Ignition/Sputtering troubleshooting?

[Luke_Healey]

I've got timing set, no vacuum leaks, the vacuum advance appears to be advancing (not sure if to spec though.) And I got my mixture tuned with the Color Tune I bought.

However, after a jog down the road, the car will start sputtering. The fact that it gets worse the longer I drive suggests to me that my condenser and/or coil are shooting craps. I've got extra condensers and points (new) that I'm going to try tomorrow and I can borrow the coil off of my other sprite until I had another one shipped, but is there any real way to tell if a condenser and coil have gone bad? The stumbling and sputtering only happens under load at about 3500-4000 rpm. Under or above, it does not happen.

 

[RonMacPherson]

A condensor(capacitor really) is just a storage device for primary voltage. When they go, they go, car dead, finito, basta, kaput, nicht running.

Coils will cut out when hot, also be hard starting,(weak output) when cold).. and when shut off and cooled down can come back to life.

However, you are throwing in a contingency that makes me question igniton. You state that problem only occurs at 3500-45oo rpm. That usually is a fuel flow problem, could also be exhaust restriction, too, but when you can partition the problem like that it does NOT sound like ignition.

Except for, is your carbon brush in your cap ok, cap on tight, rotor not cracked?

 

[Luke_Healey]

I was out driving in the country tonight with Tullamore from here and he was behind me. The longer I drove the car, the worse it ran. It idles just peachy, but would spit and sputter at all rpm except above 5000, where it would then stabilize. When it was running at its worst, it was backfiring flames, black clouds of smoke, etc... I managed to make it home, but it went from running good when cold, to annoying, to nearly undrivable.

The fact that it smoothed out at really high RPM makes me think it's coil/condenser related since fuel delivery would be in more demand. Also, as time went on, these symptoms happened at all RPM from 1500-5000. The cap is about a month old. However, on this car I'm still using the points and condenser I bought it with since gap is set right, as is timing. However, tomorrow I'm digging into it and replacing the points and condenser.

Good news though! The Gunson Colortune seems to do what it says it would. My plugs look excellent, even with the car running like complete garbage. I sounded like a shot up WWI aircraft coming in for an emergency landing by the time I rolled into my driveway.

<span style="color: #000099"> However, I have not checked the inline fuel filter for flow yet. I can pull it off tomorrow. Also, the electric fuel pump on this car is bizarre. The previous owner replaced the SU pump with what looks like a generic fuel injection pump. Obviously it is not, but I also have no idea how many PSI it flows to the front of the car. I've never even seen one that looks like it for sale. It buzzes instead of clacks, if you know what I mean. </span>

 

[DrEntropy]

eep. I'd be for checking fuel pressure. "unkonwns" are always suspect. You could get a low pressure Facet at NAPA.

 

[bugimike]

eep. I'd be for checking fuel pressure. "unkonwns" are always suspect. You could get a low pressure Facet at NAPA.

/bcforum/images/%%GRAEMLIN_URL%%/iagree.gif Everyone knocks those Facets, but apart from being a little bit noisy I have found them to be quite reliable!! /bcforum/images/%%GRAEMLIN_URL%%/grin.gif

 

[Luke_Healey]

That's what I'm running on my other sprite, a Purolator facet pump. I have an antique AC Delco of this design:

It came with my other sprite, but was stuck due to varnish. I took it apart and cleaned it and it is working now. I could try that one I guess.

I'll probably get a fuel pressure meter on there to see what's going on. My carbs are using the original valve type system instead of grose jets. The previous owner used clear fuel line from the bowl of the front carb over to the rear, so I can see fuel flowing. Obviously not at speed when I'm driving though.

 

[DrEntropy]

Stay well clear of Grose Jets. Horrible things. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

 

[Luke_Healey]

My other sprite has grose jets and would run circles around this one /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

Ok, I'm stuck..

I have the following settings:

-valves adjusted
-timing at idle is 8 degrees BTDC
-new plugs gapped to .025
-new points gapped to .015
-new condenser
-new coil
-new solid copper core wires
-carter electric fuel pump puts out 3psi up at the carbs
-new wix clear fuel filter between gas tank and fuel pump
-carb mixtures adjusted so that cylinders 2 and 3 burn 'bunson blue' with ColorTune
-plugs look great, not rich or lean
-no vacuum leaks at intake or on carb anywhere
-all cylinders put out 180psi when warm


I have no idea why the car is missing sputtering under throttle so badly. When I use the colortune, the

color remains the orangish blue throughout the RPM range, but under load when driving the car is

sputtering badly. Running it super rich so the plugs will carbon up badly makes the car run smoother,

but with a very noticible loss in power. My other Sprite will run circles around this one and it

hasn't even been cleaned out and gone through yet.

I was curious what vacuum at the vacuum advance port should be at idle? I'm pulling zero Hg at idle and

barely 5Hg at 3500rpm?? The vacuum advance doesn't even start to move until about 10Hg and fully opens

at about 20Hg. It does move though and slowly loses vacuum (very slowly.)

