85 Marathon, my recent problem and fix with another point against oil injection

[Dabble Inn]

My buggy suddenly began running crappy, seemed ok at wfo but anything less it was stumbling and smelled like gas. Coincidentally this happened immediately after I filled the tank as I ran it out of gas lol, at first I figured air in the line and it'll recover but it didn't.......

It's been 4 years since I changed the plug and it was fouled but a new one didn't help, my next thought was needle/seat or float in the carb since it was way rich rich rich but it was clean and all checked out good.....

Then it hit me:
A bad diaphragm in the fuel pump would allow fuel to get sucked directly into the crankcase, that made perfect sense and covered all the symptoms. So I changed out the fuel pump and Waa Laa success. Back to a good running buggy again........

{So now I'm wondering if running the fuel pump dry could've ruined the diaphragm with the hot pulse/vacuum from the crankcase? (no fuel to keep it cool) I have it bolted directly to the case since the insulator block broke years ago}......

But the most important and scary thought with yous out there that insist on using the oil injection system:

Since I still mix my fuel/oil there was no danger of a lean condition, but with oil injection it would be sucking unmixed straight gas from the tank into the crankcase resulting in a lean condition and possibly burn it up. Especially if you keep running it for a few days like I did......

Just a thought But what y'all think?

[trig123]

You are probably correct Dabble Inn . Glad you got things figured out .
I would always mix on one of these older carts.

[nickdalzell1]

I kinda like the oil injection for the simple reason that it adjusts the mix in a way that doesn't leave a huge trail of smoke and complaining folks. We work near a camp ground where our primary customers live or are staying there using their carts to go to and from areas there.

They have banned 2-stroke golf cars there recently due to many folks complaining about the smoke trails they leave behind their wake. Every single cart I've noticed doing that is being mixed by the customer who thinks dumping an entire case of 2-cycle oil into a 5-gallon tank means it's properly mixed. The last couple months a few 2-cycle cars came in for repair (wouldn't run, crank, no start) and the plugs were totally fouled from too much oil in the mix. Ran fine afterwards. Every cart had the oil injection bypassed.

I've seen them run nice and clean with the injection system left intact. I've never seen one fail in my life. Of course, people don't always keep track of how much oil is in the little oil injection tank because it uses so little many forget it. But that's not the oil injection system's fault. If people had any clue how to properly mix gas and oil (it's like a tiny ratio according to the service manual, NOT a 50:1) on a golf car they might not have banned them for pollution complaints. Last one we worked on was a Yamaha G1 where the gas tank had more oil than gas. It left a fog so thick you couldn't see behind you.

[Dabble Inn]

Some good points Nick, and you're right about some people mixing way too rich. I come across it all the time around here too, it's really sad that some places are banning them due to that. With the proper 128:1 mine doesn't smoke at all....

One thing I always wondered about with oil injection, when going from wfo to a long coasting stop letting off the pedal completely. The oil pump would be closed but it still takes like 5 seconds-ish for the engine to stop, is it getting a lean mix then? Or the opposite scenario, say when taking off you floor it so the oil pump would be totally open but the engine hasn't revved up the rpm's yet. Wouldn't that get a rich mix?

Maybe I'm being too picky lol, but with mixing I know I'm getting exactly the proper mix at all times throughout the entire rpm range.....

I once took the oil hose off a buggy just to watch it for a few seconds, I thought it might be a heavy or lighter spray depending on throttle position. This one just pooped out a drop of oil once in a while depending on throttle position, maybe it acts differently when installed in the vacuumed intake manifold but I wasn't impressed. Again, perhaps I'm being too picky. Obviously it works well enough so as not to burn up an engine LOL