expert help needed

[rbig]

I have a garden tractor with a K532 engine. This tractor runs absolutely great---when it runs. I mow approx 20 acres with it, so need it running during the growing season.

I restored this tractor from the ground up a couple years or so ago. A friend who used to work for a big small engine shop rebuilt the engine for me.

I have worked on equipment for years. I'm a good mechanic, but not so good as a diagnostician.

What my tractor does is:

1. Sometimes start, sometimes not

2. When it starts, it runs great, and has full power.

3. Runs for a random interval, then dies suddenly.

4. When it doesn't start, it simply won't fire, even with a whiff of ether.

5. After sitting for awhile, it will normally restart just fine.

6. Generally, the run time gets shorter, while time before it will restart gets longer.

The situation is very frustrating.

Here's what I've recently done to it:

a. new factory coil
b. new points
c. new plugs
d. new plug wires
e. new air cleaner filter
f. electric fuel pump checks OK; sounds normal, and pumps a good stream when hose slipped off carb and pump run.
g. regulator/rect unit seems OK; battery is charging fine, with just over 12vdc going in.

My impression is that the problem may be temperature related, but not sure on that (as it will sometimes restart when hot).

What's left to replace? Ignition switch (easy and cheap), and electric fuel pump (easy and not too expensive). What else that might cause this?

Sure would appreciate some thoughts on directions I can head out in getting a good fix on this thing.

I don't know this specific engine. Are there known issues with it that relate to my problem?

[Soundguy]

Here are a few basic observations.. and for the record.. I havn't a clue about the make of your engine.

If it won't start on ether, then it has no spark, or woefully low compression.. or -0- air supply. Easy to check the spark right at the stall / no start time by pulling the plug.

Quickie compression / vacume test can be done with your thumb over the empty spark plug hole.

I'd look at the points / coil / pickup area.. especially if it has a grounding switch to ground the points to shut the engine down. The wire to the switch may be intermittantly grounding out..

Soundguy

[GATC35]

Make sure the fuel tank vent is not plugged. You maybe pulling a vaccum on the tank shutting off your fuel supply. Does it run if you remove the fuel cap ?

[DavidJ]

Soundguy and Mark gave you good advice. In your list of things you don't specifically mention the condenser. If you didn't replace it then do. I've seen them give heat related problems and even just plain weird problems. I had a problem once that was identical sounding to yours. I had electronic ignition and it turned out to be the reluctor. It would get hot and not fire until it cooled which was a random amount of time.

[Deerlope]

Good thought DavidJ, I was was going to suggest that also.

[Bluecheck546]

It sounds like you got a electrical problem,.... overheating.
Either or both, coil or capacitor should be checked and replaced. Good luck. My2¢

[grafpatrick]

I once had an 2 cycle outboard that had a good spark and would not start on ether, turned out to be a bad reed valve.

[GregJ]

I had an engine recently that had exactly the same symptoms. I replaced the coil and that was it. I also have a friend that had an engine with the same symptoms. He replaced the coil and the symptoms continued. Just for grins, he replaced the new coil again and the problem disappeared. I guess the lesson here is when diagnosing, just because it is new doesn't neccessarily mean it works. [img]/forums/images/graemlins/frown.gif[/img]

Greg

[Pks]

This sounds like a coil problem. I've seen coil problems like this when the coil gets too hot. Can you mount a heat shield near it. Or mount it in a cooler location?

[ducksjunk]

Yup, a hot coil can do it, but the coil will heat up electrically, so isolating it won't make much difference.
First check for spark when it won't start. If spark is okay, then do a compression test . First when cold, second when it quits. May not see much difference but compression should at least be over 90 PSI. If it appears to be low, Put a little oil in the cylinders and retest, if this makes a noticable difference then you have a ring problem if no change then it is valves. Most likely weak rings from what you describe.

Take it from an old wrench!! [img]/forums/images/graemlins/tongue.gif[/img]