Grounding out when starter is engaged

[Murf]

When I hit the lever for the starter the juice is grounding out..The battery gauge slams to zero. Prior to this the starter would turn and I had spark at the plugs... Possible causes ? Regulator (stock mechanical) fried ?

[M37UK]

The first thing I would check is your battery(s)

I dont think the regulator has anything to do with starting the truck, only charging the battery(s).
The main positive cable goes straight from the battery to the starter so it is either the battery, starter or cable at fault.
Also make sure the negative cable from the battery has a good connection to the frame or engine.

[Murf]

I think you may be on to something....I pulled the batteries and 1 shows 45% This is even after they have been on a 24V maintainer....

[M37UK]

I think you may be on to something....I pulled the batteries and 1 shows 45% This is even after they have been on a 24V maintainer....

Its common for a battery to develope 1 or 2 bad cells and this will mean it wont charge properly no matter how "smart" the charger is. Cold weather and frost often kill batteries.

Hope this help

[majorhitt]

If you were " grounding out" there would be an arc left somewhere. That would be a short circuit. As mentioned earlier It may be the batteries. Place a volt meter across the Neg and Pos terminals of one battery and try to start the vehicle, watch how low the voltage drops, then do the same to the other battery, You may see a complete drop in voltage on the bad battery.

[Joe]

The electrical system should ground out when you hit the starter. Starters pull a LOT of current (several hundred amps!) and with a weak battery it may seem like a direct short to ground even if it isn't. The best way to tell for sure is to put a a HIGH capacity amp meter is series with the starter so that you can tell if it's pulling too much current or not. But amp meters of that sort are expensive so most people skip that step and start looking for indirect evidence of what's wrong. In most cases, it's the battery. Load testers for batteries are relatively cheap and common and can quickly tell you if you have a weak battery. A lot of the car parts stores will also load test your battery for free. In an M37 there's very little between the battery and the starter (usually just one cable) so it's easy to physically check and a real short to ground is usually obvious due to the burnt insulation and melted wire and frequently melted steel where they made contact.

Check your battery first, it's the mostly likely culprit. AND you should always verify that you have a good fully charged battery(s) BEFORE you start doing additional electrical system troubleshooting or you will end up chasing false symptoms!

It is possible that the regulator is causing your problem. It can fail to keep the battery properly charged (easy to check for with a voltmeter) or it can draining the battery when the vehicle is off. That's also easy to check for by simply connecting an amp meter in series with the battery and the regulator. (I simply disconnect one of the battery terminals and connect the amp meter between the battery terminal and the clamp). There should be no current flow when the vehicle is off. If there is any then start isolating circuits until you find the one that's drawing power.

[m15256]

Load testers are cheap and once you figure out what they do you can check the battery (s) and also the connections to the end of the + cable. Multi meters are cheap but if you get one spend extra and get one that will read high DC amps. Wire brushes,post cleaners,emery cloth,dielectric grease,any old grease,spray on terminal varnish are all cheap. Most things that go wrong (electrically) are just loose or have bad contact.
Yes you could have dead short to ground, but the odds are very very high that you don't.
Good luck