cody09

okay, ive had my 93 ucf10 for a few weeks now and it runs amazing, ac works, doesn't have low idle, doesn't misfire, bog down, shift funny or any of those things. no CEL, or any lights at all come on. the only thing on the car that doesn't work fine is the antenna, fuel gauge, and speedo and tach are intermentent. so the other day I ordered a new mast and rebuilt the antenna. I put it back in the car and turned on the key to try it out, and it worked great. 5 mins later I went to leave for work and cranked the car over. it didn't start right up as usual. almost as if it were low on fuel. I paid no attention, cranked it again and it fired right up. ran fine, no misfire or anything out of the ordinary. backed the car up, and stopped to put it in drive and it just died completely. tried cranking it back up and it did nothing but crank and crank and crank. I know for a fact it still has at least 10 gallons of fuel in it, all fuses and relays are fine, and t-belt is in tact. I ordered a crank sensor for it (haven't installed it yet) and called a buddy of mine who is a Toyota tech to ask him where the crank sensor was and after I told him what symptoms I had, he said crank sensors in these cars normally don't go bad and that it sounded like the ecu probably took a ****, but from what ive been reading, the ecu's in these cars don't just die immediately, and most people that have ecu problems are subject to the car misfiring horribly, bogging down and have shifting problems. what could this be? id like to at least have a second opinion before I dive into unkown waters here.

LScowboyLS

could be any number of things, but ECU sounds likely, as this is known trouble area on LS400 - especially 93-97 models - the original capacitors have a design defect

very fixable though

read my ECU failing capacitors thread

have you checked the obvious stuff yet like battery voltage, both running and sitting off, have you checked for gas and fire at the spark plugs?

have you dumped the ECU codes as shown here?

cody09

battery completely died from trying to crank the car. pretty sure the alt has been giving out considering the headlights have been dimming every time I hit the brakes for the past couple weeks. I just jumped the car and it started and ran for a few seconds at pretty low idle. revved it a couple times and it died again. got it to start again for just a second then shut back off.

LScowboyLS

alternator is commonly a problem on these cars, but don't blame the poor alternator, the original Nippon Denso ones last almost forever until power steering fluid leaks on to them, which it always does on these cars

get the battery fully charged, or better yet, replaced with a new one (if over 3 years old), then take voltage readings across the battery both with car off and with car running at idle and post them back here, and we can likely figure out if alternator is failing

cody09

alternator is not main concern right now. I just wanna get this car running. im pretty down in the dumps about it. also I should mention that when I put the jumper cables on the car, the alarm started going off. I unlocked the door with the key and shut the alarm off and that's when I started and ran for a couple seconds

LScowboyLS

awww, don't be down in the dumps, all LS400's are very fixable, and if you can do the mechanical work yourself, then it is usually very cheap on the parts! - most issues involve labor and very little in the way of parts!

cheer up and sleep on it!

j2b4o

It's going to be hard to get her running with a fried alt. these cars are more sensitive to voltage than your average car of this vintage. If the battery has been running the car and is now drained you will need to charge or replace it and test the system while the car is running before you drain the battery again. If your lights were dimming I would look closely at the alt before pulling the ecu and rebuilding.

You are right to think that these ecu's tend to give symptoms before they create a no start condition. This isn't to say that the ecu is fine but I wouldn't jump to that conclusion give the data.

fixmiester

You may be jumping to conclusions a little too quickly; this could very easily be a fuel delivery problem. Get your battery charged or replaced, have a can of starting fluid handy, with the air filter removed, have someone try to start it up. When it starts, spray a few short spurts of ether into the air box, and see if the engine tries to keep running longer than before. If it does, then you just need to look at the fuel system; fuel filter, fuel pump/pressure regulator. May also have a problem with the crank angle sensor, because the ECU will kill the engine after a few seconds if it doesn't see engine running pulses from the crank.

cody09

okay, little update. put the new crank sensor in the car, turned it over, still nothing. I proceeded to pull the ecm out and pull it apart. on visual inspection, there was nothing wrong. all capacitors look in tact, no corrosion of any kind but there is a slight ammonia like smell.

LScowboyLS

ammonia smell is not good in capacitors, as they are made from quaternary ammonium salts, and they are over 20 years old now

do you know anyone who is really a pro at soldering?

because the caps themselves are like $10 to your door, just make sure you don't use any caps except the ones I linked to, very few capacitors in all of the world are the correct rare type for LS400

cody09

okay, heres an odd occurrence. I got the car to fire up today. thinking that it was the security system, I locked and unlocked the doors a few times, and maybe it was just a weird coincidence but I got it to fire up, however, it wouldn't run on its own. I messed with it and finally it started to idle on its own. it ran for about 5 mins and quit. I started it again. it ran for about 5 mins and quit. I started it again, let it idle for about 10 mins, then drove it around. it started and ran absolutely fine. put the dash back together and everything and it wouldn't start AGAIN, so I locked the door, then unlocked the door and started it again and its running fine again. WTF LECKSUS

LScowboyLS

has the famous driver's trunk hinge wires breaking issue been previously repaired in your car?

that problem and ECU caps are responsible for 98% of the WTF head-scratching on an LS400

cody09

All wiring in the trunk look to be in good shape after unraveling the harness. Could this be an immobilizer issue?

LScowboyLS

did you pay special attention to the wires inside the driver's side trunk hinge, in the curve of it?

cody09

okay, okay, ive narrowed it down a little. ecm seems to be good upon visual inspection, timing belt is good, map sensor is good, crank sensor is new, battery is new and charging 14.23 yada yada volts. I just noticed tonight though, that when you turn the key to the on position the trac light and o/d light come on, the trac light will turn off but the o/d light will not. try cranking the car and it doesn't do anything but crank and crank. I went out a little later and turned the key to the on position, trac light and o/d light came on, yet this time, both lights went out. I cranked the car and it fired up and ran like a top