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No spark, ecu related?

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Old 08-09-14, 10:50 PM   #1
Dcelone53
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Default No spark, ecu related?

Hey all, my first post so please bear with me.

So I'm putting a 91 ls400 engine into a 32 ford. I am tying to start the car by wiring jumping power into certain ecu terminals. The car spins over but there's no spark. I've tyre's a few things, checked grounds but still no spark.

Any suggestions on what could be the problem? Is something in the ecu not being light up? Open to any and all feedback
(I do have the wiring manual if it matters)
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Old 08-10-14, 05:02 AM   #2
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if you have the wiring harness and the correct pinout you need to make sure you're supplying ALL the correct ecu power leads. You can't selectively power the ECU.

We need more details on what you've done to the motor. That being said, I'm surprised your sticking with the OEM harness/ECU to power this in a hot rod rather than a simplified race harness and some aftermarket management ala holley, or even a carb.
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Old 08-10-14, 07:38 AM   #3
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Right now the, battery, starter ignition switch are all live so it spins, there's power at the coil, but no spark, i haven't done anything to the engine, it's literally out of the the car and mounted in to the chassis
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Old 08-10-14, 02:52 PM   #4
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there's probably no fuel either. You didn't mention the ECU status in your post.
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Old 08-10-14, 06:23 PM   #5
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Quote:
Originally Posted by PureDrifter View Post
there's probably no fuel either. You didn't mention the ECU status in your post.
I'm spraying fuel into it, but that shouldn't effect spark right?

I'm also not sure what you mean by status.

Since there's power to the coil, my guess is something isn't telling the ecu to fire, I just have no clue what
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Old 08-10-14, 06:52 PM   #6
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this isn't a carbed car, the ecu controls both ignition firing and fuel injectors. The ECU has to have power supplied to it (multiple 12v lines as i recall) and be hooked up to all the relevant sensors before it will properly run the engine. Specifically the Air Flow Meter, cam angle sensor, and crank angle sensor are of extremely high importance.

We need details on what you've got hooked up, and how...
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Old 08-10-14, 07:28 PM   #7
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Quote:
Originally Posted by PureDrifter View Post
this isn't a carbed car, the ecu controls both ignition firing and fuel injectors. The ECU has to have power supplied to it (multiple 12v lines as i recall) and be hooked up to all the relevant sensors before it will properly run the engine. Specifically the Air Flow Meter, cam angle sensor, and crank angle sensor are of extremely high importance.

We need details on what you've got hooked up, and how...

There's power going into the starter terminal and both battary terminals, the ignition switch has 12v and the coil has 12v. I ohmed the cam sensors to make sure they had continuity and the air flow meter is plugged in as well

Do you know exactly what lines need to be powered on the ecu? I'm sure I could be missing something.

I'm sorry if this is difficult, it's tough trying to explain its kind of a different animal.
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Old 08-10-14, 10:18 PM   #8
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Quote:
Originally Posted by Dcelone53 View Post
There's power going into the starter terminal and both battary terminals, the ignition switch has 12v and the coil has 12v. I ohmed the cam sensors to make sure they had continuity and the air flow meter is plugged in as well

Do you know exactly what lines need to be powered on the ecu? I'm sure I could be missing something.

I'm sorry if this is difficult, it's tough trying to explain its kind of a different animal.
For those who don't know the 1UZ engine management system, it sure must be a different animal. Other than general 3 important items Spark, Fuel and Compression, a good ECU control is needed for it to start and run. It seems to me that your ECU is preventing the engine to start due to the lack of some important signal from sensors as PD mentioned.

The 1UZ engine management system has different levels of protection for the safety and to prevent the air pollution. The highest protection is to disable the engine to start. The lowest protection is only to turn the Engine Check Light on and warn the driver. The second highest is the limp home mode which limits the rev up to 2000rpm with the fixed fire timing 3゜BTDC. Without proper feed back signals from sensors, the ECU can't work as is expected, resulting the rough engine running or even no engine start.

Did you connect every sensor properly? The knock sensors are not needed, but others are mostly needed. Did you connect the exhaust thermal sensor? The early version of 1UZ-FE needs this, but many people forget to connect this.
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Old 08-11-14, 06:22 AM   #9
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please post an ecu harness diagram showing us which wires you have powered/connected.
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Old 08-11-14, 10:47 AM   #10
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heres a diagram, sorry about the scan, page is about 7 fold out pages

http://tinypic.com/r/dh5rwi/8

The pink represents what I have power directly too. (starter has power as well, not picture)

the blue book on the diagram (connector e11) is not on the ecu and there is no spot for it on the ecu? where would that be?

everything is connected on the engine itself.i have not tested everything for continuity but what i have tested, cam sensors, engine speed sensors have continuity at the ECU.


the 'IL' Instrument Panel connectors are the only things that arnt connected.

