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1G Dynatek ARC-2 No spark on 2/3

Jacob hoke

Supporting Member
99
45
Jul 5, 2016
West Valley, Utah
After basically finishing my build I’m left with no spark on cylinders 2/3. I switched to a COP set up with new NGK coils as well as using the ARC2 CDI BOX HOWEVER; even after switching back to OEM coils and wires there's still no spark on cylinders 2/3 which helps me say it’s none of the COP set up.

Tested the PTU and replaced it just to make sure both tested good. I replaced the CAS with a new one just to help narrow that away. I visually inspected the ECU everything looks copacetic and good but is there anyway I can test it to verify it’s good? I also plan on doing a continuity test on the harness to make sure nothing broke when I installed the harness. Mind you the car ran before it was parked, is there anything else anyone can think of that I should check or how to chase down my no spark issue?

Also what exactly is the spark path from what I understand it’s power-ecu-ptu-coil and the CAS determines what cylinders get spark

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luv2rallye

DSM Wiseman
8,441
1,202
Jun 7, 2003
Minneapolis, Minnesota
For 4g63: ECU triggers the PTU at the right time which fires the proper coil primary (2,3 or 1,4) which fires the spark plug cylinder pair (2,3 or 1,4). CAS determines which cylinder pair will fire (2,3 or 1,4) while CPS determines exactly when each cylinder pair will fire. CAS and CPS signals go into the ECU which outputs the 2 signals to the PTU to fire the proper coil.
 

Jacob hoke

Supporting Member
99
45
Jul 5, 2016
West Valley, Utah
For 4g63: ECU triggers the PTU at the right time which fires the proper coil primary (2,3 or 1,4) which fires the spark plug cylinder pair (2,3 or 1,4). CAS determines which cylinder pair will fire (2,3 or 1,4) while CPS determines exactly when each cylinder pair will fire. CAS and CPS signals go into the ECU which outputs the 2 signals to the PTU to fire the proper coil.
So with no cps then the only thing I have left to inspect would be the wires and ecu 😩 god I hate wiring work. Is there anything in a tune if someone didn’t know what they were doing could cause a no spark on 2/3 had a buddy messing around with the tune to try and get it to start (how I found the no spark situation)

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luv2rallye

DSM Wiseman
8,441
1,202
Jun 7, 2003
Minneapolis, Minnesota
Is this a 1993 4g63 turbo?
You could put a voltmeter on the PTU inputs yellow and then yellow-red while cranking to see if you have any signal from the ECU. It's a small pulse but the voltmeter should read something non-zero as it reads an average of pulses. Of course during cranking the frequency is so low that you might need an analog (needle) meter to see anything (small blips). But if you only have a digital meter you could still try and see if anything registers. At any rate the value should be about the same on each which would tell you if the ECU is outputting a signal for both cylinder pairs or not.

Did anyone rewire the CAS? If not wired correctly that can be your problem (even with a brand new CAS).
 
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Jacob hoke

Supporting Member
99
45
Jul 5, 2016
West Valley, Utah
Sorry for the late response. I’m in the process of tracking down continuity on all the major components CAS, PTU, and the harness that connects to my arc box. I did find that the plug on my CAS was pretty toast. I don’t feel this is the issue but I order a new pigtail from extreme psi just to be sure. I noticed that there’s only 4 wires on the CAS, power, ground, a second black wire pin 21 (CAS RPM) and a 4th going to the ECU as well I can’t remember the color I believe it was TDC pin 22.

I know the PTU works, I tested it and had a spare that was new old supply and switched them just to be sure.

I’m curious, if I do have continuity on all “spark propagating wiring” what is the path the system uses to trigger a spark at 2/3.

Battery>CAS>ECU>PTU>ARC-2 box

It looks like pin 54/55 (power transistor) that go straight from the ECU to the PTU, I’m assuming (big leap here), that those send a signal to the PTU to trigger the spark. Pin 55 is for cylinder 2/3 so the question is how would I test it to be sure it’s sending out a signal to the PTU.

