Ignition Problem or Carb Problem
 

Went through ignition hell this winter, caused by spiral wound ignition cables with flimsy brass connectors that broke (invisibly) inside rubber boots to the crab distributor, after a few times removing and replacing. Replaced them with copper core wires from Van Pelt. Perfect fit and they look great with the old-school Raja plug connectors.

In spite of Pertronix good advice that their electronic points would not work with copper, due to radio frequency interference with the circuit, I took the Barn person's word who said Pertronix worked fine with solid copper core wires for years. Didn't work so well for me. I got a weak yellow spark for a while and then it croaked. So, went to the Third Gen points distributor, which I always carried as a backup. Started right up, idled fine for a minute, started to get a little rough, chugged, and died. On cranking, it would chug a little but not start. Replaced the coil with the Bosch Blue; got a nice big blue spark, but still chug with no start. By this time the plugs were looking a little black, so I put in a new set of NGK, gapped to a loose 0.025. Now it will start and run for maybe five seconds, and then stumbles to a stop.

Acts like it is flooding: Smell of gas. Wet plugs.

Pulled the top of of all three 97's expecting to find a sunk float. Nope; they are all shutting flow with the fuel at about 0.5" from the rim. The rear carb bowl seems to evaporate down faster that the other two. Could it be leaking into the manifold? Common with 94 power valve problems, but not so much with the 97's. I raised main jets from .045 to .047 last year. I am maybe too cautious about overtightening the jets. Could one of them have vibrated loose, causing flooding?

Ideas?

As beautiful as those three chrome plated 97's are on that polished Offy tri-power manifold, they may be more trouble than they are worth.

Re: Ignition Problem or Carb Problem
 

Profound ! The Pertronix as well....

Re: Ignition Problem or Carb Problem
 

I’ve had tri-power on my 40 for goin on 25 years and the only problem I’ve had was a couple years ago I experience a small piece of trash inside one of the jets on the primary carburetor.
Feels real good when you stand on it and open up all three. My engine is 3 3/8 bore X 4 1/8 stroke.

Re: Ignition Problem or Carb Problem
 

I agree; when they are working right, they go as good as they look. I am just frustrated that after fighting ignition problems for months, it still won't run right.

Has anybody had main jets unseat themselves and cause a flooding problem?

Re: Ignition Problem or Carb Problem
 

Are you running a 6 or 12v system?

Re: Ignition Problem or Carb Problem
 

12v, negative ground. Pretty darn sure the problem is now carb, not ignition. It ran fine for a minute, so the timing is at least in the ball park. But then it stumbled and died. I still have a blue spark that will jump half an inch at each plug.

If the float settings are good, what could cause 97 carbs to flood?

Re: Ignition Problem or Carb Problem
 

What ohm rating is your coil and do you have a resister in the circuit?

I've found that running a 1.5 ohm coil, with direct 12V, will cause a similar problem.

Unless it's puffing out black smoke, when it runs, I don't think it can be the carb.

Re: Ignition Problem or Carb Problem
 

You are right. Not the carbs. Took all three carbs apart and found nothing that might cause flooding. All floats set correctly. Main jets all firmly seated. All power valves seated and little pop-ups working freely. Not entirely a waste of time. I did find and fix one leaking main jet plug, and all carb bases with risers really needed tightening.

Again, after the carb check, it ran at fast idle a little roughly, would not wind up with throttle; started hesitating, then after about five minutes just quit. No black smoke, new plugs not black or wet.

I am running a brand new Bosch blue coil which I measured as having very close to 1.5 Ohms. That should not need any other resistor, right?

When I set up the new distributor, I put on a new condenser. Could that cause it to run rough and die.

The spark from the coil wire is blue and will jump almost half and inch when cranking, but it looks a little thin and puny. And it seems erratic when cranking, like it is not sparking every cylinder.

Suggestions?

Re: Ignition Problem or Carb Problem
 

You need about 3-3.5 ohms resistance on a points distributor running 12V. Your coil should get hot running a 1.5 ohm coil with no external resistor on 12V. It should run more than 3-4 minutes, though, in my experience.

Pertronix runs on same coil with no resistor.

Re: Ignition Problem or Carb Problem
 

So the ballast resistor which I bypassed for the Pertronix needs to go back into the circuit?

Re: Ignition Problem or Carb Problem
 

I've run into the same thing with old Harleys. Electronic ignitions use lower resistance coils than breaker point ignitions. Put the ballast back in and try it.

