Windsor

On my 1999 LS400, the car was running great...went to crank it and battery was low. It's old, so I assumed battery problem and began charging it. Was still cranking a little slow so after cleaning the terminals and trying a jump, it still wouldn't start. Checked all fuses, OK. FINALLY got the Fuel pump relay out and I'm reading continuity across both the control circuit and the power circuit. This tells me the switch is stuck closed (even with no power on the control circuit, but curiously it does still click on and off when power is supplied --- just that the actual switch is closed all the time).

I am going to get the new relay today, but I still don't know why after charging the battery, and a "failed closed" fuel pump switch, why the car wouldn't start after the battery was recharged. I'm assuming the pump continued to run after the last time I drove it, which is what drained the battery, but I can't be positive. Is there some kind of reset? Does the ECU "know" that it got stuck on and is waiting for a correct signal? I checked the CIR/OPN relay and it's working fine. How do I access the fuel pump to check that I have power there and that it's running?

Thanks for any help...

RA40

iTrader: (6)

How old is this battery? For simplicity sake, what readings was the battery giving after the charge? I would drop in a fresh battery or jump it with another car and see how it does. Then start the hunt. An old battery not capable of producing the necessary V can lead to many issues and the fix is simple.

python

iTrader: (4)

in the trunk?

Windsor

I didn't measure the charge, but it was turning over fine (and felt like it was trying to start a couple of times). I did in fact try jumping from a separate running vehicle, with the same results.

A little more info...this fuel pump relay has me puzzled. I took the cover off and it appears to be a normally closed relay. This would explain why I'm getting continuity across the power connections, even when there is no power on the control circuit. The relay appears to open when power is applied. I don't understand how this would work to turn on the fuel pump, but evidently it is designed this way. I'm going to re-check and see if it is actually opening when powered. My first check it was closed at all times. The diagram on the cover shows it to be normally open. Anyone know what it should be or how it works with the CIR/OPN relay?

EDIT. I bench tested the relay again and it is definitely functioning as a N.C. relay. The power contacts open when power is applied. Since it does appear to be functioning properly I will reinstall it and look elsewhere for problems. Although the battery seems OK now, I had already ordered new one online on a 25% sale, and since I'll need one soon anyway, think I'll go ahead and get that installed and see what happens, as suggested.