92 occ short

Hi guys. My 92 OCC developed a problem over the summer. Got a short in the wiring that will kill the battery in less than a day. Narrowed it down to the circuit that feeds the fuel pump and ECM. Pulled the ECM still shorting. Pulled two relays under the hood pn the right side, still shorting. Near as I can see thast only leaves the fuel pump. What would cause that when the key is off? Any suggestions gratefully accepted.

Fuel pump harness is underneath the rear bumper - it's a 3-connector plug. Disconnect it and see if the battery drains.

Honestly, finding current draws is not hard. Hook up an ammeter between the battery and the positive battery cable, then start pulling fuses one at a time until the current drops to zero. The key-off draw on a car should be tenths or hundredths of an amp.

Ok. Will look for the fuel pump connector. Pulled all the fuses early on. Not any of them. Found the drain by pulling wires off the battery block about 2' from the battery on the inner right fender. Pull individually and the one that is the problem feeds the ecm and the fuel pump according to wiring diagram.Does not appear to be ECM as I pulled it and still drains. That circuit may feed something else but I dont know what.

Check your oil pressure sending unit. There is a fuel pump switch internally mounted.

its not that the fuel pump dosn't work. Works fine. Could there be a problem with the fuel pump relay that would cause the drain? But then I believe one of the relays near the firewall is for the fuel pump and I pulled both of them. Still drains. U think a short to ground on the oil pressure sending unit?

In reference to the oil pressure switch, I was not concerned with the fuel pump working. It would not be a short directly to ground. It would go through the fuel pump. If the internal switch is not opening when pressure is off, current flow through it may be draining the battery. It may be a "poor short" and just causing a slight current drain, but not enough to run the pump when the car is off. The oil pressure switch is in series with the pump, which you said was the circuit that drains the battery, and is an always hot circuit.

In reading this thread I believe the concern has been identified as external to the battery, but what condition is the battery in? An internal issue to the battery could cause this concern. What is open battery voltage? Maybe the battery just can't hold a charge???



This chart is a good indicator of the battery state of charge by measuring open voltage. Basically measuring from the positive battery terminal to the negative battery terminal with nothing connected other than a voltmeter. Take the reading and compare it to the chart to get battery state of charge.

Often times we overlook the "that can't be the problem" component.

Try this test to help determine if the battery is the culprit. Remove battery from the vehicle, or at least disconnect it, and check voltage. Recheck voltage again in 12 hours, if all is good, the battery voltage reading should be exactly the same as the previous reading. Batteries have been known to internally short out.

Make sure the battery top is clean, that alone will cause a battery to drain. Go ahead, grab a DVOM and set it to measure DC volts. Set the test leads anywhere across the top of the battery, ideally you should have 0 volts, anything other than 0v indicates a dirty battery top and requires cleaning.

Chasing down electrical issues can prove to be challenging.

Battery's fine. Brand new. Keeps a charge just fine as long as the fuel pump circuit is disconnected. I will check the oil pressure switch as I recently replaced it.

Update?

Kinda curious myself?

Havn't got time to check the car out yet. Won't be until after Christmas. Thanks for the suggestions guys. I will report back.

Well took a while but I have an answer ' sort of. Up here in the great white north we park our collectables for the winter so the car sat all winter.Got it out and started to check it out more carefully. Problem started when I replaced the oil level sensor tho it didn't occure to me at the time as I was doing other stuff to the car at the same time. Long story short the problem was with the sensor, more or less. Problem cured but not sure why. Unplugged the sensor, pulled it from the pan, made sure contacts were clean, renstalled sensor, pluged it back in and it works fine. Start the car once a week, no problem. No Damage to the wiring, no visible damage to the sensor, had to be something in the connection. If anyone else has a problem like this hope this information helps. Thanks for all your suggestions guys