91 Talon, no spark, no Inj Pulse

[Daimyo]

Hello all, new to the forums here. I've read through and found answers before but can't seem to find anything this time.

Car:
1991 Eagle Talon, 2.0 ltr non turbo, 2wd

About 2 weeks ago, driving along no problems running and the car quit. Some smoke out of the dash, turned out to be a blown capacitor in the ecm.

Got a new ecm. Before hooking up, I checked all relays and seloniods to make sure none were shorted, all ok.

Checked Ignition Module (Ignitor) and found it to also be faulty. Replaced Module.
Connected ECM tonight and still no Spark or Injector pulse.

12v to the injectors and coil, but no control from the ecm.

I checked the Crank/Cam sensor and I belive it is ok, I don't have a scope to check the wave pattern, so I could be wrong about it.

Is there any way for me to check the Crank/Cam sensor using a DVOM reliably?

Another thing that I found is that 5v ref is low. I'm not completely sure on this car, but I beleive that I should see 5v in the connector with a sensor disconected.


Any help or lead would be greatly appreciated!

Thanks,
/D

 

[huafist]

Have you checked the MPI relay and the ignition fuse?

 

[ChicksDigBoost]

Do you have a Logger? You can check to make sure your getting an RPM signal.
I know the 5v reference on my car is actually 4.75 volts. Is yours lower than that?

On the CAS, Pin 4 is the ground, Pin 3 should have 12 Volts, and Pin #1 is the 5v reference.

Good Luck

 

[Daimyo]

huafist, yes checked the relay, even opened it up to confirm operation.

ChicksDigBoost, I don't have a logger
I was hoping that I would be able to check it using a DVOM, which I can because the rpm signal generated is an on/off signal (Hall Effect) I can check it two ways:
Duty Cycle, and Resistance (Neither test is that reliable though)

I'll check them tomorrow. my 5v ref... I am going to check right at the ecm. If less than 5v then I either have a short, a bad sensor, or another faulty ecm.


I'll let ya's know.

/D

 

[styx]

check for crank and cam signals, will the spark plugs fire a few times then stop when you crank it

 

[Daimyo]

check for crank and cam signals, will the spark plugs fire a few times then stop when you crank it

There is no spark at all.

 

[Daimyo]

I just checked the 5v reference to Cavity 2 (BLK Wire) to the CAS and I only have .875, so I am checking the 5v back at the ecm now.

I'll keep this as a "live" post. I'm using a "trouble tree" diag sheet from Mitchell on Demand.

Ok Checked power and grounds to ECM, all ok.

Checked Voltage at Cavity 2 (BLK) wire of the CAS connector, .875v

Disconnected 24 way connector at ECM, Measured resistance between Cavity 2 (BLK Wire) of the CAS connector and the ECM Connector, resistance is .014 Ohms, good circuit.

ECM 24-way Connector disconnected, and CAS connector disconnected, Checked Cavity 2 (BLK Wire) for resistance to ground, OL (Out of Limit), meaning there is no short to ground on that circuit.

Faulty ECM

Another thing I checked while at the ECM is the CAS signal. (Not the proper voltage, but enough to confirm). The voltage does fluctuate while cranking, which tells me that I am getting a signla from the CAS.

I'm on my way to get a replacement. I'll post back hopefully about the car starting once I replace the ECM again.

/D

 

[huafist]

If the ECU is THAT dead, then you could've saved yourself a whole lot of trouble by checking it for a heartbeat. If you hook either a LED or an analog voltmeter to pins 1 & 12 of the diagnostic port beside the fusebox, the ECU will flash an on-off pulse indicating normal operation. (Also, your CEL should come on for a few seconds when you first turn the key on).

 

[Daimyo]

Success!...sort of.

Got the new ECM, plugged it in and the car started....then stalled.

When the car stalls, I hear the MPI Control Relay click out just before it stalls.
So I checked to see which relay in there was clicking off. It's the Fuel Pump side. I lose 12v on the Blk/Grn wire and the car dies.

I then checked the Control side for that circuit and found that I am losing signal on the Blk/Yel wire from the ECM...
The Blk/Yel wire goes to the ECM Pin 108 (Ignition Power) and to the Inhibitor Switch (Automatic) Pin 9.

I am going to try another MPI relay to see if maybe the relay is shorting itself out. This could possibly be why the ECM smoked in the first place. If thats not the cause, then I will check Amperage on the Fuel Pump circuit, as a high draw could also cause a problem.

If neither one is the cause then I guess I may be looking at an Inhibiter Switch? I'm not sure where to go after the fuel pump test.

So now I have a car that starts and runs smooth for about 5 seconds then stalls.

Any suggestion would be great. I'll also see if I can pull any codes from the ecm using an LED.

/D

 

[huafist]

Success!...sort of.

Got the new ECM, plugged it in and the car started....then stalled.

When the car stalls, I hear the MPI Control Relay click out just before it stalls.
So I checked to see which relay in there was clicking off. It's the Fuel Pump side. I lose 12v on the Blk/Grn wire and the car dies.

I then checked the Control side for that circuit and found that I am losing signal on the Blk/Yel wire from the ECM...
The Blk/Yel wire goes to the ECM Pin 108 (Ignition Power) and to the Inhibitor Switch (Automatic) Pin 9.

I am going to try another MPI relay to see if maybe the relay is shorting itself out. This could possibly be why the ECM smoked in the first place. If thats not the cause, then I will check Amperage on the Fuel Pump circuit, as a high draw could also cause a problem.

If neither one is the cause then I guess I may be looking at an Inhibiter Switch? I'm not sure where to go after the fuel pump test.

So now I have a car that starts and runs smooth for about 5 seconds then stalls.

Any suggestion would be great. I'll also see if I can pull any codes from the ecm using an LED.

