87 Marathon fuel pump issues

[sonnyk]

Bought an old marathon about 3 months ago... and she ain't no prize! But it still runs. I use it during double knee replacement surgery recovery to get around on 3 acres. It will need some major engine work but that will hopefully wait until winter arrives. I've had to use increasing amounts of choke to get it to start and now even to continue to run.
A couple weeks back I took off the fuel line to the carb and observed some fuel spurting from the line while cranking, but not much. I figured that it would be enough fuel flow for this small engine though. Now it quit completely, even using full choke. Checked pump output again, and nothing... or next to nothing anyway. I can fill the carb with fuel using a long 1/4 inch clear tube filled with fuel and it will run ok. Took off the fuel pump and I can feel an air pulse at the port on the engine. I'm going to order a pump rebuild kit and try that, but there's something I'm not quite sure about regarding the pulse of air from the engine driving the pump. (I have next to no experience with these 2 stroke motors.) I've done some reading on this site and seen that there should be a vacuum at the engine port that drives the pump. But it feels to me like pressure pulses, not vacuum. So should I find vacuum or pressure? Look like maybe either would drive the pump.
A compression check reveals around 60 psi is all I can get. So is this causing blow-by and this is the source of the pressure pulses? Right now all I want to do is get it running again until later in the year when there is time do do more extensive work on it. I'm looking for some good advice.
Sorry for the long post... but one more thought. This condition has come about since I removed the automatic oiler and started mixing the fuel/oil at 128/1 ratio in the fuel tank. Is it possible that the diaphragm in the pump doesn't like the oil in the fuel? Seems unlikely to me, and I know others have done this with no issues, I assume.
By the way, I've checked the line from the tank to the pump... no restrictions and no air leaks that I can see.

[cart around]

I'm surprised that it's running at 60 psi.

The pump should put out a healthy spurt. The two major issues are ripped diaphragms, and bad crankshaft seals. Either one will cause a pump to quit working.

Since it runs when you put gas in the bowl, it is most likely the pump. Again very surprised that it even runs at 60 psi.

Did you plug the intake hole when you removed the oiler? it needs to be air tight.

Click on my user name, and statistics. You will see a thread about fuel pumps.

You should get enough pulse to move your finger. I don't really think you can feel the suction part.

[sonnyk]

It actually seems to be pretty strong, when it's running right.
Yes, I did plug the port when I removed oil injection.
I did remove the pump and took it apart. The diaphragm is clear plastic, and feels really stiff. So stiff that it may not be flexible enough to move as it should. That's my theory anyway. Didn't see any holes or rips.
I do feel a pretty good shot of air coming from the pulse port. I'll do as you suggested and search your posts Cart Around. I appreciate the input.

The cart will have to wait a couple of weeks before I jump into it again. Tomorrow is retirement day for me, and we're heading to the mountains for a couple of weeks. YEAH!! I'll have more time to dink around with the cart after that. I'll touch base with you all then. Thanks again for the help.

[truckracing]

Did the rebuild kit fix your issue? Mine is starting to do the same thing. I'm going to take my pump off tomorrow and see what it looks like.

[cart around]

This is the thread both of you should be reading. http://www.buggiesgonewild.com/gas-e...fuel-pump.html

Remember that there are two diaphragms in there.

[sonnyk]

Originally Posted by truckracing

Did the rebuild kit fix your issue? Mine is starting to do the same thing. I'm going to take my pump off tomorrow and see what it looks like.

First time back on this forum for since summer. Life gets busy.
I did buy a rebuild kit but when it arrived, it was for a bigger pump. The diaphragms were larger diameter than my pump. However, the rubber check valves appear to be the same part. When I opened up the pump, I found a faulty check valve - don't remember which one - and I replaced it and that seemed to fix the problem. This old worn out cart has other issues, but at least that one is fixed - or maybe just in remission.

[sonnyk]

Originally Posted by cart around

This is the thread both of you should be reading. http://www.buggiesgonewild.com/gas-e...fuel-pump.html

Remember that there are two diaphragms in there.

Cart around...
I read your post about the fuel pumps, and the part about gas getting into the crankcase through the pump pulse port. Thanks for putting that info out there for all of us.
I have experienced a similar thing... When I fill the fuel tank above a certain point, and the cart is left parked for several hours, gas starts dripping under the cart.
(apparently, fuel is draining into the crankcase and seeping out through a parting surface or gasket or something. Recent knee replacement surgery is going much slower than expected, so it's hard to get down under it and see what is happening)
When I start the motor, it will start but is loading up bad until it burns out the extra fuel. It doesn't do it when the fuel tank is under a certain level, so when I take some out down to a lower level, all is well. I assume that a siphon is set up when the level in the tank is higher than the level of the engine. What I haven't looked into is whether the gas is getting into the crankcase through the fuel pump port or through a worn needle valve in the carb. Also, it seems like if either has a leak, then I would expect this to happen all the time, not just when the fuel level in the tank is high.
Anybody got any ideas?

[cart around]

I would hope that it's leaking from the tank, and not the crankcase.

The crankcase needs to be air tight for the engine to run.

[sonnyk]

But that would't explain why it is loading up when I start the engine.
I'm going to have to fill it up and just get down under it and check it out.