Ugh, Battery Drop To 10.3 When Cranking.

Greetings,
I have a 1971 cj5 with the dauntless v6. The motor has been pulled and rebuilt. I’m having issue with the battery dropping voltage, down to 10.3 when cranking. I’m running an HEI distributor with electric fuel pump, with new fuel filter. Stock rebuilt 2 barrel carb, Carter.

What I’ve done, so far.

The motor has not been run for more than a few minutes so still has break in oil in it.
new battery, group 24
New distributor, new plugs and wires
New starter
New alternator, 10si
Timing at at appx 8 degrees
Ballast resistor removed
Starter relay added
New ignition


I’ve got a 2 gauge positive wire from pos side of battery to starter solenoid , 2 ground wires, one to starter mount on block and other to alternator mounting bolt, 10 gauge wire from alternator to positive starter solenoid. I’m getting a battery voltage drop from 13.2 down to about 10.3 ish. Definitely not enough for the dizzy.

Any ideas? I’m sure I’m missing something. Thanks Todd

 

Do you have your frame and body grounded as well? Check your voltage at the ignition and also make sure nothing is touching there, also make sure battery connections are tight? Just throwing stuff out there. You can also check resistance on your coil and make sure it’s consistent and not jumping around.

 

Thanks I’ll do those checks, I’m really at a loss. Frame is grounded at passenger side engine mount. Where does body ground?

 

Ten volts isn't surprising, depending where and how you are measuring that. Are you saying it won't fire, or what?

Is the battery "known good" not just "new?" Fully charged? How do we know the 'new' starter isn't crap?

The rebuilt motor is probably tight, too, tough to turn over.

Check all battery connections, even the cable clamps to the cables etc.

Gosh I wish people wouldn't say "dizzy."

 

Thank you, at battery. No spark unless I isolate with another good battery, battery is a 24F it states 600 cca and I just purchased this week.

Should I read at the starter solenoid or battery?

ok, my cables are definitely different sizes. + is a 2/0 gauge and both -‘s, there are 2, are , they say 4 gauge.

 

PeteL, it won’t fire…

10.3 at battery when cranking, 13.4 before. On charger …

starter seems good, turns over pretty good. My first jeep, not sure how it should sound. Seems good. How do I test starter?

fuel pressure 3 psi regulated after electric pump… Seems to have a nice squirt when actuating throttle. 3 pushes, full manual choke and hit key, no fire
idle Too low?
carb adjustment screws at 1.5, hmmm

thanks for your time and patience

 

Don't assume this is a carburetor issue just yet.

I see this "The motor has not been run for more than a few minutes so still has break in oil in it."

I assume that at some point you had it running.

Then I see a long list of things you have done so far, new parts.

Were these things done before, or after you had it running?

 

Thanks for asking, I’ll answer your questions tomorrow… Todd

 

Welcome from Michigan. I would ground the frame and the Body and the motor with heavy cable too, just to make sure everything has a good ground. Good Luck.

 

Fuel
Air
Spark
Compression

 

Suggest you use your jumper cables and go directly to the starter lug and the starter ear. This is a Delco starter? I'd use a remote starter switch rather than the ignition switch. That will eliminate the body, frame and cables from the test. See if you get the same voltage drop.

Note that an electric motor draws a lot of amps, and that will be a significant load on your battery. If you have a new engine and it's (properly or improperly) tight, the draw may be excessive and the voltage drop more than expected.

Sorry if I'm repeating some of the above comments.

 

Make sure you have fluids in transmission and transfer case. Make sure you have engine oil pressure too. Easy to pull the Distributor and crank the pump on a Buick motor to verify prime. Total long shot but had a guy weld a transmission main shaft to input shaft starting a new build and forgot the fluids in transmission. Doesn't take too much extra drag to see an electrical problem that may actually be mechanical.

 

Thanks guys, all great ideas. I’m on shift for 24 hours and will be back at it tomorrow. I’ll post progress then..
Thanks Todd

 

A shifter?

 

WHEW

 

Thanks guys for your patience, I’m a firefighter, hence the 24 hour shifts…

quick update, i installed another neg battery cable in lieu of the other and got spark now… it started and ran! Yeahhh
But, it was leaking fuel from bowl gasket, so another on order. Should there be a spring where the accel pump plunger installs? Thus didn’t have one. It’s a Rochester 2g with manual choke and build number 7841185.
Blessings and thanks for all your ideas… I’ll update when parts come in.
Thank you Todd

 

Yes, there should be a spring under the plunger. See page 54 here:

https://www.carburetor-parts.com/as...Mn3qor3MEQ29yVbSWrs9s4MbYiwoPb2V3w5xFZWoNWKyw