electric power drain in 91 ranger

[sonofsong]

Greetings! my 91 Ranger V6/Automatic Has a strange power drain that no mechanic who looked at it has been able to figure out. The truck runs fine if driven every day, but when it sits for a day of two it has to be jump started. I have had the battery & Alt. replaced twice (2nd time under warranty from Pep Boys) and the wires looked at, and the problem still persists. I now disconnect the neg. terminal if I know It will be parked for some time, this has worked but is becoming quite a pain. Is this a common problem? Any ideas?
Thanks!!!
Glen
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[Mac626]

Make sure that you check to see if the interior light is not staying on after closing the door. Sometimes the door switch fails and the light stays on, draining the battery. Easy to notice if you park it at night, but easily overlooked if you park it during the day.

[sonofsong]

Thanks for the reply Mac626. Been that route and have checked all the lights (including brake lights) and removed most common fuses overnight (horn,radio,etc...)

[cpq28g72]

Pull the negative battery cable off, put a test light between the cable and the battery. Make sure every light,acc, everything is off. with a drain the test light will light. Then pull 1 fuse, and or relay at a time and see if the test light goes out. you can narrow down what circuit is causing the drain and focus on those items.

[Robinssm]

What I noticed was when I connected the negative battery cable I would always hear a relay click. This should not occur with the key off. I pulled fuses in the engine compartment fuse box until the click did not happen. This isolated it to the fuel pump fuse and relay. When I pulled that relay (under the fuse block) I noticed some powdery corrosion. I cleaned up the relay spade contacts with an eraser and when I reseated the relay, no more clicking after hooking up the negative battery cable. What was not documented in my Haynes manual schematics was in the discussion on the ECM. Apparently this relay senses fuel pressure and turns on when it is low or absent. Since it wasn't conducting (powdery corrosion) it was trying to switch the fuel pump on (energizing the relay) but couldn't since the key was off, the relay was drawing down the battery. Final cure was to put some NOALOX (anti corrosion goop) on the terminals of the relay. Best of luck.

[cpq28g72]

Thanks for letting everyone know what happened, Great job......