87 Marathon runs for 15-20 secs then dies

[bobwire]

It fires right up, and runs great for about 20 seconds, then starts to go slower, and slower until its crawling, then it starts to backfire and pop and sputter.

If I let it sit for a few minutes, it will fire up and do the same thing. Choking it does not help it keep going.

I changed the fuel filter, cleaned the carb and air filter, confirmed that the aftermarket electric fuel pump is pumping, and fuel tank is clean and vented.

What am I missing?

[BrewCityMusic]

sounds like you've eliminated most of the potential fuel-related troubles, but let's hit the few you missed before we look at something electrical.

Your crank seals could be damaged or going - usually that prohibits running at all but if one is partially damaged it's possible that your symptoms could exist. Jack up the cart (so it doesn't run away on you) and start it, running it just at or above idle. Spray a little carb cleaner or WD40 into the cooling fan at the front of the engine, then at the rear of the engine where the crankshaft comes out (between the engine itself and the drive clutch) - if either spray results in an increase in RPM's, you have a bad seal.

If not ... That's good (they're a pain in the arse to replace). Next, take the 2 bolts out that hold your muffler to the exhaust pipe so there's a gap between the pipe and muffler. Now, plug your ears (it's gonna be LOUD) and take a cruise around for a bit, if the symptoms go away, your muffler is partially (or fully) clogged, which is very common with older 2-strokes. Search for "Muffler BBQ" here in the forums for the solution.

Also, just to clarify, when you cleaned the carb you pulled all the jets, etc and made sure they were nice and clean, right? Another common culprit with these older EZGO's is the pickup tube in your gas tank - it's pressfit into the elbow on top of the tank and quite often will work itself a little loose and draw air. Also, where did you draw power for the fuel pump - if it's off the solenoid it's possible that you're powering up and pumping while the starter is engaged, but once the cart is running you're losing power to the pump so that after a bit, the float bowl empties to the point where you lose power and eventuially die ...

If these tips don't help, we'll look at some common electrical issues that cause similar symptoms - but make sure all the fuel bases are covered first.

[Dave Box]

Brew City has given you (as always) a comprehensive list of suspects and here is one more.
You fitted an electric pump because the stock pump failed yes? Now if the diaphragm has split on the old pump and you just left it in place that might be your issue. When you first start up the diaphragm holds it's integrity and so you can generate some crankcase pressure to move fuel from the crank to the piston. After a short while of flexing the crack in the diaphragm opens up and you loose pressure stalling out the engine. Let it rest a while and you restart the cycle. If you did leave a defective pump on the engine then I suggest that you take it off, tape over the breather hole and refit the pump.
Of course I could be miles away from the problem but I'm not

[bobwire]

OK so I did the seal test w/WD40 and no change in rpm. Good news for me.

Loosened the muffler and that did not stop it from happening.

When I did the carb, I pulled it completly apart, all jets, sprayed a full can of carb cleaner through every orfice, and blew it with compressed air through every orfice. I have done carbs many times on bikes and boats and I'm pretty confident its clean.

I ran an alternate fuel line from the fuel pump directly into the tank to bypass any pick up or elbow. It did not help.

The electric fuel pump is wire so as long as I press on the gas pedal, it gets power. Keep in mind that this is not a new set up. I used it for almost 2 years the way it sits right now.

My next step to take the original fuel pump apart and inspect the diaphram and seal up the breather hole.

I will advise tomorrow.

Thanks much for the help guys.

[bobwire]

I took the OEM fuel pump off and sealed the breather and still backfiring.

Does this mean electrical?

[Dave Box]

Hi Bob, Well that's a real shame I was sure that between the three of us we had it cracked. Still all we need here is fuel and a spark and a little crankcase pressure ( I guess the cylinder pressure is OK as it does start, but did you measure it?). So if you are sure that we have fuel then we need to look at the electrical side. The first and easiest thing is the spark plug. I would run the cart, let it stall out and pull the plug. Does it look wet? If so that would tend indicate that the spark had failed when the engine was turning.

Let us know

[bobwire]

The compression is 120 psi. The plug is dark brown, almost black. Indicating that its running a little fat. But thats no problem. The plug is sparking fine and is not wet.
A car mechanic friend of mine recommended to check the coil. But what does he know? He's only a car mechanic.
I guess I'll try to find a coil.
If anybody has any idea's please let me know. Otherwise I'll post my results after the coil swap.

Thank guys

[Dave Box]

I was expecting Brew City to leap in at this point as he has had a similar experience with his cart. I guess that having resolved his issues he is now out and about having fun instead of trolling BGW.

Anyway BCM discovered that his regulator was having issues and causing the generator to output 18 volts. Bad for the battery and bad for the coil which got super hot and then failed. As soon as it cooled down it recovered!

Might be worth checking your battery with the engine running to ensure you have ~15 volts.

BCM is also the leading authority on the HEI mod which (if you do discover you have an ignition issue) will save you $$$$$ and give you a much better performance.

Dave

[BrewCityMusic]

LMAO, Dave - I WISH I was out havin fun this past few days, in fact the only cart ride I even got to take was at like 4AM Sat ... Better late than never, right?

Allright Bob - let's start looking at a few other possibilities. As Dave stated above, I had an issue with my regulator (a brand new one nonetheless) and was spiking at 18v output, that's an easy one to diagnose though, just hook up a DMM and take a ride, even at full RPM's you should be hitting no more than about 15v max. If you're readings go much above that 15v point, you very well could be having the same trouble I did and a simple regulator swap should fix it.

As to the other common electrical possibility (which there are actually another couple of threads on at the moment) sometimes Ignitors will start to act up before they completely fail (your symptoms are pretty much in line with that pre-failure), and unfortunately there really isn't any way to test them other than to replace them with an overpriced replacement and see if that fixes your trouble. I personally am a huge fan of the HEI conversion, at $20-ish for the conversion and worst case scenario another $20 for a high-output coil, it's a great way to not only eliminate any potential ignitor/coil problems but you WILL run with a hotter spark and therefore more efficiently.

One other thing that everyone (myself included) hasn't commented on is the condition of your ground (from the battery to frame and engine) - that's another place where intermittent or no-run troubles often start. If the bolts, etc get corroded (as they invariably do) the engine will try to grab another ground path through the choke cable, accel cable, etc and that almost always causes intermittent running - it's a quick preventative to pull and clean up those ground points, and definitely worth a shot before you start spending $$

Clean the grounds, check your voltage, and if all looks good (except of course for the whole issue that brought you here in the first place) then you may want to look at gambling the $40 on a coil/HEI - it's a project you can easily wrap up in an hour.

Keep us posted as to your progress!

[bobwire]

Thanks for all the help guys. I swapped the coil and it works now. 22 bucks for a Chevy Astro van coil did the trick.

What is HEI? Is that where you swap out the electrical for an automotive set up coil/ignitor etc?