Sounds like you had the same problem as me. Fuel pump ECU.

Bypass it completely with 12v fuel mod...and wire in a off/on switch....my fuel pump relay for some reason is powered with the car off, which is causing my battery to drain, so im probably going to relocate my switch in the wiring to before the FP relay, to kill the power going into the relay.

check and see if your fuel pump relay is hot with the car off..or if anything in the fuse box is staying hot or powered long after you've driven and the car has been off. if it is the fuel pump relay, your car is doing exactly what mine is.

 

If you don't have a check engine light when you turn the key to on position the ecu is bad. If it is on check and see if you have any codes for the ignitors being bad. Even if one coil wire was cut the other would still work. The start/neutral safety switch was bad the car wouldn't even crank. The 92-94 ecus go bad it is a ever constant problem I would try to find a spare one they are getting cheap these days. YES # 500 post!

 

I'll go try the fuel pump ecu bypass and check the relay, thanks.

The check engine light comes on with the key, and when I jump the diagnostic connector to pull codes everything blinks like it should. I just got a replacement ecu, and the car still has the exact same problem as with the original ecu so I'm not going to buy a third ecu right yet. The ignitors are good, when the car decides to run it runs flawlessly.... it just has random trouble deciding if it wants to start or not!

 

With the new ECU, the car would take about 10 minutes to start up on a cold morning.. you would crank it for about 5 seconds and it would stumble and back up on the starter. It would take about 10 crank/stumbles before the car would finally fire right up and purr like nothing was ever wrong.

The car has been acting good for about a week, and I was out driving it around in the parking lot today, and I pulled into my parking space and shut it off. I immediately tried to start it again, but it would crank and crank and crank and crank with no stumble. I put a timing light on #1 plug wire, and sure enough no god damn spark again. I'm back to square 1 again.

I don't know if there is some kind of slight short in my wiring that kills ECU's over time??? I've replaced:
-ECU
-fuel pump ecu
-both ignitors
-drivers side coil
-battery terminals
-all ground points
-brand new battery

 

Could this be a sensor/signal problem? Are there cam sensors in the distributors?

 

There are no cam sensors on there I wish there was then i could get a tach on my 1uz supra. You might have a issue with your crank sensor. If it doesn't see that then the car won't start. If you run even if one of your coils was dead it would just run like crap. Check the crank sensor to see if you get a signal from it.

 

sounds like you have a parasitic draw stealing your voltage. get a multi-meter and check all the fuses under the hood and drivers kickpanel above the clutch pedal. if you find any unusual current draw then you know where to look in that circuit. let me know if you need wireing diagrams, i have access to alldata and mitchel

 

The battery drain came from the old ECU, I put the new ECU in and there is no more battery drain. I've had an optima red top hooked up in the car for the past few weeks and it hasn't drained any. The only issue I'm having right now is no spark.

 

Will the ECU report and store codes before the motor runs? If I have a problem with a crank sensor, will code 12 show up in the ecu after some time of just cranking it over?

 

alright, so I went out and cranked for a while and the ECU reported code 12.

From what I gather by reading, there are 3 rpm sensors total: a crank position sensor by the balancer, and a sensor in each distributor. I assume the crank position sensor by the balancer can be tested VIA resistance, but how would one go about checking the RPM signal from the distrubitors?

 

Whats up defrag. I got mine towed last night same issue. I think I am going to by crank sensor. The owner at the alternator shop said it was good. It is charging the car, disconnected the battery while running and everything was good. Ebay crank sensor 70-80 bucks. I will post if I find out what it is.

 

Great, I am looking at the same ebay sensor. I want to make sure it's not a bad pickup in the distributor, also.

 

What are the chances of both distributors being out of whack? I measured them today, and Both were coming out right at 2000 ohms?? "spec" is 950-1250

 

Guess I'll just go ahead and get some new distributors and a new crank position sensor and see if that does it..

 

All,
I have had the same battery problems with my previous 1997 SC 400 and in my current 1999 SC 400. The problem is most likely not with your battery or the alternator.

I have found by replacing the factory cable connectors to the battery with Marine type LEAD connectors that are painted, except for the areas in contact with the battery post and cables will correct the problem!

I discovered after numerous dead battery situations in both cars that the alternator was putting out the required 14.2 V (the nominal value), but the battery was not charging. Therefore the only problem could be that the charge was not getting to the battery. I replaced the connectors with new factory connectors that were flimsy aluminum. This did not solve the problem.

I finally got a good conduction current into the battery after replacing the battery connectors with plain old lead type connectors that can be purchased at any pep boys for less than five bucks.

I have since utilized the Marine connectors in my 1999 SC 400, because they are painted on any surface other than connection to the cables and the battery terminal to prevent shorts.

Hopefully this will help correct your problem as well.

PS: my brother who is a certified mechanic actually uses spray paint or grease on the battery post after tightening the connection in order to prevent oxidation of the connection.