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

[Ralph E.]

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

Surprised. Even with low octane fuel it should have started. Sounds more like it was flooded.

[Duke W.]

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

There are several ways spark plug can foul. Can you describe in more detail.

sounds to me that you might have had too cold spark plugs, or you could have excess oil consumption.

So what make/model spark plug did you remove, what did you install, and how did you determine these new plugs were correct for the engine and your driving conditions?

Duke

[Duke W.]

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

Surprised. Even with low octane fuel it should have started. Sounds more like it was flooded.

I once gas fouled the plugs on my CB 1100F. I was just doing a normal cold start after not riding it for a couple of weeks and somehow I flooded it so bad that the plugs were wet with fuel, and the only way to start it was to install a new (dry) set of plugs.

It only happened that one time and to this day I don't know how it happened.

I seriously doubt if fuel octane had anything to do with the OP's no start problem.

Duke

[Leif A.]

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

Post 2, 16, 17 and 18 have your answer. It's not the fuel. Kindly post up pictures of the plugs that you removed.

[Jeffrey S.]

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

Jeff sent me these pictures of the fouled spark plugs and asked me to post them here. As you can see they are completely black. They look to me that they are seriously cold fowled. One thing I noticed when I looked at the picture is that the boxes do not say AC DELCO on them. That raised a red flag and I asked Jeff if these were reproduction (as in made in China) plugs or AC plugs. They indeed are Chinesium. There is no way to know if the heat range listed is actually a "4" or anything from a "2" to a "6". My guess is that these are nowhere near what they are advertised. What do you all think?
Jeff

[Duke W.]

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

What's the model number written on the plugs themselves? They may not be "reproductions", but outright counterfeits.

Where were these plugs bought?

Unless you are having your car judged, use NGK B4 or Denso W14-U for all pre-'69 small blocks, which are equivalent to the out-of-production non-resistor AC 45.

It's tough to tell what caused the fouling. Dry black deposits are usually due to a rich mixture. wet black deposits are usually due to high oil consumption. In any event the primary cause of fouling is usually too cold a plug or short trip driving that don't allow the engine to get to normal operating temperature for any length of time even if relatively hot plugs are installed.

Duke

[David M.]

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

You are not finished trouble shooting yet...

Bet something is breaking down once heat soaked. Coil or condenser?

Take it for an hour long ride(with a chase vehicle & some basic spare parts). See if you can replicate the problem. Once it craps check for spark with an inline spark tester. Pull a couple of plugs and inspect.

Before the road test remove the wire shielding to make this whole operation simpler.
Run the engine in the dark with hood open to observe spark jump. Look at the cap and wires when revving the engine.

When is the last time you have cleaned the engine & chassis grounds? The ground wire from the battery to block.

Look at the distributor & coil primary wires (the small wires) for corrosion and tightness.
Verify the integrity of the black negative wire. That wire moves with the breaker plate when it advances. 60 years of that is bound to break the copper strands from repetitive movement. The outer case can look OK while the copper strands are completely severed.

Does a 66 run a ballast resistor on the ignition circuit? If so that's suspect as well.

In other-words all of what Ive said is pointing towards weak spark that became weaker with dwell time & heat soak.

[Jack H.]

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

I agree with David. In a world full of cause vs effects, the fouled plugs are an after effect of getting low and eventually no spark. Could have been the Chinesium plugs themselves not firing or more likely an aftermarket coil since those are known for these types of failures. BTW, those plugs look like 44's and as Duke suggests, something in the 45 range is preferred but again, not a the cause.