I am having cold start problems with my 53 239 flathead. I thought I read somewhere that if a 6V engine will not start, you can do a limited number of starts with a 12v battery. It was claimed that no harm will be done as long as all lights and accessories are turned off. What would this prove or indicate? Any opinions on the safety or effectiveness of this?

 

When I have problems with 6 volt powered truck I give it a jump start with my daily 12 volt vehicle without a problem. I had had my son jump start the truck with his Power Stoke diesel truck and I thought the engine was going to fly out of the trunk. His Power Stroke had dual batteries with something like 700 cold cranking amps, that's way above the average 12 volt vehicle. You have to make sure neither car is touching, especially if you truck is stock positive ground. Make sure all lights, motors and accessories are off. The starter can take the 12 volts but I wouldn't crank it for long, I would run it on 6 volt for long periods of time either, it's going to get hot.

First, what problems are you having? If it's a slow crank make sure you have sufficient battery cables. Most cables you find in MacAuto parts stores (Autozone, Advance Auto and O'rielly's) are too light, you need to either go to a good parts stores that have a better supply of auto supplies or go to a farm supply store that sells thick battery cables for farm equipment. Make sure you also have a very good ground, 6 volt systems are very dependent on having good, clean grounds.

 

I've had my 6 volt 54 since 1977. I have jumped it with 12 volt vehicles times. Follow Bob's advice above. After starting my truck I make sure I quickly disconnect the cables on my truck first. And don't keep them on too long , cranking and cranking.

Follow Bob's advice about new thick cables , at least 1 gauge or 00 gauge.

But, I haven't had to jump it in a long time. With a rebuilt starter and a rebuilt generator and new thick cables I've had no problems.

 

A cold start issue could be a fuel problem too, like no fuel in the carb bowl

 

I picked up an old Holley carb and distributor parts book this week. It has all the parts diagrams and part numbers for the Holley 94 and 0ba/7ra distributors. Neat book. Anyway, it has a nice engine and distributor spec section. Thought it was interesting that the fuel pump capacity is 1 pint at 45 seconds. That explains why after a few weeks of no driving and an empty fuel bowl due to evaporation it takes a few seconds of cranking to get enough fuel in the bowl to enrich the mixture enough to ignite.

Might explain your issue.

JB

 

BJ

if you find out it's cables...;Go with biguns... 1/0 welding cables or larger with crimped on copper connections... Bigger is better...size DOES matter

j

 

Another way to solve the issue is to put a small electric heater that has a fan under the hood where it can blow on the distributor. My theory is frost will develop inside the dist and can damp down the spark.

Here in the cold weather country block heaters and plugging trucks in is just the norm so I adapted with the flathead to a heater.

 

My problem is that the engine cranks fast enough to start when it has warmed up a bit, but will not start without ether when it is cold after sitting overnight. It is kept in a heated garage, so cold is maybe 50 F. Does anyone know what engine RPM should be when cranking properly? As for occasional cranking with a 12V battery, that sounds safe on occasion. If it cranks faster and starts cold I guess that indicates a cranking problem. I will try that with my 12V boat battery sitting on the floor next to the truck.

As for grounding, I have removed, cleaned and replaced the battery ground. Now I need to do that with the direct ground from the starter. Both cables appear to be original and I will check them with a VOM to make sure there is zero resistance. I also will look into new 1 or 00 gage cables. Are there any other grounds that I should be aware of?

Regarding the possibility of a fuel issue, I have rebuilt both the fuel pump and two carbs. The fuel pump puts out 3.5 to 4 psi and is within spec, and the glass bowl is always full. The problem exists with either of the carbs installed. When I have taken the top off of the carb while on the engine, there is always fuel in the bowl. But I cannot remember doing that right before attempting a cold start. I will do that the next time I try one.



Thanks for all the good advice as to possible solutions and safety regarding a 12V start attempt. This forum is the best I have found for good advice from knowledgeable people.

 

just a wild idea.... wonder if the coil is weak and not giving a strong enough spark to start...from your description it isn't a fuel problem... If it won't start with ether ???... I'd look further into other solutions

j

 

Thanks, but I was unclear, it will start with ether. I installed a PerTronix ignition with new coil and wires. That improved cold starts a bit but still a problem. I need to check cranking speed and grounds as my next step. I appreciate your input.

 

I suggest doing a compression check.

 

Do you have any greenish, grayish, corriosion building up on the terminals on your cable ends?
Abe can speak to this better than I can but from him we learned that it can eventually work its way inside the cable and that would of course raise the cable's resistance when the starter is trying to suck current thru the circuit. If you see that, the cables are probably shot. As everyone says get big 2/0 cables. And make sure your main ground from the battery is connected right to the block, or better yet your upper starter mount bolt. Its a good idea to ground the frame and the cab to that point too.

If someone has suggested an 8 Volt battery. Most folks I have talked to found out that wasn't necessary if your cables and grounds are good. It's hard to get an 8 volt system to work correctly because the voltage regulator also has to be readjusted to charge at a little over 9 volts to keep your 8 volt battery happy. And readjusting a voltage regulator properly is the the hard part.
Edit,
Just wanted to add that I know folks who went 8 volts, didn't bother adjusting their voltage regulator, bragged about how much better their truck was starting, but then eventually as the driving seaso. went on, had to start carrying jumper cables with them. They were perplexed why their newish 8 volt battery kept running down on them. It would of been good if, they got their voltage regulator adjusted to charge at the higher voltage. Problem is they are delicate to adjust. And if not adjusted correctly, get so out of whack, that you might as well go back to a new one, which is 6 volts again.
Didn't mean to make this a rant. Its just something I have noticed.

 

When I fixed up my truck in 1998-99 I got new 00 cables made. Several years ago my truck started hard when the engine was warm. I took the starter out and got it checked. It was good. The guy at the auto electric shop asked how my cables are. I said , "they're good . I had you make new ones in 99. That was.... 19 years ago.... " So I took my one cable off . I cut it in half. It was corroded on the inside . I got new cables made and my problem was solved. Time flies. I hadn't realized my cables were almost 20 years old.

 

I had the same problem with my Bobcat. Outside of the cables looked good. It would start after I cleaned the ends. ( moving cables must have helped the connection?) Then no start even with a jump. Inside of the cables were corroded. Replaced cables and no more problems.

 

So I have a question about jumping a positive ground vehicle. How do you go about connecting to a negative ground vehicle for a jump.
This got me thinking about traveling. We have a HALO. They are fantastic. If I could take that with me on trips it would be good insurance. I would think for that I would just connect positive to positive terminals on the battery.
But with a battery in a vehicle it's different since one battery is grounded at negative and one at positive.