Weak spark I think?........

[Jim Lee]

Hi all. Hope everyone is well, it has been some time.

Let me preface my comments by saying that it amazes me sometimes how my dear TR can be running fantastically one day and then not work at all the next. In any case, I think what is happening now is that I have weak spark. I did a video on my camera which I am trying to figure out how to give you a link to so you can see for yourself. The scenario is that it will run on starting fluid but not on good old gas. I know that it is getting gas from my electric pump, and the gas is not old. So, since it is only running on starting fluid I am thinking that a lack of spark is the problem. I was thinking of switching over to a Petronix ignition anyway so I think I will use this as an excuse to do it now. What I am wondering though is what kind of test would the forum advise me to do to verify that I do have a weak spark. Other than what I have already done and hopefully you will get to see by actually looking at the spark produced by removing the plug and grounding it on the valve cover. I am going to do some research and make sure that my points and gap are good but am just wondering what other suggestions you all might have.

Thanks very much,
Jim Lee
1959 TR3 Black Beauty

 

[dklawson]

When in doubt about the spark, remove a plug (say from cylinder #1) and rest it on the block/head with the spark plug wire still attached. Have an assistant turn the engine over on the starter while you look for/at the spark across the plug gap.

How do you know the carbs themselves are getting fuel? I understand that you have an electric pump, but that doesn't mean that the fuel has been able to get into the float bowl. One or both float valves could be stuck closed. You could also have a gummed up main metering jet and needle.

By all means check the valve clearance and all your ignition settings, but if it will run on starting fluid (or a thimble of gas poured down the carb throats) then the problem is not likely ignition related.

 

[NutmegCT]

When in doubt about the spark, remove a plug (say from cylinder #1) and rest it on the block/head with the spark plug wire still attached. Have an assistant turn the engine over on the starter while you look for/at the spark across the plug gap.

How do you know the carbs themselves are getting fuel? I understand that you have an electric pump, but that doesn't mean that the fuel has been able to get into the float bowl. One or both float valves could be stuck closed. You could also have a gummed up main metering jet and needle.

By all means check the valve clearance and all your ignition settings, but if it will run on starting fluid (or a thimble of gas poured down the carb throats) then the problem is not likely ignition related.

If it runs on starting fluid, I assume you mean it runs when you pour the fluid into the carbs. Does it run if you pour regular ol' gasoline into the carbs the same way?

You need to establish if the carbs are getting enough gas to run the car.

Tom

 

[Jim Lee]

My definition of 'running on starting fluid' is that I spray it into both carbs with the air filters removed.

Here we go....my very first online video. Jims TR3 spark or lack thereof Click on me

I have been told that an engine can run on starting fluid even if the spark is way less than it should be. It is definitely only running on the starting fluid. The above video, if it is viewable, seems to show a sad little spark.

My definition of 'I know there is gas' is because if I loosen either one of the hose clamps at the carbs I can see the gas pulsating out with the beat of the pump.
I will check the float bowls but wouldn't it at least sputter along for a stroke or two even if one bowl was stuck? The odds of both being plugged feel pretty remote.

Is there a way that I can determine that gas, supplied by my fuel system as opposed to the starting fluid, is getting to the carbs?

Thanks all,
Jim Lee

 

[BRSLimited]

Has it been a while since it last ran or did this just start happening all of a sudden? Spark may be a touch week but doesn't look like it shouldn't be running and it's hard to tell from a video not actually being there. I'd go with what the others have said and check and make sure your float bowls are getting fuel and that nothing worked it's way in and plugged up the main jets. These carbs are so simple that the littlest thing can screw them up. One thing is for sure, it will be something simple to fix. Could be something like a failing condenser too.

 

[NutmegCT]

Jim - does the engine run when you squirt regular ol' gas into the carbs?