I also saw in the diagram I posted that the PTU has wiring that crosses over to the plug for the coil packs. I’ll check continuity on those as well I’ll be honest this has been one of those daunting tasks I've not been looking forward to taking on
 
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Jacob hoke

Supporting Member
99
45
Jul 5, 2016
West Valley, Utah
Is this a 1993 4g63 turbo?
You could put a voltmeter on the PTU inputs yellow and then yellow-red while cranking to see if you have any signal from the ECU. It's a small pulse but the voltmeter should read something non-zero as it reads an average of pulses. Of course during cranking the frequency is so low that you might need an analog (needle) meter to see anything (small blips). But if you only have a digital meter you could still try and see if anything registers. At any rate the value should be about the same on each which would tell you if the ECU is outputting a signal for both cylinder pairs or not.

Did anyone rewire the CAS? If not wired correctly that can be your problem (even with a brand new CAS).
92 Plymouth laser rs the harness was cut but I did all the work on it nothing crazy just measuring and extending one at a time or shortening all joints are solder joints and heat shrinked the car drove into the shop on the same harness
 

We're on Boost

15+ Year Contributor
1,634
451
Aug 25, 2007
Seattle area, Washington
Do you still need a proper CAS connector then?
Here's a page for it, on Sheridan Engineering: http://connectors.sheridanengineering.com/JFC4PA.htm

When this happened on my car it turned out the fault was one bad terminal in the plug that goes onto the power transistor.
In that case though it was intermittent. So it wasn't that hard to find. I could stick my arm down there and put my hand on the plug and wiggle it around with the engine running, my son in the car with his foot on the gas to keep it running.
Wiggling the plug I found that pushing on it one way it would run fine and pushing it the other direction it would quit.
 

Jacob hoke

Supporting Member
99
45
Jul 5, 2016
West Valley, Utah
Do you still need a proper CAS connector then?
Here's a page for it, on Sheridan Engineering: http://connectors.sheridanengineering.com/JFC4PA.htm

When this happened on my car it turned out the fault was one bad terminal in the plug that goes onto the power transistor.
In that case though it was intermittent. So it wasn't that hard to find. I could stick my arm down there and put my hand on the plug and wiggle it around with the engine running, my son in the car with his foot on the gas to keep it running.
Wiggling the plug I found that pushing on it one way it would run fine and pushing it the other direction it would quit.
Thank you I ordered one off of extreme psi it’s on its way in I made the Mistake of ordering one off eBay first. I should have known better 😂. But I’ll probably replace the ptu plug while I’m at it it has a broken clip so may as well. If I would have known about Sheridan Engineering I would have purchased all my connectors from them the first time
 

We're on Boost

15+ Year Contributor
1,634
451
Aug 25, 2007
Seattle area, Washington
Yeah Sheridan is a good place to get these from.
I eventually made new connectors with pigtails using the connector shells and terminals and seals from Sheridan, for my power transistor and coil. He helped me get the right crimper for these little terminals that the Mitsu OEM plugs use, and showed me (pictures back and forth by email) the right way to crimp the seals onto the terminal, stuff like that.
I usually ask him to sell me one or 2 extra terminals so I can screw one up first just getting back into it, since this only happens every few years.
He is user "brads" in here. BTW he designed the ARC-2. Or developed it. I think he told me he designed it.

It might not be real obvious how to navigate his website. What I usually do, like for your CAS connector, I went to his Home page, picked "Kits" over on the left,
looked down to find 91-94 DSM,
picked "91 ENG KIT PN# KIT-91ENG $149"
and then you get the whole thing listed out what's in the kit, and each item is a link that takes you to just that one connector. LOL
 

Jacob hoke

Supporting Member
99
45
Jul 5, 2016
West Valley, Utah
Do you still need a proper CAS connector then?
Here's a page for it, on Sheridan Engineering: http://connectors.sheridanengineering.com/JFC4PA.htm

When this happened on my car it turned out the fault was one bad terminal in the plug that goes onto the power transistor.
In that case though it was intermittent. So it wasn't that hard to find. I could stick my arm down there and put my hand on the plug and wiggle it around with the engine running, my son in the car with his foot on the gas to keep it running.
Wiggling the plug I found that pushing on it one way it would run fine and pushing it the other direction it would quit.
I’ll have to email him tomorrow I was trying to figure out how to purchase looks like I just send him the parts number I have a few questions on the arc-2 so I’m glad the person who probably knows the most about it is reachable 😂
 

