jims400

Hello to all to Lexus gurus. Just bought a 1994 SC400. Car started fine when test drove and starts fine every morning. The problem is after an hour drive the car won't turn over.

All the dash lights work. Battery is good. Alternator is good. Assuming starter relay is good because it starts every morning.

Like I said, drive it for a half hour...turn it off...won't crank. Turn the key to crank, no clicking or sounds, tach and speedo lights go off, idiot lights stay illuminated, won't crank over. Let it sit for an hour or so and it fires right up. Cranks fast and starts right away.

As far as I can tell this year didn't have any special keys. All it came with was a Lexus key, no chip in the key ( as far as I can tell ) and no remote to open the doors. if there's a special key needed please correct me.

Does anyone have an idea what I need to be looking for? I tried to lock and unlock the door 3 or 4 times to reset the security but that didn't work. I'm inclined to think it's something to do with the security system but can't find any documentation on exactly how it works. It's just strange it will start in the morning but drive it and it refuses to crank, for a long time.

I'm at a point where if I drive the car I have to sit in it for 2 hours before it will start again. No fun in that. Any ideas would be greatly appreciated.

Jim

2jznosht

Its probably heat related...what is your temp gauge reading when you can't crank the car? Has it shut off while driving?

jims400

Please explain what the temperature gauge reading will affect.

Never shuts off while driving.

eknine9

iTrader: (8)

It's definitely not the security system, I've seen this problem discussed on here before, try using the search function to see if there are any older threads on it. I'll spend a couple minutes searching it myself to see if I can find any similar threads for you.

2jznosht

When the car over heats tit won't start until it cools

jims400

The car isn't overheating...lol. Are you saying that there's a predetermined temperature that shuts the car down? If so, exactly what temp is that?

jims400

I believe you're correct. This morning I cranked the car over by turning on the ignition switch and jumpered the starter relay (just a test). Car started like I thought it would, regardless of anti deterrent. Drove the car for an hour. Shut it off. Like usual, wouldn't start. Figured if it was the security crap I'd still be able to start it by bypassing the security and jumping relay terminals. All I got was sparks. Obviously the starter solenoid is crapping out from being heat soaked.

Now the question is this: How difficult is it to pull the starter? Is there a solenoid (never worked on a Lexus starter) that can be replaced or rebuilt? The starter motor seems fine, spins fast and powerful.

Bankswood

Oh brother! The starter is located in the center of the engine. Yep you read right. You have to pull the intake manifold and all that accompanies it to get to the starter. It is a HUGE job.

Make absolutely sure it's the starter.

Question? When your car wil lnot start does it crank then shut down?

jims400

No. It's a 100% NO CRANK situation. Jumpering the relay should be giving me direct voltage to the starter. When it's heat soaked it doesn't crank. Let it sit for an hour or two and cranks and fires right up. It has never had a starting problem, always a no crank situation.

Bankswood

The reason I ask is that my 93 SC 400 would crank fine when cold but after it was warmed up it would never start. It would crank then immediately die. I did the Fuel pump ecu mod and it solved the problem. There are several fail safe protections on the car such as it will not start if the computer thinks the car is over heating or the oil pressure is low. I did replace my coolant sensor while trying to solve my problem but no help. It is a cheap and easy replacement if you want to go that route.

Ali SC3

iTrader: (10)

^^^^ next time it happens stick a wire between FP and +B in the diagnostic connector and see if it will start, be careful the +B is battery 12V and when you jump it to the FP you are bypassing the fuel pump ecu and putting power right to the pump. If that solves it its the fuel pump ecu.

You are going to want to try everything before the starter its not a fun job.
also when the starter goes you normally hear the click and then no cranking, and if you keep trying to crank sometimes you can get it, especially if you have a sc300 and can just tap the starter with something that is usually good for a few cranks. if you hear no click or anything then it could be something else.

jims400

Appreciate the responses. Wouldn't sending 12v directly to the starter isolate it completely from every other possible interference? There shouldn't be any failsafe circuits or components between the relay and the solenoid. Remember, the car fires and starts great, when it does. This isn't a sluggish, rich, stumbling, hard to start, etc starting issue. It's purely a cranking issue. I understand what you're saying about all these failsafes I'm not following how a direct 12v signal to the solenoid can possibly be affected by other things behind the 12v I'm directly sending to it. If I run a jumper from the battery + post directly to the solenoid I would be basically performing a bench test of the starter. Yes? No?

Wondering if someone has the starter system wiring diagram they could post so we can analyze it.

Ali SC3

iTrader: (10)

yeah I guess that won't solve your problem if its not the fuel pump ecu. you can try and bypass the starter but the car has to want to be starting or else it will just crank over till the starter goes out. the starter not working at all sometimes even with the battery applied could mean your starter is actually going out. when you apply 12V you send a plunger down the starter that has a ring that touches 2 contacts. when the contacts are worn enough the plunger just barely contacts both of them, and then goes to contacting both of them sometimes, where it usually does work better on the first start of the day, and then the plunger stops bridging the contacts and the starter never gets engaged. normally you hear the click of the plunger bottoming out when it doesn't engage the starter but on the 400 its so buried maybe thats why you never heard it. If its the starter it should get worse soon so you will know one way or another.

the starter is easy to repair though which is good news, its just hard to reach is the bad news.
Its usually the contacts that get worn down and then you replace those. there are a few DIY's around for the repair, and maybe even one for the sc400 starter job.

Anstar

I am having this same problem with my is250 what was your solution?

Vgoodie89

We are now having the same issue

What solved your problem?