DaEvil

Hello this is my first post and all so my first Camaro . The car is a 85 Z28 automatic TPI . I drove it home and now it will not start. The car was sitting for a few years but started up fine. I have 45 lbs at the fuel rails and the check engine light stays on. I borrowed a friend's snap on scanner but it won't communicate with it . All so I can't put it in field mode. How can I test my ECM ? or any other suggestions are welcome
Thanks

kyblackss

i have a 85 with the same problems right now

FRMULA88

First clue is the scan tool cannot find the ECM which means the ECM is offline.

The ECM or power to it is dead... mice may have chewed up the harness and after your drive a component shorted the system out

check the fuses, test for power to the ECM and go from there.

If the fuses are not blown and power is getting to the ECM but no power is coming out, the unit may be done.

Take your time.. electrical problems take awhile to sort out.

FRMULA88

As a follow up when you said "It won't start" do you mean the starter won't crank the engine over? does the starter solenoid click when the turn to key to start it?

headlights work? radio work? etc.

You could simply just have a bad battery. they tend to not last long if left sitting without a trickle charger.

CHECK THE BATTERY.. with a multi-meter probe the battery posts.. you should have 12 -14 volts.. check the bulkhead fitting at the radiator.. you should have the same thing. inspect the battery cables for damage and loose connections, especially the pig tail from the + terminal to the bulkhead fitting at the radiator.
if the battery is weak or discharged.. get it load tested at an auto parts store.

install a new one if it fails the load test otherwise recharge it..

With a good battery in the car.. see if it will start.. if it does you are still not in the clear.. you need to inspect the charging system.. to make sure the alternator is charging the battery.

Any corrosion at the bulkhead fitting at the radiator will affect power output to the starter, ECM, and impair the alternator's ability to back feed the system (run the components when the engine is on and charge the battery)

DaEvil

I'm sorry I should have made myself clear . It cranks fine and it has pulse at the injectors .

FRMULA88

OK so car cranks and you have injector pulse.

what about fuel pressure? Sometime the check engine light will come on if the fuel pump is dead...

DaEvil

45 lbs. at the fuel rail

FRMULA88

Did you check for spark?

if the check engine light is on while cranking there is a problem. The snap on scan tool should work unless it's a OBD II tool only, in that case you can't even plug it into the test port. I forget which pins on the test port have to jump to put the ECM in field test mode.. but you should be able to search for that and the list of codes.

DaEvil

There is spark and the light stays on . The plug under the dash is Gen 1 and you jump A and B . Nothing happens when I try and put it in field mode .

FRMULA88

What do mean nothing happens? jump the pins and turn the key to run position, The check engine light should start blinking so you can translate the trouble codes.

if the ECM light simply stays on.. The test port or wiring may be damaged or the ECM is not getting power or damaged.
only way to tell is to inspect the fuses, the wiring to the ECM, and the ECM itself.

IF you have fuel and you have spark... all that's left is timing.. PERHAPS THE TIMING FUNCTION OF THE ECM has failed or is offline

But before you replace the ECM check the ECM fuse, then check the ECM wiring on engine bay side.

Cars sitting can get wires chewed up by mice, or the car had a damaged harness and was parked for that reason.

Wild 90

I just had this happen on the 87 i bought. Check engine light stayed on constantly. The wires going into the passenger fender to the ECM were chewed up. ECM had power but no ground. After fixing the wires, got it to show code 12. Fuel pump was bad but after changing that, it ran.

FRMULA88

yup a short to ground or a broken ground wire is all it takes... check for a blown ECM fuse and then the ECM wiring the location described by wild90 is a prone area for harness damage.

Wild 90

^^^ You can reach/inspect this area of the harness via removing the plastic inner fender. Check it under the dash where it comes thru the kick panel to the ECM also.

FRMULA88

My car was only 5 years old when it had this issue.

The fuel pump wiring was shorted out causing the pump cut out intermittantly.

Too bad it was out of warranty by then.

DaEvil

Well after checking everything I bought a used ECM from Ebay. It arrived today I installed my chips and the car started right up . Thanks for all the help

FRMULA88

Post #3 FTW !!! glad to hear you fixed it..

I did not want to jump the gun and just say the ECM was fried without ruling out the other possibilities.

Not bad for a "carb guy" LOL !