Let me start by saying that I have searched and read many forums on this matter and tried many of the suggestions with no luck. I have a 51 Merc. with its stock merc. flathead (rebuilt 8-10 years ago) with its original 6 volt positive ground system. I have had the car for almost a year and hot starts are problem. The car starts pretty good when cold, but not perfect. Sometimes I hear what sounds like a squeek coming from near the battery area on cold starts. Once I drive it and shut it off it does not like to start. It is a slow cranking dead battery type start not a vapor lock cranking with no fire type. The battery is charging good and tested at 730 cca's out of 780cca's. The cables are newer big ass welding probably 1 gauge. The ground goes to the engine block. I sanded off a little paint/rust at the block contact point to make sure the conection is good. I thought and was hoping for a starter or timing problem. I checked the timing and it was dead on. I pulled the starter and took it to a very reputable starter/gen. rebuild place. The dude took it apart and said the brushes, armature etc. looked great. He thought the starter had been rebuilt when the engine was redone. He put it all back together and bench tested it. He said the starter is not the problem. I figured I should just start replacing ignition components to rule things out. I replaced the points, condenser, cap, rotor, plugs, wires, coil and starter solenoid. I checked the breaker gap and dwell and rechecked the timing and all is good there. My starting issue has not really changed. Next in line is to add a heavy ground cable from the engine to the frame and maybe try one of those Optima battery's. The only other issue is the wiring. The engine harness is original and some of the cloth is frayed and electrical tape covered. I haven't checked continuety and voltage drop in the wiring yet. I don't mind replacing the wiring, but hope to do it down the road. I can only drive this thing when I know it will sit to cool down and it blows. Any ideas and help would be greatly appreciated!!
It sounds like a coil issue, maybe the condenser and the coil are bad. Test the coil for spark while cranking. Leave it running and feel the coil to see how hot it gets. There are a lot of purists that don't like converting to 12V but I always do and go negative ground because it just helps in a lot of ways, at least for me it does. Check your connections in the distributor too, a loose connection can short out and cause temporary problems. Probably something really simple.
How close is your exhaust to the starter? If its too close the starter will get hot and be slow to crank, might try a heat shield on the starter if exhaust is close.
Like Da Tinman sez, it sounds like a hot starter is your problem. Try pouring a bottle of cold water over the starter next time.
I replaced the coil and the condenser and would liek to keep it 6 volt for now. I really thought starter all along too. Then I pulled it out for a rebuild and was told it is practically all new inside. I will have to check the exhaust. I know it's on the starter side but not sure how close. Good idea, I will try the cold water thing. If that fixes it I will make a heat shield. The only thing is I'm pretty sure the exhaust is nearly stock and close to its stock location. I would think they didn't have this problem back when the car was new.
Can you still buy 8 volt batteries? I remember lots of 50 Olds owners would do this for their hard starting motors. The 8 volt battery gave you just the extra cranking power. You just dropped the battery in, you didn't have to change any bulbs or anything else in your electrical system.
I agree with tinman, a bench test doesn't simulate the heat a starter will encounter in an under hood environment. I have encountered this problem many times and in most cases it was bad ground or a starter that would work well after it cooled. I would really look hard at that ground wire and connections. MickeyC.
Doing a compression test hot and cold scares me. I would rather be left in the dark on that one. Ha. ha. Although that may answer my question. I thought about the 8 volt battery, but don't want to mess with the voltage regulator. I checked my ground connection at head bolt on the block. I cleaned the surface with some emory cloth. The cables look good and are heavy gauge. What are everyones thoughts on adding another heavy ground cable from the ground point at the block to the frame?
