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Sunstar fuel problem.


roma3112

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Fellas I was using one of my sunstars today out in the yard, and out of the blue the engine started acting up. The M20 started surging really bad and loosing power, i had to choke the engine to limp it back to the garage. The engine will run only with starting fluid sprayed into the inlet. I checked the fuel filter, choke adjustment,spark plugs and all came back ok. I pulled the fuel line (before the filter) and seemed to have good flow (via gravity) into a bottle i had set up. I pulled the line off the carb at the fuel inlet and cranked it over. The fuel does come out but it is a very weak spurt. I also checked the solenoid valve in the carb and that seems to work well. I was going to set up a small bottle and gravity feed some fuel into the carb inlet to check and see if it was a fuel flow issue. Well i couldnt find any gas line :( so what I did was pull the fuel line off my other sunstar and compare the two. The (working) sunstar had a Noticabely higher fuel flow at the carb inlet than the nonworking sunstar. What I was wondering was could i use a small electric fuel pump that I have kicking around. The psi rating of the pump is between 4 to 7psi. The pump is a simple "in-line " unit with no kind of return. I am concerned that just simply installing this in-line pump will "blow the jets out of the carb if the key is left on. Has anybody ever done one of these conversions to bypass the mechanical pump? If so are there any special ways of hooking up the unit? thanks john
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My D/A 1918 ran great last fall.Went to start it this winter and it wouldnt hit a lick. Pour gas in carb and it ran. To make a long story short I put a new KOHLER fuel pump on it this evening and she purs like a kitten. Funny how it didnt give me a warning????
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I take it both of you guys put in the stock fuel pumps? I was thinking about putting in an electric pump in place of the factory kohler pump.
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Yes mine was a stock replacement. The first one lasted for 20 years. I figure if it will last me 20 years I will be happy!!!!!
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Also, check the vacuum(crankcase to pump)line to insure it doesn't collapse running and the hose has no holes. I had a bad pump and hose on my V twin.
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i did notice that the rubber line from the crankcase breather to the carb base (where the airfilter sits)is ripped could this cause a problem? I did not notice a vacume line from the engine to the fuel pump. To me it looked like the pump (kohler m 20) was cam driven? It looks like i will try to source a stock engine mounted pump i guess. I just figured where I had an electric pump that it would be a quick repair vs. waiting a week or so for the pump tp get here from jacks. Do any of you folks have a link to an M20 service manual or somplace where i can look up the parts i need? thanks john
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bob thanks for the clarification I didnt think I had any vaccume lines going to the pump. I am just concerned that just wireing and plumbing in an inline pump could cause a pressure build up in the fuel system and cause damage.
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guys thanks for all the imput! I am still leaning toward the electric pump, However i am not sure if it can be done on one of these engines. I am still trying to find out if I need a return line from the carb? I looked at some articles for some members that have put elect pumps on their onan engines but I cant find any members so far that have put an elect pump on a Kohler M20 equipped tractor. I am still concerned about where all the excess fuel pressure would go if the engine was not using the fuel. It may not be an issue but this is a problem I have not had to deal with before.
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I have used electric fuel pumps on other stuff and wire the pump to the side of the coil that is only hot with the key on. I have no idea if you could do this or if there a consequences.
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That pump you have is for American cars with carbs. The pressure is pretty high for a tractor. I would get one for a Foreign car. They generally are 2 to 4 psi. There is also a way to plumb the hoses so that it sends full flow to the carb without building excess pressure. If you want to hook it up that way, let me know and I will send you a diagram.
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In this setup the fuel pump will provide full gas flow to the carb but will build only the amount of pressure needed to push the excess fuel to the top of the return line. You should run this line up to the hood to get the pressure you would have from a gravity drain tank at the same height. It definitely works, because it was used quite often on pulling tractors back when I was doing garden tractor pulling. Most people think the return must be into the tank, but it works just fine with the "T". Gravity flow from the tank will make up any fuel that is used in the carb.


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My M20 and CH20 engines all have the vacuum operated fuel pumps mounted on the side of the engine. Until now I thought that was the only one used.
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blackfarms1
Hello, had the exact symptoms you describe with my sunstar last year. The crankcase breather tube was ripped also. When I took it off to replace it it fell apart in my hands. After replacing it and the other lines she ran fine again. I would try that before replacing fuel pump. Sean
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