Tom
PS - look in the carb fuel bowls to see if they're relatively full of gas. The gas goes from the bowl to the carbs then to the cylinder. If there's no gas in the bowl) or the jets are clogged, then you've got a fuel flow problem. You need to determine if the engine will run on gas squirted into the carbs. If it does, then you've got a fuel flow problem. If it still doesn't run, then you've likely got an electrical problem (coil, distributor, lines, etc.).

Tom

 

[Jim Lee]

Tom, What is a safe (or relatively at least) way to squirt gas directly into the carb. That is an excellent idea but I am not sure how I would do it. First of course I will check the fuel bowls.

Also, I have not run the car in about a month but as I recall, one day it was running like a sled on snow and then the next day it would not run...so I guess the answer would be that it stopped running all of a sudden.

Is there any vantage point from which I could actually see fuel entering the carb?

Thanks all,
Jim Lee

 

[NutmegCT]

Tom, What is a safe (or relatively at least) way to squirt gas directly into the carb. That is an excellent idea but I am not sure how I would do it. First of course I will check the fuel bowls.

Also, I have not run the car in about a month but as I recall, one day it was running like a sled on snow and then the next day it would not run...so I guess the answer would be that it stopped running all of a sudden.

Is there any vantage point from which I could actually see fuel entering the carb?

Thanks all,
Jim Lee

Jim - I've never had a problem if I just dropped about a tablespoon of gas down into the carb throat. Then get back in and start the car; see if it fires and keeps running for a few seconds. Won't explode on you unless there's something *really* wrong in there. Do this first.

Edit: squirt the gas just like you squirted the starter fluid.

You haven't run the car for a while. That sure doesn't sound like electrical to me; sounds like crud in the fuel system somewhere.

You can't see fuel entering the carb, far as I know. But you can see if the bowls have fuel in them. I'm betting they're dry.

Tom

 

[Jim Lee]

"Edit: squirt the gas just like you squirted the starter fluid."

The starter fluid is in a can I get at the auto store. Can I just use a regular old, but very well cleaned out, Windex bottle? I am talking about the practical matter of dumping gas horizontally into the carb throat...without dumping so much that it floods.

Thanks.
Jim Lee

 

[TR3driver]

Is there a way that I can determine that gas, supplied by my fuel system as opposed to the starting fluid, is getting to the carbs?

The test I use is to squirt carb cleaner (eg Gumout) rather than starting fluid into the carbs. If the engine starts then dies, it isn't getting fuel (or at least not enough fuel that will burn). My rationale here is that it takes less spark to keep an engine running once it is running (meaning the plugs and combustion chamber are warmed up), so if it had enough spark to start on carb cleaner, it has enough to keep running on gasoline.

What they sell for 'starting fluid' these days is no doubt a lot safer than the old ether, but it also isn't as good at getting an engine running. In my experience, the carb cleaner works much better as starting fluid, at least when trying to start a recalcitrant engine under otherwise mild conditions. I've not tried it at 40 below :laugh:

 

[Jim Lee]

Here is another clip...not much different.

Sparky

 

[NutmegCT]

"Edit: squirt the gas just like you squirted the starter fluid."

The starter fluid is in a can I get at the auto store. Can I just use a regular old, but very well cleaned out, Windex bottle? I am talking about the practical matter of dumping gas horizontally into the carb throat...without dumping so much that it floods.

Thanks.
Jim Lee

That should work fine. The question is: does the engine run on gasoline like it runs on starter fluid.

T.

 

[NutmegCT]

Jim - on that video page there are other videos. Two are labeled 1999-07-01 but show the same spark test being done. What's the story there?

Tom

 

[SkinnedKnuckles]

Yeah - as all that's been said. A "weak" spark is kinda subjective. It's still a spark that jumps the gap and will knash your teeth if you put a finger on it. Sounds like gummed up needle valves stuck closed. I use Grose Jets so don't have that problem - but a fairly recent post had someone rapping on the fuel chamber which apparently freed the sticking valve.

