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Doug
Doug, ASE Certified Technician
Category: Mitsubishi
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Experience:  Mitsubishi employed and Factory trained ASE certified technician
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I have a 2001 mitsubishi montero V6 no spark.

Customer Question

I have a 2001 mitsubishi montero V6 no spark. crank sensor checks good all fuses are good
Submitted: 3 years ago.
Category: Mitsubishi
Expert:  Doug replied 3 years ago.
Hi,

If I am understanding correctly, you have connected a computer/scan tool and verified that you have a good RPM signal from the crank sensor. As well, I am assuming at this point spark is the only function you are lacking.... fueling is working as normal.

Have you checked for signal pulse from the igniter yet?
If not, do you have a digital multimeter so we can make some checks?

Thanks
Customer: replied 3 years ago.

Have not checked the Igniter and have a multimeter not to familiar with mitsubishi where is it located.

Expert:  Doug replied 3 years ago.
No problem.

The igniter is located right near the center of the intake manifold, tucked into the valley near the throttle cable, etc.

For testing we will start right at the coils before we go to on-igniter testing.
Put your tester to DC Volts, 20V range (if adjustable), and unplug one ignition coil and insert the meter test leads into the two terminals on each coil harness.
Cranking the engine, we are looking for a pulsing voltage.

Check all three coils and let me know what you find.
Customer: replied 3 years ago.
11.58 volts on all three
Expert:  Doug replied 3 years ago.
Just to be clear, when connecting the two leads of the meter to the two terminals of each coil connector, you get 11.58V pulsing while you crank?

It is important that we test exactly that way; if you use the battery for ground, the test is useless.

Thanks
Customer: replied 3 years ago.
that was the way it was tested
Expert:  Doug replied 3 years ago.
Okay thanks, XXXXX XXXXX wanted to make sure we were on the same page.

If you have a pulsing voltage there, that means your PCM and Igniter are both OK. The only thing left to fail are the coils.
Are you certain you do not have spark? Have you removed a plug and checked it out of the engine to see if it sparks?
Customer: replied 3 years ago.
yeah no spark. But seems odd that all three go bad at same time. not impossible but odd.
Expert:  Doug replied 3 years ago.
Yes it is incredibly odd. That is why I wanted to make sure your test points were correct.

The coils are charged via fused power through the ignition switch; they have voltage any time the ignition is turned on. They receive ground for discharge via the igniter (power transistor) in a pulsed pattern to match engine timing. Everything else that happens behind the scenes is mostly irrelevant at this point, as you have a pulse ground at each of the coils, which is all you need for them to fire. If you had a igniter issue, one or more of the coils would not discharge. If you had a PCM issue, the igniter would have 1 or more circuits that would not send the discharge ground. If you had a power supply issue on any coil, again you would not have the pulsed voltage reading on your meter.

Is there any back-story to when/how the vehicle became undrivable?
Customer: replied 3 years ago.
was turn off one evening everything fine. when he went to start it the next morning battery was dead. they tried to jump start with no start. the engine would turn over but not fire. when I went to check it I found the 100 amp main battery fuse blown, and replaced and checked all other fuses and they were good. battery charged to full turns over fine but no fire. so far everything checks fine just no fire from coils to plugs.
Expert:  Doug replied 3 years ago.
Wow. With the 100A blown there was a pretty big shock to the system, normally this happens with a reverse-polarity jumpstart. Even so, it can happen under otherwise normal circumstances, and when it does, all bets are off as far as what becomes damaged.

Take your meter and set it to Ohms/resistance and measure between the two harness pins on each coil, one at a time and see what the resistance measurement is.

Then take the leads and test between the high voltage ports (where the plug wires go) of each coil... meaning one lead in one plug wire port, the other lead in the adjacent port of the same coil.

Let me know what you get for those resistances on those six points.

Thanks
Customer: replied 3 years ago.
I will check in the morning and get back to you. I appreciate all your help tonight.
Expert:  Doug replied 3 years ago.
No problem at all.

I will not be at work until late tomorrow, so in the event we don't meet up at a convenient time, here are your desired test results:

Harness connector pins 0.74-0.90 Ohms

High voltage terminals 20.1-27.3 Ohms


Real world testing, you can add about 15% to that range and still be OK. If the coils are failed, I would suspect you are going to pull either a very high or an infinite reading across one of the internal coils of each coilpack.

If that is the case, obviously we have 3 toasted coils. While I'm not convinced 100% this is going to be the case, based on the test results at the coil connector, this is the only thing it could be (well apart from plugs or wires, but those are inconsistent in failure and certainly wouldn't all drop off at once).
Let me know what you come up with tomorrow, and I will get back with you as soon as I am at work and we can continue if necessary.

