Hi all, I got a new to me truck, an 87 22RE 4by. The truck was running intermittently when I bought it. When I replaced the pick up coil in the distributor it now runs great. I bought it with an extra battery, which should have been a clue to me. I have found it has a slow electrical drain somewhere in the EFI system (I think). Using a ammeter I can see no drain when I unplug the computer or when I unplug the air flow meter. (I have replaced the computer with another and have the same result.) I also see no drain when I unplug the pink fuse in the black fuse box just back from the battery. My questions are what systems does the pink fuse cover? And why would the truck run great if the computer or the air flow box had a slight short in them?

Thanks for any suggestions.

A shot in the dark...
There is one relay EFI relay or Open Circuit relay. Maybe it is stuck closed, this will drain your battery over 1 or 2 days. Or maybe someone bypassed a relay.
Check all of you relays, there are a few under your dash rt side.
You should be hearing relays 'click' as you turn the key to ON

good luck hopes this helps...

Thanks Frank,
I'll check out the relays. Is the circuit opening relay the black one above the computer on the right side?

Yes, it is up there someplace. How much current drain are you seeing? It is normal to see something in the 10-20mA range for clocks, ECU and radio memory backup, etc.

4crawler is absolutely correct.. You're going to see some drain. The way I wire megasquirt, there isn't any current to the ECU itself when the key is off and I believe the OEM ecu is the same, but don't discount that there isn't current going somewhere else - like to the OEM clock or aftermarket radio.

You really need an amp meter to figure out HOW much current you're drawing.

I need a pin out of the stock ECU to help you and my server seems to be down.. There are two pins on the stock ECU that get relay power - both should NOT provide 12v when the key is OFF.

If it's AFM related, my guess is that you're triggering fuel pump - maybe...

Thanks guys, found it!

I retrieved my dusty amp meter and went through the EFI system like you suggested.

I assumed it was in the EFI system because when I had first got the truck I was trying to make the truck run as it was running intermittently. At that time with the air flow meter plugged in the drain was 340mA. Unplugging the air flow meter the drain dropped to 300mA. This time I basically unplugged everything in the engine compartment trying to chase down a 300mA drain. From injectors to the to the wiper motor. After unplugging the fuel pump motor I went back around the front and found one more plug just below the air box. A 4 prong plug with white wires. After disconnecting this - no drain. Those wires went led to the fuse/relay behind the drivers side kick panel. Evidently the area was damp I think because the body seam above is rusty. It turned out to be the round relay below the 4 way flasher relay. I replaced the relay with another used one.

Now my battery drain is about 10.5mA. This should be OK right?
Thanks again <img src="/forums/images/graemlins/cheers.gif" alt="" />

10mA is pretty good, that would drain about 1 amp-hour of the battery every 4 days or so, so given a decent 40AH battery, you would be good sitting for many months.

Ok, I was curious about this whole battery drain thing. (I never have had a problem with my battery or alternator but just wanted to check) I found out I have a 31 mA drain. The previous guy had, what a 10 mA drain. I wonder if I should even worry about this 31 mA drain?

That is about the upper limit of what is normal. You'll be draining 0.75 amp-hours/day out of your battery, it would prabably kill the battery in 1-2 months if not run, but if you drive it frequently, probably not a big deal.