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1990 Montero 3.0 Crank, No Spark

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3 years 11 months ago #38866 by Minivandan
Hi, All

I am looking for direction on a 1990 Montero, 3.0 V6, automatic transmission, 4x4.

Crank, No spark. Was starting and running just fine then it jut stopped starting.
Sadly over the last 8 weeks and throwing a punch of parts at it as well as hiring a local mechanic to help diagnose the issue I still have no spark.

Currently I have a sending signal from the crank and cam sensors to the ECU tested at the distributor and the ECU. I do Not get a signal from the ECU back to the ICM. The ECU just out puts steady 12v signal. I was able to get a spark out of the coil by back probing the #3 wire on the ICM and tapping Ground. I do not have a Scope just a digital multimeter, analog 12v voltmeter, test light and led light.

I have put in a slew of parts sadly:
Wires
Plugs
Coil
ICM
Distributor
Idle Air control valve
TPS
Engine control Relay
ECU
And probably forgot one...

Cleaned all connections with electrical cleaner
Cleaned all ground Connections
I have been currently ohms checking every wire in the wiring harness from computer to part
And still scratching my head. I figured Paul could probably figure it out in 10 minutes but I’ll take any help at this point. I am learning a ton from Paul, and very appreciative to have access to this Information.

Thanks All wish I found this sight sooner.

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3 years 11 months ago - 3 years 11 months ago #38870 by jreardon
Terminal 1 and 2 at the distributor should have 5 volts with it disconnected, with the key on, according to service info. That 5 volts comes from the ECU so if that's there then the signal wires coming out of the ECU is most likely good. Make sure they both fluctuate while cranking. Injector's should be firing I think.

That 12 volts from the ECU is on terminal 1 of the power transistor? The white wire? That should not be there constantly. Check t this wire for a short to power.


File Attachment:

File Name: ignitionsystem.pdf
File Size:71 KB
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Last edit: 3 years 11 months ago by jreardon.
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3 years 11 months ago #38901 by Minivandan
Thanks for the quick response.
Couldn’t check it out today and should have the Ecu back tomorrow.

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3 years 11 months ago #38919 by Minivandan
Ok the Ecu I received is not correct so I’ll be waiting for the replacement. Currently no engine light.

I did some rechecking on the wires and my wiring diagrams only go up to 52. It has Been difficult trying to track the correct diagram.

First the #1wire coming out of the power transistor goes to 28 on the Ecu and has .0 ohms. I couldn’t find any brakes or places where I might have shorted to power and reeds 2.9mv with the key on.
Not sure if that tells you anything with a bad Ecu.

On the Distributor the wires on the connector are a little different. 3 Green and 4 white are swapped on my current connector which has not been replaced yet. I was getting a reading of :1# red 9 v;
#2 black G 0v; #3 White 2.3 mv ; #4 Green 2.3 mv.
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3 years 11 months ago - 3 years 11 months ago #38920 by jreardon
Time for some detective work. I've attached '89 '90 and '91 wiring diagrams.

The '89 wiring diagram has the correct wire color sequence at the distributor from your photo. Can you see if the colors match up at the ECM harness?

File Attachment:

File Name: 1989.pdf
File Size:137 KB

File Attachment:

File Name: 1990.pdf
File Size:111 KB

File Attachment:

File Name: 1991.pdf
File Size:138 KB
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Last edit: 3 years 11 months ago by jreardon.

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3 years 11 months ago #38954 by Potanist
I had a Montero once and had to replace the ECU... I actually had it rebuilt. I was getting no spark when I had the problem. And it happened exactly like you said driving it one day to not starting.

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3 years 11 months ago #38958 by Minivandan
Nice, no judgement.
Looks like the ECU matches up best with the 91 go figure. Vin plate says 89 and the engine says 90. The white and green are still flipped on the diagram for the distributor.
I did purchase a used ecu with the same model number so hopefully that does something to help out that spark.
Is there anything I can do in the meantime to help with the issue before I plug it in?
Would unplugging all the sensors before I try and crank it and plug them in one by one hurt the ECU?
Would that be advisable?
Thanks

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3 years 11 months ago #38960 by Potanist
To be really honest with you... unless that ECU has already been rebuilt I think it would be very wise to get it rebuilt. That old ecu board had problems mainly from the components becoming too aged. You might even have to match ecu too. I'm not sure it's been so long ago.

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3 years 11 months ago #39020 by Minivandan
Ok so here is where I’m at I have the new ecu not installed yet. Wiring diagram follows 91.

Question is the wires that I follow from the distributor do what they are supposed to do green goes to power Transistor, o2 sensor and ground 48 in ecu.

White goes to purge control sol,
Mpi # 5 red, idle speed control red/red, o2sensor, injectors.

On my connector those wires are switched 4 green and 3 white.
That is still the same from the factory.

Should I cut and swap those wires at the connector? Could this be frying the ecu? It is a new distributor. Or should I try to reinstall the original distributor?

Any way to test without cross wiring ?

Thanks
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3 years 11 months ago #39029 by Minivandan
I tested the wires at the distributor and the ECU with key on and all the engine side sensors disconnected. Here are the results.
There is also a click sound coming from the ECU when I test the black wire #21 to ground.

What are your thoughts

Thanks
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3 years 11 months ago #39030 by jreardon
Hopefully this is accurate since there's a picture of the internals of the distributor. Leave connector as is and use the new distributor you have already.

Focus on #4 pin terminal, it's a ground. We just have to trust this picture.

File Attachment:

File Name: TDCsensor.pdf
File Size:325 KB

File Attachment:

File Name: CASensor.pdf
File Size:456 KB
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3 years 11 months ago - 3 years 11 months ago #39032 by jreardon
The green wire should be a ground. Measure middle terminal of power transistor, unplugged, what is voltage reading? If you're reading elevated voltage, jump it to ground.
Last edit: 3 years 11 months ago by jreardon.

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3 years 11 months ago #39037 by Minivandan
I am reading 3.5 v with black on ground battery ground and positive going to # 2 black on the power Transistor. And 3.5v
With the black on battery neg and green wire # 4.
Correct?

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3 years 11 months ago #39039 by Minivandan
These are the reading I’m getting
for those tests.

Haven’t cranked it yet with the new Ecu yet gun shy after 9 weeks.

Just want to make sure I’m not going to harm the ecu.

Thanks
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3 years 11 months ago - 3 years 11 months ago #39040 by jreardon
Don't do ohm checks for grounds. Your voltage reading was elevated on the grounds, that's enough to tell you it's no good. I don't like .294 V either on the signal wires, i'm expecting around 5v (unplugged). Do you have 5v at the TPS?
Last edit: 3 years 11 months ago by jreardon.

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3 years 11 months ago #39045 by jreardon
Everything in color green should have close to no voltage with the key on. Check power and grounds at the computer with key on as well.
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3 years 11 months ago #39057 by Minivandan
2.7v at TPS green and yellow wire. With key on. Working on checking the other diagram

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3 years 11 months ago #39063 by Minivandan
These are the current readings taken with the multimeter black on battery neg and red back-probing at ECU and key on.

Haven’t tried cranking yet.
Thanks

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3 years 11 months ago #39064 by Minivandan
Here is the attachment

Happy Easter!!
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3 years 11 months ago #39080 by jreardon
I don't like 2.7V (pin 23) on the 5V reference wire going to the airflow sensor and TPS. Try unplugging both of those sensors and retake voltage reading for pin 23, key on of course. Happy Easter to you as well :)

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