what Terry was trying to get you to do when he asked you to reroute the line.

 

[landscapercarl]

We have had the same problem but usually in the fall and early spring We never got an answer form Robin or Power Trac but after 900 hrs the rings were froze and valves shot had to have engine rebuilt. Power Trac said thats about how long it should last and for 3000 they would put in a new engine that was bigger. They didn't want to sell us what we needed to mount a Kohler in it. They wanted to do the work.
I'am not pleased with this engine nor have we been since day 1 We will replace this engine in the off season with a Kohler since I know they will last. We are sure it's all heat related and are going to mount a fan to get more cool air around the engine.

 

[tracdoc]

Still waiting for Jack from Robin to engage in this thread...

 

[pairodime]

Pajoube, yes it is the first run 425 with the Robin engine

JJ- Thanks for the tip. I did pull the hose and check the fuel pump. I get a very minimal flow so I'm very sure that the problem is the fuel pump. Just need to get it replaced. Until then, as long as I keep the gas tank full enough, there seems to be enough flow to run the engine.

I do believe that it is all about heat management. I've rerouted the fuel line and insulated it where it was immediatley adjacent to hot components.