Re: Ignition Problem or Carb Problem
 

The Bosch blue coils I run on a 12v system measure around 3.6 ohms. No resistor needed.

Re: Ignition Problem or Carb Problem
 

I run ,045 mains with #71 PVs in dual 97s on a 221 at 500 feet above sea level. I think .047 is toooo rich. Also connect an ohmmeter to distributor terminal on coil and the other clip to ground and turn engine over by hand with ignition off and see if point resistance goes to zero. Burn points without ballast resistor? I would take a look at the points. Report back.

Re: Ignition Problem or Carb Problem
 

I am having the same problem. I now have the Bosch Blue (internally resisted coil)but will toast points within less than 20 miles. Would like to get this problem solved for sure.

Re: Ignition Problem or Carb Problem
 

That almost sounds like a weak condenser to me.

Re: Ignition Problem or Carb Problem
 

It sounds like the Chinese condensers may be attacking again.

Sal

Re: Ignition Problem or Carb Problem
 

Have you ever checked the coil resistance to be sure what it is. I remember something about Bosch knock-offs being out there.

Re: Ignition Problem or Carb Problem
 

Tried a different condenser, this one reads .3 mfd. Difficult to find one that reads 3.5. I have a pile of them and all but 2 read about .26 which I understand is not enough. The 2 odd ones, one reads .4 and the other reads .45 which may be too much.

I installed a 1.5 ohm resister in front of the internally resisted Bosh Blue (which reads about 3.0 ohms resistance). These 2 combined helped bring my voltage to the coil down but it may not be enough.

I am running a 12 volt neg ground system after the coil I am seeing 8 volts is that still too many amps at the points?

Re: Ignition Problem or Carb Problem
 

The capacitance of the condenser depends on the inductance of the coil. Just about all "modern" coils are best matched to a condenser in the low .20's micro-farads range. I have a piece of Ford literature that lists all of the original Ford condensers and most are rated at less than the .35 micro-farads usually stated. It also says the "under-capacitance will accelerate point wear while over capacitance will hurt performance".

That being said, the actual capacitance of the condenser makes little difference. It is much more important that the condenser maintains a reasonable value under different temperature and transient voltage conditions. Many older condensers will read fine and rapidly deteriorate when they heat up. Testing a condenser without heat-cycling it says very little about it's suitability in service.

Re: Ignition Problem or Carb Problem
 

Sounds like way to much resistance. You should not need a ballast resistor with a 3.0 ohm coil, something isn't right here. Any idea what the system voltage is at higher rpms?

Re: Ignition Problem or Carb Problem
 

As I have stated previously you can measure voltages and resistances till the cows come home but to really know what is going on in the coil primary circuit the current draw needs to be measured with the engine not running and dist timing points closed so as to complete the circuit and then with the engine running at idle speed. Use a good quality digital multimeter with a 10 amp capability. Engine not running with ignition switch ON should be 3 to 5 amps. Test quickly so Ign. is not on longer than a minute. Run engine at idle speed and reading should be about 2 amps. If you are in this ball park then all is good. These readings are for both 6 volt and 12 volt systems. Regards, Kevin.

Re: Ignition Problem or Carb Problem
 

I don't know anything. But Pertronix?


Spiral wound wire for electronic ignitions, solid for points.

Re: Ignition Problem or Carb Problem
 

Put the ballast resistor back in the (1.5 Ohm blue Bosch) coil circuit. Coil volts read 12v with points open, 10.5v with points closed. That is with the resistor cold. Does that sound right?

The bad news is that the engine will still barely run; stumbles; won't take throttle and build up rpm past about 1200.

Will swap condensers next. It is not shorted, but if the capacitance is too far off, the mismatch with the inductance of the coil could cause a problem.

Will report back when checked out.

Re: Ignition Problem or Carb Problem
 

For what it's worth, we made the first prototype "Trash Can" reproduction condenser with a .047 micro-farad capacitor (it was all we had that would fit). The engine (a flathead, of course), ran fine. I wouldn't make a large bet on point life, but that's really not that important. Unless you are concerned with the difference in point life to be 20K miles vs 25K, don't worry about the exact capacitance. A .22 and a .36 are virtually interchangeable on these engines.

If you are going to test condensers, heat cycle them. (You should also check for voltage spikes above the rated value of the condenser being evaluated. I don't know how to do that, so I use capacitors that are designed withstand 600 volts, which seems to be enough.)