1990TSIAWDTALON

Moderator
9,880
5,760
Nov 14, 2013
Independence, Kansas
@brads has always sent me extra stuff, just in case I make a mistake. Now, that is when I deal directly with him. If you go thru Extreme, you won't get that treatment. Super good man to deal with! I'll vouch for him any day. :thumb:
 

We're on Boost

15+ Year Contributor
1,634
451
Aug 25, 2007
Seattle area, Washington
Yeah I always email him directly at the link he shows on his web pages: [email protected]
Then when he emails me back, the "From" I see in my inbox is usually "Brad S". (That's the most recent, 2022)
Usually we go back and forth once or twice.

Basically in your first email to him you tell him what you want with his part numbers, and you mention if you have any questions.
For example the seals are sensitive to wire OD. Sometimes there aren't any seals. Sometimes the terminals are sensitive to wire gauge. So whatever choices there are for alternative seals or terminals, possibly different connector styles, you get all that talked out, then when you get it finalized he tells you how much $ to send him by paypal.

With me, it always seems like there is something that needs to be talked about. Usually it's wire gauge and wire insulation OD. Or it's 2 different styles of connector available. Or it's like on the 1990 stock PTU plug there was a rubber boot over the back side of it where the wires come out. The plugs from Brad S use individual rubber seals for each wire instead of the single boot, which I like because I can see what position each wire is in just by looking at it (they aren't covered up by a boot). And the boots get torn and don't always seal very well anyway. Stuff like that.

I had already figured out a long time ago that there is such a thing as actual engine compartment wire (higher temperature rated insulation). Usually it's refered to as GXL or SXL, which refers to the thickness of the insulation which is XLPE material. So if I tell him I'd like to use 16 gauge SXL wire if possible, he knows what I'm talking about, and we can take it from there. Or he can tell me what size wire to use if I don't have any idea.
 
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Jacob hoke

Supporting Member
99
45
Jul 5, 2016
West Valley, Utah
Pics I took in 2015 of the Power Transistor plug I made after getting it all figured out:
(1990, 6 position connector with one position blank)

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Your an artist sir

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Jacob hoke

Supporting Member
99
45
Jul 5, 2016
West Valley, Utah
I think I found the series of issues that are the cause of my problems. I've rewired the COP, swapped ECUs with a known good one, and now the kit is on it way so I can replace the plugs.

My only real concern is the correct wiring for a coil on plug. My brother is an electrical engineer and followed the write up just as I did that was found here on tuners and it still didn’t work, however when he swapped wires around he was able to get spark on all 4 cylinders.

I’ll get the diagram made of what he did but it seems weird if no one else has noticed it before.

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We're on Boost

15+ Year Contributor
1,634
451
Aug 25, 2007
Seattle area, Washington
however when he swapped wires around he was able to get spark on all 4 cylinders.

Man I don't know. The only thing I can think of is that the diagrams you show in post #3, I haven't seen them before, don't know where they came from. The one I've seen used before and have used myself is, I'll post it. It might all be exactly the same, I don't know.

Nuts, the original jpg I have of this diagram is 2507 x 1901 pixels which gives you pretty good reading resolution at full size. But posting it here with our limit of 2000 pixels on the long edge, it comes up only 2000 x 1517. Poor. Eye strain no doubt. If you'd like a copy at full size, it must still be up somewhere at full size, I'll look around.
For a while in here our photos would go in at up to 3000 pixels on the long edge and photos from that period are still that size, haven't been downsized.

Ok update, the diagrams are still up on Hot Rod Coffeeshop. One for 1990 and one for 91-94.
Here's the link:
https://blog.hotrodcoffeeshop.com/2013/02/23/4g63-wiring-diagrams-schematics-for-engine-swaps/
So at that link you can still get a 2507 x 1901. The one you see below is only at 2000 x 1517.

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