Why won't my L79 engine start? Could it be an electrical issue?

[Jeffery F.]

I have a '66 Vette with a 327/350 SB. I keep the car in my garage, covered up and only drive it occasionally - I have put a little over 1000 miles on it in my 1 3/4 years of owning it. I normally use 93 no ethanol gasoline in it. Last Saturday I was driving home from a car show and needed fuel but I could not find 93 no eth. So I found and put in 10 gallons of 90 octane no eth thinking this would get me home OK with mostly interstate driving. After driving about an hour the engine starting missing / hesitating and I'm thinking this low octane gas is the problem. Coming off the interstate on the ramp the engine idle is very low then cuts off. I get it restarted but had a lot of missing / jumping / hesitating all the way home (thankfully made it!). So I emptied the gas tank of the 90 octane and added 5 gallons of 93 octane no eth. Knowing it was going to take a few minutes while cranking the engine to get the "good" fuel back to the carburetor, I patiently tried over and over again and could not get it to start. I checked the oil, coolant level and all the connections on the distributor, coil and spark plugs and everything was good. Distributor was not loose, rock solid. Recharged the battery (after so much cranking) and the next day tried to crank it again using starter fluid sprayed directly into the carburetor. Still no ignition, not even beginning to fire. What do you suggest I try to get it to crank?

[Leif A.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

Jeff,
Pull the spark plug boot off #1 spark plug, hold it very close to the exhaust manifold and have someone crank the car. Look for a spark from the spark plug boot. Need to be sure you're getting spark before going anywhere else. If you're getting spark, it may be a weak spark (not enough to start the car) and could be caused by a weak ignition coil. The hesitation you describe after refueling is, most likely, not caused by the 90 octane ethanol fuel. Do you have an Ohm meter you can use to diagnose the ignition coil? Let's start there.
You, also, state that you "tried over and over again and could not get it to start"...possibly flooded.

[Arland D.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

Driving back 600 miles from a regional meet, had a similar set of symptoms with my 57 fuelie and nursed it home on mostly highway. Pulled the distributor cap and the points were not happy. Replaced and adjusted a new set of points and it ran fine from then on.

[Duke W.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

Or if you have a loose spark plug, pull off a wire, connect it to the loose plug and use a jumper wire to ground the plug shell to the engine. You most likely have an electrical problem, and you need to fully inspect and troubleshoot the ignition system. Study your CSM.

BTW, where do you get 93 PON fuel without ethanol.

Duke

[David M.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

Agree keep it simple at first, basic troubleshooting. Do you have spark and fuel?
What part of the world are you from. I could assist if you are local to me.

[Bill M.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

My friends 65 died on the road we went nuts trying to figure it out. Tried everything good spark but no fuel out of carb turned out we had a clogged gas cap vent. I guess it oxidized closed. New cap no more problem. Take off the cap and try to start.

[Jack H.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

I had a failure with my '67 327/350 just like that and it turned out to be a bad fuel pump. However, since you said you tried starting fluid directly to carb and it didn't even begin to fire, I guess it rules that out and probably rules out Bill's bad gas cap theory too?

Engines need four things to fire...fuel, spark, compression/timing, and air. Fuel and spark are the easiest to check...is it getting fuel? i.e. is there fuel in carb and does squirts when throttle lever is moved?...is it getting spark?, i.e. see checks mentioned by others...compression/timing usually fail suddenly, i.e. timing chain break or chain jump and that doesn't really match you mode of failure, although I guess its possible that it was shearing nylon teeth on cam gear and gradually progressed from misfire to failure?...air is all around us so unless air cleaner was completely sealed and clogged that's not the issue.

[Tim S.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

Like others have suggested, check the spark. My Dad ran into a VERY similar circumstance this past summer (problem after fueling). It proved to be the points. The refueling was just coincidental. Don't overthink it (and that's easy to do).

Tim

[Jeffery F.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

Thanks to everyone who has responded! These are some great suggestions to try and I will try them until I uncover the true issue. To answer some of those questions within your responses, I live in Western North Carolina and I can find 93 octane no ethanol gas at a number of gas stations in my immediate area because I live near a lake and most of the boaters want / must use high octane no eth gas so the gas stations carry that fuel due to demand.

[Jeffrey S.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

Jeff,
Sorry to hear you are having trouble with your car. When you were getting it ready for the regional, did you replace the condensor in the distributor? I have seen several cars do just what yours did and they had done a recent tune up and put in a new auto parts store condensor made in China. Failed and caused the same no start after getting where they wanted to go.
Jeff

[James W.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

Many years ago, my '64 quit when pulling off the interstate. I would crank but not start. I replaced the condenser on the distributor and no more problems.

James

Jeff,
Sorry to hear you are having trouble with your car. When you were getting it ready for the regional, did you replace the condensor in the distributor? I have seen several cars do just what yours did and they had done a recent tune up and put in a new auto parts store condensor made in China. Failed and caused the same no start after getting where they wanted to go.
Jeff

[Jeffery F.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

Thanks for your response Jeff S. I hope you are doing well. I will add a check to the condenser in my troubleshooting if I don't find the problem before that!

[Keith W.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

Many years ago, my '64 quit when pulling off the interstate. I would crank but not start. I replaced the condenser on the distributor and no more problems.

James

How do you know if the condenser is bad?

[Jeffrey S.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

How do you know if the condenser is bad?

You replace it and if the car starts you know it was bad.
Jeff

[Jeffery F.]

Re: Why won't my L79 engine start? Could it be an electrical issue?

Again, thanks to everyone who had input on my 327 / 350 engine not running properly / not starting after introducing low octane (90) fuel. Today I finally got a chance to work on the car. Checked oil, OK. Checked gas squirting into the carb when the accelerator linkage is moved, OK. Checked spark coming out of distributor, OK. Checked spark coming out of spark plug wire at plug, OK. Checked spark plugs - EVERY ONE OF THEM WAS FOULED! No wonder it wouldn't start. Seems like the low octane fuel caused the detonation / hesitation / back-firing during my trip home from the car show which, in turn, fouled the plugs. They were so badly fouled the engine wouldn't even try to start. So I replaced the plugs, filled my tank with the 93 octane no eth and with no other electrical changes (no new points, no new condenser), the engine started instantly and ran as good as it ever has.