 

[Andrew Mace]

Jim, I'd like to echo one of the suggestions Doug made earlier. If nothing else, check, clean (if necessary) and regap the points. That might at least help your "weak spark"; of course, it won't clear any fuel blockages! :wink:

 

[vettedog72]

No weak sparks with Pertronix; no points to adjust, no dwell to adjust and no condenser to be concerned about. They even have a new module that automatically adjust dwell as a function of RPM and the whole electronic ignition shuts off if the ignition switch is left on with out the motor running.

 

[TR3driver]

No weak sparks with Pertronix;

Hah! Mine was so weak with the Pertronix that the engine wouldn't start until after I let off the starter button and sometimes not even then. Ran the battery down several times grinding away before I figured that one out. Switched back to points and it started much better.

I guess sometimes the magic works, and sometimes it doesn't.

 

[Jim Lee]

I had a bad Petronix experience on this very car but I am willing to try again. It fooled me big time as I was absolutely sure it was a dirty fuel line or tank as it would run great for about 15 or 20 minutes and then all of a sudden we would go to two cylinders....then nothing. Got stranded a few times with that. Went back to points and all was well again. What I theorize was that whatever the electronics were in the Petronix would get heated up to a certain temperature then give up the ghost. The running on two cylinders for a while was what really fooled me. I kept reassuring myself it was not the Petronix by asking everyone like I was leading the witness "Electronic stuff doesn't work and then not work does it?".

The only thing that is keeping me from believing this is a fuel problem is the fact that we have two carbs and therefore two fuel sources for the engine. What are the odds that both would stop working at the same time? I will be out there taking apart the carbs tomorrow but is that not an obstacle to this being a fuel problem? Remember that I already have the engine running on the starting fluid for more than few seconds...even if one carb was shut down for whatever reason wouldn't it at least try to run on 2 cylinders? It is pretty clear that it is only running on what I am spraying in there.

Thanks for all your responses. I will report back tomorrow after I take apart the carbs and spray some regular gasoline in there.

Jim Lee

 

[TR3driver]

What are the odds that both would stop working at the same time?

What about bad fuel? I'm guessing the weather has been damp around there recently, and our modern "oxygenated" fuel has a tendency to absorb water from the air and then suddenly separate into burnable and non-burnable fractions (especially when cooled, as might happen sitting overnight). It could easily have already been "wet" when you bought it, and then picked up enough more in the tank to separate.

 

[eschneider]

Regarding your original question - "weak spark" applies much more to misfiring or hard-to-start than a no-start.

As for the pertronix system, they are a wonderful thing to reduce maintenence and arguably improve performance. No doubt, they can make life easier (until there is a problem). However, the points system is much cheaper and easier to diagnose - if you take the time to understand and test it properly.

A pertronix by itself will not give you a "stronger" spark vs. points. It's just a high-speed on/off switch, and any performance gains are in that a transistorised switch is more consistent at 4000 RPM than mechanical points.

Maximum spark voltage has to do with the coil, and actual voltage has to do with gap, fuel mixture, resistance.... If only 5000 volts are needed to create a spark, no coil in the world will force 20,000 volts across the terminals.

The only thing that is keeping me from believing this is a fuel problem is the fact that we have two carbs and therefore two fuel sources for the engine.

It runs when you add fuel (starting fluid). IMHO that's the biggest clue.

What are the odds that both would stop working at the same time?

pretty good odds, actually. If something gummed up a needle (bad gas, grit...), it could easily gum up both. And I might have missed whether you checked for fuel in the bowls, but if both bowls are dry, the fuel supply is likely the culprit.

even if one carb was shut down for whatever reason wouldn't it at least try to run on 2 cylinders?

probably not. It *might* lope on 2 cylinders at half throttle if the plugs are fresh, battery and ignition are perfect, and you had warm weather.

best of luck, and don't forget to enjoy the process. It's supposed to be fun.