Dealer 1425 carb, gas or dealer issues ?

[hogi]

Well, at this point my plan is to drain the crankcase, change the filter, re-fill with oil and install a manual shut off valve for the fuel. Now, at some point last fall/winter I may have let it sit too long and the fuel may have started to go bad because I have had sticking ,and debris / corrosion problems with the fuel solenoid, i have had to clean it out several times as it will stick in the closed position. I will not go back to this particular dealer because of the ignorance he has shown by assuming what the cause is without ever looking at it. Debris in the float valve seat is a possibility. If I go to another dealer and they find debris in the float valve, will I get billed? If I take it apart first, will I void my warranty? My owners manual states " if fuel tank is mounted above carburetor a fuel shut off must be mounted to prevent fuel from flooding the carburetor. Power -trac obviously missed that, as mine came w/out one. Yet, it hasn't been a problem before. At this point it seems if Robin isn't responsible, then Power-trac is, for failing to follow Robins installation instructions. But, it may be be less of a hassle to just install the shut-off and be done with it?

 

[J_J]

Hold the phone. Does that Robin have a mechanical fuel pump? Some mechanical fuel pumps can leak gas into the crankcase if their rubber diaphragm ruptures. Under the right circumstances, it can be an explosion hazard.

How was it determined that the carb was at fault? Has anyone actually looked to see what caused the problem?

That was an educated guess on my part, partly because, I have seen that happen many times. However, you could be right in that it leaked through the mechanical fuel pump if it has one. He also added that the fuel solenoid was sticking, and that would allow to much fuel in the bowl. I have also cleaned out many of those fuel solenoids. If the fuel filter does it's job, then it must be something in the fuel that is forming, maybe crystallization of some elements and that can happen with gasohol. He also said that the fuel was old. I bet it smelled like old varnish.

Debris in the float valve. Trash in the fuel has nothing to do with warranty. You put the fuel in the tank. I have found trash in my backpack blower enough to clog the filter. The tech poured the fuel out through a cloth filter, and showed me all the debris/trash. A new filter in the tank. and was good to go. I have noticed that when a backpack blower can not rev up, it is usually a dirty fuel filter, or the screen is clogged in the muffler. I usually throw those screens away.

 

[SnowRidge]

If the carb float sticks, fuel can enter the cylinder through the intake valve. If the exhaust valve is also open, it may enter the exhaust system.

To get into the crankcase, it would have to also leak down past the rings or valve seals, or possibly go directly through a carb float vent connected to the crankcase or valve cover. However, I believe carbs are usually vented to the intake, not the crankcase.

I'm not familiar with Robin engines, owning exactly none, but from my perspective, the first thing I would check is the fuel pump diaphragm, assuming it has the mechanical variety similar to that of the Kohler. Hopefully, checking it would involve nothing more than removing a couple of screws like on the Kohler.

 

[Marks481]

I am not a small engine expert, although I have read their posts on the internet.... ;>

The Robin Service Manual does infer that it is possible to get gasoline in the oil:

Phenomenon: Oil dilution
Possible causes: Breather faulty
Remedy: Repair or replace

The "breather pipe" must serve the same purpose as the PCV (Positive Crankcase Ventilation) valve on an automobile engine, which draws a vacuum on the crankcase based upon the suction at the intake to the carburator.

Find a new dealer, and report the old one to Robin America.

The breather pipe goes from the carburator to the #1 cylinder head, and of course there is a direct path for oil to drain from the cylinder head into the crankcase.

It appears to be just a rubber hose (not a check valve like the PCV to prevent oil from getting into your carburator). I don't think their "remedy" is correct, since how could this hose be "faulty" enough to cause gasoline to flow into your crankcase? It is very possible, however, that if the carburator overflowed that some quantity of gasoline would get into the crankcase (even if the hose wasn't "faulty"). A fouled needle valve/seat would cause this overflow.

Looking at the geometry, it seems that only a small percentage of gasoline overflowing would go into the crankcase, and the rest would just pour out the sides of the air filter. I think you would notice this long before any significant amout of gasoline got into your engine. Is your air filter soaked in gasoline or smell like gasoline? Minus one point for the dealer.

