JKBHEAT

iTrader: (5)

Long story short...My battery has been dying after only sitting for a day or two for an extended period of time and after months of prodding and testing I've finally found that when the EFI fuse is removed the battery does not die.

Does anybody have an ideas of what component/s, that utilize the EFI fuse, could be causing the drain? Ways to test the specific component?

Thanks!

NemeGuero

iTrader: (15)

Check your engine grounds. You know what EFI is right? Electronic Fuel injection?

That probably means that your injectors aren't grounded right or your ECU ground..

That is where I would start.

O. L. T.

iTrader: (17)

Sounds like a sticky relay or a fault in the ECU.

JKBHEAT

iTrader: (5)

I was just reading through a lexus workshop manual and that's exactly what I was thinking. I hope that it's just a bad relay; I need to fix my voltmeter to check continuity on the relay. Is there another way to check if the relay is faulty or do I need to buy a $20 fuse?

Thanks,

O. L. T.

iTrader: (17)

It would be most helpful to know if the relay were fused on the hot side or the switch side. If it were fused on the switched side and you pulled the fuse it wouldn't matter if the relay was stuck closed and it would answer your question...... however I can't find a good reason to fuse a switched control wire to a relay.

The bad news is the stuck command can come from a bad ecu as well. You'd just have to find way to remove the acc to the relay once running to know if it is sticking.

O. L. T.

iTrader: (17)

We both have 400's so I haz the FSM's

Here's one circuit.

O. L. T.

iTrader: (17)

Actually screw that, here's the money shot........

Full res: https://www.clublexus.com/gallery/da.../IMG_01755.JPG

That's going straight into the ECM. You can see the injector fuse (30amp) center bottom of this pic below.

JKBHEAT

iTrader: (5)

I'm kind of just learning about all this electronic stuff so I got a little lost;did you believe that the relay was the problem or not? And the switch side is the side between the relay and ecu not the battery and the relay, right?

I can't post a pdf pic here but what I is see is from the manual: Battery - Main 60A fuse - EFI 30A fuse - EFI Main Relay - Main ecu & Fuel pump ecu

And one last question I have is if the relay is the problem, then wouldn't I get a big drop in parasitic drain (ma) when the efi fuse is removed; b/c I don't

Thanks for the help!

JKBHEAT

iTrader: (5)

Update:

Alright I went to radio shack (10 min drive) and got the fuse I needed for my dvom. So I then open the fuse box to take out the "main efi relay" to test it and, to my surprise, I almost burn off my fingertips

After letting it cool, it pass all of the tests: There is continuity between termials 1 and 3, no continuity between 2 and 4, and there is continuity between 2 and 4 when 1 and 3 are connected to the battery.

Now about the relay being super hot; is this normal? I've heard that a hot relay is a bad relay but then I've heard that a relay that works with fuel may get hot during operation. I know, being THAT hot, has to be a problem but I just want someone to confirm.

Can someone with an SC please touch their "main efi relay" (under the hood fuse box) after more than 5 minutes of operation and tell me if it's really hot or not?

Thanks!

JKBHEAT

iTrader: (5)

Anybody?

"Now about the relay being super hot; is this normal? I've heard that a hot relay is a bad relay but then I've heard that a relay that works with fuel may get hot during operation. I know, being THAT hot, has to be a problem but I just want someone to confirm.

Can someone with an SC please touch their "main efi relay" (under the hood fuse box) after more than 5 minutes of operation and tell me if it's really hot or not?"

JKBHEAT

iTrader: (5)

Also, can someone with a fairly stock SC, and a voltmeter, check what's a normal drain reading for an SC300/400? (in milliamps)

Thanks

TroySC300

iTrader: (1)

This exact thing was happening to my mom's LS400. Turns out the main ECU was bad and causing the fuel pump to stay on all night (you can hear it under the hood or in the trunk behind the carpet). We replaced the main ECU and it fixed it.

JKBHEAT

iTrader: (5)

I can't really hear the fuel pump come on at all. What do you mean the "exact same thing", what symptoms were similar?

Thanks,

JKBHEAT

iTrader: (5)

Can anybody check if their EFI relay (under the hood fuse box) gets extremely hot after the car runs (even if it'd only a couple of minutes)?

Also (if you have a multimeter), what normal parasitic draw do you guys measure on your SCs?

Thanks

MAJones

Your relay being hot may just be from excessive current being pulled through it, it could be bad also having a high internal resistance. Bad grounds would not kill a battery, that would create the opposite effect as far as current flow goes, the rest of the circuit would not have the voltage it needs because of the added resistance of a bad ground. Current draw with the car off differs from car to car, it prob shouldn't be more than 5 milli amps. I have notice aftermarket cd players sometimes have a higher current draw for the memory than stock. That shouldn't be your prob if pulling efi fuse stops the excessive draw prob.

Start unhooking things that are in the EFI circuit and compare the current draw(with the car off and key off). I would start with the ecu. Other than the ecu you could have a direct short from any hot wire to chassis ground. Isolating individual parts of the circuit and comparing the current draw is the way to find the problem.

The ecu grounds the injectors so I doubt any of them are the problem. It would be continually dumping fuel when the engine was off and that would most likely be from a bad ecu.
Hope this helps, good luck