Also, im not trying to run the engine to drive,im just trying to get it running for it bit before i bolt down the body. If the engine sparks, and turns over and runs for a minute or so, ill be happy, im just trying to power the things absolutely necessary, the rest will be fit on after.


well get it soon enough, gonna be the most unique street rod on the road...
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Old 08-13-14, 08:55 PM   #11
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Quote:
Originally Posted by Dcelone53 View Post
heres a diagram, sorry about the scan, page is about 7 fold out pages

http://tinypic.com/r/dh5rwi/8

The pink represents what I have power directly too. (starter has power as well, not picture)

the blue book on the diagram (connector e11) is not on the ecu and there is no spot for it on the ecu? where would that be?

everything is connected on the engine itself.i have not tested everything for continuity but what i have tested, cam sensors, engine speed sensors have continuity at the ECU.


the 'IL' Instrument Panel connectors are the only things that arnt connected.

Also, im not trying to run the engine to drive,im just trying to get it running for it bit before i bolt down the body. If the engine sparks, and turns over and runs for a minute or so, ill be happy, im just trying to power the things absolutely necessary, the rest will be fit on after.


well get it soon enough, gonna be the most unique street rod on the road...
The ecu has to be grounded to the engine so maybe that is all you need to do,I had the very same thing happen to me once even if you test 12 volts at the ecu you still need to ground the unit to the engine separately.
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Old 08-14-14, 09:49 AM   #12
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First off Im not a Lexus electronics expert, but most ECUs use ground switching (vs positive switching) so having 12 volts to the coil or injectors doesnt mean it will run. The ECU must have all the sensors reading correctly before it allows a start.
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Old 08-16-14, 06:35 PM   #13
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Quote:
Originally Posted by Nelexus88 View Post
First off Im not a Lexus electronics expert, but most ECUs use ground switching (vs positive switching) so having 12 volts to the coil or injectors doesnt mean it will run. The ECU must have all the sensors reading correctly before it allows a start.
All the sensors are hooked up, I've stuck a spark plug in with a jumper wire and I sometimes get the tiniest of spark when I ground the igniter through a jumper, I'm pretty sure all the ground terminals are grounding from ecu, the igt and igf wire have continuity from the ecu, could the problem be there?

How does the ecu trigger the igniter?
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Old 08-17-14, 07:49 PM   #14
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Quote:
Originally Posted by Dcelone53 View Post
All the sensors are hooked up, I've stuck a spark plug in with a jumper wire and I sometimes get the tiniest of spark when I ground the igniter through a jumper, I'm pretty sure all the ground terminals are grounding from ecu, the igt and igf wire have continuity from the ecu, could the problem be there?

How does the ecu trigger the igniter?
The ECU triggers the igniter driving a 5V DC's negative going signal. Right before that, it energizes the ignition coil supplying the igniter a constant 5V DC after every condition is confirmed OK by the processor. Every condition here means signals from rotation sensors, other signals for the timing compensations and no inhibit signals generated by abnormal conditions.

If you want to check the igniter and the coil independently from the ECU, supply a 5V DC to IGT1 or IGT2 via a current limiting resistor 56-100 ohms and then stop the supply. You should have a strong arcing at the secondary winding of the ignition coil at the moment when the 5V DC supply was stopped. The arcing should travel more than a half inch. Less than that means that the igniter or the ignition coil is not fully working OK. If a 5V DC unit is not available, you can use the battery 12V DC but in this case, you need to use a 150-270 ohms resistor.

These need to understand some basics of electronics affairs. I hope you are familiar with those. The ECU and the Igniter input circuit have sensitive semiconductors and those might be damaged easily when the low impedance energy is supplied because of too much current. You also have to be careful for the static discharge.

The Youtube video below helps you some although the guy's explanation is partly not correct.

Last edited by Yamae; 08-17-14 at 08:51 PM..
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Old 08-17-14, 08:48 PM   #15
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cant u just ohm the coils? we also have a igniter/control module tester at work..ur local napa might have it also. seems like a lot of work and skillful knowledge that can be tackled easily by dumbazzes such as myself
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