I think Snowridge is spot-on, and would check the diaphragm of the mechanical fuel pump. That provides a direct flow path into the crankcase. Of interest, the parts manual does not give a part number for the diapragm, although it shows it in an exploded view.

Diagram from the Robin EH72 service manual: http://www.robinamerica.com/media/manuals/128450737920567500.pdf

I thought the Robin engine had a fuel solenoid valve, but I guess not. Another $25 to spend, I guess...

 

[J_J]

It soes not have a mechanical fuel pump.

I believe that engine does have a solenoid fuel shut off, item #19. Ia also think the fuel pump is a pulse operated fuel pump, and is just mounted to the metal housing, and has no access to the crankcase. . It is very possible and probably that the fuel drained down through the cylinders, or the crankcase breather tube.

The engine illustration shows a fuel shut off valve, but if the crankcase was full of oil and gas, then it might be bypassing fuel due to crud keeping the valve open. You can test it by removing the output line and see if any gas comes out with power off,and then apply power to see if it is operating correctly.

You can see the solenoid item # 19 where a breakdown of the carb is displayed.

 

[ponytug]

Just FYI: It is possible to get a small bit of grit in a float valve that causes some gasoline weeping. If the fuel tank is above the carburetor, you can flood the oil over time. By the manual description, I would hazard a guess that the Robin fuel solenoid is designed to shutoff the engine, but not seal the fuel completely, so it probably would leak as well.

I would go with the extra fuel shutoff; it is a belt and suspenders approach. Since it sounds as if you leave the tractor over the winter, it might be a good idea to drain the fuel completely in the future.

All the best,

Peter

 

[Gravy]

On my Robin 25hp, the fuel pump is pulse operated and cannot leak into the crankcase. The fuel solenoid only blocks the main jet, not the float valve. A leaky float valve can definitely flood the engine and dilute the fuel just from gravity feed.

Hope that helps.

 

[Marks481]

On my Robin 25hp, the fuel pump is pulse operated and cannot leak into the crankcase.

Could you explain that for me? The pump is pulse operated by crankcase vacuum; it seems to me if the diapragm had a hole in it, that would make a straight path for fuel to flow through the vacuum hose into the crankcase. I must not be understanding the mechanical process.

Although that seems unlikely to be the failure mode since the engine is so new with so few miles.

A leaky float valve can definitely flood the engine and dilute the fuel just from gravity feed.

Guess it is time to by a shutoff valve. $10 now could save some pain later.

 

[J_J]

It does not have a mechanical fuel pump.

I believe that engine does have a solenoid fuel shut off, item #19. Ia also think the fuel pump is a pulse operated fuel pump, and is just mounted to the metal housing, and has no access to the crankcase. . It is very possible and probably that the fuel drained down through the cylinders, or the crankcase breather tube.

The engine illustration shows a fuel shut off valve, but if the crankcase was full of oil and gas, then it might be bypassing fuel due to crud keeping the valve open. You can test it by removing the output line and see if any gas comes out with power off,and then apply power to see if it is operating correctly.

You can see the solenoid item # 19 where a breakdown of the carb is displayed.

I retract my statement about no access to the crankcase. Please don't beat me or take my rice bowl. I didn't mean to make a boo boo.

I believe it would be possible to get fuel in the crankcase if the diaphragm was violated. However if you can check it out, you would prove to your self if that were the case

 

[Gravy]

Could you explain that for me? The pump is pulse operated by crankcase vacuum; it seems to me if the diapragm had a hole in it, that would make a straight path for fuel to flow through the vacuum hose into the crankcase. I must not be understanding the mechanical process.

Although that seems unlikely to be the failure mode since the engine is so new with so few miles.


Guess it is time to by a shutoff valve. $10 now could save some pain later.

I can explain it quite easily - I was wrong! I didn't think it through. A hole in the diaphragm could indeed fill the crankcase with fuel.