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Re: 1995 Montero LS Won't Start [Re: fasteddy] #1062175 07/23/13 07:49 PM
Joined: Apr 2008
Posts: 135
bamashooter Offline OP
Wheeler
Here you go buddy.Performed the following:
Key on: probed the 3 coil wires at ecm w/ dmm. Each one showed .02 vdc.

Same test and results on the terminals on the inside of the input connector to transistor.

Everything connected w/ key on showed full battery voltage at each of the 2 terminals on each coil pack.

With the black wire removed from coil #1 and key on I had the following readings:

CPs 2&3 had full voltage on both terminals

CP 1 had .40 vdc

With key on or off and the output connector removed from the transistor, there is zero voltage from the output terminals residing inside the larger transistor housing.

Perhaps the next test will consist of the following:

As the coil wires enter the input side of the transistor, cut 2 of the 3 wires a few inches back toward the ecm and cross the wires. For example, the wire from the ecm which would ultimately feed coil 2 would be now feeding coil 3. My responses are slow due to him living miles from me and for some reason, I cannot log into the forum from his pc. When I click Login, it never goes to the username/password windows.

Last edited by bamashooter; 07/23/13 08:06 PM.
Re: 1995 Montero LS Won't Start [Re: bamashooter] #1062176 07/23/13 08:19 PM
Joined: Jan 2001
Posts: 13,649
fasteddy Offline
Web Wheeler
*****
Go to the ecu and probe each of the output terminals to the PT assy and crank the motor. You should see a vaying voltage as the ecu PT's trigger the PT assy pt's to fire the coils. This will test the ecu PT's. Repair of the ecu should be simple, just replace a PT once you identify it. I would hold off on cutting wires. Use jumper wires from the PT plug to the PTassy and move the jumpers around.

The ecu terminals you probed should show the voltage you found until the ecu want's spark, then you should see about 5v in bursts as the ecu tells the PTassy PT's to break the ground path from the coil to induce spark.

I may be preaching to the choir here, but the way the coils work is pretty simple. 12v dc flow thru the coil primary windings with the ign on, creating a magnetic field in the primay windings. When the current is interrupted, the magnetic field collapses past the secondary windings, creating a large voltage there, on the order of 30k volts to the plugs. The ecu controls the ground path thru a normally closed power transistor, one that lets current flow until it's base wire is powered up by the ecu. When the ecu wants spark, an internal PT is triggered to send a current to the base of the PTassy PT for the proper coil. This causes the PTassy PT to open, breaking the ground path, and you get spark.

The cranking test I outlined will tell you if the internal PT's are working. An LED test light might be a better test, as the current flow is very brief, and the damping circuits in the DMM may not show it. An analog voltmeter will also work, as you can see the needle twitch upward, and may be easier to source in Jasper


Not responsible for advice not taken...
Re: 1995 Montero LS Won't Start [Re: fasteddy] #1062177 07/23/13 10:33 PM
Joined: Apr 2008
Posts: 135
bamashooter Offline OP
Wheeler
Actually Crane Hill area (lol). Funny, I mentioned that level (while cranking) of test to him this morning to see if we could detect a difference between the 3 wires when cranking. The coil wires exiting the ecm appear to be on the same connector as the 12 volt power to the ecm, thus, the tests must be performed with connector attached to the ecm. I'll try to construct a jumper. Continued thanks for your help my friend.

Re: 1995 Montero LS Won't Start [Re: bamashooter] #1062178 07/24/13 12:01 AM
Joined: Jan 2001
Posts: 13,649
fasteddy Offline
Web Wheeler
*****
Back probe the connector while attached, using some fine metal probes (straight pins, straightened paper clip), or pierce the wire with straight pins. Heal the pierces with liquid electrical tape (auto parts/home depot).

"Sweet Home, Alabama..." - Is the Lizzard Lick restaurant still open?


Not responsible for advice not taken...
Re: 1995 Montero LS Won't Start [Re: fasteddy] #1062179 07/24/13 01:32 AM
Joined: Apr 2008
Posts: 135
bamashooter Offline OP
Wheeler
Quote
Back probe the connector while attached, using some fine metal probes (straight pins, straightened paper clip), or pierce the wire with straight pins. Heal the pierces with liquid electrical tape (auto parts/home depot).

"Sweet Home, Alabama..." - Is the Lizzard Lick restaurant still open?


Never heard of it except for the tv show. Location?

Re: 1995 Montero LS Won't Start [Re: bamashooter] #1062180 07/24/13 01:42 AM
Joined: Jan 2001
Posts: 13,649
fasteddy Offline
Web Wheeler
*****
Got it wrong. Lizzard Thicket, somewhere off AL 69...


Not responsible for advice not taken...
Re: 1995 Montero LS Won't Start [Re: fasteddy] #1062181 07/24/13 04:00 AM
Joined: Apr 2008
Posts: 135
bamashooter Offline OP
Wheeler
Long gone but led to a very successful chain of them in South Carolina (internet info).

Re: 1995 Montero LS Won't Start [Re: bamashooter] #1062182 07/24/13 07:10 PM
Joined: Apr 2008
Posts: 135
bamashooter Offline OP
Wheeler
Purchased an analog meter today and some clips and stuff. Hope to resume testing tomorrow.

Re: 1995 Montero LS Won't Start [Re: bamashooter] #1062183 08/08/13 05:33 AM
Joined: Apr 2008
Posts: 135
bamashooter Offline OP
Wheeler
Have not performed any additional tests. Been bad sick last 2 weeks with some kind of respiratory ailment. Talked to my friend yesterday and he told me the driver side timing belt is off by two teeth. Is the ecm so robust that it will tell coilpack #3 to not fire under that condition? I do recall a few months ago when he replaced the belts that the belt in question was a real struggle. Told me he needs to rotate the driver cam sprocket 2 teeth clockwise.

Last edited by bamashooter; 08/09/13 05:00 AM.
Re: 1995 Montero LS Won't Start [Re: bamashooter] #1062184 08/09/13 12:15 AM
Joined: Jan 2001
Posts: 13,649
fasteddy Offline
Web Wheeler
*****
I don't think that will keep it from firing. However, may have damaged the cam position sensor or crank position sensor somehow while installing the belt.


Not responsible for advice not taken...
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