I think my 99 blazer has a short some where but i cant find it. The battery keeps draining down and when i pull off the neg. cable & try to reattach i get a spark so im thinking something is on but every thing is off.I put a test light between the neg cable & the neg side of the batt.& pulled all the fuses one by one but it lights up every time. Any help Jim

 

Best to use a multimeter which can measure both voltage and current. Using the meter set it to DC Amps mode and make sure the test leads are plugged into the terminals for current measurement. Most meters should have a 10 or 20Amp range. Test with the vehicle completely turned off no lights etc. Now just disconnect the ground cable and connect the meter in series with negative cable (one test probe) and the negative battery terminal (the other test probe). You should have a nominal reading of under 0.5 amps for sure maybe even lower possibly 0.2 or less for memory circuits on the electronic control modules. Anthing 0.5 amps or higher is a higher than normal draw and could be causing the battery to drain. (** make sure you unplug the under hood light if your vehicle has one while testing)
My neighbor had a draw of about 4.5 amps on his Ford - the alternator had a shorted output diode causing the alternator to suck the battery down. Because it had been doing this for a while he had to replace the battery as well as the alternator.
Good luck.

 

I bought a meter & hooked it between the neg cable & neg post I get a 12. 5 volt reading. that dosent sound right does it? The car wont start i think its the pump but dont want to change it till i find out where the short is.Like i said took the fuses out one at a time & the test light kept coming on .I,m not to good at testing elec . parts so could use any help at all

 

Had the alt . checked its good.Still cant find how to go direct to fuel pump, i seached for which relay hole to use but cant find it.

 

Set your meter for AMPs not VOLTs... 12.5 is good voltage for the battery when not running. You want to see the draw, not the voltage. Then unhook the alternator from the battery and see if the draw changes.

 

the amps read 0.74 the same with the alt disconnected.

 

0.74 is high, it should be less then or about 0.05, because of clock memory ,alarm, etc.., at this point start pulling out fuses and disconnecting any added accessories one by one, if you can't find that way, start moving wires around and look for anything obvious...beyond that you'll have to just disconnecting anything you can find


whats the problem with fuel pump?

 

Car wont start ,cant hear pump.Iwant to try to go direct to pump but dont know how.

 

You can remove the fuel pump relay and jumper the switched side of the relay.

 

There are no markings on the relay or the fuse box i dont know which holes to jump.

pulled fuse 50A says bat int & reading went to .09 what now?