Suddenly Won't Start - Carbon on Plugs

[donerehart]

I have been trying to start my 76 Spider every two weeks or so this winter as it sits in sadness in my garage. All of a sudden, it won't start and the electric fuel pump is pumping gas into the carb. I checked the number 1 spark plug and it is full of carbon. So, I am asking for a list of things to work through to find the problem. (It has worked great for 2 years!) Replace plugs? Check Distributor? What is a logical sequence. I know this is basic, but I could use a little direction...thanks.
Don

[bradartigue]

If it has fuel and compression then you're lacking spark. Buy a multimeter and a test light, or use a timing lamp, and sort it out. Timing lights are great because you can diagnose each line and check the timing, but at some point you need a multimeter if you own an old car. If the plugs are nasty then just clean them up with a wire brush and carb cleaner.

Start simple, most problems where it ran fine then doesn't run are due to the failure of a complete system (no spark, no fuel, no compression, that kind of thing).

[RoyBatty]

If you are just starting it and letting it run for a short time, you could be doing more harm than good.
You need to get the engine and the oil up to full operating temp for a minimum duration of probably 1/2 hour maybe more, to cook out any moisture that may be present due to condensation.
If you just start the engine and warm it up without cooking out the condensations, you are just redistributing the nasty corrosives that collect in the oil during normal use.
As for the fouled plugs, you are probably not burning off the buildup from these startup periods. IF you don't run the engine through a normal driving cycle then you aren't going to let the plugs clean themselves out with the heat that is generated from road driving type operation.

[donerehart]

Thank you Brad and Roy. I have never used a timing light, so I guess it is time to expand my horizon.

[majicwrench]

Hmmm, timing light, timing is not off unless you have messed with it. You could use T light to see if you have spark. SImply jhook light to any wire, point at windshield and crank engine. Light should flash. Or you could simply pull a plug and check for spark.
You don't need a voltmeter to check for spark either. Let's fix your problem.

If you are not sure how to check for spark( am sure you could youtube something) throw a set of fresh plugs in it and give it heck.

Stricktly from an engine wear point of view, it would be nice to get it up to temp. Still, all the wear takes place in first minute or two. Yes, if you are really worried about condensation, better run it a long time. But for a carbed car, tis very nice to simply run some fresh fuel thru carb. I start my 72 a couple times a winter. Due to go out there now and start er up. Will only let it run for a minute or two. Come spring she will fire up and move out. One winter I never did start it. Fuel in carb had dried, all sort or idle mixture issues that year!

[bradartigue]

Hmmm, timing light, timing is not off unless you have messed with it. You could use T light to see if you have spark. SImply jhook light to any wire, point at windshield and crank engine. Light should flash. Or you could simply pull a plug and check for spark.
You don't need a voltmeter to check for spark either. Let's fix your problem.

If you are not sure how to check for spark( am sure you could youtube something) throw a set of fresh plugs in it and give it heck.

Stricktly from an engine wear point of view, it would be nice to get it up to temp. Still, all the wear takes place in first minute or two. Yes, if you are really worried about condensation, better run it a long time. But for a carbed car, tis very nice to simply run some fresh fuel thru carb. I start my 72 a couple times a winter. Due to go out there now and start er up. Will only let it run for a minute or two. Come spring she will fire up and move out. One winter I never did start it. Fuel in carb had dried, all sort or idle mixture issues that year!

I make the assumption people who have cars that no one else can work on have timing lights and multimeters. I'm often wrong. If you get one then you can hook it to plug wires and see if they are getting power, it's easy to do.

But I'll have to agree, nasty plugs may be all that's wrong. Clean yours or go buy a set of Champions from the local auto store and see what's what, then drive it.

[donerehart]

Cleaned the plugs, and it started right up. Ran it to temperature until fan came on. Seems to be back running well. Not sure if I created the problem by reapetedly starting it up and not letting it warm up enough, or what. Thanks for all your helpful advice - Brad, Roy, and Magicwrench! This is the first car I have ever had to work on - I know, I know...my dad was an engineer for GM and we always had new cars. I am having a blast troubleshooting through my 76 - It has completely been gone through by me, and the engine by a mechanic - so the engine still scares me! I had the engine rebuilt two years ago. Appreciate your help!

[bradartigue]

Not sure if I created the problem by reapetedly starting it up and not letting it warm up enough, or what.

Glad it worked. Absolutely the problem can be caused by starting it up cold and not letting it warm up - the way old cars "warmed up" was to choke the carburetor to a super rich mixture. Until that leaned out you had a lot of half-burned crud floating around.

Either that or you have twin IDFs, they can foul plugs just because they're having a bad day.

[donerehart]

Not sure if I created the problem by reapetedly starting it up and not letting it warm up enough, or what.

Glad it worked. Absolutely the problem can be caused by starting it up cold and not letting it warm up - the way old cars "warmed up" was to choke the carburetor to a super rich mixture. Until that leaned out you had a lot of half-burned crud floating around.

Either that or you have twin IDFs, they can foul plugs just because they're having a bad day.

Thanks Brad! I have great respect for your wisdom and experience. Thanks for helping all of us out so often!