Edit to add:
If the resistance checks come out OK, go over that voltage check while cranking again and make sure the voltage is pulsing on/off while you crank and not stuck on. It is possible for the igniter to fail and deliver constant ground, showing your batt voltage while you crank but never going away... if it never shuts off, the coils can not discharge and hence no spark. I know we went over that once before, but just to be 100% that the ground side from the igniter is pulsing and not just stuck on.
Customer: replied 3 years ago.
on harness pins I get .000- .001 on High voltage side I get 24.2
Expert:  Doug replied 3 years ago.
Thanks.

Those low power coils are way out of spec. What is interesting however is that I would be more expecting to see a open circuit there or very high resistance rather than very low. I am curious as to how that happened.

I had edited the previous post with more information that does not appear to have taken, I'm not sure if you can see it on your end or not, so I will repeat it here...

When you were checking pulse voltage at the connectors (and I apologize for bringing this up again), you are certain that the voltage did pulse while cranking... it went on and off in rhythm while you cranked, indicating the igniter ground signal was going on and off? The reason this is important to clarify (and I did not make it entirely clear before) is that if the igniter were to fail in such a way that the signal grounds were stuck on, you would still have voltage at all three coils, it just would not pulse (nor release of the ground = no discharge of the coil).

If the voltage most certainly did pulse, then I see no other issue you can have apart from the failed coils. While the resistance measurement on the lower power coil is way out of spec, it is a bit suspicious that it is not blown out completely. I would suggest replacing one coil and verifying the spark returns on that unit, just because this is such a peculiar way for it to fail.
Obviously if the voltage is not pulsing like we were speaking of before, we will need to do further testing to see if the igniter is failed or if the PCM is sending erroneous signals to the igniter.
Customer: replied 3 years ago.
It was a solid voltage no pulse
Expert:  Doug replied 3 years ago.
Okay thanks, XXXXX XXXXX some more work to do then.

To make sure I get wire colors correct for your instructions, can you tell me if this is a regular 2001 Montero or a 2001 Montero Sport?

Thanks
Customer: replied 3 years ago.
sport
Expert:  Doug replied 3 years ago.
Thanks.
We are going to want to test your PCM fire signal ahead of the igniter. We will test via the wire harness at the igniter, as this is the easiest location to access.
The igniter is in the valley of the engine, just in front of the intake manifold/throttle body area. It is a ~3" square box, 3/4" thick and is mounted vertically with 12mm bolts. The connector on the end has 6 wires in a straight row.

With your meter set to DC volts (low scale / 20V if adjustable), set your black probe on the negative battery terminal.

One at a time, use T-pins or similar to probe pins 1 (blue wire), 2 (black/yellow wire) and 3 (white wire) of the igniter and connect your red lead to them. Check for voltage while cranking.
Again this will be a pulsing voltage, and will likely be very low if present... so if it reads in millivolts, that is okay just make sure you get an accurate reading.

Check each of the three wires while cranking and let me know what you find.
Customer: replied 3 years ago.

On the blue wire I have 1.4 - 2.4 volts

on the black and yellow wire I have 1.4 - 2.4 volts

On the white wire I have 1.4 - 2.6 volts

Expert:  Doug replied 3 years ago.
I am assuming this is again a pulsing voltage, on and off? If so, that's outstanding.

Specification is 300mV to 3V peak, so you are right where you want to be.
What we just did was test to make sure the signal to fire is being sent to the igniter. With a good reading, we know that first off the PCM is ok, which is a real common failure point when we have voltage spikes like you did. It is also very expensive, so if the voltage is pulsing on/off, this is good and it is working. If the voltage is stuck on, that would be a bad thing.
On a side note, the pulsing also indicates the crank sensor is working properly, but we already knew that.
Now if I misinterpreted and the voltage is stuck on at all times, we will have either a burnt out PCM or a bad crank sensor. Considering you had verified the crank sensor signal already, that should be out.

With a pulsing voltage, at this point, we have all necessary functions working up to the igniter, but nothing coming out of the igniter.
Since the igniter is fed power through the ignition switch, and we are presuming no other power problems exist (all other functions work when the key is in the On position), this leaves nothing but a bad igniter or bad wiring between the igniter and the coils (highly improbable).

If you would like to verify that there is no output right at the igniter, check for pulsing voltage at pins 11, 12 and 13 while cranking. You would expect to see ground pulsing on and off in rhythm .
Customer: replied 3 years ago.

are pins 11 12 13 on the other plug it is a three wire plug

Expert:  Doug replied 3 years ago.
Oh geez I'm sorry, I was in a hurry as I had to step out, I should have indicated that those are the wires on the three pin connector. For whatever reason, they numbered the six pin connector as pins 1 through 6, and the three pin connector as 11-13.

