Hey fellas. I just joined. I pulled a 50 merc out of a barn a few weeks ago. I've been working on getting her running and driving. It for the most part is an unmolested car that hasn't been customized in any way... rusty for sure but stock aside from an electric fuel pump. I'm in the process of putting all new brake lines on it. I have a brand new 6V battery, replaced the starter, flushed the coolant system, fuel tank, lines and the list goes on. It will start with ease with a 12v battery hooked to it but it seems as soon as I put my 6v battery it doesn't want to start. I did install a new 6v fuel pump (it had one that was shot). It'll turn over slowly. I've read a lot about 6v set up and I'll admit this is my first one. I know it's a positive ground car and everything is hooked correctly. Any idea what I may be missing or overlooking? I have started it a half a dozen times with the 12v battery only for a short time with all the electronics off.
Make sure the battery cables are big enough and connections are real clean. 6v is a high amp system and the cables they tend to sell at the parts stores aren't heavy duty enough to do the job.
This is what the car has on it. I haven't changed them and am new to a 6v system. Do they look correct?
Thanks. Hopefully that's my whole problem. My battery is fully charged and she spins over a little slower than I'd expect. I don't believe my fuel pump is kicking on with the 6v battery since I can't hear it but have yet to verify.
i ran 12v on a '48 panel, brother had a 12v '50 pick up, the bendix would slam the ring gear so hard it would start to slide it off the flywheel... my cure was a smaller ga. cable and made it as long as possible... did the trick for me
The fuel Pump should still come on, even with 16 ga wire. But 6 v engines turn over much slower than you may be used to, even with the proper battery cables. Be mindful of running it too long on 12 volts, the coil and points may suffer. It’s okay to jump/boost them to start with 12, but take the jumper cables off and let it run on 6.
I disconnected the fuel line at the carb and found that my brand new 6V fuel pump isn't pushing enough volume. There's hardly a trickle coming out of the fuel line. When I hook up my 12v battery to it, it fires up like it's fuel injected.
If you have the heavy cables as the car calls for and fuel pump mounted close to the tank. And a good 6 volt battery (not a cheap tractor battery). Should be no problem. I would by those tractor batteries Now step up and get the Interstate Workaholic Cranks like a 12 volt.
Those battery cable ends are junk. Always corroding and are really intended as a temporary fix. Get some real cables with real ends with the cables as big as possible. My flatheads are all 6 volt and no problem cranking over. Dave
Some voltage drop tests while cranking will point out which cables are undersize or have busted internal srands , which battery terminals are inadequate or need cleaning. Even if the ground connection between the starter and block is hinky. I don't like to spend money. So I don't buy parts until I've bought the few tools necessary for solid diagnosis.
John, it is difficult for us to see the actual size of the cables in the pictures. Should be as large as a thumb. 2 aught [00] is what I use. You may have to get a starter/generator electrical shop to make them. then Be certain all clamping /mounting surfaces are shiny clean. Ben
That’s what I though! He said it won’t pump , but a trickle of fuel on six volts! If it is a six volt fuel pump it should pump a lot of fuel at pressure on the six volt battery! I think he may had a combination of problems! Bones
The fuel pump says 6V right on it. I bought it specifically because it was a 6V. I'm beginning to think I got a 12V that was mislabeled! That's the only thing that makes sense. Hardly a trickle of fuel with my 6V battery but it starts like it's fuel injected on with 12V. I'll be buying another fuel pump soon. I did manage to wrap up all my brake lines today. I'll be digging into cylinders and shoes here soon.
Also: Ground cable should go directly to engine, then another heavy gr. cable from there to a sanded clean hole in the frame. I'd also remove the starter and replace brushes and bushings, drive end bushing especially. You'll be surprised at the performance starting and running a 6 volt system is, providing all the loose ends are repaired.
^^^^^^. If the cables and proper fuel supply don’t solve the 6 volt problem, look at the starter like Mike said. 12 volts on a 6 volt starter covers up a lot of problems.
Yes, I tried wiring the fuel pump the wrong way and it did nothing. I did manage to get a few feet of 4/0 good for 1000 amp and some temporary ends for troubleshooting. I'll be trying that out tomorrow. I'll also check the engine to chassis ground and replace that if it doesn't look up to the task. It looks like my original ground wire is 6 gauge. The rest of my wires appear to be 0 gauge going from the - post to my starter. The car did come with another starter that appears to have been rebuilt. It is installed. The original starter that was on it I thought was junk. After I pulled it I realized that the gear was just frozen all the way out so it wouldn't engage the flywheel. The brushes look good on both... I know this by accident. It took me about an hour to get them back together. It's my first flathead. If I'm still having the same fuel delivery problem after install I'll get another fuel pump. Thanks for the help so far everyone.
The new fuel pump from summit came in and I got it installed along with making a new ground from the motor to the battery. I also upgraded the cable ends to military style. She spins over much better now and I'm not having any other issues, for the time being. Thanks for the help.
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