No spark all good components. look wisemen

[spoolinawd27]

Ok so to start off I have worked for jeep and other shops for 12 years as a tech.so I know alittle about cars,but I guess not enough.
The car is a 1991 tallon awd with a maft-t. And I have checked everything from the coils to the power transister and the ecu,the cas has a good wave form and the car ran two days ago kind of lost at this point. I pined out all the grounds and powers on the ecu and the cas,also the coils have power on all three pins but I dont have a pulse on the two trigger wires. pick your heads cause I give up.


ps: I have searched for like 3hrs and no one has a issue like this:

 

[Eclipsegst2312]

I had the same problem with my 2g after I put in a new motor. The plug that came and hooked into the coils was the wrong one. In my car there were two identical plugs that fit to the coils. I had no spark at all good components. I switched the plugs, I believe the harness comes from the back of the engine bay, like under the intake manifold. So I just switched the plugs and bam it started right up. Hope you have the same two plugs as my car did.

 

[NN4S]

Have you tried a fresh set of correctly gapped plugs? That'll at least give you a chance at getting some spark. When you say you checked the power transistor and coils, do you mean you checked the connections or that you measured everything with an multimeter per the FSM?

If you've got a waveform from the CAS for both the cam & crank signals, then you've got your trigger pulse for the ignition; it just has to find it's way to the ECU and the ECU will determine when it wants to fire the plugs. It'll send it's trigger pulse for each coil to the power transistor to be amplified enough to make the coils fire. Lose your signal anywhere along this path OR get the two signals mixed up (shouldn't be likely since you said the car was running fine until a couple of days ago). More likely is a failure in the electronics or a connection that's corroded on you making the signals weak or non-existant; I'd look in the ECU for signs of electrolytic capacitor failure or other damage since it is the brains behind the whole spark timing thing.

Eclipsegst2312- the 1g engine doesn't have the two plugs you're thinking of; both of it's signals come from the CAS on the passenger end of the intake cam. On your 2G, one comes from the sensor on the nose of the crank and the other from the sensor tucked behind the intake TB cam gear. The 97-99 4g63T engines still have the crank sensor, but use a cam sensor sort of like the one on the 1g (it's in the same place as the 1g, but only puts out a cam signal & isn't adjustable like the 1g is).

 

[luv2rallye]

With key on try momentarily touching the coil yellow/black to ground. Two plugs should fire (either 1,4 or 2,3). Do same with yellow/green for other two plugs. If this doesn't work the coil is bad. If works test the power transistor: http://www.dsmtuners.com/forums/articles-electrical-wiring/229419-how-test-power-transistors.html. If works suspect ECU (possible caps leakage).

 

[spoolinawd27]

I will try to trigger the coils but I suspect the harness is bad somewhere because as I said before all componets are good I know this because I switched them with a running car of the same year. I guess next step is to pull out the harness

 

[luv2rallye]

First check the devices connectors for broken wires and pins that are not locked or making good contact. Then disconnect battery and continuity check all signal wires from CAS to ECU to power transistors to coils. Check the last first since it's the easiest. Did you also swap ECU's?
Here's the ECU pinout (CAS goes to pins 21,22): http://www.vfaq.com/mods/ecu-harness-1G.html

 

[turboglenn]

Sorry if i didn't catch it some where in this post, but did you try swapping out ignitors? Or at least testing yours?

It sounds like you've covered abotu everything though.

 

[spoolinawd27]

First check the devices connectors for broken wires and pins that are not locked or making good contact. Then disconnect battery and continuity check all signal wires from CAS to ECU to power transistors to coils. Check the last first since it's the easiest. Did you also swap ECU's?
Here's the ECU pinout (CAS goes to pins 21,22): http://www.vfaq.com/mods/ecu-harness-1G.html

I will check for continuity from the cas to the ecu to the transister and to the coils friday as I just got home and it is 9pm. I have a fealing that I will find the problem from the cas to the ecu. I will let you all know what I find.


And turboglenn yes I have tried a know good transister.

 

[turbizzle]

when you checked the coils were you checking primary or secondary? you could have power at the primary but have an open at the secondary and that could cause your problem. I haven't heard of coils failing much on these cars but it is possible. Is the ICM in the PCM? Or do the coils bolt onto the module? I would check your secondary and retrace your power supply on a wiring diagram. I bet if you just check over it again you'll be able to find your problem. hope this was helpful

 

[Locke]

Is the ICM in the PCM? Or do the coils bolt onto the module?

Ignition is controlled directly by the PCM.

 

[spoolinawd27]

Well brought the DRBIII home from the shop and I have a good 5volt square wave in to the ecu but nothing out to the power transister which tells me that the "test ecu" is dead.
I opened the ecu and the caps are leaking (suprise) any way I am towing my friends 91awd over saterday to put a clutch in it I am going to do some more parts swaping and testing well let you know what I found.




STILL

 

[spoolinawd27]

Well I put the ecu in my buddys car and no spark so who has an ecu? I have not been in to the dsm scene for a long time how much are ecu's going for?I found one that is eprom for 160$, I plan on getting dsm link later so I will need this anyway. is this a good price? He said the caps are good also I know how to socket and put the caps in my self which I will do just to make shure.

 

[NN4S]

Glad to hear that you've got it licked; the price doesn't sound too bad since I've seen non-eprom units selling for $75 and up lately. Be sure & examine the traces around the caps & the other components that they connect to when you do the socketing; better to catch a possible problem before you put it in the car!

 

[dsmtalontsi95]

I had the same thing happen to me. Now it's one of the first places I check (pareniod).

 

[Old Mitsu Tech]

There's a few guys in here that repair them. It's a little more than just soldering the caps. You have to neutralize the liquid that the caps leech onto the board first. Ask around. Or buy a reman pcm. Easier and faster.

 

[kenamond]

I've been "window shopping" in the classifieds off and on over the past year for eprom ecus, and they tend to be $200. The non-eprom units are much cheaper (~$100). So $165 for an eprom looks like a good buy.