[stasha]

This is a 1973 Spider with slightly racy cams, 45DCOE Webers, and Crane ignition.
The original SPICA fuel pump is used, with a fuel pressure regulator set at 3-5psi (there is a fuel P gauge), and a return line back to the tank.
The car is new to me, and I have only driven it on 6 occasions.

Of concern is that 3 times (50% of the time) that I start the car when the engine is cold, it will start right up and sound good. I can even gun the engine and it sounds good.
BUT WHEN I START DRIVING, it is anemic in power, acting and sounding like it is running on 3 cylinders or like the plug wires are incorrectly hooked up, with kicking and some backfiring. Chitty chitty bang bang.

On two occasions while this was happening, there was a 5-8 second run of static and zapping sounds from under the hood, almost like a MIG welder stitching some plates.
I have even let the car sit and warm up a few minutes before driving, and the underpower/backfiring will STILL happen.
The underpower and kicking persists for several miles (maybe 1-3 miles?), then suddenly it "straightens up" and will run perfectly the rest of the time.

BUT, sometimes under identical weather conditions (cooler to cold weather), the car will start right up from cold and run perfectly with none of the kicking and power loss.
Once the car starts running smoothly, there are no further problems. I can stop the car and have left the car for up to an hour, and it will restart and run perfectly well. There is no further loss of power while driving -- until the next morning.

I have checked the plug wires and they are firmly in place on plugs and dizzy cap. I don't see any loose wires coming from the ALT or the coil.

Of possible significance, when starting, I get a lot of water and black carbon-soot onto the ground from the tailpipe, although there is no smoke (like I would expect from an overly rich mixture, stuck choke, etc).
I have checked the oil and the radiator coolant, and there is no evidence of oil or water mixed in the fluids.
I cannot see any type of choke mechanism on the carbs; there is no cable linkage indicating that there might be a manual choke.
I guess there could be water in the gas tank, but I'd think the car would always be running poorly, right?

Any suggestions what might be causing this intermittent problem loss of power when driving the car with a cold engine?

Can something be sticking in one of the carbs that loosens only once the engine is hot?
Can this possibly be an ignition problem? (the zapping sounds under the hood on 2 occasions)

Appreciate any recommendations or specific tests I should do?.
Thanks.

 

[Gubi]

Can this possibly be an ignition problem? (the zapping sounds under the hood on 2 occasions)

I mean, sure sounds like it, dunnit? That noise ain't normal, and if it's happening at the same time as the problem, ignition system seems like a culprit.

Wires can look good but be bad. Try starting it in a dark garage, you may be able to see the wires or coil arcing if they're bad.

On a car that's new to you, if you don't know how old they are it may just be worth doing a tuneup and replacing ignition stuff (wires, plugs, cap, rotor). Then at least you know they're good for a while.

 

[Alfar7]

Loose the Spica pump. Regulators often don`t regulate. black water out of the exhaust system is carbon residue from a rich mixture and condensed steam from combustion..

When you put a wideband O2 meter in the system you can tune the carbs correctly.

Here`s the pump I use in all my builds with no regulator:

https://www.amazon.com/A029F887-Ele...9Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

 

[alfaparticle]

Crane and similar CD systems are hard on ignition components due to the very high voltages they can produce. I agree with Tom to replace the distributor cap and rotor and look for discharges when it is dark.
I also agree with Richard to install a low pressure fuel pump and I would use a good quality pressure regulator such as a Filter King set at 3 psi.

 

[stasha]

Good inputs so far.
I will do the following:
1. Shut out all the light in the garage and have wife start the car while looking for sparking.

2. I'll start replacing components one by one until the problem resolves.

3. IF it's the "50% of the time" sputtering running, I'll start with replacing the plug wires (I have a spare set of wires from another forum member)

4. The car's too loud for my taste anyway, so I plan on changing some component of the exhaust to quiet it a little, so might as well get an O2 sensor bung installed to add an AFR gauge. ANY SUGGESTIONS ABOUT THIS? ...SUCH AS TYPE OF GAUGE, WHERE TO PUT THE BUNG, WHERE TO MOUNT THE GAUGE, ETC.?

5. ALFAR7 - thanks for that link to a different fuel pump - should be easy to install. BTW, I'm attaching a pic of my present fuel pressure regulator. I could not see any markings on the regulator itself -- I do not think the VDO gauge means it is a VDO reg.
BTW, I spoke without verifying, but I just assumed that the original SPICA fuel pump is in place. I have attached a pic of the pump. Is it for an orig FI system?