I'm at a loss as to why it's running so badly. I might take some photos down the carb necks to show

where I have the jet bearings set. They seem 'low' to me according to what I read, but I don't know

what they're supposed to look like.

Also, the car only runs when I have the coil hooked up in one direction, but it seems the opposite

direction of what my wiring diagram states. I have the yellow wire with black stripe hooked to the

positive side of the coil and the plain yellow wire hooked to the negative side. The wiring diagram

seems to state otherwise, but the car won't even start in that case.

Thanks for any further help. The car has run OK in the past, so I have no idea what is going on unless

I totally goofed up seating the needle to the base of the carb on the rear carburetor. The piston is

allowed to 'clunk down' though.

 

[Luke_Healey]

OK, using the gunson colortune, I notice that when the engine misses, there is no firing going on. Even at idle it might do four complete strokes without any firing happening. It's intermittant with no rhyme or reason and it's happening on every cylinder.

The car runs like complete crap right now, but everything is installed and adjusted to spec.

Could it be the points arcing causing the lack of firing? All of the wiring to the distributor seems to be intact. The breaker points I installed were new old stock ones and I have some cheaper looking GP Sorenson ones from the auto parts store I can throw in. I'm at a loss. It should not be missing with the mixture set and everything other than the distributor itself being new.

 

[Billm]

I know that you have already looked at this but it really sounds as if you are not getting enough fuel to the carbs on heavy use. A fuel pressure gauge hooked up at the carbs (preferably the rear one to get the worst possible case) would tell you a lot about the problem. You need to have about 2 PSI min at all times.
Bill

 

[Luke_Healey]

I don't own a dedicated fuel pressure gauge, just a vacuum/pressure gauge I can stick in the fuel line to get the pump's pressure. No stores around here sold any sort of inline fuel pressure gauges. Do you happen to have any web links to places that would sell something I could hook up inline with the fuel line?

The racing style one the stores sell has a 3/8" pipe thread fitting, so it's no good to me without some sort of brass T fitting to use it with.

I'm pretty sure fuel delivery is OK though since the clear fuel line to the rear carb is full of fuel and the color of the flame in the ColorTune stays the bunson blue/orange without turning bright blue (lean.)

 

[Keoke]

Hi Luke, there is something wrong here. Reversing the voltage polarity to a coil should not prevent the engine from starting and running. Unless the higher output voltage required to fire the plugs, when the coils polarity is reversed, is braking down the secondary system. Just a thought ---Keoke-??

 

[Luke_Healey]

Yeah, I didn't understand that either.. I've run coils backwards (on accident) and it didn't do anything to the way the car ran. Does the positive or negative side to go the distributor? Right now, running, I have it hooked up with the positive side to the distributor.

According to this article:

https://www.britishmotoring.net/bm0404/techQA/tech.html

The way I have it hooked up is correct with the positive side of the coil going to the breaker points.

 

[Luke_Healey]

Well, I was at wit's end, so I pulled the old cap, rotor, and -resistor- plug wires off of my other sprite....

And it runs right! What gives??? The cap and plug wires I removed are less than a month old and have no visual signs of anything bad happening. The rotor I'm using is a NOS german part, but I suppose it could be the weak link somehow??

So, 20 years in a barn cap/rotor with incorrect style of wires trumps my new stuff I've put together??

Here's what I removed:

 

[Luke_Healey]

Furthermore, can any of you explain this?

The bad cap with the new yellow Accel copper core wires has the following measured resistances to the cylinder wires (basically zero resistance from the wires to their attachment points.) It has 37 ohms measured through the carbon button and zero ohms through the coil wire to brass connection.

Meanwhile, the 'good' distributor cap with resistor wires has all kinds of resistance, yet the car runs much more closely to the way it should. Measured resistance at the carbon button is 14,000 ohms.

I specifically bought the ignition coil that states 'no resistors required' which is the proper part lookup for the 66 Sprite.

Can anyone shed some light on this for me?

Thanks.

 

[Luke_Healey]

Well, here's the wrap-up as far as I can tell...

I spent 70 bucks today on a new coil and low pressure vacuum/pressure gauge.

Final verdict: The carbon button in the new cap I was using somehow started making a bad connection to the coil lead. I pulled it and the spring out of there, and pushed it back in tight with a screwdriver.

The car runs fine now.. I tried swapping out the four known items (cap1, cap2, rotor1, and rotor2) in all combinations and the car runs fine (and the same) in any variation.

So frustrating! So now I have a spare OEM Lucas coil when I need it I guess. I'd been meaning to pick up an accurate vacuum gauge too, ha!

I'm sitting here pecking this out holding a cold glass of iced tea to my forehead over this throbbing vein.....

Thanks for playing along. This problem has got to be one of those freak things. So now I have an entirely new ignition system and the car has been gone through -several- times to get it tuned to spec.

 

[DrEntropy]

I missed it. Stuff like that can drive ya gonzo... outwardly none of it makes sense until you hit that one weird bit. Then it's only a "mebbe THAT could be the issue" until you light the thing off again.

Glad ya got to the bottom of it.