Another ground wont hurt anything, just cost $, Check your heat riser valve on the exhaust and make sure its opening when hot. I had this problem with my 49 windsor, hard start when hot.
i had a ground cable to the the engine and to the frame and to the firewall same problem as yours i gave up sold the car
is the starter geting a good ground, maby oil ang grease on the starter and mounting plate. also check your starter solinoid. i had the same troble on my 36 ford, after you are cranking , check your conections by fiealing , if they are hot you have a bad conection, good luck
I agree about the solenoid. It could be cruddy inside, not getting a clean contact. Also hot starter. One other thing... I've known an engine or two that would boil the fuel out of the carbs while sitting for a few minutes. If you left it for 15 minutes or so, it would almost sound seized up it was slow to crank, and on 12V. 15 minutes later and the gas would dissipate and it would crank fine. You are working with 6V, so I imagine it would only be worse. Maybe insulate the fuel lines? I would crank it a bit, bump the starter till the hard spot was past and then when it would spin freely I would actually try to start it. Just a thought.
I was thinking that since my problem is only with hot starts I may not have a ground issue. Could heat create a bad ground somewhere? I replaced the solenoid. The cables at the solenoid and and starter look to have good connections. I don't know if where the starter meets the bellhousing/flywheel area is perfectly clean. Again, could heat create a ground issue? I'll have to check the heat riser vavle and hot connections. On my days off this week I'll try these suggestions and hopefully fix the problem......thanks for everyone's help!
I have an update. I added a 1 gauge ground strap from the engine to the frame. I cleaned the ground surfaces at the solenoid and starter mounting surfaces and used better battery cable terminal connectors. I also added some Marvel Mystery Oil for the hell of it. I then wrapped the exhaust near the starter with heat tape. The thing started way better when cold. I drove drove it for about 45 minutes to get it nice and hot. I shut it off and waited about 10 minutes for the heat to soak. Then the thing started up pretty good. It was still a little slow cranking compared to the cold start, but it looks like the heat tape helped a lot. The starter stills feels a little warm to the touch. I ordered one of those starter insulator blankets from Summit. Hopefully that will help a little more.
Is there any possibility the starter was rebuilt to 12 Volt specs? Or possibly a later 12 V starter was bought at a swap meet and installed by accident? Your starter guy may not have recognized that the windings were the 12V variety. That would definitely cause your hard start issues.
I would change that starter. They are dirt cheap and good used ones are out there by the dozens. You can jump a 6 volt starter with 12 volts. Most run the 6 volt starters with the 12 volt conversion.
how about a remote solenoid. up on the fire wall. worked for me. Never did one on a flathead set up. Should still work.
The solenoid is mounted on the inner fender by the battery. And a very reputable local starter rebuild guy took the thing apart and said it was recently rebuilt. I have thought of buying a new high torque one from Mac's. However, I think it may be getting hot from the exhaust. The exhaust is ony a few inches away from the starter. It's been replaced at some point and think it may be closer to the starter than the original. The wrap has helped and i'm hoping the starter blanket will help more.
I had a 52 Ford Sedan Delivery and I changed it over to 12V pos system but kept the 6v starter. You had to release the key from start to on to see if the engine was running as it would spin the motor about 3 times faster than it would idle
I just put a fresh 1200 cranking amp 6 volt battery on the wife's DeSoto. Powers right through the heat, old corroded wires, worn out motor... Someday I'll make up some fresh cables.
I had the same problem with my stock '51 Ford. It got bad after I replaced the battery. I had always tried to get Group 2L batteries for it, but lately, they're not available, or very expensive, so I put a Group 1 battery in it, which is much smaller. I had all kinds of hot start problems after that. I checked everything (like everyone else has said here), and finally put in an Optima battery with 800 CCA. It immediately solved the problem. I've got to believe that if the battery is not up to snuff, the little bit more that it takes to crank over when it's hot draws enough current so the voltage to the ignition drops to where it's marginal and doesn't want to start. Anyway, it worked for me.
53sled where did you get that 1200cca battery? I've thought about an Optima, but have heard bad things about them recently since they moved production to Mexico
Update: I've been driving it a lot and there has been a little improvement in the hot starts. When I drive it on the freeway and get it really hot it is still tough to startthough. I know this may sound weird, but when cranking it I hear a humming sound coming from near the drivers side firewall/inner fender area. Any one know what the hum could be from?
Another update: I went for the sure fix route. I replaced all the frayed, corroded wiring and then converted to 12 volt. Now it starts with a bump of the starter button when it's hot or cold. It was a tough job, but worth it!
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