Engine turns over but wont fire. changed battery and hooked up wrong to where the ground got fried. have all lights but volt gauge not reading in the positive side

Run a good ground wire from the battery to the body. Also one from the engine to body.

Bad ground.

Did you connect the engine ground strap to the frame. Also check that the engine turns over by hand. Use a socket on the crankshaft nut to turn engine over. I f it turns the check all wires going to stster for power. You should have power at the S terminal only when the key is in start position. If you have a voltmeter check voltage at starter battery terminal. It should read 12.6 volts or higher. If your not getting 12 volts then it is possible you have too much resistence in the positive battery cable and it needs replacing.

I'm having a problem with my 1998 dodge ram all of my gauges read 0 before cranking it over all gauges work when cranked over accept my speedometer...odometer and my gas gauge goes to 3/4 full and stays there...im wandering if the speed sensor is causing the fuel gauge to stick along with the ABS light check engine light and break light..any answers?

You need a better battery. When you hook the amp meter and read 0.3 the ECM needs to sleep

It sounds like you might have a poor ground connection somewhere. You can test each individual gauge for full travel by grounding the wire the goes the each gauges individual sender. In other words to check the temp gauge, ground the wire that goes to the temp sender. The temp sender is in the left cylinder head between the #1 and #2 spark plug ( looks like a brass pipe plug with a single wire coming from it) if you ground the wire with the key on (engine off) the gauge should go to the end of the scale (hot) with the wire off it should go to full cold. You can do this with the gas gauge too but not the amp gauge or volt meter. If the volt gauge is reading low (if it has one) and you know that battery voltage is good (don't guess, measure with a multi-meter) there has to be a poor connection somewhere.

i have a 1990 nissan pathfinder with fuel gauge reading problems,at 1/4 tank the gauge reads full,and at other times it reads the actual quanity any ideas/

sounds like you fried the computer and likely the coil too
salvage yards love people who dont read the chilton books

With Ign. off what is your batt.voltage reading than take neg. cable off and take another reading 5 min. later. It sounds like a intermitten short, try to isolate voltage drop when acting up. Gauge circuit would be a good start. Schematic would be helpful.

It depends on how long you had the battery hooked up backwards but check for any ground wires/straps from the engine to the frame or body that are burned in to.