1948 case vac is very hard starting

Casefarmsmi · Aug 4, 2021

Back in 2016 I bought a 1948 case vac. For a while it was very consistent in starting and was never a problem. but a few Years back it developed a problem of not wanting to start. And to this day it will start but it cranks for a long time. I have put on new coils, new plug wires, new router, and new spark plugs. I am taking it to a big show this fall and I need it to start consistent. Any help or advice would be much appreciated. thank you all so much.

rrlund · Aug 4, 2021

How old is the gas? I had an Oliver 70 that started great with new gas, but when it sat and got old, get out the ether.

Steve@Advance · Aug 4, 2021

Is the choke closing completely? Some choke plates have a spring loaded vent door, be sure that is in place and working, if equipped. The carb may have some partially blocked passages, common with ethanol gas and infrequent use.

How is the compression? low compression will cause hard starting, possibly run the valve setting just to be sure they are right.

Is this still 6 volt? If so, everything has to be right for it to start. It needs a healthy battery, size 0 or 00 battery cables (not auto supply cables), a fresh starter with good bushings, good grounds.

Assuming this is battery ignition, check the voltage at the coil with the points closed. It should be near battery voltage. If low, could be a failing ignition switch, a high resistance connection (loose, corroded). The coil you replaced, are you sure it is the correct coil? Is there a part number on the coil itself? Often they are reboxed and get sold under the wrong part number. A good spark will jump 1/4 inch at the plug end of each wire to ground while cranking.

Janicholson · Aug 4, 2021

Low cranking voltage at the coil can cause this difficulty. Low coil voltage at startup can be caused by several things. A battery that drops
voltage when subjected to starter motor load. Voltage across the battery terminal studs while cranking should stay above 5 volts. If lower, there
will not be enough to fire the plugs. Voltage can also be lost in a failing battery terminal connections, or small battery cables. Cable size should
be 1-O (big as a 1st grade pencil) copper wire. 6 volt systems require 2X the amps that 12v does. Internally corroded wires are also a source of
voltage loss. This can be invisible, and found by feeling the cables after cranking for heat all along them. Failing ignition switch connections, or
the switch contacts can lower coil voltage as well. To check this jump from the non-grounded battery terminal directly to the switch side of the coil
and give it a start. if it fires easily, the switch, connections, or wires could be suspect. Good luck with a repair, and let us know what you find.
Jim

racered57 · Aug 4, 2021

If fuel, choke, and spark are good , check valve lash.

teddy52food · Aug 4, 2021

Jim; If the magnetic field comes from the amps, why does it crank so slow on 6 volts and twice the amps as on 12 volts? And on 12 volts & half the amps it spins much faster??????????????????? I still say it comes from the atoms of the conductor excited by the VOLTAGE!

Crazy Horse · Aug 4, 2021

Our club owns an 8N Ford that unless the gas is shut off after use, it is very difficult to start. If the gas has been off, it fires up quickly.

Janicholson · Aug 4, 2021

One can excite electrons with a thousand volts from a cattle prod, but the starter won't spin. Power is measured in watts. Watts is volts times amps. 200 amps at 11 volts while starting gives 2200 watts. So a 12v battery develops enough work effort to spin it well. At 5.5 volts cranking a 6v system to 400 amps, the watts is 2200. Because lower voltages require higher amps, they loose more in motor efficiency and wire resistance losses. 6v batteries have thicker plates, and are subject to the same internal resistance issues. Look at the trend in battery powered hand tools. from the 12 volt tools years ago, we now can find 60 volt battery driven powerhouses. It is delivered energy that makes watts turn starters. Voltage provides that force, through small resistances (way less than an ohm on both 6 and 12v starters) to drive amps making watts. Jim

Goose · Aug 4, 2021

That sounds odd.

We had two VAC's, and they were the ones we could depend on to always start, even in sub zero weather.

Pete in Holland MI · Aug 5, 2021

6 or 12 volt?

Dad's Jubilee was always hard to start. Every time we ended up properly jump starting it off a 12 volt vehicle, it fired
right up. Deemed the 6 volt system had some weaknesses in it some place and too much juice was headed to the starter and not
enough to run the spark system. Converted it to 12 volt and fires up instantly now.

teddy52food · Aug 5, 2021

When you said voltage provides that force, that is what I am saying all along! In your examplethey both use 2200 watts but the higher voltage lower amps starter spins faster than the high amps low voltage one.

1948 case vac is very hard starting

Casefarmsmi

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