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What do you all do if your 6v battery dies while cranking. I have looked high and low for a 6v jumper pack and can't find one except for a $1000 one.
Can tow companies jump 6v batteries?
I ask because I have had some hard starting experiences and am super nervous about winding up with a dead battery trying to start it. So far I have been able to get the motor to catch but some close calls.
In the 49 years I have owned my truck I have used 12 volt cars to jump start my 6 volt truck many times. A battery pack like service garages have should be able to jump a 6 volt battery.
I find it is best practice to directly energize the starter with the 12V jumped straight to the starter terminal on the solenoid as to not feed 12V through the whole truck (as long as the solenoid is not triggered). I've seen to many stock clusters that have failures that could be attributed to being connected to 12V for too long...
Now, on the other hand, it may be best to investigate the cause of hard starting. You can have your battery tested to make sure it is up to snuff. Many of the parts chains will do this for free. Is your spark still strong? How do the spark plugs read your carburetor tune?
Describe for us the starting symptoms if you can recall. Do have slow, labored, cranking, a long with a lot of clicking from the solenoid? As Brian mentioned battery tests good? These items you probably have already but do you have the good 2/0 battery and starter cables? Is the battery grounded right to the engine block?
Or is it cranking fine, but the engine is not firing? Which gets us to spark, air and fuel issues.
A friend of mine has an old I think '38 John Deere G.
For years he was having issues getting it to run. As you tractor guys know, there us no electric start on it. You have to open pet-valves to relieve the compression, then physically turn over the flywheel to spin the engine. When it won't run it's a lot of work. We had spark, the carburetor was getting fuel, but it just wouldnt run. We checked spark, checked it for flooding,compression, etc. So we are out in his pasture, with another friend, using another tractor to try to pull start it. Sometimes it would fire and pop, but most times, it was just sort of a futile exercise. 3 guys pulling a tractor around. So just before we quit for the day we are talking over what could we be missing? We got spark, we got fuel, BUT are we getting AIR? So the oil bath air cleaner pan gets pulled off, it was over the top filled with water, and of course, old dirty, digusting, milky looking oil. We cleaned it up, dried it out, added new oil only up to the full level indicated on the pan, and it fires and is running like a top. And now its fires right up with just a roll of the flywheel. And to think he was fighting this problem for years. Just a hidden problem. And it makes sense as that tractor sat outsde for years.
Describe for us the starting symptoms if you can recall. Do have slow, labored, cranking, a long with a lot of clicking from the solenoid? As Brian mentioned battery tests good? These items you probably have already but do you have the good 2/0 battery and starter cables? Is the battery grounded right to the engine block?
Or is it cranking fine, but the engine is not firing? Which gets us to spark, air and fuel issues.
A friend of mine has an old I think '38 John Deere G.
For years he was having issues getting it to run. As you tractor guys know, there is no electric start on it. You have to open pet-valves to relieve the compression, then physically turn over the flywheel to spin the engine. When it won't run it's a lot of work. We had spark, the carburetor was getting fuel, but it just wouldnt run. We checked spark, checked it for flooding,compression, etc. So we are out in his pasture, with another friend, using another tractor to try to pull start it. Sometimes it would fire and pop, but most times, it was just sort of a futile exercise. 3 guys pulling a tractor around. So just before we quit for the day we are talking over what could we be missing? We got spark, we got fuel, BUT are we getting AIR? So the oil bath air cleaner pan gets pulled off, it was over the top filled with water, and of course, old dirty, digusting, milky looking oil. We cleaned it up, dried it out, added new oil only up to the full level indicated on the pan, and it fires and is running like a top. And now its fires right up with just a roll of the flywheel. And to think he was fighting this problem for years. Just a hidden problem. And it makes sense as that tractor sat outsde for years.
-It cranks pretty strong
-Battery is good
-distributor has a Petronix electronic ignition module.
-I out a generator light in so I know it is charging
-Battery cables are 00
-Grounded from battery to block, Block to frame, engine to cab all with 00 cables
-When I fire it up cold I pull out the choke and it fires up every time. I push the coke back in about 3/4 right away to keep a little high idle and once I have driven a mile or so and it is warming up I push the choke all the way in. It idles very nicely.
-The issue is the next time I stop and shut it off and it sits for the time I am shopping or getting gas, so 5 mins to 1/2 hr, when I go to start it, it just cranks and cranks.
-I keep trying different sequences to get it to start. I push the pedal to the floor twice or pull the choke out halfway, or all the way, or hold the pedal to the floor or a combination of all of the above. I can't get it to follow a repeatable pattern. Sometimes if I try those things and then let it sit for 2 minutes and try again it will start.
