No Spark, ECU has been rebuilt. Need help.
03-23-15, 10:26 AM
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No Spark, ECU has been rebuilt. Need help.
Car is a 92 SC400 from California.
So the problem I have is no spark from coil wire to ground when turning key and cranking engine, also when trying to pull codes the ECU light stays on solid and doesn’t blink. I feel like I’ve tried everything, so I’m going to very detailed about what has happened and what I’ve done.
Backstory:
My mom had been driving the car so I can't describe performance or feel but it was running the battery down and not starting, needing jumpstarts, and finally the last time the car would not start even with a jump.
Based on what happened 10 years ago I thought this was a repeat of where the power steering pump leaks into the alternator and either kills or reduces its charging. So rebuilt the pump, replaced alternator and fixed a coolant leak with a new thermostat gasket.
Started the car a number of times in the drive way while making sure power steering fluid and coolant are full and free of air, car seemed fine. Later went back to do a test drive and car wouldn't start.
Trying to figure out why it won’t start:
From a combination of the Shop manual(4000 page PDF I downloaded here a long time ago), searching here and on google here is basically what I did:
First I did “On-Vehicle Inspection Spark Test” from the shop manual and found there was no spark when cranking the engine with key.
Bypassed ECU to test Ignitors and Coils and got spark.
Tested Wiring from Ignitors to ECU plug for wires IGT1, IGT2, IGF2, IGF2
Tested Cam Position Sensors, and Engine Speed sensor.
Tested wiring from sensor plugs to ECU plugs. Going to see if they get voltage from ECU tomorrow.
Tested Ignition Main Relay.
Tested EFI Relay.
ECU does send M-Rel voltage to EFI relay Plug 1 at 11.something volts. Plug 2 has power. Plug 4 has continuity to ECU plugs +B, +B1. Plug 3 has ground.
30 Amp EFI fuse has continuity to “Batt” on ECU plug.
Tested Every Fuse I could find that has anything to do with Ignition System.
ECU sends 3.0V to Throttle position sensor, I believe it’s supposed to be 5.0 but it’s not zero so I’m not worrying about that right now.
Tach doesn’t move when cranking. I do not remember if it is supposed to normally. Got idea from video on a different kind of car that would tell me if speed sensor/ecu was working for that function, but I can’t find if it supposed to move on SC400 or Lexus in general.
Trying to get codes/Check engine light Behavior:
While doing the power steering pump and alternator changes the battery was disconnected, in part because the car was sitting a lot and I didn’t want the alarm system running the battery down to nothing.
When the car first wouldn’t start, the battery had been disconnected so any codes were probably cleared even if the ECU was able to give them.
ECU was sent to Darryl Gellar to be repaired
Before sending ECU for repair:
Trying to pull codes resulted in a solid Check engine light, and I want to say O/D off and Trac Off were solid and stuck on too, but I’m not 100% on my memory of that.
After getting ECU back:
Solid non blinking Check engine light, Constant blinking O/D Off (which I believe means no Transmission Codes) and no other warning lights stay on.
So the problem I have is no spark from coil wire to ground when turning key and cranking engine, also when trying to pull codes the ECU light stays on solid and doesn’t blink. I feel like I’ve tried everything, so I’m going to very detailed about what has happened and what I’ve done.
Backstory:
My mom had been driving the car so I can't describe performance or feel but it was running the battery down and not starting, needing jumpstarts, and finally the last time the car would not start even with a jump.
Based on what happened 10 years ago I thought this was a repeat of where the power steering pump leaks into the alternator and either kills or reduces its charging. So rebuilt the pump, replaced alternator and fixed a coolant leak with a new thermostat gasket.
Started the car a number of times in the drive way while making sure power steering fluid and coolant are full and free of air, car seemed fine. Later went back to do a test drive and car wouldn't start.
Trying to figure out why it won’t start:
From a combination of the Shop manual(4000 page PDF I downloaded here a long time ago), searching here and on google here is basically what I did:
First I did “On-Vehicle Inspection Spark Test” from the shop manual and found there was no spark when cranking the engine with key.
Bypassed ECU to test Ignitors and Coils and got spark.
Tested Wiring from Ignitors to ECU plug for wires IGT1, IGT2, IGF2, IGF2
Tested Cam Position Sensors, and Engine Speed sensor.
Tested wiring from sensor plugs to ECU plugs. Going to see if they get voltage from ECU tomorrow.
Tested Ignition Main Relay.
Tested EFI Relay.
ECU does send M-Rel voltage to EFI relay Plug 1 at 11.something volts. Plug 2 has power. Plug 4 has continuity to ECU plugs +B, +B1. Plug 3 has ground.
30 Amp EFI fuse has continuity to “Batt” on ECU plug.
Tested Every Fuse I could find that has anything to do with Ignition System.
ECU sends 3.0V to Throttle position sensor, I believe it’s supposed to be 5.0 but it’s not zero so I’m not worrying about that right now.
Tach doesn’t move when cranking. I do not remember if it is supposed to normally. Got idea from video on a different kind of car that would tell me if speed sensor/ecu was working for that function, but I can’t find if it supposed to move on SC400 or Lexus in general.
Trying to get codes/Check engine light Behavior:
While doing the power steering pump and alternator changes the battery was disconnected, in part because the car was sitting a lot and I didn’t want the alarm system running the battery down to nothing.
When the car first wouldn’t start, the battery had been disconnected so any codes were probably cleared even if the ECU was able to give them.
ECU was sent to Darryl Gellar to be repaired
Before sending ECU for repair:
Trying to pull codes resulted in a solid Check engine light, and I want to say O/D off and Trac Off were solid and stuck on too, but I’m not 100% on my memory of that.
After getting ECU back:
Solid non blinking Check engine light, Constant blinking O/D Off (which I believe means no Transmission Codes) and no other warning lights stay on.
Last edited by Caanon; 03-24-15 at 06:36 PM.
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