The wire colors should be 11-Brown/Red, 12-Brown/White, 13-Brown.

graphic

Also just to confirm, the voltages you had on your previous post were in fact pulsing on and off, correct?
Customer: replied 3 years ago.

yeah they were pulsing sorry i didn't comfirm that

0.6 volts on pins 11 12 13

Expert:  Doug replied 3 years ago.
No worries, that is a good thing.


Okay we want to look for ground on 11 12 and 13... you can either set your meter to resistance and connect each wire with one lead and the other lead to the negative battery post, or you can set your meter to DC Volts, and connect one lead to the positive terminal.

If you use the negative post and resistance, we 'want' to see 0.000 pulsing or very close.
If you use the positive terminal and DC volts we 'want' to see battery voltage pulsing.
Customer: replied 3 years ago.

did test both ways on resistance couldn't get meter to read

set meter to dc volts with one lead to positive post of battery and other to pins

11 12 13 and battery voltage was pulsing

Expert:  Doug replied 3 years ago.
Deleted previous post.....



So with the meter set to DC volts, one lead to positive, and one lead to each of the 11 12 and 13, you got pulsing battery voltage?

If so, can you recheck with the lead at pin 2 of each coil (other lead at positive bat terminal) and see if you have a pulse again?
Customer: replied 3 years ago.

9.6 volts - 11.2 volts pulsing

Expert:  Doug replied 3 years ago.
Okay, that is strange... as when we tested this before a few days ago, you had solid ground there, no pulse.

If you have a pulsing ground there at the coils and the pin 1 has constant voltage with the ignition on, there is nothing left but bad coils.
Customer: replied 3 years ago.

I'm going to go back over all test that we have done to recheck my work and I will get back to you. I appreciate you patience.

Expert:  Doug replied 3 years ago.
No worries, I'm here until it runs again.

Double check the pulsing at each point. Again the ground wire at the coils is the primary concern. If it pulses ground on all three coil connectors, the rest of the ignition system is working normally and we are back to those goofy resistance readings on the coils.
Customer: replied 3 years ago.
Sorry it took so long to get back with you. Have had computer issues and took awhile to fix. Went back over my work and noticed on the coils that my reading were 1.0 ohms on harness side of all three coils and on the plug wire side my reading is 24.8 Kilo ohms in a previous post you said 20.1 ohms- 27.3 ohms don't know if this means anything. Thanks
Expert:  Doug replied 3 years ago.
No problem.

If you have 1 ohm across the low voltage and 24 on high voltage terminals, you should be good on the coils.

Did we ever verify for certain that you did have pulsing ground on each of the three coil harness connectors? I know there was some confusion for a bit about whether or not the ground was solid or pulsing.

If you have the low voltage readings going into the igniter (you indicated pulsing 1.4 to 2.4V), and no pulsing ground coming out, the igniter is shot. If you have pulsing ground coming out.... well with your good readings on the coils you should have spark.

Something isn't adding up.
Customer: replied 3 years ago.
just to make sure were on the same page when I say it is pulsing I get a fluctuation in my readings while turning engine over.
Expert:  Doug replied 3 years ago.
Right, while cranking you would see (for example when tested the ground on the coil harness) the meter fluctuate from 0.000 trying to reach 0L, but likely would just show 0.000 then 0.100 0.300 etc before it reverted back to 0.000. Just an indication that the ground is being applied and released.

In regards XXXXX XXXXX voltage test same thing, you would see 2V then peter out to less than 1V then back to 2V or thereabouts.
Customer: replied 3 years ago.
thats what I get but to verify the ohms on the high side I'm getting 24000 ohms
Expert:  Doug replied 3 years ago.
Correct, sorry that was crummy shorthand.

20.1-27.3 k-Ohms is spec, so you are in range there.

One reading has to be off here.

If the coils are in spec, the signal must be out... again this can either be via the PCM output or the igniter output. You said you verified the crank sensor/RPM signal so we know the ignition input is good.

It's just a matter or whether the low voltage drivers in the PCM are out or the igniter ground signals. I'm sure it is just an issue of the pulse either being misinterpreted or the meter reading being skewed and looking good.

Considering when a bad PCM driver occurs, it will not get stuck on, but rather will go low, this makes the 1.4-2.4V driver voltage look good... if you had a blown driver we would expect to see 0V or <150mV.

Perhaps try checking both with a different meter and see if you get more suspect results? The only other option at this point would be to get a new/good used igniter to pop in there and eliminate it that way. I hate doing that though.
Customer: replied 3 years ago.
I will try this and get back to you tomorrow. Thanks
Expert:  Doug replied 3 years ago.
No problem, keep me posted.
Customer: replied 3 years ago.