-Last year it started every time without hesitation no matter the conditions. Ot would turn over 2 or 3 times and catch right away. Occasionally I would have to pump the accelerator once.
-I do have an oil bath so I will verify the fill level is correct.
The carb only has 2 adjustment screws. I assume one for the mixture and the other adjusts the choke plate/idle.
The carb was rebuilt last year by my neighbor who works almost exclusively on vintage cars.
Thanks for the detailed reply! It sounds like you got a good strong crank, good cables and grounding sounds good. Have you tried leaving the hood up after a run? If so does it start easier?
Thanks for the detailed reply! It sounds like you got a good strong crank, good cables and grounding sounds good. Have you tried leaving the hood up after a run? If so does it start easier?
Will try that on the next run. Raining today. Also need to get a 12v jump pack just in case.
8pack... I feel your pain. I have been there too. I have had the issue where my starter cranks and cranks but will not fire off. I have learned that as soon as I let off the key it fires up as if the starter is drawing too much power for the ignition to work. I have installed that second bypass wire from the starter relay to the coil on the '51 and a new bypass relay on my VW that mimicks the same concept, (both are 12 volt).
My other issue seemed to be the aluminum intake drawing so much heat that vapor lock seemed to be the issue. Phenolic carb spacers seemed to help there too.
Like yours, everything is new, rebuilt, heavy duty cables, etc. And I still have occasions, although not nearly as often, where it will not fire off right away, particularly in the hot southern summers. It has not left me stranded, but it gives you that "oh no" feeling and your brain quickly goes thru the "what if" scenarios.
8pack... I feel your pain. I have been there too. I have had the issue where my starter cranks and cranks but will not fire off. I have learned that as soon as I let off the key it fires up as if the starter is drawing too much power for the ignition to work. I have installed that second bypass wire from the starter relay to the coil on the '51 and a new bypass relay on my VW that mimicks the same concept, (both are 12 volt).
My other issue seemed to be the aluminum intake drawing so much heat that vapor lock seemed to be the issue. Phenolic carb spacers seemed to help there too.
Like yours, everything is new, rebuilt, heavy duty cables, etc. And I still have occasions, although not nearly as often, where it will not fire off right away, particularly in the hot southern summers. It has not left me stranded, but it gives you that "oh no" feeling and your brain quickly goes thru the "what if" scenarios.
I have the factory gaskets stacked as per the manual. Maybe I can get a phenolic spacer made or I think I saw one on eBay.
What's funny is that I have driven in mostly cooler weather so far this year, meaning 80* or below and mostly 55- 72* and last year I was driving in much hotter weather without issue.
My wife rarely rides in my older car/truck and my big anxiety is having a no start somewhere and we get stuck or even have to jump the truck. She will never ride in it again if we "break down" somewhere. We took a 50 mile trip earlier this week with several stops and each time it was a nail biter getting it to start, but it did eventually fire!
I feel better after being reminded by @bmoran4 that the 6v starter motor will handle 12v and I can jump straight to the motor if needed so I don't have to worry about having a 6v jump box.
Yep, the gas boils at a lower temperature than in the older days. Fuel injected vehicles run higher pressure which raises the boiling point. I would keep a shop rag with me and wet it down with lots of water, then wrap it around the carburetor base for a few minutes. Then starting got much easier depending on how much gas boiled out of the carburetor and into the intake manifold.🥵
I know you have a 6 cylinder so I'm not sure how you fuel line runs to the carb. But I did a trick that pintoplumber taught me. He and then I put a rubber fuel hose over my hard line where it is close to the block and the crossover exhaust pipe. I haven't had vapor lock occur since then.
But you haven't been driving in 90° weather this spring. So it might not be vapor lock.
I wonder if it’s running rich or leaking a bit of fuel into intake. Cold you need the extra fuel, hot it would cause flooding issues. Are you running points etc still?
Last edited by Christopher2; May 3, 2026 at 05:34 AM.
The fuel lines run in the stock location. From the pump up along the front of the block, cross over the front of the valve cover and due the valve cover to the carb. Pic below.
I eliminated the points and am running a Petronix electronic module in the distributor.
How would I know if it is leaking down fuel into the intake? When I get it fired up again I will try adjusting the mixture screw as I suppose it could be out of adjustment as the engine and everything has been broken in.
I think I have some fuel line insulation left over from my Camaro and can try putting that around the lines. The trick is finding it!