In regards to "...black water out of the exhaust system is carbon residue from a rich mixture and condensed steam from combustion..."
Attaching a pic of the pattern of water/carbon that the exhaust tip makes on garage cardboard.
This implies that the cold start is too rich, so is it the idle circuit jets that are too large? I could go leaner, but I prob need to have some kind of choke mechanism just in case I need to compensate for leanness on startup? ...which brings me to the next question: how and where do I install a choke on these DCOE's? I thought I knew this, but it's been over 40 years with DCOEs....
I suppose an AFR gauge will certainly give me data to more accurately diagnose the water/carbon soot finding.

Thanks to all so far.

 

[Gubi]

You should definitely verify your fuel pressure. Looks like you’ve got a gauge on there? If it’s 2-3 psi you’re good.

That said, even with correct pressure it’s normal to get a bit of black spray out the exhaust when cold. It’s just water in the exhaust condensing and picking up carbon from the exhaust tubes. Don’t base your tuning off of that.

 

[alfaparticle]

I have had good experiences with Zeitronix Wideband instruments, ZT2 if you want to datalog with rpm input and ZT3 if you just want to eyeball it. The sensor should be in a convenient location after the merge into a single pipe and before any cat, resonator, muffler etc.
Stock DCOE's have cold start systems actuated by the levers closest to the engine.

 

[Gubi]

Also if I'm seeing your photo right there's a fuel return line there in front of your fuel pressure regulator. That's required if you use the original Spica pump with carbs, as the Spica pump is high pressure/flow and is also fuel cooled. At first glance, whoever converted your car appears to have done things properly and you may not need to mess with it. I'd verify the fuel pressure is <3 PSI at the carbs and if it is I'd just call it good.

Note that if you do decide to replace the Spica pump with a carb pump you'll need to remove that return line.

 

[stasha]

Findings:
1. Started car and ran it in darkened garage -- no arcing or sparking noted
2. Fuel pressure gauge reading 3psi
3. Removed the spark plugs - all 4 were very black/sooty, but not wet - plugs are NGK B7ES

 

[alfaparticle]

Sooty plugs means rich mixture. Possibilities include:
idle jets too big
idle mixture screws out of adjustment
fuel level too high
cold start valves not fully closed.

Even with pretty good mixture you can get somewhat sooty plugs if they do not get up to temperature. Drive it at 70 mph on the interstate for 10 minutes and then take a look at them.

To clean the plugs I hold them one at a time in a vise and hold a propane flame on them until the electrodes glow orange them use a wire brush to clean off any loose material.
They take a while to cool so handle them with pliers.

 

[stasha]

Sooty plugs means rich mixture. Possibilities include:
idle jets too big
idle mixture screws out of adjustment
fuel level too high
cold start valves not fully closed.

Even with pretty good mixture you can get somewhat sooty plugs if they do not get up to temperature. Drive it at 70 mph on the interstate for 10 minutes and then take a look at them.

To clean the plugs I hold them one at a time in a vise and hold a propane flame on them until the electrodes glow orange them use a wire brush to clean off any loose material.
They take a while to cool so handle them with pliers.

1. Thanks for carb throubleshooting
2. Right, the sooty plugs were only after startup and minimum idle. Will drive, stop and pull plugs
3. Never heard of that; never thought it it. Will do.

 

[Gubi]

Well, my suggestion would be to sort out the cold running problem first, then focus on tuning the carbs. The sudden on/off description of your running problem makes it very unlikely that it's the fuel system, and if it drives well when warmed up the carbs can't be too far out of tune.

It sounds reasonably likely you've got an ignition problem, but beyond that you may need to swap parts to sort it out. I'm not familiar with the Crane system so can't help you there, but you might still have bad plug cables or a loose electrical connection or something simple like that.

Don't ignore the carb tuning, that's always something you should verify on a new car, but I'd treat that as a separate issue.

 

[alfaparticle]

I'm not familiar with the Crane system

I had a Crane on my GTV6 and I threw it in the trash can. I had an MSD on my Spider and I gave it away. IMO multispark CD ignitions are more trouble than they are worth.

 

[Lear]

How are you starting it. Weber’s do not need choke to start, just a few pumps on the gas pedal. If you using choke sounds like a choke plunger is getting stuck up