1 minute ago, Zed Head said:

Sounds like normal behavior.  Right?

The skip noise it makes is normal?  I don't remember it doing that in the past when I didn't use the CSV.  Does your 280 do that?

5 hours ago, chaseincats said:

It's the opposite where if I manually trigger the CSV it starts right up, but if I don't use it, it stumbles like it's not getting enough fuel

I meant normal in general. from what you described above.

I just listened to the video and that sounds normal too.  There's just not enough vaporized fuel for all of the cylinders to fire consistently.  Cold fuel is being squirted almost directly in to the cylinders.  Much of it just gets pushed right out the exhaust valve without fully vaporizing and burning.  When the CSV squirts, the stream and puddle of fuel sits upstream in the intake manifold with all of the incoming air rushing over it picking up vapors.

Incomplete combustion of fuel in cold weather is a problem so well-defined that the fuel suppliers produce two different grades of fuel - winter blend and summer blend, with different vaporization profiles.

https://www.gasbuddy.com/go/summer-blend-and-winter-blend-gasoline

Did you mention in a previous post that the injectors had been cleaned and tested? Pretty sure you’ve seen the volume and spray tester they use when you send them out.

Don't overlook also that the old 1970's injectors squirt a solid stream of fuel.  Today's injectors are designed to spread the stream for better vaporization.  Also, batch fire injection shoots the stream at the back of closed valves on two cylinders, and somewhere between opening and closing intake valves on the others.  It was high tech in the 70's but it's pretty crude today.  Better injectors, higher fuel pressures, and sequential fuel injection all help starting, emissions, and efficiency.  

The hard starting without the CSV actually means that your system is very clean.  No leaking injectors and clean injector tips.  

You are about at the point where it's time to start modifying.  Megasquirt, Haltech, etc.

20 hours ago, chaseincats said:

The skip noise it makes is normal?  I don't remember it doing that in the past when I didn't use the CSV.  Does your 280 do that?

My 280 starts smoother and easier than that. Even when cold and without a CSV. And if I prime the fuel system first, it starts even easier.

What temperature?  Philadelphia fuel versus Dallas fuel.  Ethanol level (it varies).  Engine specs?  Ignition timing, miles, etc.  There are many variables.  If a press of the CSV button or reinstalling the thermotime switch produces a good start why modify?  

Probably worthwhile to compare the variables as a starting point for further discussion.  This thread started as "something changed after a fuel line blew".

1 hour ago, Captain Obvious said:

My 280 starts smoother and easier than that. Even when cold and without a CSV. And if I prime the fuel system first, it starts even easier.

Did you put the ZX distributor on your 280? I've got one on mine and it fires right up with all that cold start stuff removed.

I'll mention it again, how about the valves? 

@Yarb They're about a year old remanufactured Bosch OEM units, so we should be good on that front

@Zed Head Fair point about the the clean injectors contributing to how it starts, but it's just odd that it used to start without that stumble before all of this.  

@Captain Obvious Trying to get back to that and figure out what the issue is

@siteunseen Mine is the standard '78 distributor but I confirmed everything is in spec using the FSM (including the air gap between the reluctor wheel and pickup coil)

Edited February 18Feb 18 by chaseincats

Update: I took the car out today with about 1/8 tank of gas and added the small lucas fuel additive bottle in full and the car ran great - definitely 100% of what it was before which is fantastic.  I really wanted the lucas bottle liquid fairly undiluted which is why i didn't fill the tank first.  After driving it for about an hour with no issues and awesome results, I filled the tank, took it around the block to make sure nothing changed and parked it in the garage - thanks for everyone's help!

 

case closed

Awesome. Let's hope this is the end of it and it's smooth sailing from this point forward!!  Good work!  

UPDATE: after driving it for about 100 miles, here is what my plugs look like.

The spark plug tips are quite white on some of these, but the ceramic in the middle isn't as charred. Besides burning some oil, what do you think? Looking at these, I'd say a good chunk of this engine is running lean, but my AFR numbers look great. Just as some extra info - before I started driving it heavily again (after we fixed it) I pulled the plugs and noticed cyl #5 was the only one with a dark plug, so I swapped it with cyl #6. The cyl 6 plug is now dark, but the cyl 5 plug did not clear up.

The spark plugs are NGK BPR7ES (5534)

Any ideas?

Edited Saturday at 03:45 PM1 day by chaseincats

That is a "colder" than spec spark plug. Might be why the electrode on 1, 2, and 5 are dirty. The white ash on 3, 4, and 6 looks pretty good, but still on the cold side.

Have you adjusted the valve lash? It looks like you have some cylinder imbalance.

https://www.ngk.com.au/technical_info/heat-range/