/D

Where did this "new" ECU come from? What you're describing is a classic symptom of capacitor leakage. Try grounding pin 7 of the MPI relay and start the car. If the car stays running the problem is the ECU.
DO NOT drive your car like this! Your fuel pump will be running nonstop. This is for diagnosis ONLY.

 

[Daimyo]

Where did this "new" ECU come from? What you're describing is a classic symptom of capacitor leakage. Try grounding pin 7 of the MPI relay and start the car. If the car stays running the problem is the ECU.
DO NOT drive your car like this! Your fuel pump will be running nonstop. This is for diagnosis ONLY.

The ecm is from a local rebuilder here in florida.
I tried the ground at pin 7, and yes the car stays running

Can anyone direct me to a reputable rebuilder? I'm kinda gettin bored with running back and forth to this one.

Thanks,

/D

 

[huafist]

Where did this "new" ECU come from? What you're describing is a classic symptom of capacitor leakage. Try grounding pin 7 of the MPI relay and start the car. If the car stays running the problem is the ECU.
DO NOT drive your car like this! Your fuel pump will be running nonstop. This is for diagnosis ONLY.

The ecm is from a local rebuilder here in florida.
I tried the ground at pin 7, and yes the car stays running

Can anyone direct me to a reputable rebuilder? I'm kinda gettin bored with running back and forth to this one.

Thanks,

/D

PM steve here. He's one of the best if you ask me.

 

[TotalEclipse112]

If you are reading "OL" from the black wire off the CAS "OL" means open loop on a DVOM. If there is no ground on a hall effect sensor its not going to be sending the on/off signal because the voltage has no where to go, henc no on/off signal from it. If this is the case the injectors and the coil should be dead since the ECU sees no voltage it thinks the motor isn't moving. Check that wiring for the CAS its probally a bad ground. Also the refrence signal is 5 volts but the ECU will NEVER, unless something is bad, see 5V. It will usually see like 4.75v maybe 4.8v but never 5v. Also if you can get it use All Data the diagnostic flow charts are much more accurat and easy to use that Mitchell, Mitchell is just plain confusing. Hope this helps somewhat.

 

[Daimyo]

I used both Mitchell and AllData trouble trees.

With the first ecm, the "5v" reference wasn't even about 1v. I knew I wouldn't see a full 5v, but less than 1v is a problem.

Got another ECM. "5v" Ref signal about 4.7v, good circuit.

At the lastest point I was losing the control signal from the ecm to the MPI Control relay for the fuel pump and inhibitor switch. I tried grounding pin7 at the MPI relay and the car ran fine....Returned another ECM.

The guy at the parts store was in disbelief at first. So I asked him to come outside to my car. I still had the center console area open to get to the ecm (I borrowed a friends ecm, thats another way I confirmed a faulty ecm again))

I started the car and ran it for about 5 minutes, even offered him a ride to show that all is working ok. no complaints at all. I then shut the car down, installed his ECM and the car would start and stall.

I should be getting another in a day or two. Hopefully all is ok this time.
With all the time I've lost and spent on gas in my Dodge Ram Gas guzzler, I could have purchased a Brand New ECM from Mitsubishi/Chrysler by now WTF

I'll post back when I have the next rebuilt ecm.

/D

 

[huafist]

My guess would be they replaced the caps and cleaned up the electrolyte, but didn't check for microscopic trace damage. They plugged it up and got a heartbeat and called it done.

 

[Daimyo]

Ok. So I got another ECM ( #3 ) and no good there either...

Next day I ordered one from another supplier. It arrived next day air. Popped it in and the car started right up. Haven't had any engine/running problems since then.

I'm still waiting for the original seller to even up with me... I think I'll be going to court, unfortunately. He doesn't seem to think it's his ecm's that are bad. Even when I went to him with the running vehicle.


So, a few weeks pass, and another problem comes back. Only this time it's the transmission
This problem was intermittent for some time, then didn't happen for months. The trans would shift normally, and then outta nowhere, it would stop shifting and stay in drive at all speeds. Hot, cold didn't matter, I had reverse and drive, no 1st, 2nd or OD.

I grabbed my Mitchell and AllData trouble tree's and started looking. I don't have a scanner that interfaces this car, so I looked for the obvious, broken circuits, terminals, etc.
All ok...So I figured why not start with the Pulse Generators? Since they have a direct effect on shift points, maybe one or both are bad. I checked them both and they check out ok. Problem is that there is no voltage coming from the computer...ack!

Here's the learning experience....
Next step, check 14 pin connecter at the computer. I checked my computer 10 times and seen no 14 pin connector. "ok maybe it's a misprint"... I unplug the computer and start checking for a short between the connectors at the controller and the plug at the PG's. hmm, i have grounds. Let's look for a short in the harness.

So I go under the hood and open the wiring harness from the trans to the firewall, all is ok! I go in the car under the dash to trace them and start to pull things apart to get to the harness..."Hey whats this"? another computer! WTF

I've been working on cars for some 20 years now, and I feel foolish to say this, but I never knew about a 2nd computer on these vehicles. Mitchell and AllData both state "The controller is located behind the center console". And thats stated for the Controller Not the trans controller or engine controller, just the Controller...Grr Hey Look! there's a 14 pin connector!... I trusted the diag books and figured that the controller, was the controller I had just put in previously.

Needless to say, I checked the 14 pin connector and found no shorts..checked the voltage output, and the Trans controller was not putting out voltage. I replaced the Trans controller and now the trans is shifting fine now.

So I learned a few things here:
Never trust the printed data from Mitchell or AllData.
Seek and you shall find!
Always come to the forums for hands on knowledge and advice


Thanks to all for the replies, they really helped out!!

/D