What is the likelyhood of fthe coils checking good for resistance but being bad when voltage is applied. Have recheck pcm at the igniter and it is pulsing and check the output of the igniter and it is pulsing I get 12.7 volts at coils on the harness and it pulses from 12.7 to 6.9

Expert:  Doug replied 3 years ago.
It's possible, not terribly probable though. I suppose you could try replacing one and see if you get spark on that unit. Seems pretty fishy to have all three get blown out, but none of them show any indications of testing bad.

I'm really at a loss here as you have valid driver signal, you have voltage at the coil and you appear to have signal ground from the igniter. There isn't any thing else needed to fire those coils.
Customer: replied 3 years ago.
I'm going to try a coil and will get back to you tomorrow
Expert:  Doug replied 3 years ago.
Sounds good.

With the verified crank signal and the solid voltage from the drivers it just has to be one or the other.
Let me know what you come up with, I should be here most of the day tomorrow.
Customer: replied 3 years ago.
changed coil no difference is there a way to check crank sensor with ohm meter.
Expert:  Doug replied 3 years ago.
Not really.... if you are getting a good RPM signal on your scan tool, you should be fine.

You can ohm the sensor as it is a hall effect type transistor based sensor.

You can verify you have ignition voltage (12V) on pin 3 (red), and ground on pin 1 (black).
For pin 2, you would want to see a fluctuating 5V, however it is a square wave signal so really you would need an oscilloscope to read it correctly. You could theoretically check pin 2 for voltage and maybe see the fluctuation however it would be entirely possible to see what appeared to be a good signal, but when inspected with an oscilloscope it could be a train wreck.

Again, if your scan tool showed a readable RPM signal, the sensor should be working sufficiently to run the system.
Additionally, since you had what appeared to be correctly pulsing low voltage from the PCM drivers, this would also indicate a functioning crank sensor; if there was no usable signal from the crank sensor, these drivers should not have fired.
Customer: replied 3 years ago.
any idea what to check next. Had rpm indicated with scan tool but out off ideas
Expert:  Doug replied 3 years ago.
Well again it is down to those test results. Did you find another meter to try testing with?

If you have a good crank signal, it powers the PCM drivers.
If the PCM drivers are working, it drives the igniter.
If the igniter is working, it drives the coils.
If the coils are working, it sparks the plugs.

So far all of the tests have appeared to com up OK, so something is not testing right.

Theoretically if you have a bad signal from the cam sensor it could cause a similar issue, it is unlikely you would lose fire on all coils though; typically it only kills fire on two of the coils.
Customer: replied 3 years ago.
Have rechecked all test 4 times with three different meters one of which was a flute meter which is supposed to be one of the best, but still no spark. How do I check the cam sensor. I get 12.4 volts at the coil on the harness when I turn the key on. When I crank the engine it pulses.
Expert:  Doug replied 3 years ago.
If you have 12V at the coil and the ground side pulses, then it should be charging and discharging that coil; that is all it does... constant power is fed, the ground is held to charge the coil then released and the coil discharges through the plug.

Cam sensor is identical to the crank sensor as far as testing goes; even pin out is identical. Same scenario with oscilloscope for proper testing.

I would be concentrating on why you have normal pulsing ground and ignition voltage on the coil connectors and no spark. You have everything perfect up to the coil if it is behaving the way you describe.
Customer: replied 3 years ago.
will do more checking and get back to you thank you for all your help
Expert:  Doug replied 3 years ago.
No problem, I wish this was more straightforward, something is definitely weird here. Just for fun, have you tried putting a different wire and plug on one of the coils to see if it sparks? I know it was running prior to the voltage spike, just curious.
Customer: replied 3 years ago.

No but i will try and get back to you

Customer: replied 3 years ago.
tried different plug and wire and still no spark.
Expert:  Doug replied 3 years ago.
I kind of figured, but it was worth a quick check.

At this point I don't know what to say other than what I have already. According to the test results you've given me, you have a clear signal to fire at the coils. You replaced a coil to no effect.... something is missing, and it has to be in your test results, as the way it is now, based on your results,it should fire.

There are very few things that can kill your ignition;
Crank sensor
Cam sensor
PCM
Igniter
Coil
Plug
Wire

The crank sensor you said was verified good
The cam sensor should only be able to kill 2 coils, not all three
PCM - input pulsing voltage to the igniter was tested OK
Igniter - output pulsing ground tested OK
Coil, Plug, wire, all exchanged.

Based on a voltage spike, your only likely candidates are PCM and igniter, as both have low current transistors that like to explode during jumpstarts.
Based on your testing however, both look fine.

Much as I hate saying it, the only thing really to do here is try swapping out an igniter next. I like physical confirmations before replacing anything, but that just isn't a possibility here, as all the test results being perfect, you should have ignition.

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Doug
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