TroySC300

iTrader: (1)

So my mom's 93 LS400 will not start. The car cranks hard and you can hear the starter trying but it just won't fire up. Also, when I take the key out I can still hear fuel moving in the engine bay and I can hear the fuel pump on in the trunk. I checked the EFI fuse and even swapped it out but it still won't start.

We just replace the battery but I still can't get it to start, not even by jumping it. Any ideals CL?

avalon42

iTrader: (1)

Auto theft system would be my guess...try that and see if you have any luck. You didn't by chance accidentally reverse the positive and negative terminals initially, did you?

TroySC300

iTrader: (1)

I didn't reverse the terminals and I don't think it has anything to do with the alarm. For some reason the fuel pump stays on after that car is shut off and it is draining the battery, then the car won't start even when jumped, I think because the plugs are flooded.

avalon42

iTrader: (1)

Fuel pump should definitely not be staying on. Is your car stock or has it been modified?

You said that all of this problem started when you replaced the battery...can you be more specific on why you needed to replace the battery? Was there a constant drain on the system? Have you noticed that your car was running rich all the time?

Lot more info needed to diagnose the problem here.

TroySC300

iTrader: (1)

The car is stock. We only replaced the battery because we thought it wasn't holding a charge. It wasn't until yesterday when I realized that it was being drained by the fuel pump staying on. The only way I can get the pump to turn off is to pull the EFI fuse.

I don't think the car was running rich, it ran well before all this mess. We just recently replaced both front O2 sensor too.

TroySC300

iTrader: (1)

Ok I got the car to start by following the procedure in the owner's manual for starting a flooded engine. First I connected the battery in the LS to the battery in my SC and let it charge for a bit, then I got in the LS and tried to start it. At first it cranked but didn't fire up. I pressed down the gas peddle to the floor then turned the key and it fired right up and idled perfectly.

But there's still a major problem, the fuel pump stays on still when I turn the car off. I located the main EFI relay and swapped it with other relays but that didn't do anything. Also, I tried unplugging the fuel pump ECU in the trunk to see if that would turn off the pump but it didn't.

So basically there is a relay somewhere that is giving power to the fuel pump even though the car is off... and it's not the EFI relay.

avalon42

iTrader: (1)

Any alarm or aftermarket audio system, fog lights, anything tapped recently? Something must be supplying the power. I would first check it at the relay point and see if the relay has been switched on constantly, then trace the wire triggering the relay.

TroySC300

iTrader: (1)

So I thought I had fixed it but something new happened today. While I was driving, slowing down to a stop sign, the car died. It wasn't a loss of power, just a loss of fuel.

The good news is that the fuel pump does not stay on anymore when the car is off so the battery isn't being drained. The bad news is it has never died while running before and it won't start even when jumped.

My buddy thinks it's a bad ECU, any ideas?

TroySC300

iTrader: (1)

Will a 91 LS400 ECU work in the 93 LS400?

PureDrifter

iTrader: (10)

no.
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