No Spark...ECM??

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I have an 88 Chev Cavalier Z24 with a 2.8L MPFI.

You start the car and it runs 5 mins, shuts off, and will not start again.

After starting the car, and waiting till it dies and will not start again...I checked for spark, no spark.

I've changed the module and coil pack 4 times, and it still does the same thing. The next thing i'm thinking is ECM? Could this be my problem, and would an ecm from any 2.8L MPFI fit my car? please help.

posted by  Red-Dog

Now I am going to ask some questions which need straight answers I can help you (vwhobo can do this better than me)

1. is the no spark and no fuel happening @ the same time? (it is confusing to start new threads for existing issues)
2. Exactly when is the stalling or dieing occuring (I am looking for specifics such as 35-40 mph
2. how adept are you at reading and understanding (no bull crap please) wiring diagrams and using a digital (NOT ANALOG) multi-meter?

I am not trying to be a butt head but trying to get you to troubleshoot before buying ignition modules when the issue has not been diagnosed

If no spark is involved as well as no fuel, you are going to need to make sure the 1 ECM is getting power (hence the question about a wiring diagram) and there are no loose connections which would cause an intermittent problem.

2. Your wiring connections are solid (both power and grounds)

3. The crank and cam shaft position sensors are within GM specs

Then I would look @ the replacing the ECM.

GM and most other manufacturers use a ECM with a removable PROM chip of some sort (called memcal, Calpak, etc). The prom will need to be moved to the new ECM

This is about the best one can do over the internet. If you are not familiar with electronics, you may want to elist the services of someone who is

posted by  tbaxleyjr

[QUOTE=tbaxleyjr]Now I am going to ask some questions which need straight answers I can help you (vwhobo can do this better than me)

1. is the no spark and no fuel happening @ the same time? (it is confusing to start new threads for existing issues)
2. Exactly when is the stalling or dieing occuring (I am looking for specifics such as 35-40 mph
2. how adept are you at reading and understanding (no bull crap please) wiring diagrams and using a digital (NOT ANALOG) multi-meter?

Answers:
1. Just no spark...Fuel seems to be fine.
2. It dies after 4 or 5 minutes just idling...but i guess if i drove...5 mins after i start driving.
3. 8 out of 10. I have used multi-meters before also.

posted by  Red-Dog

The first thing I would do is to get a hold of an elementary wiring diagram for your car. It would make life easier Autozone.com has some of these in their on-line repair manuals for your car.

Next I would check the wiring connections @ ignition switch, the ECM, the ignition module, the crankshaft position sensor. Make sure they are solid

jiggle the ignition switch while car is running and see if run contact on switch is worn (I had this happen on an 1986 Mazda)

Use a digital multimeter - no analogs to check this stuff or else you will fry the electronics

Next, check the crankshaft position sensor.

The hard way to do this - This is how the car gets its speed signal through the ignition module This particular vintage GM uses a hall effect type crankshaft sensor will cause a car to die after a few minutes of operation. This sensor is almost impossible to troubleshoot at home since is is a hall effect/reluctor device similar to the mid 1980's vintage Chrysler distributors. Start the engine and let it warm up. When it stalls, use vwhobo's special tool (the paper clip) and pull the codes. This sensor will usally throw a trouble code 19. If it does not stall, wiggle the connectors @ the ignition module and the crankshaft position sensor and see if you can get the car to stuble or stall. check the codes. This identifies a loose connection. Since I don't have reference voltage and reistance values for the crankshaft position sensor for your car, try the following: Get the car running. shut down the car and check the resistance across the crankshaft position sensor. Run the car until it dies and check the resistance again - we are looking for an open circuit through this part when the car dies thus suspect we have a bad crankshaft positon sensor.

The easy way to trouble shoot this part (although I advocate testing) is to spend $20-25 and buy a new crankshaft position sensor

If after the car dies, with KOEO, there is battery voltage to the ECM (orange wire c16 and ground) and battery voltage to ignition module (pink wire/black stripe), then provided the ignition module is a known good module (you said it was recently replaced) and the coil pack is good, and the crankshaft sensor is good, then the only thing left is the ECM.

To give you an idea on parts costs, you are looking @ $50 to $100 + exchange for a remanufactured ECM (you will have to transfer the prom from the old computer to the new one) and about $25 for a crankshaft position sensor.

posted by  tbaxleyjr

I have an 89 Firedbird with the 2.8L V6. was driving on the freeway about 2 months ago and the car died......It seemed like it was running outa fuel or something. So, I changed the fuel filter and checked the fuel pressure and its fine. When I checked for spark, there is no spark from the coil. There is good power to the coil. I replaced the coil, entire distributor (including ignition module, and pick up coil) and there is still is no spark from the coil. I am at a loss with this thing and am seeking any advice that might help me. I havent check power to the ECM yet, but that what I plan on doing next. There is no knock sensor on this vehicle by the way. Any Help you can give me is appreciated.

posted by  surethingracing

i saw this problem once ,and it was a bad lead wire.the voltage spike caused the ecm to shut off.get a can of freeze spray.its -50 degrees.blast some on the module.if the car starts ,the module is no good.check the schematic,some
have another module with some power transistors that drive the coil pack.
check all grounds especially if the car was ever in a collision.if you want to know if any 2.8 l ecm will work you have to check the cross reference from gm .

posted by  the lobster

were the trouble codes checked? could lead to a crankshaft or camshaft sensor.

As far as ECMS go,there are cross references out there with which GM ECMS work in which GM engines. One ECM does not fit all. http://www.cruzers.com/~ludis/p4xref.html#1228706 is one of those references. I have not studied this reference in depth thus can not swear if it is the best or not. Note in these ECMS, the calibration and car data is in the memcal or PROM

posted by  tbaxleyjr

i have 13 years as an audio video electronics technician.i have actually seen it where a transistor itself can have an internal fracture.if you look at what an ecm really is is a whole bunch of chips resistors etc.most module failures are not from ic chips but from capacitors.the capacitors(those small cylindrical shaped things that say 50 mf at 16v are filled with electrolytic paste and last about 10 to 15 years )computer switch mode power supplies blow these things all the time.now it is common practice to use 105c capacitors which are much more reliable .the ecm only works with control signals from sensors.if the tach pulse or signal from the magnetic sensor in the distributor(hall sensor) goes the ecm will not let the engine run.if you have a defective component or a dry solder joint in the ecm,freeze spray will find the problem.i have fixed alot of intermittent electronics in cd camcorders,televisions etc. .i had a 1986 mitsubishi colt at the dodge dealer where i worked a couple of years ago,the OBD 2 computer kept saying the ecm was no good .i got the service manual,and after looking at it ,realized that the 5 v control into the ecm from the disributor was at 2.2 volts.after we changed the distributor,it ran perfect.THREE specialists looked at it and were all saying the ecm,which is 1200 dollars on that car.you never know what you find,man.a 50 $ used distributor,and i fixed it.do not always trust the diagnostic computers because the analysis is based on having certain
input signals.....best of luck

posted by  the lobster

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