87 Marathon Starting Issues

[hiperf2007]

Looking for help for a very annoying starting issues. Long story short, my farther never has had issues with this cart since purchased new back in 88/89. He pasted in 15 and it was given to me. I have since changed spark plug, fuel pump, lines, fuel filter, air filter, carb, just for maintenance. Ran it for a few years and it was fine. Then came the problems of not starting. Has spark and smells like fuel. It can sit over night and never start. I get it to start by removing the plug and cranking it over a bunch of times, then reinstall and plug and it takes right off. It will run and run all day without an issue until it sits again.
The spark looks fine. I know it's getting fuel because the plug is wet from cranking. Does anybody have any ideas?

I had a fuel issue before so I installed a new carb.
New spark plug that looks to be sparking good grounding on the muffler.

The reason I changed the carb was because it was doing something LIKE this and it turned out the carb was flooding and blowing back into the intake. Found fuel sitting in the bottom elbow. New carb fixed that problem.

It just seems like it will run all day long. Start and stop. Then the next day it's probably a 90% chance that I will have to remove the spark plug, crank it a few times, and then it will fire up instantly.

Does it almost sound like the carb is coughing too much fuel in at first and getting the plug too wet? Might make sense but when I remove the plug, I don't dry or burn off the tip and it's sparking just fine.

I would appreciate any help on the topic.

[Dave Box]

Hello,
I used to hang around here many years and years ago. My 86 Marathon is long gone but having a quiet Thursday I thought I would revisit an old playground and here is your post.

I am sure that you will appreciate remote diagnosis is a little risky but never one to hide my light under a bushel here is my prediction.

The diaphragm in your fuel pump is very old and brittle. In fact it is so brittle it has split. This means that fuel is leaking past the diaphragm, down the air passage and into the crankcase (thanks for nothing gravity). This causes a flooding situation on your first start and you have learned to clear this by blowing gasoline out of the spark plug hole.

The reason that it runs fine all day is that the weeping is slow enough to need an overnight rest to cause flooding.

So buy a new fuel pump (or if you can be bothered a rebuild kit) and you will be back to fogging up the neighborhood.

All the best
Dave

[newtjl]

The cheap chinese carbs will leave you chasing gremlins indefinitely. Any chance the OEM carb is stiil around somewhere?

[hiperf2007]

I actually pull the old carb back out. I gave it a good cleaning and it does the same thing. I read the post about the fuel pump and I wouldn't still out rule it but I ahave already changed it.
Same thing tonight. Had to pull the plug and crank it a few times. Then cranked it for about 10 seconds and it fired up.
It's getting old.
I should mention that before when I had the carb problem I was messing around with the adjustment screws on the side. The screws people say are not adjustable.
Maybe I have those set wrong?

[hiperf2007]

Does anyone else have any other ideas?

Seems to be better if I just barely push the throttle and maybe give it a quick choke. Still cranks for an unreasonable time.

[cart around]

I would have put money on a ripped lower diaphragm in the fuel pump.

What ratio are you mixing your fuel?

[hiperf2007]

We have always ran 87. My son runs around on this thing during the day and burns an ungodly amount of fuel.
The factory oil pump has always worked fine but I always throw some extra in when I refuel. The amount I add has never caused an issue in the past.
Maybe tomorrow night I will pull off the fuel pump and sew if it's wet on the wrong side.

[cart around]

There are 2 diaphragms. The lower one is the one that rips allowing gas into the engine. That is why the oil pump should be removed, and you should be mixing your own oil. A ripped diaphragm allows straight gas directly in to destroy parts. By mixing gas and running the oil pump you are slowly clogging your muffler and fouling the plug

[hiperf2007]

Could definitely be but I never run a lot of extra oil. Just maybe two small caps in 6 gallons of gas. Doesn't really smoke either with adding a bit more. I could delete the pump but after all these years I would be very concerned about accidents and forgetting the oil once and having a melt down.

[Dabble Inn]

When, not if. But When that 35 year old oil pump quits on you you'll have a melt down too and without warning, are ya feeling lucky? LOL.....

Why not have one or even two 5 gallon cans of premixed fuel ready and designated just for the buggy? You'll have less moving parts and one less thing to worry about on our old buggy's...

I have a friend with a broke down 88 right now, I suspect fuel pump too as it flooded out but ran but very very rich on fuel (also meaning lean oil ratio). Luckily she didn't run it very long and a new fuel pump is on the way, I've been trying and trying to persuade them to go to premix but like you it's just to inconvenient. I may be rebuilding theirs soon, just sayin'. Good luck