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Discussion Starter #1
So, my 1999 3kgt is sitting kaput, did some research into the problem (car ran, then sputtered and died; turns over but wont start), and decided to fix all the symptoms.
From the research done - my problem could be the ecu, sending faulty signals, the PTU acting st00pid, or the CAS/CPS not doing it's bloody job. Possibly spark plugs/wires - swapped those out just now. Thing is, I cannot find the PTU or CAS locations :(
Supposedly they are near the ignition coils, etc, thing is - I can't find the bloody coils! If I had a DOHC, it would be all nice and pretty (lotsa pictures and whatnot), but it seems that the SOHCs aren't geting as much love...
Help?
I would greatly appreciate a description, or a picture with some giant "HERE IT IS" on it, or something of the likes.

P.S. my expertise with cars is limited to basic mechanics and common sense. If I bit off more than I can chew, please say so. I'd rather send my car to a stealership than end up with a 3000lb 165hp manual doorstop
 

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Curmudgeon
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Well I can see your frustration. The problem is the SOHC is pretty much the minority here and most of the information you found is for the DOHC. The SOHC has a completely different set up. It has a distributor, which the DOHC doesn't, and uses a single coil instead of a "coil pack". It uses a single power transistor, located beside the distributor, instead of the PTU under the coil pack. The CAS and CPS are built into the distributor instead of mounted on the engine they way they are on the DOHC.

The first thing you should do is download a service manual from someplace like 3SX (they're free!) 3SX Performance - Service Manuals Backups 3000GT / Stealth - Mitsubishi 3000GT / Dodge Stealth Parts
They don't have a '99 manual but the '92-'96 one should be close enough. It will at least have diagrams an drawings that will help you find stuff.

I'd recommend you get your hands on a code scanner and check for any stored codes. Any generic scanner should work with your '99.

If that doesn't turn up anything go for the basics. Cap and rotor. It's more of an old school system that needs old school maintenance..
 

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Discussion Starter #3
well, I tried an OBDII scanner, and it couldnt get a single read, kept popping up with 'error'. Any decent mechanic in Dallas/Plano area that could diagnose the problem for cheap?
 

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Wheee! 2 wheels is fun!
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A great start is to use a timing light and see if you have ANY spark.

If you do use some starting fluid to see if it can run.

Sorry you got all the DOHC info. I understand the frustration of looking for parts that arent there.

The SOHC ECU's seem to not have the wacky troubles the DOHC's had, and since your car is a 99 I would rule that out and look for other possible problems.

-SP
 

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Discussion Starter #6
Not one that you would like; I poked about a bit, found nothing. As Wizard currently has his hands full (and he might as well have built these cars from scratch), I put the project unto a hiatus /=
Gonna pick it up when I save up a few grand for the tinkering...
If anyone makes a breakthrough - please post :)
 

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1991 Dodge Stealth Base SOHC ATX
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Did you ever solve your problem? Sorry I know this thread is old...
I have exactly the same problem. Replaced the ECU, cap and rotor, plugs and wires, and ignition coil. I'm not getting any spark.
Mine is a 91 sohc.
 

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93 NA ATX 3000gt DOHC
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Did you ever solve your problem? Sorry I know this thread is old...
I have exactly the same problem. Replaced the ECU, cap and rotor, plugs and wires, and ignition coil. I'm not getting any spark.
Mine is a 91 sohc.
Did you check for 12v to coil with key turned on?

If you've got 12v to coil, you could have wiring problem some where else in circuit. Or maybe PTU which seems to be only thing you haven’t replaced.

https://www.oreillyauto.com/shop/b/lighting---electrical-16777/modules-coils-25074/ignition-module-control-unit-ignitor-12521/e281cd9fff15/1992/dodge/stealth?q=ignition+module/control+unit/ignitor
 

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1991 Dodge Stealth Base SOHC ATX
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Did you check for 12v to coil with key turned on?

If you've got 12v to coil, you could have wiring problem some where else in circuit. Or maybe PTU which seems to be only thing you haven’t replaced.

https://www.oreillyauto.com/shop/b/lighting---electrical-16777/modules-coils-25074/ignition-module-control-unit-ignitor-12521/e281cd9fff15/1992/dodge/stealth?q=ignition+module/control+unit/ignitor
I checked the voltage at the plug for the coil, and with the ignition on I got battery voltage. But when I cranked the engine the voltage dropped to about half. Just wanted to make sure that is normal?
Also thank you for sharing that link! Unfortunately the sohc uses something different, essentially one transistor for the single coil and not an enclosed ptu. I can't find the part anywhere online. I might try to pull one from a yard if you think that is the problem.
 

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93 NA ATX 3000gt DOHC
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...... But when I cranked the engine the voltage dropped to about half. Just wanted to make sure that is normal?
........
No that’s not normal and most likely where your problem lies, it should stay at same voltage read at battery when cranking.