Re: Ignition Problem or Carb Problem
 

You state that the spark is erratic when cranking like it is not hitting every cylinder. I still think that the points need looking into for spring tension and closing or binding. Points hanging open? I have had that happen - tightened the spring tension solved the problem. And you might put s drop of oil on the pivot point.

Re: Ignition Problem or Carb Problem
 

To answer my own question and put an end to this comedy or errors, I can definitively state that a bad condenser (New original-look-alike from Macs, part #32-882338-1) can show a fine spark when cranking, and then not run worth a damn. When this saga of missing and lurching started (ultimately traced to spiral wound spark plug wires with internal/invisible broken connectors), I bought a condenser from Tubman. Thought about returning it because it was too big to mount at the normal spot on the side of the crab distributor. In the mean time I went through the distributor and replaced the condenser with the Mac's thing). Then I went down the carburetor rabbit hole and fixed some little things there; then I put the ballast resistor back in the circuit. Still barely ran, and after a few minutes would die.

With good advice from members of this board, I pulled the Tubman condenser out of the "return" pile and mounted it so it connects to the coil end of the black wire to the distributor, instead of on the distributor itself.

Still need an all out road test, but in the garage it is running like a champ!

Thought I knew something about flathead ignition. What I did not know is that a nice blue spark when cranking does not necessarily mean that the problem with running rough is in the carburetor.

The other thing I learned is, like starter switches, never buy a condenser from just anywhere.

Re: Ignition Problem or Carb Problem
 

Good news. Sounds like that condenser would work on start up but then fail immediately.

But I think you are not done yet. You said: "I am running a brand new Bosch blue coil which I measured as having very close to 1.5 Ohms. That should not need any other resistor, right?" With your 12V, that will allow too much current, will cook things. You want about 3.0 ohm, either a 3 ohm coil with no resistor, or use your coil with a 1.5 ohm resistor.

Re: Ignition Problem or Carb Problem
 

Thanks, "drolston". I have been looking for that returned condenser for a while, but it never showed up. I guess I now know why. I'm glad it worked out for you.

"squirrel" on the "H.A.M.B." did a little research on the "intermittent condenser problem" mentioned and found that the connection from the lead wire to the the internal workings of the condenser was faulty. It was held in contact only by the crimping together of the condenser body. It would be fine when tested statically or with the engine not running, but when the engine was started, the vibration from the running engine would cause the connection to become intermittent and fail. This why you can run into failures with multiple new condensers.

I do mine differently.;)

Re: Ignition Problem or Carb Problem
 

See post #23.

Re: Ignition Problem or Carb Problem
 

I’ve been reading these posts and when I saw erratic spark I thought the problem might be the distributor cap. A crack in a cap can be hard to see and a manufacturer defect even harder. What ever it is I know you can solve it. Good luck

Re: Ignition Problem or Carb Problem
 

Pleased that you found the problem. I have had straps break off condensers, and a new condenser fail with a no start, but your problem was an education for me too.

Re: Ignition Problem or Carb Problem
 

Final report. (maybe)

Did the road test and it runs like a scalded dog. Wound right up to 4800 in first and second without a miss. Got a little spark knock at full throttle in second. Because that "ping" could have been detonation, I first will go back on the heat range on the plugs from the NGK B5HS to the B6HS. If that doesn't take care of it, I will pull back from 4 degrees advanced to 2 degrees advanced.

Thanks again to all who walked through this with me.

Re: Ignition Problem or Carb Problem
 

Since you have a modified engine (heads, carbs, etc.) I will indulge in a little shameless self-promotion and say it looks better too.:o

Re: Ignition Problem or Carb Problem
 

To answer my own question and close out this thread, the cooler B6HS plugs did not solve the pinging problem, but backing off 2 degrees advance did. The B5HS plugs go into the parts box in the trunk as spares in the event that the cooler plugs get fouled somewhere along the way. Another lesson learned is that once fouled, cleaning and torching the electrodes may not bring them back. Better to pony up for new plugs.

Re: Ignition Problem or Carb Problem
 

I'am running a "H & C" ignition with ( 2 ) "Bosch Blue" coils and two "Tubman" condensers. Engine temp got to 200 dg. shut off and would not start. ( No fire at the plug.) Engine cooled down to 180 dg. and fired right up and ran fine.!! We are still looking.??