Ignition diagnostics - symptoms of a bad condenser

[bkahler]

I'm helping someone trying to get a Cushman Truckster 3 cylinder engine to start and stay running. 

 

The symptoms are it will sometimes start and run for a few seconds and then it dies.  It will do this multiple times and eventually not fire at all.  You can go back and try again later in the day or the next day and the same thing happens.  Many other people have worked on it before it came to me trying to resolve this issue.  To the  best of my knowledge they all focused on the carburetor and fuel system.   I know for a fact that the fuel system is/was messed up.  It was supposed to have a bypass fuel filter that would bleed excess fuel back to the fuel tank, however the bypass filter was not installed until just recently.  The other issue was the original carburetor had two faulty solenoids and parts are no longer available so I replaced the carburetor yesterday with a new replacement.  The new replacement carburetor has been used in the same application before without issues.

 

 

Before trying to start the engine I also replaced the three spark plugs.  Here's a picture of what they looked like.  See any problems?

 

 

After installing the carburetor I tried starting it and it fired right off after a cranking for a bit.  It ran for about 10 seconds and died.  I restarted it and it fired right up and ran pretty good for about 10 seconds and died.  This repeated a couple of times but each time it ran for shorter periods and ran rougher.  Now it won't fire at all.  This sort of behavior is what others had reported as well with the original carburetor although they reported that it always ran really poorly. 

 

My gut feel is the condenser in the distributor is likely failing.  I'm not knowledgeable enough on what symptoms a bad/failing condenser can exhibit but I'm thinking as the condenser is getting hot it starts to fail and after it cools down it works for a bit until it gets hot again.  I'm going to try and start it again later this afternoon to see what happens. 

 

I guess the bottom line is, I think it's got an electrical problem of some kind. 

 

Thoughts?

 

 

[Los_Control]

What is really helpful is to have a spark plug tester

Just to check and see if you still has spark while it is dying then wont start.

Chances are if it has a good steady spark it may not be electrical .... I suspect you may be on the right track.

 

No idea about this engine, does it have a distributor? or are the points condenser behind the flywheel and have to remove it to get to them?

 

Either way, it might be a good idea to replace points and condenser and check the wiring closely.  Is there a pinched wire that might be grounding out or has poor insulation ...

 

Like our old distributors where the insulation fails and grounds out the points ... not necessarily bad points or condenser, but the wiring going to them.

I would just replace the points and condenser but mainly to inspect the wiring while there ... possibly remove the distributor if needed to really inspect it.

[bkahler]

Oddly enough I have an spark tester exactly like yours

 

I did test one spark plug before I wrote posted about it and I didn't see any spark.  I tried starting it a few minutes ago and no spark and it obviously didn't start.

 

Here's a little more background information.  The Cushman was purchased with out a distributor.  The correct distributor was sourced and new points, condenser, and cap were installed before the distributor was installed to the engine.  I'm going to start by pulling the distributor (it can only be fitted one way so it can't be 180 out) and looking things over inside and verifying all is correct. 

 

I find it odd that the previous owner had misplaced the distributor.  That kind of leads me to think there was some sort of electrical issue which is why the distributor was removed.  I'll let you know what I find.

[Sniper]

He condenser is not required for the ignition to work. It is there to help her then arcing across the points. You can remove for testing purposes

[bkahler]

1 minute ago, Sniper said:

He condenser is not required for the ignition to work. It is there to help her then arcing across the points. You can remove for testing purposes

 

Thanks for that little tidbit

 

[Los_Control]

12 minutes ago, bkahler said:

find it odd that the previous owner had misplaced the distributor.  That kind of leads me to think there was some sort of electrical issue which is why the distributor was removed. 

Most people do not remove the distributor for nothing ... sounds like you are on the right track.

 

I do not think there is a definitive test that follow steps one, two, three and if you get this result ... the condenser is bad.

Seems they can fail in such a way and the electricity just disappears into a black hole.

Sometimes they fail and when you test the spark it is unusually bright and that can mean it failed .... failed condenser is my go too, when I dunno.

[bkahler]

A number of years ago, the reproduction condensers for Triumph sports cars were all crap.  We all started hanging onto our 30 year old condensers and used them instead of new replacements.  I'll be digging into the ignition system tomorrow morning so stay tuned....

 

[oldodge41]

Possibly a coil issue. If it has one? I have seen coils fail with temperature rise.