Unfortunately the sohc uses something different, essentially one transistor for the single coil and not an enclosed ptu. I can't find the part anywhere online.
That’s same PTU shown for SOHC engines on 3sx.com site.

https://www.3sx.com/ignition-coil-pack-and-module-ptu-for-sohc-3000gt-stealth
 

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1991 Dodge Stealth Base SOHC ATX
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No that’s not normal and most likely where your problem lies, it should stay at same voltage read at battery when cranking.



That’s same PTU shown for SOHC engines on 3sx.com site.

https://www.3sx.com/ignition-coil-pack-and-module-ptu-for-sohc-3000gt-stealth
I find the information on sohc engines to be inaccurate or missing, even on stealth316. I'll send a picture of what I'm working with, I'm pretty sure the linked ptu isn't for the sohc.
https://drive.google.com/open?id=1XtHyLdUKPEhft8R-t1wSRD8rHei-k4ib
Thanks for the tip! So do you think a faulty transistor unit could be my problem?
 

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Curmudgeon
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I don't think that's your PTU. I think that's the "condenser assembly". It's just a noise filter.
The PTU bolts into the bottom of the distributor and looks like this:
https://www.rockauto.com/en/moreinfo.php?pk=1192875&cc=1098727&jsn=1064

It's available from Rockauto (beware, the last one is for DOHC)
https://www.rockauto.com/en/catalog/dodge,1991,stealth,3.0l+v6+sohc,1098727,ignition,ignition+control+module+(icm),7172

If you look at their distributors you can see where the connector is, poking out the side.
https://www.rockauto.com/en/catalog/dodge,1991,stealth,3.0l+v6+sohc,1098727,ignition,distributor,7108
 

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93 NA ATX 3000gt DOHC
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.......So do you think a faulty transistor unit could be my problem?
PTU could be problem, but I'd be more concerned about voltage dropping in half at coil when cranking. I'm not sure 6-7 volts at coil is enough.
 

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1991 Dodge Stealth Base SOHC ATX
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I don't think that's your PTU. I think that's the "condenser assembly". It's just a noise filter.
The PTU bolts into the bottom of the distributor and looks like this:
https://www.rockauto.com/en/moreinfo.php?pk=1192875&cc=1098727&jsn=1064

It's available from Rockauto (beware, the last one is for DOHC)
https://www.rockauto.com/en/catalog/dodge,1991,stealth,3.0l+v6+sohc,1098727,ignition,ignition+control+module+(icm),7172

If you look at their distributors you can see where the connector is, poking out the side.
https://www.rockauto.com/en/catalog/dodge,1991,stealth,3.0l+v6+sohc,1098727,ignition,distributor,7108
Ohh that makes so much more sense! Pardon my ignorance
Thanks for the links, I will check that out.
 

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93 NA ATX 3000gt DOHC
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Ok I see. Any ideas about the cause if not the ptu, just bad wiring?
I would think wiring or connector problem wouldn’t vary voltage between switch on or start mode. I’d think maybe ignition switch could cause that, but if that were the case I imagine starter solenoid wouldn’t get full voltage either causing the “click click no crank issue”.

I’d check voltage across battery post while cranking and compare to voltage at coil when cranking. If not same then we can all scratch our heads.
 

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1991 Dodge Stealth Base SOHC ATX
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I would think wiring or connector problem wouldn’t vary voltage between switch on or start mode. I’d think maybe ignition switch could cause that, but if that were the case I imagine starter solenoid wouldn’t get full voltage either causing the “click click no crank issue”.

I’d check voltage across battery post while cranking and compare to voltage at coil when cranking. If not same then we can all scratch our heads.
Ok that does make sense. From visual inspection the ptu looks pretty pristine if that means anything, and I can't find a test for the sohc type so I'll check elsewhere for issues.
I'll fiddle around with it for a while, thanks for all the help!
 

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93 NA ATX 3000gt DOHC
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.....I can't find a test for the sohc type so I'll check elsewhere for issues......
My perceived PTU test for SOHC engine, see below diagram. Keep in mind this is three blade connection pins on PTU itself, not connector on wire harness.

Note: meter + (red lead) should be touched to pin 2 and meter – (black lead) should be touched to pin 3 when taking continuity/ohm readings.

1. Take continuity/ohm reading between pin 2 & 3, should be some resistance elevated ohm’s reading (no continuity).
2. Connect 1 ½ volt battery negative end to pin 2 and positive end to pin 1. Again take continuity/ohm reading between pin 2 & 3, ohm reading should be near zero (good continuity).

If the above works out to be correct, that indicates transistor inside is switching and PTU is good.

SOHC PTU.JPG
 

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If the above works out to be correct, that indicates transistor inside is switching and PTU is good.
Thanks, I will try that as soon as I am able. I've been busy with school and I'm not able to put a lot of time into the car, but I will slowly continue work on it when I can.
I appreciate all the help, if the issue gets resolved someday I will post about it!
 

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Curmudgeon
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When you do, keep in mind that the polarity of most DVM test leads is the opposite of most analog (needle type) meters.
If White's instructions are from the manual, they were written for an analog meter. If you're using a digital meter you'll probably have to reverse the red and black leads. You may have to put it into "diode test" mode instead of "ohms" or "continuity" as well.
 
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