A strapping good answer

XJ owner: Electrical/wiring question: Originally the negative on the battery runs to an engine bolt and another runs from the engine to the frame. Is this 2 step necesary, or can you run the negative from the battery direct to the frame. I'm a noob when it comes to wiring, as you already noticed.Thanks for your input.

Intelligent Tinkering: All major components of any vehicle using a negative-ground battery system need to be electrically "bonded" even when steel fasteners hold them together. This is typically done with braided stainless steel or tinned copper strapping meant to last the life of the vehicle and capable of withstanding vibration over many years where copper wire would get brittle. This is done to make sure that large metal items like engines or car transmissions do not become energized accidentally when isolated from the ground. The result can be sparks and welding of components, and it can lead to fires and other hazards. It can also prevent safe and normal operation. So an engine wouldn't run right if the ground strap were missing or damaged making it isolated from the ground, because the plugs wouldn't arc, and so on. You can buy new ground straps in various widths and lengths.

Fire, fuel, compression

Someone on our local community assistance FB page couldn't start their car. I wrote this to help. It should be taught to everyone in schools.

There is a sequence of basic tests to do to repair a non-starting vehicle or any gas piston engine. You do them in order and do them thoroughly, so that you are sure you've eliminated each cause as you go. The mnemonic is "fire, fuel, compression." 

Fire means spark. You remove a spark plug from a cylinder, lay it somewhere metal on the engine where you can see it and you're sure it's grounded, crank briefly with the help of a friend if your arms are short, and hope to see a spark. If there isn't a spark, try very hard to check that it was grounded just to be sure. 

Still no? Problem is "fire." You then need to troubleshoot the ignition system. There are too many possibilities under the category of "bad ignition" to go into over FB, but with high miler cars it's often the spark plugs that are so worn that the spark gap is too large. The gap should be around 30 thousands of an inch, which is about the thickness of thin cardboard. No spark and a large gap, change the plugs. 

If there is spark, move to "fuel." The easiest test is to spray starter fluid in the intake manifold, replacing the gas experimentally. If the car fires, you know by logical elimination that it was fuel, so troubleshoot the fuel system. 

For compression you need a compression tester and the knowledge to use it, but most mechanics can tell if an engine has very bad compression in one cylinder by turning the engine over by hand with a wrench on the crankshaft pulley or by using the belt, comparing the compression resistance between cylinders. 

Don't be tempted to jump to random causes. It's necessary to use a logical troubleshooting scheme to fix the problem.

How to trace a parasitic draw

Use a multimeter (not a VOM). Put the multimeter in ammeter mode (<10A). Make sure to switch the common to the correct socket. Make sure the key switch is off and the key removed. Take off the negative terminal of the battery. Put your foot on the brake pedal to drain any remaining current in the circuits. Hook the red probe to the disconnected negative terminal connector and the black probe to the battery. Look to see if there is a current draw, any more than a milliamp or two. If there is not, revise your hypothesis and suspect the battery. If there is, pull the fuses and replace them one by one until you find the fuse that makes the number on the multimeter readout drop significantly when you pull it, then troubleshoot that circuit. Trace it backwards from whatever utility it runs, disconnecting connectors in sequence moving towards the battery, until you unhook the connector that makes the number on the multimeter drop. The faulty circuit is now isolated.